RALPH N. SARGEN * OUR LAST COPY! Please Return to Media Arts Program/Room 720 National Endowment for the Arts 1100 Pennsylvania Avenue, NW Washington, DC 20506 PRESERVING £ 202/682-5452 Laura Welsh Digitized by the Internet Archive in 2015 https://archive.org/details/preservingmovingOOsarg Preserving the Moving Image Some background in the art of moving image preservation. A survey of opinion on conditions in the field. The prospects for new image technologies in the laboratory and in the marketplace. Detail from Thomas Edison's Patent number 589,168, August 31, 1897, for a Kinetographic Camera. t MaaaaaBaaiiMaagaaaaa ^ a a a a a a, a, a aya a a a a a, a a a a a a \\ UCIlf is, ^ Preserving the Moving Image RALPH N. SARGENT edited by Glen Fleck published jointly by the Corporation for Public Broadcasting and the National Endowment for the Arts 1974 Any proceeds from the sale of this book shall revert to the Corporation for Public Broadcasting, for use in projects for the preservation of moving images. Library of Congress Cataloging in Publication Data Sargent, Ralph N 1941- Pre serving the moving image. Supt. of Docs, no.: NF 2.2: Im 1. 1. Moving -picture film- -Preservation and storage. 2. Video tapes--Preservation and storage. I. Title. "3 <307 77ft c-»P 7)1 4 Introduction members of the advisory group: American Film Institute Lawrence F. Karr Sam Kula George Eastman Flouse James Card Library of Congress John Kuiper Paul Spehr Museum of Modern Art Eileen Bowser Willard Van Dyke The moving images of film and television have become the truest record of our time, the richest source of information on the spirit, the attitudes, and the daily life of the 20th Century— not only as an art form, but as an absolute historical resource. Now, the importance of gathering and preserving American films and television programs has suddenly come into focus with the realization that a large percentage of the historic films from the first half of this century, and a major portion of the television programming from the last 25 years, has been lost forever. At least two-thirds of the theatrical films made in this country are not known to exist in any form. The same is probably true for newsfilms, television programs, and documentaries. Nitrate-base film, in use until 1951 , has turned out to be hazardous to store, and can decay even in archival storage after 40 years or less. No way has yet been found to prevent the self-destructive processes to which every foot of nitrate film will eventually succumb — but there is no mistaking the end. The film’s surface becomes sticky; the emulsion separates from the base; the image is soon beyond recall; the celluloid itself turns into a coagulate, and finally into brown powder. At that stage, the flash point is lower than that of newsprint, and where the gas given off by the decomposing celluloid can build up pressure, spontaneous ignition is possible. Even sound films on nitrate base, which are available to television, are not free from danger. The original nitrate materials have often been copied only to 16mm duplicate negatives of generally inferior quality, which, in any case, are subject to regular printing with its attendant handling risks. The nitrate originals, once copied to 16mm, usually remain untouched until the 16mm negative has been worn out or ruined. In numerous instances, the nitrate originals have been found decayed beyond rescue when needed once again. Before the introduction of triacetate safety film, each generation of archivists was forced to reprint each film it wished to preserve. After 1951, even though a rather permanent film base had been invented, the archivists in this country were frustrated by a lack of funds. This is the heart of the challenge. The technology for proper archival storage has existed since 1951 . What has been lacking is a general awareness of the value of preserving our film heritage. As an indication of the artistic or sociological importance of motion picture, numbers are meaningless — whether numbers of titles, or numbers of feet of film. But they do suggest the extent of the loss, as it is now understood. Between the turn of the century and 1951 , more than 25,000 feature films were produced in the United States. Only about 50% of these survive today in any form. Presently in the United States, there are four major archives preserving nitrate film: The Library Of Congress The Library of Congress accepted its first motion picture for copyright on January 9, 1894. During the following 18 years, approximately 5,500 films were registered for copyright in the form of partial or complete prints on paper rolls. A 12-year restoration project for these so-called “paper prints” began in 1953, with the initial support of the Academy of Motion Picture Arts and Sciences, and subsequent funding through a special Act of Congress. Approximately 3,050 films survived to be rephotographed to 16mm stock, and are available today. In 1912, a revision in the Copyright Act made it possible for producers to deposit descriptions of films as evidence of copyright, to avoid the hazards of storing nitrate prints. It was not until 1942 that a very select sample of nitrate feature films was again accepted for deposit. In 1952, with the widespread acceptance of safety film for theatrical exhibition, the Library of Congress began to systematically select and acquire prints of current releases, which continue to augment and update the National Film Collection. Except for several notable collections of films donated to the Library of Congress by various individuals, few motion pictures were in the National Collection to represent the 30 years of 5 production during which the American film gained its style, artistic acceptance, and social influence, until the large influx of acquisitions stimulated by the work of the American Film Institute began to arrive in early 1969. Approximately 96 million feet of nitrate film are now stored in the Library of Congress, and some 80 million feet of this remain to be copied. The Museum of Modern Art In 1935, the Museum of Modern Art Film Library Corporation, with Iris Barry as its first curator, began to acquire prints and negatives of significant feature and short films for showing, circulation, and preservation. Although the Museum’s collection is not enormous in terms of aggregate footage, it was very wisely chosen, and is extremely important, both for the significance of the films and the beautiful quality of the copies in which they are held. Films were acquired and stocked under observation in the certainty that they would have to be reprinted every few years. In 1969, the Museum of Modern Art Trustees made funds available for the transfer of much of the Museum’s accumulated nitrate, and since then, approximately $800,000 has been spent on film copying. Approximately three million feet remain to be copied. The George Eastman House The collection of the International Museum of Photography at the George Eastman House, established in 1948 by James Card, is also very valuable for the rare original prints and many original negatives it contains. Like the Museum of Modern Art’s film library, the George Eastman House Film Study Collection is catholic and international in scope. In American Film, it is particularly strong in silent films produced prior to 1930. Transfers to safety film at Eastman House have been limited by a rather stringent budget, and nearly 16 million feet of important film still await reproduction. The American Film Institute The American Film Institute was established in 1967 as a private, non-profit organization by the National Endowment for the Arts, with major support from the Ford Foundation and the member companies of the Motion Picture Association of America. The institute’s first priority was the preservation of the American Film. Though their program has also been focused on the nitrate film era, the AFI negotiated a collaborative agreement with the Library of Congress, rather than operate a separate physical plant to house and service its film acquisitions. Since the summer of 1968, in addition to carrying out its own preservation activities, the AFI has assisted the Library by providing research and technical support, and operational funds, to expand the Library’s capacity to absorb and transfer nitrate film. This includes the installation of a specialized film copying facility on the Library’s premises. Through negotiations with various corporate and private owners, AFI has augmented the Library’s collection with approximately 10,000 films, which are designated as the American Film Institute Collection. Archivists have learned not to regard any film as preserved that exists only in private hands, whether they be in corporate storage vaults or basement collections. Film producers and distributors are in the business of earning money from their productions, but not in the business of preserving them. They cannot be expected to invest in the saving of films which, in their judgment, lack the commercial worth to earn money over and above the cost of keeping and printing them. It is believed that approximately 16,000 titles, or 163 million feet of nitrate film survive outside of archives, and that most of this could be preserved if funds became available. These figures are just for nitrate. In these same archives, vast amounts of acetate-base film is piling up— black-and-white and color, which, due to the transient nature of color dyes, is rapidly becoming as critical a problem as nitrate. And the archival preservation of television programming has scarcely begun. While efforts are now in progress to bring selected kinescopes of early television broadcasts into the Library of Congress, the great majority of television programs are held— if they are saved at all— in the vaults of the television networks. A recent estimate puts the number of television programs held by the three major commercial networks at over 90,000. Combined with the holdings of Public Broadcasting, and the syndicators, this might represent as much as 200,000 hours of programming. Attempts to preserve any significant part of that total for future generations are hampered by how little we know about the archival qualities of videotape. This survey reviews the situation in the field, in the laboratory, and in the marketplace. It will give the reader an idea of how moving image technology is doing, where we can look to find new answers, and, in some cases, when we must carry on with the answers we have. Frequent mention is made in the following pages to FIAF (Federation Internationale des Archives du Film)— The Internation Federation of Film Archives. It is composed of 48 member archives from around the world. 6 Table of Contents Foreword 8 Specifications for Archival Media 9 SECTION ONE: Keeping Film 10 BASE, BINDER, IMAGE 11 Discussion: AMPTP Research Center 12 The Base 16 Stability Criteria 18 Evaluation of Physical Properties 19 Evaluation of Chemical Properties 19 Shrinkage Behavior of Bases 21 Discussion: E.I.du Pont de Nemours & Co. 23 Photographic Gelatin and Synthetic 28 Colloids for Emulsion Use by Thomas T. Hill Discussion:Fuji Photo Film Co., Ltd. 32 The Image 34 Discussion: Eastman Kodak Company 36 TREATMENT AND STORAGE 40 Treating the Image 41 Fuji Photo Film Co., Ltd. Part 2 45 E.I.du Pont de Nemours & Co. Part 2 46 Storage Conditions 47 Discussion: National Film Board of Canada 49 CONDITIONS IN THE FIELD Discussion: National Film Archive, London 53 Discussion: Cinematheque Royale 60 de Belgique Discussion: Nederlands Filmmuseum 64 Discussion: Cineteca Nazionale 67 Discussion: Staatliches Film Archive 71 Interview with Herbert Volkmann 75 RECOMMENDATIONS 79 NEW TECHNOLOGIES 98 Discussion: Peter C. Goldmark 99 Non-Magnetic Video Recording Systems 105 Discussion: RCA Corporation 107 The Design Concept of the Sony Color 112 Video Cassette Total System by Kazuo Iwama Disc Recording Systems 115 T.V. Programs on the Disc 117 by P. Kramer and K. Compaan Discussion: Teldec 120 Discussion: Battelle Memorial Institute 124 RECOMMENDATIONS 127 SECTION THREE: Videotape 128 Magnetic Recording Systems 130 Videotape Storage 136 AMPTP Research Center Part 2 1 36 3M Company Part 2 1 37 E. I. du Pont de Nemours & Company Part 3 1 38 Fuji Photo Film Co., Ltd. Part 3 138 Recommended Environmental Conditions and 139 Handling Procedures for Magnetic Tape Videotape to Film Transfers in Color 144 by Richard B. Glickman RECOMMENDATIONS 149 Index 150 Acknowledgments 152 SECTION TWO: New Approaches 80 Vesicular Films and Dry Processes 82 Discussion: Kalvar Corporation 84 Eastman Kodak Company Part 2 89 Discussion: Agfa-Gevaert AG 90 Discussion: 3M Company 93 Color Separation Systems 96 7 Foreword Chtoe Aaron Philip Rubin In December, 1971 , I was contacted by Chloe Aaron, who is in charge of Public Media for the National Endowment for the Arts, about doing a survey of moving image technology and preservation. She had asked a group, consisting of representatives of the Library of Congress, the Museum of Modern Art, the George Eastman House, and the American Film Institute, to come together to define the needs of the field in film preservation. In their meeting, it had been agreed that the problem was not only one of finding money to preserve existing collections of nitrate film, but included certain key questions. Before launching on a large-scale program of preservation, can we: (1) determine the ideal archival conditions under which to store film? (2) discover more reliable tests to predict the remaining life of the nitrate films we are storing? (3) find out if new materials, or methods, now being developed in manufacturers’ laboratories might have better archival qualities than present- day systems? (4) establish priorities for funding more research, and development, of promising materials? Early in 1972, this group, along with Chloe Aaron, met with me at the executive offices of the Museum of Modern Art. In that meeting, a study of the archival aspects of film was set into motion. In addition, the group recognized that such a study would be far from complete if it did not also make a serious, in-depth inquiry into the archiving of videotape. For this reason, Philip Rubin, the Director of technology for the Corporation for Public Broadcasting, was invited to participate with the advisory group, and assist in the establishment of guidelines for the project. From February to October plans were made, a research staff hired, and itineraries prepared. We wanted to conduct an exhaustive literature search covering the areas of the study, and to establish contact with a large number of leading individuals, corporations, archives, and government agencies in the field. We hoped to amass enough information so that significant areas of agreement on the problem could be reported, and areas of disagreement could be investigated, and placed in order of priority for future research. A key feature of the study was an around-the- world, in person, “survey through discussion” held with individuals intimately associated with the problems of manufacturing image recording materials, and those charged with preserving them. These discussions took place in the United States, Canada, England, Belgium, the Nether- lands, East and West Germany, Italy, and Japan. Critical to these discussions was a set of specifi- cations which precisely delineated our desired materials and/or processes. After much dis- cussion, three major areas of materials usage emerged: (1) dead storage materials of the highest quality, from which all future materials requirements could be met, and high-quality prints made for theatrical use; (2) projection materials of a somewhat lesser quality than Category One for showing to small groups; (3) materials for individual scholarly use. It is difficult to attempt to define a new medium in terms developed from an older one; this problem is inherent in our attempt to pinpoint those aspects of existing media which we wish to preserve, while at the same time leave enough flexibility for the vagaries of new media. Our specifications for the three archival media are a blend of motion picture and television terms, with enough amplification in terms indigenous to both media to make them comprehensible to technicians working in either field. For the purposes of the discussions held in the course of this survey, the following specifications were established as “launching points”. These various figures are based, not necessarily on materials presently available, but on environ- mental conditions readily achievable. For this reason, it was not, necessarily, expected that any existing material would be found that satisfied all of the various requirements. These specifications were not chosen arbitrarily and left unmodified throughout the work. They were arrived at after much discussion and head scratching; for that matter, we do not consider them final even now. Ralph Sargent Los Angeles, California March, 1974 8 CRITERIA FOR PROPOSED ARCHIVAL MEDIUM # ONE ARCHIVAL MEDIUM # TWO ARCHIVAL MEDIUM # THREE ARCHIVAL MEDIA High-quality, long-term storage materials Projection materials for showings to small groups Materials for individual scholarly use. 1. RESOLUTION 1200 cycles (line pairs) per horizontal field 1 ,440,000 picture points per fr. 600 cycles (line pairs) per horizontal field 360,000 picture points per fr. 350 cycles (line pairs) per horizontal field 122,500 picture points per fr. 2. GAMMA RANGE 0.5 - 1.5 1.0 - 1.5 PRODUCT GAMMA 1.0 - 1.5 PRODUCT GAMMA 3. DENSITY RANGE ~ 2.1 ~ 2.1 ~ 2.1 4. COLOR SENSITIVITY Panchromatic Type B Monochromatic Monochromatic (B&W) Trichromatic (color) Monochromatic (B&W) Trichromatic (color) 5. STABILITY (useful life) Over 100-year period Allowable shifts (delta) a. Image Density ± 0.05 ND ± 0.10 ND ± 0.15 ND b. Gamma ± 0.05 + 0.10 + 0.15 c. Fog ± 0.02 ND ± 0.05 ND ± 0.10 ND d. Binder Transparency ± 0.01 ND + 0.025ND ± 0.05 ND e. Signal-to-noise Ratio 3 DB 6 DB 9 DB f. Flexibility 20,000 folds 20,000 folds 20,000 folds g. Geometry + 0.00015” + 0.0003” ± 0.00045” h. Resolution 0.5 mHz 0.5 mHz 0.5 mHz 6. STORAGE CONDITIONS a. Temperature 70° F. ± 15° 70° F. ± 20° 70° F. ± 20° b. Relative Humidity 50% ± 20% 50% ± 30% 50% ± 30% c. Release of Harmful by-products none none none d. Requirements for Conditioning none none none e. Ability to Support Life Forms none none none 9 10 SECTION ONE Keeping Film The basic elements of motion picture film haven’t changed very much in the last 80 years. Thus, on the storage of conventional motion pictures, opinion is pretty well jelled on the basics: film should be protected from the elements. But merely putting a roof over a stack of film cans is not enough to give the average archivist peace of mind. It is this question— what should be the degree of sophistication in the treatment and testing of motion picture material, and its subsequent storage— which is the subject of this first section. It should be borne in mind throughout this section that, most frequently, there is no unanimity in approach, research, or evaluation of work done in this field. Almost everyone questioned during the preparation of this work had conflicting answers on almost every question— what should the temperature and humidity be for the storage of various films? How does one best store nitrate? How do you protect from atmospheric pollution? What are the best color preservation techniques? Do special aftertreatments provide any protection? And so forth . . . Therefore the recommendations which appear at the end of this section represent trends of opinion, and should be taken as such. Each and every archival question will have to be evaluated in terms of existing conditions at a particular archive— its facilities, manpower, budget, and the desire of its people to do everything in their power to preserve the moving image. BASE, BINDER, IMAGE From the archivist’s standpoint, no matter what system is used to record an image, if the material upon which that image is captured deteriorates during storage, no degree of refinement of the recording system will save the process from being an archival flop. The last four stages of the decomposition of nitrate film. It is important, therefore, that we first examine the physical and chemical characteristics of the various media — with special emphasis on those points which determine their keeping qualities. A handy method for this analysis — one defined in more detail by Wilton Holm on the following pages — is to conceive of film in terms of base, binder, and image. The following sections analyze conventional silver photographic products in these terms. It’s true that the concepts of “base” and “binder" apply as well to videotape. These considerations are discussed in Section Three. 11 AMPTP Research Center Los Angeles, California H: Wilton R. Holm, Executive Director S: Ralph Sargent In searching for someone to give an overview of the problems of preserving moving images, one of the first names to come to mind was that of Wilton Holm, a noted spokesman for the motion picture industry, and an author of works on optics, photography, and color television. At the time of our first interview he was the President of the Society of Motion Picture and Television Engineers. Trained as a physicist, Mr. Holm worked for many years at Du Pont as a motion picture specialist, before taking on his present role as Vice-President of the Association of Motion Picture and Television Producers and Director of the Motion Picture and Television Research Center. The section of our discussion dealing with the electronic printer was taken from a recent talk with Mr. Holm. S: What are we going to do about saving films and tapes? H: Why don’t you just think of it this way: what you have is a technological problem, right? And you have three principal facets to this problem: you have a material which carries your image, your information— this is the gelatin. (If that’s kept in a reasonable condition archivally, it's good practically forever. But there are possibili- ties of making so-called emulsions out of poly- mers— plastics— which are non-degradable, non- biodegradable.) You have a base problem which touches on the nitrate thing. You have to have something, which can’t contain your information, to carry this very thin emulsion. You have to have the emulsion bonded to the base so that the bond doesn’t fail. These are the three facets of your problem. Nitrate base was the only base around for years and years. That’s why all these films are on nitrate today. The fact that there are millions of feet of images that are valuable and haven’t been transferred from nitrate is simply sloppy human error. This has been known for fifty years: the work that has gone on during this time on various kinds of acetate bases, ending with a triacetate, has all been aimed at getting away from the fire hazard of nitrate, which is tied to its degradation and decomposition. In a sense, fire hazard and the lack of archive stability are related. So you have to say, “Okay, somebody knew better— they should have transferred this material long ago.” True. But, if they don’t transfer it now, well, they’re asking for trouble— they’re going to lose some of it. When triacetate came into the picture, of the three constituents of film, the binding, the emulsion, and the base, the base was the biggest problem. Triacetate base became a standard in the motion picture industry. It was safe, but not stable: not stable dimensionally, not stable archivally. Now because the manufacturers didn’t want nitrate in the homes of people who didn’t know about it, acetate was used. Acetate was stable and fire safe, safer than newspaper that you take into your home. Now, polyester came along; it is more stable than acetate. In fact, I doubt whether in our lifetime anybody will come up with anything more stable. Polyester is a tremendously stable material. S: One of my associates has been going over the available information on bases. We’ve collected probably eighty percent of all the articles ever written on bases of any kind going back to early articles of 1915-1920. We’ve searched all the journals of the SMPTE. A number of problems have cropped up in trying to arrive at a really definitive statement about bases. Practically all of the experiments or tests which have been conducted on bases seem to have no normalized values. As a participant in the Cronar study, I’m sure that you went through the existing printed information and are familiar with it. How did you arrive at the particular tests that you did and how did you go about making nor- malized comparisons between the new tests and the tests that had gone before? We have found it to be very difficult to relate information for the particular values we wish to examine. H: What you do is to start out defining your problem in terms of the base you have. The problem with triacetate base was its dimensional stability, not its decomposition. Actually, triacetate is moisture sensitive. Nitrate base was also moisture sensitive: moisture and oxidation caused it to decompose. Triacetate simply changes size with moisture, it doesn’t decompose. The Cronar project was aimed at getting a base that was dimensionally and spec- trally stable. Then, when you come to a chemical compound like polyester— polyethylene teraph- thalate, an oxygen chemical, a long chain polymer — you can make chemical tests that will tell you how easy it is to oxidize. This is usually the thing that gets bases. These tests are done chemically. There’s one thing that you try to do: you try to accelerate time. This is quite difficult, bu,t if you know what you’re trying to accelerate for, namely, oxidation, you look for things in nature that will hasten oxidation, like ultra-violet light — and you get it everywhere. You normally wouldn’t think that there’s ultra-violet here, but there is; you get some from flourescent lights and it gets reflected in from outside. On a cloudy day, you can get sunburned. Ultra-violet is all over. So you put these materials in machines that flood them with ultra-violet, and have high moisture content so that you can make the most hostile environment you know in order to accomplish the chemical 12 reaction that you know breaks down the bases or the compound. Polyester went through such tests with flying colors. Polyester is like many of the other plastics today. People complain that they’re not bio-degradable, so from an ecological point of view, they’re lousy materials, but from an archival point of view, they’regreaf materials. They’re going to be around a hundred years from now! What you want is exactly what the ecologists are against. So, these are the kinds of tests that you have to go through. The tests also help determine the method of bonding the gelatin emulsion to the base. Sometimes the bond will come loose. They found many problems with Cronar. Normally with nitrate or triacetate, you use a sub-material. Gela- tin won't stick to the base, but it will stick to the sub-material and the base will stick to the sub. The sub is a polar compound; one end hooks on to the base and the other end hooks on to the emulsion. S: That was a very difficult thing to find for Cronar, was it not? H: It was difficult. They had to go to a double subbing; first a resin which had the right polar properties and then a sub which would hook to the resin and in turn hook to the gelatin. The reason is that practically nothing will dissolve Cronar. Carbolic acid, and the phenol group, are about the only chemicals that will. S: Because of this, image stripping has been one of the most severe problems with respect to polyester bases. Do you think the problem of image stripping has been solved? H: I think that it has. At least to my knowledge, Kodak, under their licenses from Du Pont, and Du Pont have made a lot of polyester film for instrumentation use that is archival, and is being stored. S: The base study tells us that some of the tests have been done with emulsion-coated materials and other tests have been done with strictly base by itself. As part of this, the gel /silver ratios of the emulsions have had an influence on the curl factor, the sort of bi-metal strip effect— more hydrophilic on one side, forcing curl up. Do you know of any work that’s been done which in effect eliminates the hydrophilic nature of gelatin, or at least reduces it to the degree that curl wouldn’t be a consideration. H: I think you’re facing an impossibility. Gela- tin has to be hydrophilic. S: I mean as a final step in the processing of film. H: No, unless you destroy the gelatin property, that is, the composition of gelatin which is in itself a polymer. If you keep the structure of gelatin, and don’t destroy it, then it retains this hydrophilic property. To try to make it hydro- phobic is just about an impossibility. What can be done is to coat it, for one thing, with a very hard gelatin overcoat which is less susceptible; but in the beginning it must be made so that the pores will open in order to get the processing solution in. Then you get them out. You have a continual in-and-out going on all during the processing cycle. What you’d like to do is what you say: you’d like to close these doors forever, but this is not possible. However, you can put things into the gelatin structure. Some of these vacuumate processes claim to do this. They claim to put materials into it. They may be marginally successful, but archivally, I don’t think they are a great deal of help. As far as the curl goes, as long as gelatin is moisture sensitive (and I’m thinking now of vapor as opposed to water) it will react. Gelatin is pretty strong, it will pull a base. One way is to make a thick base because the stiffness varies by the cube of the thickness difference. As you start going from a quarter mil to five or six mils, it gets very hard for the gelatin to produce curl. The other approach is to put a hardened coating of gelatin or some other material on the back, but it too has to be hydrophilic in order to pull propor- tionately. S: Earlier you mentioned a silver image being prone to attack of various kinds. There have been several articles written about gold treatment of images. What do you think about having this type of treatment as an additional step for archival purposes. The gold treatment, coupled with a tanning, hardening agent? H: You mean substituting gold for silver? S: Yes, on a one-to-one basis. Eastman had two articles in the SPSE about a gold plating bath that essentially displaces silver on a one-to-one basis. It had tremendous effect as far as the image stability was concerned: the business of the silver image being attacked by peroxides or other substances in the form of dust particles or vapors in the air. Have you considered this? H: Well, I think it works. It’s a very expensive process, for one thing. And the question is, how necessary is it? Now, if you’re going to have your films around where there are peroxides, where there are compounds that will oxidize silver to oxides or sulfides or intermediate compounds and then into something else, then, of course, this would help a great deal. S: To sum up this area of discussion, let me ask you whether or not you believe that there are any significant improvements in conventional silver halide photography that would be applicable to the archival problem. H: I don’t really know of any. If you talk about color storage, then I think something like my friend Pete Goldmark has done — where you go black and white and you keep a coded color record, as in EVR, or in the case of old cartoons where they made separations on black and white— is going to be the safest preservation method. Today, there are no known dyes that are stable, as you probably know. But if you keep dyes carefully, color film will last a long time. I’ve got Kodachromes of my own going back 30 or 35 years that are as good as when they were first stored. S: Post-1939, though? H: Yes. Even before 1939. S: That you know were diffusion developed? H: To tell you the truth, I assume. I don’t know— at that change-over period, I don’t know whether these were or not, but some of these go back to ’36, ’37 and ’38. I guess I don’t have any- thing earlier than ’36. There was a change-over period right in there, as you point out. Even then, these dyes will fade if they’re not kept in the dark, and so on, so that no color could be depended upon except in terms of silver or something of the sort. S: For group two, there has been a great deal of interest in using cassettes, and such things as EVR. 13 Dr. Goldmark and I had a four-hour discussion on this and it was his feeling that it would be possible to optically produce— either using optical or a combination of optical-electronic techniques— on an EVR-type format something that would be quite useful. We were talking about an order of upwards of 750-800 horizontal TV lines. His feeling was also that materials of this nature could be reconstituted to conventional motion picture images and would be quite satisfactory on relatively large screens. H: If you want to go to something that you could reconstitute, 35mm is about 1200 lines— full field. Now on a reasonably sized screen, two or three widths back, for example, this would give you a good looking picture. 800 lines would certainly be pretty good. I’ve seen people like Technicolor who have done 500 and 600— that’s 525 and 625— the British standard. Even a hundred lines helps a great deal. But you see, with Pete’s approach if you put the image on optically, again you have to get back to the base, the image layer, and the binder. His work is on a film base— lllford film. I don’t think he's ever gone to American film on anything, lllford does have a version of polyester called “Teralyne.” I don’t know if he uses it or not on EVR— I don’t think he does. It could be used; it’s a black and white, very fine grain emulsion. They don’t make a thing today that Kodak couldn’t make if it wanted to, if they don’t already— and maybe do it better. It’s a very fine grain black and white negative, and it uses gelatin. Now the problem with emulsions other than gelatin is that they do not know how to make them fast enough. S: For EVR-type recording? H: EVR-type recording is something else. However, if he produces his images optically, and I’m not sure what he’s talking about, then this means silver halide photography. The only difference being that he exposes it with an electron beam and you get a lot of energy there. If he processes it, it is processed as normal film is processed. If he has some other idea in mind, I wouldn’t know what to say about that. S: However, it does use essentially a third less material than color separations. H: Or even less. If you think of it in 16mm, it is roughly a third less. Again, the base has got to be stable and the emulsion has got to be stable and the binder has got to keep binding— no matter how you put it on. Now you’re back to your three original problems again. S: With the number two materials, I have a feeling that they are not being considered as being the ultimate archival material so that in this case, we have a certain amount of flexibility. For this type of use, perhaps the EVR approach or something similar to it would be more satisfactory than conventional photographic images. H: You’re talking about a compromise, right? S: It is a compromise— primarily in terms of quality . . . H: But in longevity? S: No, we’re not allowing too much of a com- promise on that. H: If you’re not, then you’re back with these three problems again. You can compromise quality in many directions, but if you’re talking archivally, you cannot compromise longevity. You may say that there are many ways to go. If you look across the board at what’s available in the small format, you will see color film which can be reduced to black-and-white images on polyester base. S: Right now the estimated figure is $.25 per foot to produce “safety” archival material— and I put that in “quotes” because I think that there’s a lot that could be done to improve what’s being done now. H: That seems high for an ultimate figure. S: I think that that includes fine grains and dupe negatives. H: Unless you get into plating the images with gold: then the price goes up. S: I think that we’ve got to hit that sort of figure or below before any other technique can be presumed to be economically viable. H: There are other areas that you touched on that I think are completely unknown— thermo- plastics, for example. I saw Glen’s first demon- stration years ago at G.E. Howard Shin at CBS got very high on this. But every little surface imperfection is an agent for degrading the image and nobody really knows how stable the impression that you get is— it’s plastic, and plastics flow. The same is true with the vinyl process that RCA started calling “Selectavision,” (now called Holotape). Any plastic has a memory, but it’s a question of how good a memory. If you emboss directly on a base material this would be ideal because you’ve got no binder, no gelatin, nothing. You just emboss the base. But the base is a plastic, and plastics do flow. If you take a material, for example, which is molded under heat like stamping out a phonograph record on vinyl, then you wouldn’t have any problem. But when you emboss something at room temperature, you have a built-in force for cold flow— and impermanence. S: RCA is not using any heat, as far as you know? H: They may be using some, but they can’t use it to the extent necessary in making a vinyl record. With a vinyl record, you start with a blob of vinyl and the press squishes the vinyl into a stamper which puts the grooves in. In the RCA system they start with a photograph and convert it to a hologram which is a tanned image. Then they plate that and use it as an embosser. S: What about the plating? Why couldn’t the image be kept in terms of metal deformations? A reflection on it from a laser could be used to reconstitute the image. H: That would seem to be considerably more stable than the other. Would you keep it as a holographic record? S: Right. That way you’d avoid the problem of plastic flow. In essence, a metal tape would be the archival material. Fromfhaf , you could recon- stitute what you needed. Do you think that there might be some merit to this plating idea? H: I would look into this because for your small record, anyway, it is a possibility. S: In our telephone conversation you brought up the G.E. light valve— I presume you mean the Talaria system of color television projection, is that correct? H: Yes, the color television projector. S: Any reaction to that particular machine? 14 H: Actually, it’ll put on a pretty good picture from video, to about a ten-foot screen. It’s fairly bright at ten feet; at 20 feet, it’s just not bright enough. It starts with too small an area. This is a detraction process. They'd have to go to a big area to get more light through. It’s simply a matter of ratios again. From our point of view, I don’t see— in the near future— video information going in theatres. We looked at this very hard, especially in view of satellites. By the middle of this decade, about 1976, there will probably be movies on satellites but they’ll be going in the homes via CATV. By the end of the decade, with big satellites, they’ll be going right to homes from satellites. S: With some sort of pay box on the individual sets? H: Yes, there will be two-way transponding. This is a big problem right now, but there’ll be some way to do it. I think that the route you’ve got to go is with these three variables that you’ve got. You’ve got your base which carries the emulsion which in turn carries the information; and you’ve got these bonded together. If you can get rid of any two of these, you’re far ahead. But if you can’t, if you’ve got to go the route of film as we know it today, or even tape as we know it today, all three of these things have got to stand the ravages of time. If you have the magnetic coating coming off the tape, it’s not worth much! If you have the film emulsion strip off the film base, it’s not worth much! H; We’re pretty convinced— and I’m sure I’ve got Kodak convinced at this point— that the future of film lies in enhancing a film, just as is done now with videotape. Right today, you can take a picture with tape and, if you don’t enlarge it too much, it’ll look better than film because of the sharpening . . . the increase in acutance. The tape image looks sharper than it has any right to look, because they simply pre-emphasize the high frequencies. And this is the future for improving the quality of film images. With film, the modulation depth is very low, so you’re never going to make film look better than it has any right to look, but if you put the picture into video form, then simply boost the high frequencies, all your fine detail is sharpened. S: Well, this is presuming of course that, first of all, you start off with an ordinary camera, a good one, and ordinary motion picture film. H: You must. Now tape doesn't have much resolution, so you can’t sharpen the fine detail because it isn’t there. But film does, so you can raise the modulation depth so that the amplitude, if you will, of the modulation is increased by pre- emphasizing the highs. S: Yes, but what happens to signal-to-noise ratios in that sort of situation? H: Depends on your system. If you’re on a digital system, you don’t worry about signal-to- noise ratio. Now if you go analog, then you wouldn’t want to get beyond, oh, I’d guess, 20 megaHertz. S: I’m assuming that you’d use something like an electron beam recorder or a laser recorder to reconstruct the film at the end? H: Or you could do it with a CRT. They have CRTs that’ll go 5,000 lines. S: Is anyone trying this yet? H: We’ve been working on an electronic printer. We’re hoping that this thing will get started within the next couple of months, and in a year from now we’ll be doing it. This will not increase resolution, but it will increase acuteness, sharpness. Now let me give you an example: suppose I have a girl in a lace dress who’s standing by a picket fence. Now the lace detail is very fine— all those threads, dark and light, let’s say— and the picket fence is very coarse. Now if I shoot this through an optical system, I will get a gradient on the picket fence, as you know. Now in that same picture, the lace threads would be just a blur- solid white or solid grey. In this detail, the modulation depth is so low that you can’t see any contrast between the skin behind the lace and the threads of the lace. But if you enhance this so that you’ve increased the contrast between the flesh and the threads, you see the definition. I haven’t increased the resolution— I’ve got to have that in the original — but I can increase the contrast between light and dark. S: I'm wondering whether this system may not have its best application in the creation of inter- positives and internegatives— as printing materials— so that they have an artificially heightened acutance for printing purposes when the material goes back to the release prints . . . H: I’d say— the negative across the board. Today, for example, you lose the faces of people in longshots. You are now able to increase the contrast of the fine detail, and the features now once again become recognizable. You won’t get any finer detail than you had originally, but the contrast between dark and light in that fine detail is increased. This makes for sharper film. Wilton R. Holm 15 The Base Many of the critical decisions regarding film mater- ials and their storage conditions are dependent on the inherent chemical and physical characteristics of motion picture base. In the historical development of film, the base has been the most variable element. For this reason, a thorough examination of film bases is essential if one is to understand the con- clusions drawn from testing bases under various storage conditions, and the opinions that these tests have generated. The motion picture as we know it today depends upon film which is light sensitive, flexible, capa- ble of being moved at precise rates of speed, and indexed at fixed intervals of both time and geome- try. Essential to such a material is a base which is flexible, transparent to light, can be perforated, and can be coated with a light sensitive emulsion. Indeed, the advent of motion pictures followed quickly on the heels of the development of cellu- loid, a material first invented as a replacement for the ivory in billiard balls by Hyatt in 1868; later modified by John Carbutt; then acquired by George Eastman to be modified further into the first practical fully transparent, flexible film base. Late in 1888, Eastman’s demonstration of this film for use in his amateur box camera, the Kodak , caught the eye of W. K. Laurie Dickson, an assistant of Thomas Edison, who had been working for Edison on the development of motion pictures. Dickson knew immediately that this was the material needed to make motion pictures a practical reality. Early motion picture film base, called cellulose nitrate— a pyroxylin plastic— did not fulfill all of those criteria which today we think of as essential to motion picture film; it is unstable chemically, tends to curl and buckle, is dimensionally vari- able, and is not particularly resistant to moisture. On the other hand it is colorless, optically homo- genous, transparent, and when made properly is reasonably free from impurities which would de- tract from its optical and chemical functions. In addition, it can be subbed with reasonable ease to accept a photographic emulsion, and within limits its chemistry will not affect that emulsion once coated. Cellulose nitrate is a nitrate ester of cellulose whose chemical composition is as follows; [^6 h 9 0 5( N0 2^] n During preparation, cellulose, in the form of cot- ton or wood fiber, is treated with a mixture of nitric and sulfuric acid; then further processed by the addition of solvents, plasticizers, and flame retardants. The initial reaction is carried out in such a manner that only two and a fraction hy- droxyl groups are esterified; this procedure has a significant effect upon the chemical stability and solubility of the finished base. However, in spite of these procedures, cellulose nitrate remains a close cousin to gun cotton, and as such cannot be made chemically stable; it has a low flash point and contains its own oxidant. Once ignited, cellulose nitrate film cannot be easily extinguished. This characteristic alone makes cellulose nitrate a dangerous material to manufacture, use and store. Yet, for good reason, its use persisted throughout the first 50 years of the 20th century. In spite of the early recognition of the dangerous properties of cellulose nitrate, alternatives to ni- trate did not readily fulfill certain basic, necessary properties of a motion picture base— that it re- main flexible, and maintain its geometric shape over a reasonable period of time. It was not until 1948 that an alternative material was developed which possessed these qualities. Nevertheless, during this early period some other materials were tried. The following three bases are most com- monly found: CELLULOSE DIACETATE Before World War I the first “Safety Base” motion picture film appeared. This was cellulose diace- tate. Though unsuccessful as a professional mo- tion picture base (because of poor geometric sta- bility, tensile strength, and flexibility) its use spread after 1922 as a base for 16 mm amateur film. The manufacture of cellulose diacetate begins with the treatment of cotton or wood fibers with a mixture of acetic anhydride, glacial acetic acid and sulfuric acid. If we may represent the cellu- lose molecule with the formula: |^ c 6 H 7 0 2( 0H )3j n then the reaction for the acetate formation may be formulated as J CeH 7 O 2 ( O H )^~j n + 3n(CH3C0)20 ± j^ 6 H 7 0 2 (0C0CH 3 )J)-| n + 3nCH 3 COOH The triacetate [^6 H 7 0 2(° C0CH 3)3^| n is then partially hydrolyzed with dilute acetic acid 16 such that the final product contains about two and a half acetyl groups per glucose unit. As such, this “diacetate” is actually a semi-triace- tate. MIXED CELLULOSE ESTERS The search for a safety film base with improved chemical and physical properties led to the intro- duction of mixed cellulose esters base type in 1931. Cellulose acetate propionate and cellulose acetate butyrate were the chief ingredients used in the making of this film base. The chemistries of their manufacture is, in prin- ciple, the same as that of other esters previously discussed. Both acetyl components (CH3CO-, CH 3 CH 2 CO-) in the form of their acid anhydrides (CH 3 C0) 2 0 and (CH 3 CH 2 C0)20 or (CH 3 C0) 2 0 and (CH 3 CH 2 CH 2 C0) 2 0 are placed in the bath and allowed to react with the cellulose. Mixed cellulose ester film base displays greater dimensional stability and flexibility when com- pared to Cellulose diacetate; however, like cellu- lose diacetate it is not a tough enough material to withstand 35mm theatrical use. Not until the de- velopment of cellulose triacetate during the early 1940s was there a material which potentially could compete with nitrate for the 35mm market. CELLULOSE TRIACETATE (“HIGH ACETYL”) When cellulose is completely esterified, cellulose triacetate is formed. However, such triacetate is only limitedly soluble in conventional solvents, and this characteristic limited its application for many years. By 1948, a slightly less esterified form of cellulose triacetate, called “High Acetyl,” was manufactured which overcame the solubility problem, and the years 1948 to 1951 saw a rapid switch-over to “triacetate” as the preferred base for 35mm theatrical production and exhibition. SYNTHETIC RESINS The di-, tri-, and mixed acetate ester film bases all showed quite remarkable improvements in their physical and chemical properties over cellu- lose nitrate film base. However, their low mois- ture resistance rendered them unsatisfactory. Thus, the search for a superior film support was continued; and for motion picture purposes some success appears to have been achieved in the development of the synthetic resin, polyethylene terephthalate. POLYETHYLENE TEREPHTHALATE Polyethylene terephthalate, a polyester which was invented in 1941, but which came in for extensive development after World War II, was, at first, heralded as the ultimate solution to the base “problem.” For many applications, this claim is true, yet its lack of extension to the motion picture industry has been held up for two rea- sons: (1) its limited solubility makes it difficult to splice by conventional means; (2) an excessive propensity for producing static electricity attracts undue amounts of dirt and dust. In addition, its high tensile strength 1 has led some workers in the field to believe that its use might cause dam- age to conventional motion picture machinery if buckling or jamming were to occur. All three of these problems have been satisfac- torily answered: (1) ultrasonic splicers have been developed to produce splices which are quite literally, welds; and also chemicals have been produced which can be used for conventional hot splices in conventional splicing machines; (2) coatings to increase surface electrical conduc- tivity of the material have provided the necessary “circuit” to bleed away any electrostatic charges which might build within the material; (3) it has been well proven that situations in which damage occurred to machines handling polyester base could as easily have happened with conventional film-based materials. In the field of videotape, polyester base has all but completely superseded “acetate” as the base material of preference. In motion pictures, more and more film stocks are becoming available on polyester base. Unfortunately, however, its use has not been extended to the “intermediate” films so often produced and stored as the chief archival record of a production. ij.M Calhoun, P.Z. Adelsteln and J.T. Parker, “Physical Properties of Estar Polyester Base Aerial Films for Topographic Mapping," Photogrammetric Engineering, Vol. 27 (June, 1961), pp 461-470. First produced by Du Pont and trademarked “Cronar,” then later licensed to Kodak and called “Estar,” both materials are the best photographic grade of the basic substance polyethylene tereph- thalate. The non-photographic grade is often re- ferred to as “Mylar,” also a trademark of Du Pont. Polyethylene terephthalate is obtained by reacting ethylene glycol (OH-CH 2 CH2-OH) with dimethylterphalate (CH3-0 C0-(0)-C00CH 3 ). This is, in principle, an ester interchange process and along with polyester, methanol is liberated. CASTING Because of its insolubility, polyester terephthal- ate cannot be cast into a film using the tech- niques of “Solvent Casting” employed for cellu- lose nitrate or cellulose acetate products. It can only be made into a film by what is called “melt casting.” Solvent Casting: In the case of cellulose nitrate and cellulose acetate materials, a viscous solu- tion of base material, solvent, and plasticizer is spread on a slowly moving, heated, chromium- faced drum, or belt. Upon evaporation of the solvent, a layer of film forms as a thin sheet. The sheet is then stripped from the drum and passed through a series of heated chambers in order to remove the residual solvent. Not all of the resid- Solvent casting drum. 17 ual solvent can be removed in this production step, however, and its continuing loss results in a shrinkage of the film, noticeable within two to three years after its manufacture. The control of solvent casting, as this method is called, requires a high degree of precision, be- cause, aside from the requirement that the base be of uniform thickness, irregularities in either the surface or the transparency of the base must be avoided. Melt Casting: Melt casting is the general method of casting for polyester bases. Molten polyester is forced through a narrow slot onto a casting cylin- der. The hot material is then rapidly cooled and, after application of a special chemical layer to promote subbing (see below), is stretched with automated machinery in both width and length at a carefully controlled temperature. Stretching in this manner improves the flexibility and strength of the film. In this expanded form, the film base is then “set” by heating at still higher tempera- tures. SUBBING Subbing is the process of preparing the surface of a raw film base to receive a photographic emul- sion. Photographic emulsion will not adhere to clean film base. Therefore, an intermediate sub- stratum, usually gelatin dissolved in water and combined with a solvent that can dissolve the film base, is coated onto the film base prior to emul- sion coating. The solvents and water from the gelatin are allowed to evaporate, leaving a thin gelatin layer on the surface of the film base. This layer pro- vides the necessary conditions for the photo- graphic emulsion to stick to the base. COATING In coating, liquid emulsion is brought in contact with a continuously moving belt of prepared film base. The speed of the movement of the base, and the temperature of the emulsion, are impor- tant factors in determining the ultimate thickness of the coating. Immediately after leaving the coat- ing trough, or roller, the freshly coated material is cooled by looping the film over rollers in fes- toons. At the far end of the coating machine, the finished material is rolled up to await additional coatings, slitting, and perforating. It should be pointed out that even the simplest films receive a number of coatings, in addition to the initial coating of emulsion. These coatings serve various purposes: coatings on the back side of the film help prevent excessive curl; coatings over the emulsion help to protect it from abra- sion, and so on. Stability Criteria Film bases are generally evaluated for stability by subjecting them to standard physical and chemi- cal tests. For each base type, such tests aim at ascertaining the following: (1) tensile strength; (2) break elongation; (3) flexibility; (4) cold flow; (5) Young’s Modulus; (6) tear strength; (7) vis- cosity retention; and (8) free acid. Briefly, the following techniques are employed in the determination of these properties: (1) Tensile Strength: To determine its tensile strength, a specimen of the material is progress- ively loaded by increasing tensile stress until the break point is reached. The tensile strength is then given as the maximum tensile stress sus- tained by the specimen prior to its breaking point. (2) Break Elongation: In the case of break elonga- tion, the material is stretched until its breaking point is reached. The break elongation is then given as the difference in length between its original length and its length at the breaking point. This difference is then expressed as a percentage of the original length. (3) Flexibility: To test its flexibility, a specimen of the material is folded back and forth until it breaks. Special machines are available for this process. The material is then evaluated on the basis of the number of cyclic revolutions it sus- tains before breaking. (4) Cold Flow: Within the elastic limits of a material, loading produces an elongation in the material which regains its original length when the applied load is removed. However, if the material is loaded beyond the yield point, recov- ery of its original length upon removal of the load might be delayed for some time; in this event, the material is said to “creep.” A stage of loading will also be reached when the material suffers a per- manent (plastic) deformation; the original length cannot be completely recovered. This non-recov- erable portion is generally termed plastic flow, secondary flow or cold flow. (5) Young’s Modulus: For F = load applied per unit area of sample L = original length of sample AL = extension produced in sample Young’s Modulus (E) appears as a material con- stant linking F and L according to the following relationship: L E is measured as the slope in the straight line portion of the curve obtained in a load versus elongation (AL) plot. Young’s Modulus actually measures the stiffness and rigidity of the film support; and it serves a very important function in the evaluation of film supports, particularly on the basis of temporary and permanent deformations. (6) Tear Strength: To measure tear strength, a tear is first started by hand. The partially torn material is then brought onto a weighted revolving disc which continues the tearing process while an indicator simultaneously measures its tear resis- tance. (7) Viscosity Retention Test: This test is usually carried out on both heated and unheated samples. Test samples having the same average silver den- sity (an already-processed film material is usually used) are generally selected. Test samples are dissolved in suitable solvents. The temperature is carefully controlled and kept constant throughout all measurements. Ostwald’s viscometer is usual- ly employed for this purpose. (8) Free Acidity Test: All cellulose ester film bases tend to decompose, in the course of which an acid is set free; thus, the extent of decomposi- tion can be estimated by determining the amount of acid that has been released. Generally, a sample of the cellulose ester is dissolved in a solvent, such as methylene chloride. Acidity is then determined by direct titration with N/10 so- dium hydroxide solution. Acidity is expressed as the difference between at least two titrations in ml of N/100 sodium hydroxide solution per gram of film used. DIMENSIONAL CHANGES IN FILM BASES Changes in the geometric dimensions of film bases are a common occurrence, and are caused 18 by, among other factors, changes in age, tem- perature, relative humidity, stress and strain dur- ing processing, storage and handling. Such changes could affect, for example, the distance between film perforations, and consequently, the perforation pitch. Camera, printer and projector sprockets are designed to accommodate films having well defined longitudinal and transverse perforation pitches. Two types of dimensional change predominate. There is (1) reversible (temporary) expansion and contraction of the film base brought about by fluctuations in the ambient temperature and rela- tive humidity; and (2) permanent dimensional change. Permanent dimensional change is caused by the following factors: (1) loss of residual solvent from the surface of the base; (2) plastic flow (deformation of the base); (3) release of strain or recovery from deformation. The loss of residual solvent is strongly favored by heat and moisture. However, it appears to be hindered by prevailing access to free air. The effect of moisture is presumed to accelerate the diffusion of the solvent from the interior of the base and also to render the emulsion more permeable. The force with which the emulsion presses down upon the base may result in a permanent plastic flow or shrinkage of the base. Such changes are also a function of heat, moisture, the force of the impression and the duration of action. Release from deformation may result from the manufacturing process itself. Thus, if the film is stretched during manufacture under conditions which preclude a reorientation of the cellulose nitrate or acetate molecules, a deformation or creep may occur with a consequent extension lengthwise and a contraction in the width direc- tion. At some time in the life of the film, the strain may be released and the final result would be concentration and shrinkage. It is more than likely evident from the foregoing discussion that one cannot predict with any rea- sonable precision, the direct causes of photo- graphic film shrinkage. There appears to be gen- eral agreement that loss of residual solvent accounts for most of the shrinkage normally observed with film bases.* Evaluation of Physical Properties The information in the following table comes from tests conducted during the period 1944 to 1970. The various groups conducting the tests did not use the same testing methods, or the same cri- teria in evaluating their results. Therefore the values given have had to be normalized, and there are a number of gaps. Evaluation of Chemical Properties The chemical stability of a photographic film is best determined by measuring its resistance to viscosity degradation. Tests performed by various scientists are inconsistent with respect to pro- cedures, but general conclusions can still be drawn from the results. The majority of tests have been performed under conditions of accelerated aging; that is, film samples have been exposed to high temperatures and various relative humidities. Film viscosity * Methods in use for the measurement of dimen- sional changes in film bases include the pin gauge, the optical gauge, and the rotating grid methods. A paper by Meerkamper and Cohen, “Design and Ap- plication of Precise Electronic Gauge for Dimen- sional Changes in Films," in the Journal of Photo- graphic Science, Vol. 12 (1964) discusses a method which uses an even more precise measuring device — the electronic expansion gauge. TENSILE BREAK FLEXIBILITY COLD FLOW YOUNG'S TEAR PHYSICAL PROPERTIES STRENGTH ELONGATION (Schopper) PERCENTAGE MODULUS STRENGTH Ibs.pr sq.inch PERCENTAGE FOLDS 10 lbs. /sq.inch (Thwing)grams NITRATE length 15,800 17 15 0.42 6.99 59 width 13,400 15 16 0.58 6.05 66 ACETATE PROPIONATE length 1 1 ,900 12 15 0.62 4.42 50 width 10,400 10.5 16 0.83 4.02 57 HIGH ACETYL length 14,500 * 14 0.51 5.54 43 width 13,000 * 15 0.63 5.00 46 TRIACETATE length 16,000 26 40 * 4.50 65 width * * * * * * POLYESTER length 28,800 115 * * * * (EK-Estar) width * * * * * * *data not available 19 decreases with increased temperature and relative humidity. The objective was to measure viscosity retention under these conditions; on the assump- tion that if, under critical conditions, viscosity degradation were less for a particular film, it would also excel under normal storage condi- tions. However, temperature and humidity are not the only influences on the viscosity of film; in the case of nitrate base, other factors, such as nitro- gen oxides and free acidity, must be examined. VISCOSITY RETENTION TESTS In the following summation of the tests, it should be kept in mind that there are two kinds of tests: the first compares nitrate and cellulose ester base photographic film; the other compares polyester and triacetate (fully esterized) base material. A seven-year test was made placing polyester base in moderate storage conditions. One batch of processed experimental microfilm on Estar base was stored as 35mm x 100-ft. rolls in card- board boxes at 50° C. at 20% RH, and another batch was stored at 40° C. at 78% RH. At periodic intervals, samples were removed and the viscosity noted. Viscosity retention remained at 100% of the original value for both test conditions. NITROGEN OXIDES Decomposition of a cellulose nitrate material is usually accompanied by the release of nitrogen oxides, specifically nitrous oxide (N 2 0), nitric oxide (NO), and nitrogen dioxide (N0 2 ). The latter is formed by the instantaneous reaction of nitric oxide upon exposure to air. 7 The freeing of the oxides begins slowly. With time, however, the production of oxides increases rapidly. If the material is stored in a closed con- tainer which inhibits the escape of the dioxide, the gas will eventually enter into combination with the gelatin of the emulsion, forming a sub- stance which possesses great affinity for mois- ture. The combination “wet” gelatin and dioxide makes the emulsion sticky, and causes the release of acid which attacks the silver image, causing it to fade. The acid will also eventually decompose the base itself. This problem is even more alarming in archives which store nitrate and safety film in close proxi- mity, since the release of nitrogen dioxides by nitrate film has been found to cause serious decomposition to images on safety film as well. Tests 3 evaluating the effect of nitrogen oxide gases on processed acetate film found nitrogen dioxide the most dangerous gas, while nitrous oxide and nitric oxide had almost no influence upon the stability of acetate films. Nitrogen dioxide affected the density of processed film in direct ratio with increased humidity; it affected the acetate support and, in the case of color film, the color dyes as well. In treating film with 0.4% nitrogen dioxide at 50% RH researchers esti- mated the length of exposure necessary to de- grade each of the film’s components so badly that each would make the film impossible to copy. “The silver image fades severely in about two hours, the gelatin becomes seriously sticky with- in about two days, and the triacetate safety sup- port softens and loses its shape in about two weeks.” Thus it can be assumed that a film which emits little or no nitrogen oxides or which can be stored in a manner such that nitrogen oxides have no access to it will have a longer life expectancy than a film exposed to the gases. FREE ACIDITY Nitrate film base shows an increased acidity while decomposing. This is due to formation of nitric acid by the combination of emitted nitrogen dioxide with residual moisture in the emulsion of the film and in the air. Acidity increase, however, is not restricted to nitrate bases only. All decom- posing cellulosic materials have a tendency to show increased acidity. Hill and Weber 3 tested three types of standard acetate against three of nitrate to determine whether aging was accompanied by any increase in acidity. The films were exposed for thirty days to a temperature of 100° C. (Relative humidity was not given, but the authors indicate that tests with this temperature were conducted under “dry” conditions.) Acetate showed almost no change in acidity for any period up to thirty days, retaining a pH value (acidity) of about 6.2. On the other hand, the plotted curve for nitrate showed a marked increase in acidity over the test period. Starting with an original value of 5.4, it reached a value of 2.3 after 30 days. Film samples of visibly deteriorated old nitrate film (as a result of natural aging) also showed high acidity and thus confirmed the validity of the accelerated aging tests. Adelstein and McCrea 4 compared polyester (EK- 2 J.F. Carroll and John M. Calhoun, “Effect of Nitro- gen Oxide Gases on Processed Acetate Film,” Jour- nal of the SMPTE, Vol. 64 (September, 1955), pp. 501-507. 3j.FI. Hill and C.G. Weber, “Stability of Motion Picture Films as Determined by Accelerated Aging,” Journal of the SMPE, Vol. 27 (December, 1936), pp. 677-690. 4 P.Z. Adelstein and J.L. McCrea, “Permanence of Processed Estar Polyester Base Photographic Films," Photographic Science and Engineering, Vol. 9, No. 5 (September-October, 1965), pp. 305-313. % LOSS OF VISCOSITY RETENTION Accelerated aging test 100° C. Dry oven, for 30 days Accelerated aging test 98° C. 95% RH for 4 doys Accelerated aging test 71 ° C. Preconditioned at 2 1 °C 50% RH for 100 days Accelerated aging test 71° C. Preconditioned at 21 °C. 50% RH for 500 days NITRATE 64 total decomposition ★ * CELLULOSE DIACETATE 5 4 * * TRIACETATE 5 * 6 66 POLYESTER (EK-Estar) 0 * 4 36 *data not available 20 Estar) to cellulose triacetate for free acidity. In a test measuring the effect of accelerated aging of humidified film support at 100° C. (pre-condi- tioned at 29° C. at 50% RH) it was found that polyester remained stable, having a free acidity (ml N/10 NaOH/g) of about 0.6 for up to forty- two days, dropping to 0.5 within one hundred days. Cellulose triacetate, measured for twenty- eight days, turned brittle forcing the cancellation of further testing. However, starting with an initial acidity of 0.3 the levels in triacetate increased markedly after about seven days to 7.4, then slowly leveled off to a final value of 10.9 before discontinuation of the test. Shrinkage Behavior of Bases Another test was conducted to measure the shrinkage behavior of processed triacetate posi- tive motion picture film. Under the same condi- tions (78° F. at 60% RH.) after six years, shrink- age varied between 0.34% and 0.48% , a higher shrinkage than with negative film. Again there was a steep increase in the first year, with a gradual leveling off during the following years. Even more shrinkage can be expected in the years following the test period. Testing of processed 16mm film on acetate pro- pionate support (Kodachrome Commercial and Ektachrome Commercial) under the same condi- tions as above, produced the following results: after six years the average shrinkage was 0.21% within a total range of 0.16 to 0.3%. The curve was similar in its form to the 35mm negative film on triacetate base. Shrinkage increased rapidly during the first year, less rapidly during the second, and then leveled off afterwards. Processing, age, cutting or perforating of the raw stock, humidity and temperature all affect the dimensions of motion picture films. Only the first two factors cause what can correctly be called “permanent shrinkage.” The remaining factors produce reversible, or temporary, dimensional change. In the case of cutting and perforating, the standard, industrial dimensional tolerances are well within established limits. PROCESSING AND AGING Calhoun conducted a test on processed nitrate film (positive) comparing the effect of free access to air on the shrinkage rate of processed film at 70° F. at 50-65% . Film strips were exposed to the open air, while test rolls were stored in untaped and taped cans. Over a period of fifty weeks, the unprotected strips showed a shrinkage increase of 0.5% , the rolls in the untaped cans an increase of 0.32%, and the rolls stored in taped cans an increase of about 0.15% . The magnitude of the film dimensional change due to photographic processing is dependent upon initial processing, subsequent drying condi- tions, and residual solvent content of the film. After subjecting Type 5233, 35mm black-and- white film to processing under trade conditions, Calhoun 5 measured these changes. The average dimensional change was -0.03% , ranging from + 0.02% to -0.05% . A test conducted over a six year period at 78° F. and 60% RH on processed triacetate negative motion picture film to determine shrinkage with age yielded the following results: after six years the combined effects of processing and aging shrinkage varied between 0.12% and 0.24%. The curve showed severe shrinkage during the first year after processing, leveling off to equilibrium in two years. A frequency distribution test was made which showed that the majority of the tested films had shrinkage midway between the two given extremes. Polyester film base, stored at 70° F. and 40% RH Aging shrinkage of processed motion picture film after keeping at 78° F .-60% RH . for a period of six months, showed no shrinkage at all, while triacetate shrank as much as 0.02% under the same conditions. Under non-uniform temperature and relative humidity polyester showed a shrinkage of 0.05% compared to a 0.09% shrinkage for triacetate base film. CUTTING AND PERFORATING VARIATIONS A random group of 259 35mm negative films were selected and measured for their average longitu- dinal pitch. A 20% locus of samples was found to be accurate to the ASA Standard of 0.1866 inches. Another 20% showed a slightly lower pitch. How- ever, all samples were well within the recom- mended tolerance of ±0.015 in a one hundred perforation measurement (18.645 to 18.675 inches). RELATIVE HUMIDITY Relative humidity has a considerable influence on the dimensional stability of motion picture film. Of the three basic constituents of film— base, silver halide, and gelatin— the latter is most 5p.Z. Adelstein and J.M. Calhoun, “Interpretation of Dimensional Changes in Cellulose Ester Base Mo- tion Picture Films, ” Journal of the SMPTE, Vol. 69 (March, 1960), pp. 157-163. 6j.M. Calhoun, “The Physical Properties and Dimen- sional Behavior of Motion Picture Film,” Journal of the SM PE, Vol. 43 (October, 1944), pp. 227-266. Moisture content of typical motion picture film on cellulose triacetate base at 70° F. 0 20 40 60 80 relative humidity. % 21 susceptible to relative humidity. Calhoun® com- pared these three materials at 70° F., 50% RH, and concluded that the equilibrium moisture con- tent of the gelatin was 16% , for black and white emulsion 7%, and for nitrate film base 1 to 2%. “Post-1973” safety film bases are quite similar to nitrate film in equilibrium moisture content. The capability of gelatin to absorb large amounts of moisture makes photographic film vulnerable to increased linear expansion as well as possible permanent distortion of the photographic image. While the absorption of moisture by the gelatin layer causes the whole film to expand due to the lateral expansive force exerted by swollen gelatin on the base, the reversal of this process is of more immediate concern. During processing the photographic film is sub- merged in liquids until the drying stage. During the drying process, moisture is withdrawn from the gelatin producing lateral contractive forces on the base which can cause film to shrink and curl. Because drying intensifies these effects, proper control of drying temperature and relative humi- dity is very important. In a test of the expansion and contraction of cellulose ester based film, black-and-white 35mm motion picture negative film, when submitted to relative humidities ranging from 20% to 80% , showed considerable dimensional change. 9 At 20% RH, the 100 perforation measurement averaged 18.62 inches. At 80% RH, it averaged 18.70 inches. Any significant departure from a 60% RH condition (the relative humidity at which ASA standard measurements are taken) can cause differences in the 100 perforation measurements which are much greater than those caused by normal variations in the perforating procedure. TEMPERATURE Dimensional changes caused by temprature are reversible. Film exhibits a tendency to contract as the temperature is lowered, and to expand as the temperature increases. Dimensional changes of 18.64 to 18.68 inches have been noted with tem- perature variation between 40° and 100° F. Mea- surements have shown that the thermal coeffi- cient of expansion for photographic film base is about half that of the humidity coefficient of expansion; that is, the influence of temperature on the dimensional stability of motion picture film base is less than that of humidity. In addition to this, there is a partial cancellation of the dimensional changes caused by tempera- ture due to the fact that often relative humidity drops as the temperature increases. Thus film dimension may decrease in spite of a temperature increase, due to the predominant effect of low- ered humidity. In 1944, J. M. Calhoun6 conducted tests on shrinkage behavior for acetate and nitrate film. He concluded that “the influence of various storage variables on the rate of shrinkage described . . . applies qualitatively to the majority of motion picture film.” That is, regardless of base, the influences of humidity and temperature upon the majority of films are alike insofar as temperature has less effect on the shrinkage behavior than humidity. CURL BEHAVIOR OF MOTION PICTURE FILMS Photographic film has a well known tendency to curl. The direction of the curl is either toward the emulsion side (positive), or away from the emul- sion (negative). Under regular working conditions a slightly posi- tive curl is preferable, particularly during projec- tion and handling when the emulsion is recessed between the edges of the film, restricting its contact with a solid surface. The main factor influencing film curl is humidity; high humidity will cause the emulsion/gelatin structure to ex- pand; low humidity will make it contract. Gelatin absorbs more moisture than base; it is this characteristic which causes film to curl. Cal- houn, in his 1944 test,® compared the moisture take-up characteristics of Fine Grain positive emulsion (undeveloped) with those of nitrate base. When relative humidity decreased from 70% to 20%, the stripped emulsion contracted from 0 to 1 .8% , while the uncoated base con- tracted only 0.25% ; and the two together (stan- dard film) contracted a total of 0.35% . The latter result shows that the base has a significant limit- ing influence upon the contraction of the emul- sion. Nitrate base, being less prone to moisture sorp- tion than the gelatin, inhibits the contraction and expansion movement of the emulsion. In terms of arc altitude (35mm film, maximum distance in inches between the curl arc and the cord) this tendency demonstrates as follows: at 70% RH, film curl is negative (that is, away from the emul- sion) due to the relatively great power of emulsion expansion. At 50% RH, a positive curl of +0.05 inches occurs, increasing + 0.20 inches as rela- tive humidity decreases to 20% . Tests 7 on the humidity related properties of polyester (EK-Estar) base aerial films as com- pared to cellulose acetate base films confirmed Calhoun’s earlier work. With high humidity, poly- ester showed a larger negative film curl radius than that encountered at a relative humidity of 50% . A decrease in the relative humidity to 20% , caused the curl to change to positive, and to increase considerably. Compared to cellulose acetate base films, polyester showed significantly less curl and seemed more resistant to the expan- sion/contraction movements of the emulsion. However , the tests were made with the polyester base coated on both sides with gelatin, while the cellulose acetate base was coated with gelatin on one side only. On the other hand, emulsion thick- ness for this polyester base film was less than the thickness for the cellulose acetate base films. As pointed out above, emulsion thickness and the presence or absence of an anti-curl backing (gela- tin) have a considerable influence upon the curl- ing behavior of film. Effect of relative humidity on curl of 16mm motion picture color film. 06 0 20 40 60 80 relative humidity. % 7 J.M. Calhoun, P.Z. Adelstein and J.T. Parker, “Physical Properties of Estar Polyester Base Aerial Films for Topographic Mapping, " Photogrammetric Engineering, Vol. 27 (June, 1961), pp. 461-470. 22 E.I.du Pont de Nemours & Company Wilmington, Delaware M: Emery Meschter W: David Woodward S: Ralph Sargent M: There are two or three things I could say. First, we, at Du Pont, have been just about out of the motion picture business for a good many years. For a while we were concerned with archival films, but the business wasn’t there so we just put our efforts elsewhere. For a long time we didn’t even have microfilm on the market; I think we do now, but I don’t think anyone has thought about it as particularly being an archival product. W: We have COM film, a computer microfilm, but it’s high-contrast. M: When these things were a concern, there were great hopes that polyester based products would be better (there was no doubt that it would be better than nitrate), even better than acetate, though the current standards established back in the mid-1950s are written around acetate and triacetate. I think that polyester itself, as long as you don’t heat it and you keep it out of the sun, is going to be pretty good. Polyethylene terephathlate, the support, is a pretty stable article both chemically and mechanically. Then you wake up to the fact that this is not enough because it has a low coefficient of humidity expansion, a low coefficient of thermal expansion, etc. We thought we had it made, and that we were going to run glass plates out of business. But, by the time you put an emulsion on top of it, the strength of the gelatin is appreciable compared to the strength of the support, you find that the characteristics of the finished film are not nearly as good as the plain base. The gelatin is contributing here; it has a pretty good-sized coefficient, particularly of humidity, and when it gets dry, it gets high modulus as distinct from the words “mushy” and “wet.” We were able to improve this considerably by putting in dispersions of rubbery polymers and mixing it in with the gelatin to deliberately reduce its strength. The characteristics of a film and its life are affected by the characteristics of the binder and the particles that make up the image, and the bond between that and the base, and the base itself. Polyester is so damn stable that it makes it awfully hard to stick anything to it. I think this might be one of the “unknowns.” Over a long period, would the image really stay stuck on the support? Would you agree with that, Dave? W: Yes, but for archival purposes, you’re going to keep environmental conditions under control. M: Control up to a point. It’s not going to be perfect. W: You’re not going to cycle between 10% R.FI. and 90% R.H.? S: No, but, we’re trying to loosen up the standards for archival storage as far as temperature and humidity control are concerned. This does not work in the favor of classic. silver halide photography, but it does as far as vesicular work is concerned. There is such a vast amount of material going into the archive right now, that having to build high-cost storage facilities becomes impractical. There’s a certain point of no return with respect to costs. So our temperature cycling right now is ± 15° F. off a center of 70° F., with 50% as a mid-point for humidity, ± 20% . Given these figures, the question is: will poly- ester survive better than other base materials? The answer is probably “yes.” M: “Probably yes”— I think that’s right. W: There’s no base better than polyester. It’s good enough for all practical purposes — and maybe some special uses. M: We’re not trying to find a better base than polyester. There is none. Little work in our department is done to find and improve material; rather, we're putting our efforts into improved processes for making the products we have. That is, marginal improvements — how to make it a little bit clearer, a little less color, a little more uniform in thickness— this type of thing. No basic chemical changes. We have never set ourselves the task of trying to find the best possible archival material as distinct from the best possible microfilm. People come to us and say “We want to buy microfilm.” And we say “Fine, we’ll sell you microfilm. By the way, when you use it, do this and this to get the best results.” As far as starting with a complete fresh approach and open mind as apparently you’re trying to do, we’ve never gone out like that. W: We’re in the business of making money and unless someone can come to us and say “We need archival film and it’s got to do this and this,” then maybe we’ll look at it. M: Maybe we’ve missed a bet because if we’d had something like this, maybe we could have made money out of it— if we’d thought of it soon enough and developed the right product. W: Providing the market for it is big enough. 23 S: I hardly think that our estimate of half a billion feet is considered a big market. M: It depends on how much you get per foot. S: Right, but it can’t be too much. Right now, we’re talking about a finished, produced price of $.25 per foot or below— not just for the film but including all handling of pre-print materials and processing. M: That's not unreasonable, though. Is that per linear foot of 35mm? S: 35mm, black-and-white. M: Are you talking about both microfilm and continuous tone? S: We’re always talking about continuous tone — not graphics film or microfilm. M: How would you approach color? In separation negatives? David l/V. Woodward Emery Meschter S: Separation negatives are the classic technique for storing color. I don’t believe we can possibly stretch Kodak’s conception that their CRI materials can possibly go for more than 25 years under rigorously controlled conditions. Even so, CRI might fade in a much shorter time than 25 years, so I think it would have to be in some form of separation. The obvious classic ones— either three-film separation or sequential separation on one film— have the greatest appeal if you’re going to go the traditional route. M: I guess there are other systems where you have all these magic images and detraction effects? S: Yes, you’re thinking of the ABTO system and EVR. The inefficiency of the ABTO system is the major factor that scared us off. It’s not the elegance or lack of elegance of the idea; it’s simply that the process is punching out a tremendous amount of light and getting back practically nothing. We question whether or not this is practical in terms of the speeds at which we’re obviously going to have to run at to handle 200 million feet of film. For example, if it were all color, it could be done if you're willing to give it five seconds or ten seconds exposure per frame, but this is ridiculous. M: At that speed, you couldn't even keep up with the rate at which it was coming in. S: Perhaps some modified form of EVR might be practical. There is no reason in any of our thinking thus far to retain sprocket holes, for example. The area that’s now used up by sprocket holes could logically be fitted with color information. A general re-design of the image format on that size film might satisfactorily handle what we’re looking for in color. Right now, I suppose the problem is about “50-50:” half is color, half is black-and-white; and that’s split safety and nitrate. W: Are you familiar with Du Pont aerial duplicating film? S: No. W: This is a positive emulsion on polyester base which we sell to the Air Force. M: I think this is mostly in five-inch and nine-inch rolls; I don’t know if we perforate any of that or not. W: We don’t, but it could be perforated. It’s on polyester. S: Is it well subbed so that there’s no problem with it stripping or anything? W: Yes. The Air Force uses it for duplicating aerial shots; it’s a Fine Grain positive. M: I think it’s called Aerial Duplicating Negative. S: Do you think it would work as a Fine Grain material in this application? W: I don’t know. It’s pretty much the old standard Fine Grain positive emulsion. M: I thought it was the master positive, with a somewhat lower gamma. W: It’s designed to duplicate aerial negatives. Just what their gamma is, I don’t know. The point is that those negatives have a tremendous amount of information, and the Air Force is very inter- ested in obtaining all of that information. S: Has Du Pont done any work in Dry Silver? W: We’re familiar with what’s been done, and in our experimental program, we’ve looked into Dry Silver. I don’t think that there’s anything there. In the first place, these are mostly products that are not processed further and they contain all the original contaminants in them. Their shelf life, I would think, is not very good. Kodak has a Dry Silver system which I haven’t heard anything about in two or three years, but I would think that heating up to 100° C. or so to process it would probably disturb the base. W: One of the most elegant methods, if it were ever developed, would be holography. You know that RCA had its Selectavision which was a rather crude holographic method using photoresist to make the master. Holitron Corporation worked out a process for making photographic images on a film which could be made quite stable and wouldn’t have quite as high an inhalation content. But nobody has carried it through or developed the systems of technology, hardware, for recording. It might be the most elegant method. M: They haven’t been able to find any better use for holography than taking pictures of chess? W: Actually, Holitron Corporation did take some pictures of their own, and they’re pretty good. It’s just that an awful lot of systems development will have to be done. 24 S: What I’m doing right now should have been begun five or ten years ago. Most people tend to wait until the fire is just on the other side of the door. I talked to a person familiar with holography yesterday at Battelle, and he was not very cheerful about the possibility of this system being commercially usable or practical within ten years. That leaves us no alternative at the moment to which we can turn. W: It could be developed faster if there was incentive to do it, and people were willing to put the money into it. I think that holography, for information storage, has it all over so many other systems in its ability to store an awful lot of information. The optics are simple— especially for microrecording. When you get into microre- cording, to get 100 to 1 reduction your lens and optical system is pretty expensive and you have trouble locating it. But with holography, every- thing is always in focus and the optics are very simple. Someday, it’s going to be there, but unfortunately, the driving force hasn’t come yet to get people to do the work. S: Let me get to these questions concerning polyester base. What is the degree of post-production outgassing or the degree of retained chemicals after production? Is there any? W: The polymer is finished at a pressure of around 10 to 15 millimeters vacuum. It's heated up to 250° C., so everything is pulled off that’s coming off. M: That’s fairly good residence time because this is where your polymerization is taking place. No plasticizers or anything of that sort. It just comes out of a slot onto a wheel, then chilled. Nothing you’d call drying or outgassing after that. M: Gas goes into it, but nothing comes out. It gets heated up to orient it; it gets heated up to make the sub stick. W: The same thing isn’t true of the layers that are put on, such as anti-static on the back, the substratum layer to anchor the emulsion, and the emulsion itself. Those are all coated in water dispersion solutions and they may have other chemicals in them. M: You put on the sub according to our process which is applying the sub as a dispersion of a resin in water immediately after casting, before orienting. So, this is applied, the water dries, the sub-resin is there in globs, so to speak. As it proceeds through the orienting process where it gets to fairly high temperatures, about 120°C., the globs fuse and spread around; this is the way that the first resin substratum is applied. After orienting, you put on a thin gelatin substratum from a water solution. About the only thing left on the film is water. You dry that off during the heat relax step which goes to about 1 20° or 1 30° C. for not very many minutes. That is quite comparable to the emulsion which is applied later where the drying conditions are not really that severe. If there’s anything left in it, it’s retained because of what went into the sensitive emulsion rather than what was applied to the support itself, or its anchoring layer. S: Is there any way of conditioning the base material to get predetermined dimensional changes, such as humidification or extreme temperature shift? W: I don’t think so. Our base is heat-set and heat-relaxed in the process. It’s as stable as it’s ever going to be; you can’t improve the stability beyond the process of making it. S: What about the subbing material itself? What happens when you’re selling polyester to other companies? How do they go about subbing it? M: The product that’s made by the Photo Products Department is trademarked “Cronar Photographic Polyester Base.” I think we sell a little bit of it now, already subbed, but darned little. Mostly it’s for in-house use. For unsubbed polyethylene terephthalate— that is sold as’ “Mylar” by the Film Department, and this is used primarily for insulation, packaging, etc. Until recently, these just haven't been good enough optically for photographic use. If someone were to buy this from the Film Department and try to make a photographic base out of it, they could not use the subbing process which we use because this has to be applied before orientation. What the Film Department sells has already been stretched. If you want to put something on after that, you would have to go to some kind solvent system— which we have stayed away from. We don’t use any solvents at all. I think the answer to your question is: first, there are not many people who buy it for that purpose; and second, how do they sub it? I don't know. W; There are published methods for improving anchorage by flame treatment, by electrical discharge treatment, all kinds of methods whereby you can modify the surface. S: One of the difficulties we’ve had in trying to relate the various films is that very few people have done much experimental work— outside of articles like this or at least earlier articles. There is no such thing as a classic experiment in this field. All of the criteria change from one set of researchers to the next, and the measurement values don't line up. It’s difficult to make an accurate, down-the-line comparison. W: Talking about the test of stability within the range of polyester: in the first place you have to have a pretty sophisticated piece of equipment to make accurate measurements. You’re talking about very small changes. S: The Library of Congress lab uses a two-way micrometer base device that measures the perforation dimensions of the films, and they compare this, through a microscope, to the standards. W: You’ve got to be careful that you don’t change the dimensions of the film just by stretching the film to get it flat. One way is just to put it down with a bar on top so that the pressure flattens it this way because if you try to pull it on the edge, you’ll stretch it. S: What thickness of base are you talking about? W: We make two: four mil and seven mil. M: Seven mil is mostly for graphic art film. I don’t know of any that was ever made in 35mm form that was seven, though. It’s too stiff. In fact, four is a replacement for triacetate, which is five mil, because the mechanical properties are more or less comparable. W: Actually, the mechanical properties of four mil are better than needed, except for stiffness. If you had a higher modulus film you could make it thinner because the tensile strength is great enough; but going through the camera and projector is difficult. It won’t go through the gates and loops without jamming. 25 S: I know the problems well. I worked for some time with Kalvar film. The early films were three mil films and it was like dealing with paper. It took a lot of fighting to get the Kalvar people to put it on four mil, but when they did, it made a significant difference. M: You would appreciate the problems that Hostler & Co. are having. They’re making magnetic tape now with chromium dioxide. What is that stuff: one-half mil thick? Six-tenths? Slitting it .185 inches wide. W: The stiffening goes off as the cube of the thickness so a little bit of an increase in thickness makes it a lot stiffer. S: It certainly does make a difference as far as film materials are concerned. Would either of you venture a guess as to why, since you made a sizable quantity of nitrate at one point, color dyes placed on nitrate by the imbibition process have lasted considerably better than those on acetate? In fact, films made in the late 1930s on nitrate by that process look as good today as they probably did the day they were made. M: Where have they kept the nitrate? Has this been in deep-freeze or something? S: No, they’ve been subject in most cases to very poor storage conditions. W: The only guess I’d make is that a lot of dyes fade by reduction— the releasing agents in the gelatin and what not, and maybe in nitrate, you’re always getting off little oxides of nitrate. M: Would these same dyes be around today? That’s right, you said imbibition dyes. So these would be your Technicolor acid dyes rather than color developed through couplers. S: However, it’s in reference to Technicolor of later years which is still, we presume, the same dyes, but on a different base. W: It must be something coming out of the nitrate that’s keeping these dyes. The chemistry of dye fading is very complex; it’s pretty difficult to draw any conclusions. W: They must inspect nitrate quite frequently. Because if a roll starts to go bad, you’ve got to get it out right away. S: Arid printed as quickly as possible. Yes, there is supposedly a procedure whereby they go through it can by can on a repeated basis. When they get to the end, they start at the beginning again. But the quantity is increasing so greatly that it now takes about six months’ or a year’s turnaround time to get through it. These tests really do little more than tell you that it’s decomposing. M: Your nose is probably as good a test as any. S: Also, there are certain things you can spot for image fading and the like, but when it starts to go, it’s going to decompose at a faster and faster rate. M: I still don't understand why some nitrate doesn’t go. It must go back to the original batches of the treatment: sometimes it’s good, and sometimes it isn't. W: Or, it depends on the processing. M: Yes, but I’ve got nitrate at home 30 years old and those negatives are just as good as the day they were made. I’ve got them in a metal can down in the cellar — in a dry spot. I don’t keep them in the attic or anything like that. They’re in excellent condition. This is just stock Superior II negative. W: I think that the processes ought to come into it: if no catalyst, acid or whatever, starts the thing, it stays fairly stable. But once it gets going, it generates more catalyst which decomposes it. S: What about the possibility of storage in a pressure nitrate atmosphere, a nitrogen atmosphere. Sealed aluminum pouches loaded with nitrate? M: I don’t think that’s any guarantee because nitrate will burn in a completely closed container. As it starts to decompose, it’s going to use its own oxygen. S: Even under a pressurized nitrogen atmosphere, it would not tend to decompose more slowly? M: It wouldn’t hurt, but I doubt if it would help. In fact, under vacuum control you’d be better off because any volatile material that comes off gets away. But, it isn’t easy to store a large quantity of film under high vacuum. S: You're sure that the vacuum approach wouldn’t increase the decomposition, or at least the conversion to powder form? W: You’d have to run experiments. You do have two things there, but it would tend to pull off the acids that are formed. M: Of course, you’re talking about film that’s rolled up tightly. W: Closed up off the edges but most of the middle is going to get it very badly if the diffusion is bad. I suspect that the most important thing is to keep it dry, because moisture and air can start decomposition. S: Do you know of any technique to either stabilize nitrate chemically or to reverse the decomposition? W: No, not to reverse it. I don’t know whether you can stabilize it. People who have made nitrate for years, the smokeless powder people, probably know more about stabilizing nitrate. There must be some government publications on stabilizing cellulose nitrate. S: We haven’t come across them yet. M: I would be very pessimistic about this because, after all, we’ve made nitrate for 30 years before we went out of business in 1950, which was the last of it we made. If there had been any stabilization possible, given the interest and all, I think we would have found it then. W: We used the best techniques that were available at the time. The cellulose nitrate used for film bases has a little less degree of nitration than gun cotton, but I think the chemistry is pretty much the same. S: To reiterate, do you have any in-house material that would serve, in your opinion, as “end-all/be-all” information with which to face this polyester situation and say that this is the way to go? We have the published articles, but the question is what other in-house material exists? M: I don’t think we’re holding anything. I think that material of this nature has been published; we’re inclined to publish what we have. Information on process or manufacture we won’t publish, of course; but when it comes to beating a drum for desirable properties, this is going to make a point to sell. Having stuck our necks out a little too far in the early days by claiming too 26 much for polyester base without realizing the importance of the associated emulsions, we’ve been inclined to be pretty conservative. This is particularly true with respect to archival films, where it's a guess. You're talking about what’s going to happen 20, 30, 50 years away. We got burned once— before the War, when we made some claim about permanent film. Somebody complained that the film wasn’t permanent because they could destroy it with a match. Some government agency gave us “hell” for claiming that our film was permanent. Yet, it was intended to be a microfilm. So, we have been inclined to claim less rather than more. Even if we think it’s pretty good, to the best of our know- ledge, we’re not going to rush into print with claims that we can’t substantiate. And you can’t substantiate what’s going to happen to a new product 50 years from now when it’s only been in existence for ten years. W: We don’t have any in-house data that hasn’t been published regarding the stability of polyester base. It's all in the literature, back about eight years ago. We haven’t done any more because we’re satisfied and our customers are satisfied. It isn’t worth our while to go looking for trouble. S: The binder method that you’re using in Cronar is built right into the process; it simply doesn’t get out to the other customers. They have to develop their own, right? M: Right. For a long time, we did not sell subbed Cronar to anybody because we simply did not have enough. If people asked to buy it, we said we were sorry but that we did not sell it. In the last year or so, I think we have sold some because we have the capacity now to be looking for business. W: Only a very little. It depends. M: Luxembourg is “coming on stream,” and this will take care of our German plant. We’ve built a plant in Luxembourg which is going to take care of a pair of our German subsidiaries so we will not be supplying them from the United States. Temporarily at least, we’ll have some extra capacity. W: I really think that the archival problem is not the base, but the silver emulsion. Will polyester base alone handle the problem? Nitrate film was base-limited, but as soon as you go to polyester, it becomes image-limited and binder-limited. The better you process it, the more you are sure that the film is properly washed and fixed, the longer it will last. The gelatin is not all that great, nor will the binder polymers last forever; but if it’s washed and cleaned under reasonable limits of humidity and temperature, this will help. M: We’ve poured a fair amount of money down the synthetic binder route, too; but we don’t have that much to show. Polyvinyl alcohol and all these things. Big programs on that in the past. They thought that if you used a synthetic binder, then you didn’t have to depend on “what the cows eat.” But it turns out to have just as many “bugs” as gelatin— different ones, but problems nonethe- less. W: Gelatin is subject to bacteria and mold, and we were concerned about that. We were then investigating polyvinyl alcohol binders, etc. In preparing a paper, I took samples of gelatin films and polyvinyl alcohol films and put them in high humidity and low humidity. The gelatin got moldy, but the pictures weren’t quite good enough so we got some more samples and put them down there again. This time mold grew on the polyvinyl alcohols. I think we concluded that anything that is biodegradable in some way, some organism will learn to attack it given the right culture. S: Any attitudes about Kalvar photography? W: I think it’s probably a pretty stable image. Its problem is going to be to get a good photographic response— a long, straight-line curve. Silver halides are a pretty sophisticated product and its sensitometry has been developed so that it gives a pretty good straight-line curve. Whereas with Kalvar, I suspect you get more of an “S” shape in your “straight-line” portion so you’re going to lose information in the high and the low density regions. This is why copying of aerial negatives has been almost all photographic. A lot of people have come along with fast dry processes, such as Dialux, that are beautiful. You look at it and say, “What a fine wave.” Then you give it to a photo interpreter, and he reports that you’ve lost a lot — simply because the curves didn’t match. I don’t know whether the vesicular process can be made to give the kind of photographic response you want for this use. S: That is also one of my concerns, along with the way in which the image is bound to the polyester. Early materials of this type that I used had a great deal of difficulty sticking to the polyester— literally keeping the image stuck to the base. W: It’s probably not inherent but related to their technology. S: Just quickly, I’d like to review the discussion on gold imaging we got into during lunch. M: We were talking about gold, and I remarked that I could recall gold being the deluxe product of the old-time portrait photographer who turned out an image which was both permanent and beautiful. You said that you’d been considering gold from the standpoint of permanence. We all agreed that gold metal is about as permanent as you could imagine— in the same class with some of the ceramics and oxides. There’s just the little matter of cost. An operator visually inspects polyester film base after it has been stretched and heat set. 27 Photographic Gelatin and Synthetic Colloids for Emulsion Use By Thomas T. Hill The binder is— according to Webster’s third defini- tion of the word — “Something which produces or promotes cohesion in loosely assembled sub- stances." This definition most closely covers an essential function in both photographic and mag- netic products. In photography, this function is performed by gela- tin. Gelatin holds the silver halide crystals in col- loidal suspension, and contributes in many other ways to the photographic process. The following article by Thomas Hill so well de- scribes the importance of gelatin as a binder that it is reprinted here, by permission, from the Journal of the SMPTE, November, 1968. Effects of mold growth at high relative humidity on processed triacetate motion picture film: right, moderate damage; left, complete destruction. The persistent question: “Why are we still using gelatin as the hydrocolloid in photo emulsions?” has the implied question of why, with so many useful plastics available from the modern chemi- cal industry, do we continue to use a natural colloid of lower uniformity and one containing so many troublesome impurities? The first part of our reply is that the purpose of gelatin in photographic emulsions is not as simple as first appears and that we should exam- ine all of its effects on the photographic process. We all are aware of the use of gelatin as a transparent support for the silver halide crystals (which become silver grains after processing), holding them onto the film-base or paper-base. However, there are at least a dozen other ways in which gelatin contributes to the photographic process, so that any synthetic replacement has to meet many difficult specifications. What is gelatin? According to the U.S. Pharma- copoeia, it is “a product obtained by the partial hydrolysis of collagen derived from the skins, white connective tissues, and bones of animals.” It is a colloid cooked out of skins such as scraps from leather tanneries, pigskins from the meat packing plants, and bones from East India. We will only mention here that the process (described in the Refs. 3 and 10) starts with a conditioning period of weeks or months in strong acid or alkali (such as saturated lime water), followed by a thorough rinsing and a carefully controlled cook- ing-out in water, concentration in evaporators, and drying of the chilled, shredded jelly thus obtained. To correct a common error, photographic gelatin does not come from hoof and horn materials, as the keratin they contain extracts to make glue, worthless for photographic emulsion use. Specifi- cally made, lots of gelatin are carefully selected, tested in emulsions and blended into larger batches for photographic emulsion manufac- turers. This discussion covers the use of gelatin in pho- tographic emulsions, but it is important to re- member that gelatin is also used on a large scale for other photographic uses such as anti-halation and other backing layers, anti-scratch and anti- curl layers, filter layers, etc. While a somewhat lower quality will suffice for these and some synthetics have been successfully used, these layers are in contact with emulsions, and in pro- cessing solutions with them, so that specifica- tions are still quite strict. As an emulsion vehicle, gelatin is: (1) a protective colloid for the silver halide crystals; (2) a transparent support for them and the silver grains of the image; (3) stable enough to hold a silver image of archi- val permanence; (4) 99.96% pure (except for water); (5) water permeable, allowing access of process- ing solutions; (6) thermally reversible, from liquid to solid to liquid by temperature change; (7) easily coated, with good adhesion to a sup- port; (8) relatively uniform in lots as supplied for emul- sion use; and (9) desirably contaminated, with microquantities of specific “impurities.” These essential properties must also be found in any synthetic replacement for gelatin. Some de- tailed consideration of each of these functions follows: Serving as a protective colloid is the most impor- tant function for emulsions. Colloid is defined as a state of matter, so finely divided as to remain in suspension as a sol (liquid) or a gel (semi-solid jelly). Gelatin in its use in desserts is the most familiar example. Incidentally, food gelatin is one of our purest foods, but it is still much less refined than photographic gelatin. A protective colloid is one which, when added in surprisingly small amounts, can “protect” or keep in suspen- sion other larger particles, such as, in this case, the newly formed silver halide crystals. This pro- cess can prevent the crystals from agglommerat- ing, clumping and settling to the bottom of the mix. As a transparent support gelatin holds the silver halide crystals onto the base and allows light to reach them during exposure. After processing, the gelatin is clear and transparent so that prints may be made by projecting light through the negative or the positive transparencies; few of the synthetic colloids that have been made to date are as transparent or colorless and many of the other- wise desirable ones are milky or translucent. It took a long time for chemists to come up with our 28 flexible film-bases, first the dangerous cellulose nitrate, later the acetate, and now the new tereph- thalates, polycarbonates, and so on. But in pure form these are more expensive than gelatin and they do not have the other necessary properties. For instance they are not hydrocolloids; that is, they do not form colloids in a water base, as does gelatin or polyvinyl alcohol. Stability is a key quality. Although chemicals can soften it and hot water dissolve it, gelatin is more stable than many common materials such as the paper we use for important records. It enables us to have archival permanence of silver images on microfilm and microcards. Gelatin is also quite stable in the pure form as a raw material for the photographic emulsion maker. The author has experimented with old lots of gelatin that had been stored in a warehouse for twenty years (not under special conditions) and later shipped back to the manufacturer. Made into a test emulsion formula they compared well with the original tests made when freshly manufactured. Such test results as actual coated emulsions, exposed and processed, are retained by the gelatin manufac- turer for just such later checking. 99.96% pure: While we complain often about the photographically-active impurities'! ,12,20,22 that are present in this natural hydrocolloid (without which we would not have photography as we know it today), the total amount of all the impuri- ties (other than water) in emulsion gelatin is at the most about 400 parts per million, and usually less. While we work hard to keep it that low, and to control known impurities, the search for a really “inert gelatin” has gone on for over thirty years; photogelatin is still a very pure material compared to many of the modern synthetics. These require the presence of catalysts to start polymerization, and stabilizers, plasticisers, etc. Many of these latter are complex organic compounds based on sulfur, and react violently to form fog in a photographic emulsion. And most of the catalysts are noble metals or salts thereof, which are also of high activity from a photo- graphic standpoint, even at a few parts per mil- lion. To purify the synthetics which could replace qelatin would take more processing, and thus increase their cost far above that of gelatin, under present conditions. Water permeable: Since photographic processing is done with water-based solutions of developing agents and fixing agents, the colloid support for exposed silver halide crystals must be penetrated by water, and preferably (as with gelatin) swelled by water to facilitate this operation. But it does not dissolve in the water, and leave its base, and it dries down again to the thin, hard, permanent layer we need. Incidentally some new processes are called “dry,” but still require and use water at some stage, even when the processing chemicals are all included in the emulsion layer. They then include a water-holding chemical, such as hy- drated sodium sulfate or acetate, which on heat- ing releases enough moisture to activate the pro- cessing chemicals. Most of the clear, flexible synthetics, as with our film bases, will not permit the entry of water or water solutions, which rule them out as gelatin replacements. Thermally reversible: This characteristic is impor- tant to the emulsion maker before you get your raw stock. 7 It is necessary for the various cooking stages of the emulsion making process to take place with the emulsion liquid, and of course it must be liquid to flow onto the film-base or paper-base at the time of coating. But it must also be solid at other stages of the manufacturing process, and it must be solid to stay on the base between coating and drying down. With gelatin, this can be done simply by changing temperature, which reverses the liquid/solid states. At about 90 to 95 F, the emulsion is a liquid; below that it is a solid jelly; it is an even more freely flowing liquid at 110 to 115 F. Yet after the water has been removed during drying after coating, changes in temperature, even in processing solutions, no longer turn the emulsion to a liquid. This is another gelatin property difficult to duplicate in synthetics. Easily coated: Because of these just-mentioned properties, it is possible to measure out a thin layer of liquid emulsion onto a base and have it set to a solid by simply cooling or chilling, with- out any chemical treatment. In some newer coat- ing techniques the liquid emulsion is chilled as it is extruded from carefully adjusted slots, so that it is jelled by the time it reaches the surface of the base, allowing even closer control of thickness and uniformity of this operation. On a properly prepared base, this coating will dry down to a thin layer which will tenaciously adhere to the film or paper base, surviving liquid treatments during processing which would disintegrate many other materials. For example, one can treat a letter- head, or magazine page with developer, short- stop, fixer and wash as a photo material, and see how far it survives through the process. Uniformity of lots: The gelatin blends sold to be used for photographic emulsion making are pro- ducible in uniform lots. Gelatin is, of course, a random mixture of “chains” of molecules of dif- fering lengths and molecular weights, as with any protein, depending on the pre-treatment and the temperatures of “cooking-out” during gel manu- facture. But it is made in very large quantities, and after testing, large batches are blended from selected lots of the required purity to get the required physical properties. These batches have a surprising chemical and physical uniformity, meeting very narrow specifications. Many of the synthetic hydrocolloids are also mixtures of par- tially and completely polymerized materials, hav- ing a variety of structural composition. This is particularly the case with some of the graft-poly- mer mixtures, developed to get the desirable pro- perties of more than one plastic by grafting one structure onto another during the polymerization to solid form from the liquid monomers. There- fore with this property we do not get much im- provement in trying to use synthetics instead of gelatin. Desirably con tam i nated^ .12,1 4,20,22 : As men- tioned, there are some few parts per million of each of many non-gelatin compounds present in photographic gelatin and this is still one of the most cogent reasons for retaining it in our pro- cess. These components, or “microimpurities,” are all photographically active; that is, they affect the progress of the preparation of the emulsion, and the results of exposure and processing favor- ably or unfavorably. But we have so far identified only a few of all these important active compounds; mainly those which sensitize, or increase the speed of the silver halide to light. There are others which re- tard the Ostwald ripening, or the digestion during the manufacture of an emulsion. Much valuable research has been done on these, and some is published, particularly in the past fifteen years, but even now we cannot add the known items to an “inert gelatin” and duplicate the photographic properties of an emulsion made with a natural “active gelatin. ”3 So how could we add these necessary and unknown compounds to a syn- thetic colloid? Another section of the story is the unpredictabil- ity of action of a particular compound; some act desirably at parts per billion, and fog emulsions if 29 present in the parts per million range. Other com- pounds, identified in gelatin after much research, do not show effects if added to an inert gelatin; they may produce their expected action only after being altered or broken down in structure during the digestion process, or in the presence of other specific ingredients. This mention of breakdown reminds me to point out that we should not blame the many researchers for not learning more, more quickly. Most of these minor compounds are deli- cate organic molecules which are easily destroyed or changed by the methods used to separate them from the gelatin. In his search for the true “inert gelatin,” the originator of that idea, Dr. Albert Steigmann, found that to completely remove all such “impurities” required such vigorous treat- ment with strong reagents that the resulting “pur- ified” gelatin, which he called “ultra inert, ”12 had been so degraded by the treatment that it could not be used, alone, to make up a photo emulsion; the physical properties such as bloom strength (setting power), and viscosity had been reduced too low for normal use. He deduced from this that some of the elusive active ingredients he was trying to remove and identify are actually a part of the gelatin molecule, combined with it, rather than just mixed in as a separate accidental im- purity. OTHER USEFUL FUNCTIONS Gelatin has some other valuable, though not essential functions, four of which are considered below. These could be sacrificed if we could find a synthetic colloid that had all of gelatin’s essen- tial qualities. Variable viscosity: In addition to adjusting the viscosity of a mix for an emulsion by using higher proportions of the long-chain molecules of a par- ticular gelatin, or a larger percentage of gelatin, we can also vary the viscosity without changing percentage, by adding specific chemicals. Some will raise, others lower, the viscosity; this quality is important in handling and coating an emulsion. Most of the synthetic colloids do not react in this manner. It is particularly important in color film emulsions containing couplers, since couplers increase the viscosity in many cases, and we have to add something to adjust viscosity to a normal working level. Or if we want an emulsion with a high silver-gelatin ratio, as in emulsions for re- cording ultraviolet radiation (for which gelatin is a filter), we can raise the viscosity to workable levels by adding surfactants of some types. Controlled hardening: This is the property of be- ing hardenable to a specific controllable degree, as in preparing emulsions intended for hot-pro- cessing, or by adjustment of the processing solu- tions used at normal temperatures; and, while the swelling during processing does reduce the hard- ening temporarily, the gelatin can be rehardened in the fixer or another bath before being dried. Imagewise hardening: Gelatin, like glue and some other colloids, can be locally hardened during processing; the silver image being formed cata- lyzes the hardening so there is more hardening where the image is, that is, a “tanning develop- ment” or forming a matrix. This can be used in many ways: as a resist against an etchant for a metal support as in printing processes; as a ma- trix for imbibing a dye; as in wash-off relief color printing, or the familiar Technicolor process, etc. Some synthetic materials, by different mech- anisms, can give relief images, and are being used in large quantities, as in the Kodak photo- resists used extensively in microcircuit manufac- ture, and printing plates such as Du Pont’s Dycril. Reactivity: Gelatin is reactive in several ways. First, it takes part in some of the image-forming and image-processing reactions, as discussed in a detailed manner in several of the references. 2, 11 '25 | n some cases, this improves the “covering power” of the silver of the image, to result in a higher effective density with lower silver content. In another way reactivity bridges the gap between the necessary properties of gelatin and the de- sirable properties of synthetics. The patent litera- ture shows two main trends in this present prob- lem. Not being able to find fully satisfactory synthetics, the chemists have turned to adding synthetic components to the gelatin structure or backbone, thus keeping the advantages of gelatin and adding some of the advantages of the syn- thetic. 5,6, i9, 21 ,23 Examples are greater resis- tance to hot processing solutions, greater flexi- bility and ease in manufacturing emulsions. One large group of patents, led by those of Ko- dak, 9.1 9.21 ,23 teaches use of these mixed poly- mers to avoid the time consuming operation of washing out the unwanted reaction products dur- ing the manufacturing of an emulsion. Simple changes in pH (by adding an acid) will precipitate the colloid and the wanted silversalts, which after rinsing, can be reconstituted as a colloidal sus- pension by raising the pH (by adding an alkali), or some other simple treatment. To recapitulate, gelatin does so many things so well (or at least has been forced into cooperating so well) that equivalent synthetic hydrocolloids are difficult to find, especially at the equivalent low price. Several photosensitive products have actually been marketed, based on some synthetic replace- ment for gelatin, but none of them has been kept on the market because each met unexpected diffi- culties. The first of these was Kodak’s Velite contact-printing paper, sold for use by the home- darkroom amateur photographer, since this paper could be handled under quite bright white light. However, it required a photoflood bulb in the contact printer. It was discontinued in 1960 be- cause the demand for this narrow application was not enough to justify continued production. There was also the Du Pont color film introduced for motion-picture work in the early fifties. In- stead of gelatin a synthetic replacement was used and cleverly designed to be part of the color- coupling system, so that the colors when formed were well fixed in place. Long testing in Holly- wood produced many promising color examples, but in the long run technical difficulties prevented it from being used on a large scale. A few years ago the progressive Japanese firm of Mitsubishi put out one of their main projection printing papers with an emulsion based on PVA (polyvinyl alcohol) and published papers discussing its pro- perties. 15, 18, 26, 27 However, the storage stability before exposure did not live up to expectations, and after about a year it was removed from the market. The second major trend in the research on new emulsion-vehicles as shown by the patent litera- ture, is that of preparing and using “compatible” synthetics, mixed with gelatin in various propor- tions. 4 ^ That is, the emulsion is prepared with the normal photographic gelatin, digested as usual in the presence of the known and the un- known impurities mentioned, and then the syn- thetic colloid is added to bring the viscosity and “body” up to normal coating level Several advan- tages have been claimed, and one at least is well known: that of increasing the “covering power” of the silver image. Some improve the flexibility, and reduce curl on coated films or papers. At the International Congress of Photography in Tokyo last September, some papers on gelatin replacements were presented, particularly one by a Japanese group who got “gelatin-equivalent” 30 results with a mixture of three synthetics, which had been especially prepared to put onto their chain-molecule structure those very substitution groups found in natural gelatin, such as amino groups, carboxy groups, etc. 27 But, such careful tailoring of synthetics requires a more than nor- mally complicated process, and more careful con- trol, so again, costs are higher. Economics is of course important here, and gelatin has an advan- tage in that its raw materials are low-cost scrap- materials such as leather-tannery scraps, pig- skins, bones, etc. However, this low-cost, low- price, low-profit situation means that the gelatin industry cannot support expensive basic research programs, which is why most of the important work done in recent years has been done by photographic manufacturers and educational institutions or governmental agencies. One of the most promising trends of recent years already has increased the knowledge of gelatin. Under the direction of Dr. Hans Ammann-Brass of Switzerland; an international cooperative program wherein many laboratories evaluate and test iden- tical samples of a number of photo gelatins by many analytical methods, and develop improved testing methods. Results are correlated by Dr. Ammann, a consultant who is also professor in the Photographic Institute at the ETH in Zurich. Publication of these findings has added much to the scanty literature on photo gelatin. Papers are now appearing in the British Journal of Photographic Science which were presented at an international conference in Cambridge last Fall. 2 Theoretical and practical studies were re- ported from all over the world and several speak- ers raised radically new ideas, so it is apparent that some useful controversy will result, causing more new research on gelatin to be done by those who disagree. For those who wish to follow up some of the points mentioned, there is a short bibliography appended to this paper, mainly of review papers with long lists of articles, and important state of the art studies. An excellent book on gelatin3 was published in 1965 by Focal Press, authored by Croome and Clegg of one of the British gelatin firms, which for the first time gives a full descrip- tion of the making and testing and selection of photographic gelatins. Another recent paper8 was prepared for the American Chemical Society as a section in a volume on “Literature Resources of the Chemical Process Industries.” The section entitled “The Literature of Gelatin" is an anno- tated bibliography, aimed at chemists and listing the important sources of information. References and Bibliography 1. J. N. Armes, “The nature and amounts of alde- hyde in gelatin," Jour. Phot. Sci., 14: 143-148; 1966. 2. H. Borginon, “Photographic properties of the gel- atin macromolecule,'' J. Phot. Sci., 15: 207-214 ( one of the many excellent papers at the Cambridge, Eng., Conference of the RPS on Gelatin), Sept. 1967. 3. R. J. Croome and F. G. Clegg, Photographic Gelatin, Focal Press, London and New York, 1965, (monograph). 4. H. Dehio, G. Polla-Mattiot, M. Gillio-Tos and G. Saini, “The Influence of molecular weight of syn- thetic hydrophilic colloids on their protective action and on the ripening of silver halide crystals,” J. Phot. Sci., 10: 302-305; 1962. 5. U.S. Patent 3,184,312: J. W. Gates, Jr., 1/1/ . G. Lovett and P. E. Miller, “Photographic Emulsions Containing Carboxymethylated Pigskin Gelatin,” May 18, 1965 (appl. 11/14/58), assg. Eastman Kodak Co. 6. British Patent 976,391: M. N. Vrancken, A. H. DeCat and J . F. Willems, “Improvements in or Relat- ing to Gelatin Derivatives,” July 18, 1961 (appl. 7/18/60), assg. Gevaert Photo-Producten, N.V. 7. T. T. Hill, “Laboratory-scale photographic emul- sion technique,” J. Chem. Educ., 43: 492-498, 1966, (tutorial paper). 8. T. T. FliU, “Literature of gelatin,” chapter in Liter- ature Resources of the Chemical Process Industries, 2nd Ed., Vol. I, June 1968, American Chemical So- ciety, Washington, D.C., (annotated bibliography). 9. U.S. Patent 3,168,403: W. Himmelmann and H. Mader, “Flocculated Gelatin Emulsions Containing Sulphonated Copolymers of Styrene," Feb. 2, 1965 (appl. 1/10/61). 10. B. Idson and E. Braswell, “Gelatin,” Adv. in Food Research, 7: 235-338; 1957, (state-of-the-art review with extensive bibliography). 11. T. H. James and W. Vanselow; “Adsorption as a factor in the rate of photographic development,” Phot. Eng: 6: 183-189, 1955. 12. W. D. Kelly, Jr., “Purification and chem. sensiti- zation of phot, gelatin,” J. Phot. Sci., 6: 16-22, 1958, ( paper presented at 1957 spring ACS meeting in Miami). 13. C. E. K. Mees and T. H. James, “The Theory of the Photographic Process,” Third Edition, MacMillan Co, New York, 1966, Chapter 3, (“Gelatin”). 14. G. H. Nawn; “Interferences with the abribat test for labile S in gelatin, and some implications with respect to chemical sensitization rates,” Phot. Sci. & Eng., 12: 108-16, 1968. 15. Y. Ohyama, “On the action of some chem. sen- sit. as ‘anti-retarders' or ‘physical ripening accelera- tors'”; Proceedings of RPS Centenary Conf., Lon- don, 1953, publ. as “Science and Applic. of Phot.,” Royal Phot. Soc., London, 1955. 16. Y. Ohyama and K. Futaki, “Grain growth of silver chloride susp. in polyvinyl alcohol," Bull. Chem. Soc. Japan, 28: 243-248, 1955. 17. Y. Ohyama and K. Futaki, “Mar. alkyl amines & ammon. comp, as accelerators for grain growth of silver chloride susp. in polyvinyl alcohol sol’n.," ibid: 31 : 10-16, 1958. 18. Y. Ohyama and K. Futaki, “Relation betw. accel. and retard, tendencies of some active subst. in phys. ripening of silver chloride suspensions,” Pho- to Sci. & Eng., 2: 128-30; 1958. 19. U.S. Patent 2,768,079: F. G. Russell, “Method of Preparing Washed Photographic Emulsions,” Oct. 23, 1956, (appl. 1/25/54), assg. to Eastman Kodak Co. 20. G. Russell and D. L. Oliff, “Nucleic acids in gelatin," J. Phot. Sci., 14: 9-22; 1966. 21. U.S. Patent 3,186,846: W. H. Ryan, “Process for Prod. Silver Hal. Emulsions cont. Gelatin Deriva- tives,” June 1, 1965, (appl. 6/10/60), assg. Polaroid. 22. W. Tim son, A. Steigmann, G. Nawn and W. Kelly, Jr., “Microconstituents in gelatin, etc.,” Pho- to. Sci. & Eng., 10: 281-286, 1966, (1 of 3 papers in same issue, from 1964 SPSE Conference). 23. H. M. Wagner; “Competition for gelatin,” Per- spective; 4: 208-15, 1962, (a review). 24. H. W. Wood; “The Process of silver-digestion and implications," J. Phot. Sci., 6: 33-38; 1958. 25. H. W. Wood; “Role of gelatin in phot, emul- sions," J. Phot. Sci., 9: 151-6; 1961, (78 refs.). 26. T. Yano, N. Itho, and S. Iguchi, “Behavior of hydrophilic polymers as protective colloids for silver halide crystals, Part V," J. Soc. Sci. Phot. Jap., 30(2): 83-89, 1967. 27 . T. Yano, N. Itho, and S. Iguchi, “Influence of the kind of cationic groups in polymer molecule on the growth of silver chloride crystals ,” Preprint, Vol. II from the International Congress of Photography, Tokyo and Kyoto, 1967, (to be published later). 31 Fuji Photo Film Co. Tokyo, Japan F. Shuichi Ogura Tadashi Nagae Shigeru Morishita S: Ralph Sargent Ltd. S: In going around the world, talking to various archivists, I have found that in spite of the fact that manufacturers make very strong recommen- dations about how their films should be stored, there are almost no archives actually following those recommendations. F: It is quite easy to say that, in general, your observations are the same as ours. There is no evidence to support storage specifications very different from these that you have recommended: temperature of 70° F., 50% R.H. But, I think that this temperature is rather high for present films. Exactly how much leeway do you think can be allowed in these figures? S: Temperature control is one area in which most vaults do have some flexibility. Most of them are running at approximately 55° F. to 60° F. Perhaps our new specification is set too high. We’ve found that most vaults can go lower than these temperatures. But this is the case for existing vaults. There is an enormous amount of material being generated, and this is straining the storage capacities of present vaults. If it were possible to make vaults more economically by leaving out air-conditioning requirements, or in any case, loosening the requirements, this would be far more desirable. This is the reason for specifying a higher temperature for the new material. F: When the material must be accessed, then the higher temperatures you have stated would be preferable. Of course, the temperature difference from storage to use is not so great in this case. But when the film is kept for a long time in storage and not taken out, then a lower temper- ature would be better. In such a case, one must raise the temperature in order to use the material, and then lower it again to return the material to storage. This cycling of temperatures is not good. Speaking for a lower center temperature, one would find that only refrigeration, not heating, is required. This would lower the machinery requirements for the vaults. In this case, perhaps 30° F. would be the preferred temperature. We have experience in storing photographic material at lower temperatures than freezing point, and we found no problems with the material when it was stored at such a temperature. S: What sort of film were you storing? F: Color film on both polyester and triacetate base. These were films that we had manufac- tured. S: Was there anything special about their con- struction? F: No, they were of standard construction: 100% gelatin emulsions, conventional couplers. Let me say that our experience has been mainly with raw film before processing, with couplers, but no dyes. But we can say similar things with respect to developed film. The constituents of processed images are not so different from those of raw film. A question arises concerning your use of stored films: you want to keep them 100 years. During those 100 years, will those films be taken out of the vault? S: There is a philosophical problem implicit in my answer. Some archives, especially in Europe, consider that the material they store is inviolate. Once the archive material has been made, it is put into the vault and accessed only when there is a need to make working copies. Other archives use xneir material on an almost routine basis. It is hard, therefore, to give a definite answer to your question. Personally, I subscribe to the first view. I believe that the material should be touched only when it is absolutely necessary to make distribution copies of some sort. This is what I believe I will recommend in my final report. Therefore, I think it would be best for you to speak in these terms: the material will be touched only when it is necessary to make duplicates. F: Then I shall assume that the film will be accessed once every two or three years. Mr. Ogura has pointed out that he feels your temperature specification for present film is rather high. We would prefer to recommend a temperature of 30° F. It would be necessary to condition the film to temperature and humidity conditions of the working area. But if such conditioning equipment is not available, perhaps it would be best to recommend a more normal temperature of 70° F. This is to avoid dew. 32 S: Thus far, I have seen only two places that have conditioning equipment: the East German archive and the British archive. In the other places, there are conventional atmospheres. It isn’t impossible to make conditioning equipment to accomplish this end; but it seems that from a practical standpoint, there are not too many places that have succeded in this. F: You have been asking about photographic films which do not employ gelatin, but use some other synthetic for a binder, such as polyvinyl chloride. We’ve been doing investigations into these, but for archival purposes, we think that gelatin photographic film is the best. S: Can you say why? F: Considering the gradations, sensitivities and color tone of the image. S: Are you using synthetic binders in your color film? F: Right now, that is a trade secret so we don’t want to answer you. S: Alright, then let me ask: are you using them in your black-and-white material? F: Actually, you are asking whether or not such materials can be used commercially. This is a very difficult question to answer. Right now, we cannot say anything. The trouble is that there are only a few manufacturers of film materials in the world. S: . What about color? What do you think the prospects are for materials which might be avail- able in the next five years having improvements in archival characteristics? F: One method is EVR, and there is the method of coupler-in-developer type films. Also, we have to consider the Technicolor system. In any case, all these methods have some disadvantages. To some extent they are good, and to some extent they are not. Right now, color films last longer than they used to; but along with that, the fungus problem is more serious. Since we are talking about the best method of preserving color, we have to consider fungus. Is there any good way to solve this problem? S: The present method is to control humidity. That was why I asked about the use of a formal- dehyde hardener. F: We thought so, but still it is not good. It does not solve the problem. S: The possibility of using synthetic binders is aimed at this problem. F: In the case of the Technicolor method, we could use synthetic polymers for the receiving layer. Thus far, we have considered the Techni- color method the best, but the dyes are soluble dyes and that is the problem. Even though they use a mordant to make the dye insoluble on the receiving layer, the dyes are still fugitive and non- permanent. S: In summary, your company has no color films which you feel would (a) meet our specifi- cations, or (b) survive better than films presently being used for these purposes. Also, you feel that you have no processes in the laboratory right now that will reach those figures. Is this true? F: The first specification: “loss of image density 0.05 ND in 100 years”— right now we have no such material. But regarding the rest of the requirements, we could maybe come up with something. We have no experience with film base stored over 1 00 years! I’m afraid that all polymers have a tendency to crystallize, and we have no way to predict the rate of crystallization when the film is stored for many years. The one exception, of course, is cellulose nitrate. S: That’s what everyone says! 33 The Image Search through any film archive, and you will find that 99.44 % of its film materials contain images generated by the action of light on silver-halide. Whether the final image is in black-and-white or in color, somewhere along the line silver played its part. Yet, crucial to the archivist is not how an image was produced, but how long it will last. In the 1970s, as more and more productions are being photographed in color, genuine concern is being expressed regarding the tenure of dye images. The following section deals with images; images produced by “traditional" technigues, both black-and-white and color. WET SILVER PROCESS Although photographic processes utilizing sensi- tive mechanisms other than silver halides are available, wet systems which depend upon silver are in predominant use by the motion picture industry today. A number of reasons account for this: 1. Tradition. Silver has played an important role in the historical development of photography. Dif- ficulties were encountered at first in fixing silver images, but once fixing methods were discov- ered, experiments using elements other than sil- ver did not proceed very far. 2. Ease of Preparation. Only two basic chemicals are needed to create a silver halide. All other manufacturing processes and ingredients added to the basic emulsion merely capitalize on the inherent capabilities of silver halides. 3. Sensitization. Silver halide emulsions can be adjusted for sensitivity and color response. They can be super-sensitized, and they can be adjusted to capture invisible radiation— ultraviolet, infra- red, X-rays, gamma, beta and alpha rays, etc. 4. Catalyzation. Silver is used to catalyze various photographic reactions. In both internal and ex- ternal dye coupler systems, the presence of a Eastman Fine Grain Duplicating Panchromatic Nega- tive Film 5 234 (35mm) and 7234 (16mm). Eastman Fine Grain Duplicating Positive Film 5366 (35mm) and 7366 (16mm). 0.8 0.7 0.6 0.5 0 4 time-qa'mmd 4 8 12 .DEVELOPMENT TIME (minutes) Exposure: Tungsten, 1/100 second, with Kodak heat absorbing glass. No. 2043 Process Kodak developer D-96 at 70°F.(21 °C ) Densitometry: Status M (Blue) 1.00 0.00 1 .00 log exposure (mcs) - 0.6 0.4 0.2 0 0 34 silver image will catalyze the coupler to produce a dye image. In imbibition systems, silver is used to catalyze the differential hardening reaction pro- duced by a tanning developer. This reaction, plus others, is used to produce matrices essential to the subsequent printing operation. In addition, the presence of a trace silver image in a film is sufficient to catalyze peroxide to produce a full vesicular image (see silver vesicular). 5. Storage Density. No other image recording system is capable of as high a storage density as a fine-grain, silver halide system. In this parti- cular respect, photographic systems based on silver far outdistance the informational capabili- ties of any other existing, practical image record- ing system, gauge for gauge. 6. Permanence of Record. Providing it is properly protected, metallic silver can be as stable as any archivally suitable element— such as platinum or gold. 7. Cost. Considering the performance levels of which silver systems are capable, no other sys- tem offers as high quality a product for so little investment. 8. Transfer Curve. Silver image systems designed for continuous tone photography exhibit a known Eastman Fine Grain Release Positive Film 5302 (35mm) and 7302 (16mm). 0.00 1 00 2.00 log exposure (mcs) and accepted grey scale response and brightness range. In addition, the number of discernible steps of grey— from blackest black to whitest white— far exceed the capabilities of other image recording systems. For the past 80 years, black-and-white silver image prints have been the staple of the motion picture industry. Thus, the bulk of materials presently stored in film archives is comprised of silver images. Unfortunately, metallic silver re- mains one of the most reactive of metals, and it is therefore subject to attack from numerous sources. COLOR A thorough discussion of the various techniques for forming color photographic images would be out of place in this survey if for no other reason than bulk. Over the years, hundreds of processes have been tried and several dozen have been commercialized with varying degrees of success. There is no doubt that a major film archive could easily produce examples of a wide variety of these processes. Suffice it to say that for practical purposes, the majority of color motion pictures have been made utilizing one of three dominant subtractive* color processes. These processes are: (1) imbibition; (2) coupler-developer; (3) inte- gral coupler. IMBIBITION DYE IMAGES Imbibition printing, commercialized in 1928 by Technicolor Motion Picture Corporation (USA), was the first practical method of color image production utilized by the motion picture indus- try. The process involves the preparation of separa- tion positives on a special material called “ma- trix” film. This film differs from standard black- 'If one starts with white light projected upon a screen and subtracts from it the colors one does not wish to see upon the screen, one would have the essence of the subtractive color system. In three- color subtractive systems, true yellow (minus blue), cyan (minus red), and magenta ( minus green) are used. Subtractive techniques allow for the deposi- tion of all components necessary to the final colored image within the same geometrical location. There is no reason for the various colored images to be separated in the color print; indeed, no full colored image would result if the various components were maintained in a separate fashion. and-white print film in that its emulsion is thicker and unhardened. During development, a tanning developer is used which produces a positive image inscribed in gelatin in a “hill and dale” fashion. The darker an area in the original scene, the more gelatin is retained in the matrix film; the lighter an area, the less gelatin. In a machine called an imbibition printer, the matrix film, suffused with the appropriate dye, is brought into contact with a blank film which will eventually be the release print. Dye in the matrix is transferred to the blank film and imbibed or “drunk up” by it, leaving the matrix void of dye. After the films are split apart, the matrix is cleaned, dried and reeled up to await further use. The final release film is completed by continuing through the machine to receive similar treatment from the either one or two more matrix films corresponding to the remaining colors. The technique of imbibition printing formed the basis of Technicolor’s rise as the dominant color system in the first half of the 20th Century. Its use, originally for two-color photography, was extended to three-color photography in 1933 with the construction of the Three Strip Technicolor camera. Dyes used in the Technicolor process are unique in color photographic processes in that they need be chosen only to survive relatively mild chemical and mechanical processing procedures; hence, a greater choice of dyes is available for this pro- cess. The choice will naturally settle upon those dyes which perform their optical functions as near to theoretical perfection as possible. This has not always been the case with the following two color systems. COUPLING DEVELOPER SYSTEMS Kodachrome, introduced by Eastman Kodak in 1935, was derived from the work of Leo Godowsky and Leopold Mannes. This early film carried three specially sensitized emulsions, separated by var- ious filter and subbing layers, on a single side of a single film base, but contained no coupling (color forming) agents. During development, spe- cial techniques were used to diffuse developers containing couplers into the appropriate layers of the tri-pack emulsion, and a full color picture resulted. The development techniques used to produce Kodachrome pictures have been greatly simplified through the years, but still force the return of the material to specialized laboratories for processing. INTEGRAL COUPLER SYSTEMS Integral coupler systems are best typified by those products which contain the total coupling chemistry in the film at the time of manufacture. Processing of these materials is much simpler compared to Kodachrome. Reversal integral coupler color films achieve color by incorporating three emulsions, each variously sensitive to the different color primaries, and separated by appropriate filter layers. During de- velopment, all three layers are converted to silver negative images, re-sensitized, and then re- exposed to light. The remaining silver halides are developed to metallic silver with proportionate amounts of dyes formed in the various layers. All silver present in the film is bleached away, and the dyes remain as the final image. Typical examples of this type of film are Ektachrome, Anscochrome, and Agfa- chrome. Negative-positive integral coupler color films are constructed in a fashion similar to reversal mater- ials, incorporating color couplers directly within their structure. The negative portions of such systems usually incorporate masking techniques to maintain correct dye transmission, but such techniques cannot be used in positive color films. Developing procedures are substantially different, and simpler, for negative-positve integral coupler color films than for reversal. Typical examples of these materials are Eastman Color Negative, East- man Color Print, Ferrania Color Print, and Gevae- color Print. It should be noted that, because of the complex chemical nature of coupling color systems, the choice of couplers is limited to those substances which will survive a wide variety of chemical procedures during processing. Thus, the eventual choice of dyes produced by such systems are frequently the result of compromises made throughout the design, manufacture, and pro- cessing of these materials. For this reason, color images rendered by these systems, though of frequently excellent subjective quality, remain approximations of the original scene and some- thing less than ideal. 35 Eastman Kodak Co. Rochester, New York K: Lloyd West Peter Adelstein Various Research Scientists S: Ralph Sargent S: Dl\ West, I am familiar with your recom- mendations with respect to preservation tech- niques using three-color separation. Do you feel that there is available now, or might be available in the next five or ten years, any alternative to this as an archival technique for color motion pictures or television? K: No. All I can say is that in the research labs we are continually looking for better dye stability, and if we had it, it would already be on the market. But whether it will be here in two years, five years, or ten years, there is really no way to predict. A lot of this is— if there is a market, then you try to serve it. Maybe the people from your organi- zation ought to talk to a marketing organization to see what we are talking about here, to give an objective you could try to meet. You must remember that motion picture print film, whether it is made by us or any of the other manufacturers, is one of the lowest priced materials, so that you can have this large, exten- sive use to which it is put. S: You are saying that since it is an inexpen- sive material that maybe stability has been cut in reference to cost? K: No, I did not say that stability had been cut. I’m just saying that you might be able to do things if you had a specific program to make a more archival color film, and were willing to compromise on other properties. This ought to be discussed— if we can serve those needs by aiming our direction at one specific market. S: As of this moment, such a film— an archival color film— would be something that is hoped for, that is wished for immediately. The question is the actual cost of development; who is going to put up the money, and how is it going to be used. Also, whether the film is going to be ultimately satisfactory in terms of any changes that may occur in the future as far as the business of gen- erating images goes. However, given the backlog of materials that exists right now, there is a tre- mendous immediate demand for a practical solution to the problem. K: The point is, if you want something five years from now, we should be working on it today. It takes lead time. I think you are implying that something may be produced which might not be possible. Actually, when you are talking about 100 years, Koda- chrome film is a pretty good material. You do not have to worry about lead time there. S: What evidence do you have to support Koda- chrome film as an archival material? K: We put it on the market in 1940, and it is still around in the 1970s. Images made then are still usable today. They have not, as far as we know, deteriorated appreciably. That’s not an accelerated test, this is an actual test. We had comparative accelerated tests with Kodachrome film vs. other products. S: And Kodachrome has held up the best of all of them? K: Kodachrome film, in the dark, is better than any other color product that we make, from the standpoint of stability. S: The question is then one of the procedures which we might have to undertake to derive rea- sonable printing material from Kodachrome masters— storage masters. What were the condi- tions for storage used for these Kodachrome materials? K: Home conditions; room temperatures. S: No other forms of control whatsoever? K: No, sir. The film experienced the normal changes in humidity encountered in regular climates. S: You have actually compared step-wedge tests? K: No, we are just reporting what those of us individually have observed and have heard from others who have used the Kodachrome product, starting back in 1940. But, is this a really practical solution to your problem? You have miles and miles of this stuff — I’ve seen some of your Government archives. Can you talk of printing or reproducing all you have- even once? It sounds like a tremendous job. S: There is that question of stability. How viable is the proposition of using Kodachrome as a storage material? Do you know of any actual comparative research work on this? 36 K: No, we don’t know of anyone else who has reported or published anything. S: What would be the drawbacks to it? K: We should really have somebody from our Marketing Division tell you about the applications of such products as Kodachrome film. We don’t have anyone here today who represents our Marketing Division. I don’t know how practical that would be. S: I do not remember that being suggested by your color preservation article. Was this con- sidered? K: No. The only reprinting we suggested was on black-and-white separations, which is still, I would say, the ultimate; but you will have three times as much film to store. Berkey published an ad about making separation negatives and storing them in their vaults for their customers. The ad has been in various publica- tions. “Technical Photography,” September, 1972. It’s the only firm I know of offering a stor- age service. I notice in your outline that you hope for storage conditions, room temperature, that is, 70° F. plus or minus 15° and you are hoping that the products will be sufficiently stable at that condition of temperature to be archival, right? Well, those are fine to hope for, but what if no product will stay as it is for 100 years at these conditions? Would you be willing to go to a lower temperature? S: We would be forced to, of course. Ultimate- ly, we can not be slaves to figures; we’ve got to stick with hard facts. At the same time, however, we must be alert to new products which might more easily be archived. We have to come across with materials that are going to do the job. The figures are aim points. The same is true for all the figures on the page. K: I think on the relative humidity figure we could be very hardnosed and say that 70% RH is completely unrealistic. You will have problems with fungus growth. I think that if you are being serious about this, you should let 50% be your upper limit— maybe you could get by with 60% , but if you are putting a lot of money in something of this nature, don’t play around for 10% RH. S: What about the possibility of using synthe- tic binders? K: Other than gelatin, you mean, to prevent fungus? Well, there aren’t any right now on the market. That’s a development program itself. There was once a motion picture film put out with a synthetic binder. S: 1951 or 1952—275 Du Pont. I was talking to the Du Pont people and they were doubtful about whether or not that particular binder was more impervious to fungus growth than gelatin. Their tests were inconclusive from that standpoint. Maybe it is the wrong one to look at. What about base materials, for both black-and- white and color? Would there be an advantage to be gained from a change to polyester? K: Some of our motion picture films are now on polyester. One of the problems with polyester is its difficulty to splice. S: Presumably that has been solved by ultra- sonic techniques or tape splicers. K: I would like to recommend tape for what you are talking about. Ultrasonics would work. It is expensive, but for an application like this, it would be satisfactory. I don’t really know what you are going to gain by going to polyester. Certainly as far as the stabil- ity of the material itself, the base, polyester is superior to cellulose triacetate. But we are now talking in terms of 500 years to 1000 years or beyond. It’s not the critical factor. You tend to worry about dimensional stability of the cellulose materials where you don’t have to at all with the polyester, but at least in cellulose materials the dimensional stability is vastly improved over what we manufactured 30 years ago. I remember that with cellulose nitrate you could encounter shrinkages something like 3% ; we just don’t make acetate materials that shrink that way today. So I don’t really think there is enough to be gained. S: What about the possibility of relaxing the storage conditions by using polyester base? K: No, I don’t really think so because I think the critical thing in the storage is the image, not the base. We are afraid of a higher relative humid- ity because of fungus— which is the image, not the base. The base layer is fairly good— those bases that are made today. If you wanted to store something for 1000 years, and get the ultimate, I would say, “Yes, polyester is better.” But I don’t really think you are talking in those terms. S: Well, obviously the longer something would be around, the better. K: Yes, but it is the old “weakest link” story. S: How long are the silver separations good for theoretically? Is there anything stated? I read your paper recently. K: I remember seeing some Brady plates, and they looked beautiful. The one advantage silver has over many other means of storage of information is that silver has been around for a long time and we know it to be good. S: What about the use of after-treatments of silver images: gold substitution, formaldehyde hardening, etc. There were several articles that mention this. What are the advantages and dis- advantages of such treatments— besides cost? K: I think that there is an advantage in that there is actually a migration of silver in the micro- spot problem; if you have a gold coating, I think that as the various papers have pointed out, more stability would be expected— fewer microspots. Microspots were a problem with the fine grain emulsions which were stored in the presence of peroxides. I think it makes more sense to eliminate the peroxides from the storage area, than to go to a gold treatment. But we know that silver can be good if it is stored properly, so I’d say store it properly and don’t change the silver. S: The other question relates to whether or not, by the use of any of those treatments, you can loosen up the storage requirements and up the RH point at which attack by fungus would occur. K: I don’t think so. It’s a gelatin binder which you are going to have in any case. We know for sure that gelatin will support fungus, so you can’t loosen up that RH. S: Do you have any way of predicting the extent or direction of dye fading of a particular batch of color material? 37 K: The Arrhenius equation. That’s what Mr. Larson has been doing. It’s published in this paper by Dr. Adelstein. We use that as a part of our in-house testing. We also use common tests— those in the American Standard which is based on a publication put out on this subject. We suggest that if you are going to test motion picture positive and reversal films, that you not test them in simulated daylight xenon arc— because that is not applicable. You should test the films in tungsten radiation. No florescent testing because florescence is not applicable. Then for heat and humidity, 140° F. 70% RH for seven days and fourteen days, and 170° dry for two days and seven days. We say in several places in the article that if the product is so unstable that two days is sufficient to produce enough damage to make good measurements, then two days is the right number to use. If on the other hand, it is twenty-eight days or a year or any other time, you alter these figures as the keeping times and run your test accordingly. You can use the figures regularly, from that point on. S: Let me get some definite statements: you are suggesting Kodachrome film as a method of archivally storing color. K: (Dr. West) I’m the one who suggested it and I’m the one in this group who knows least about the stability of dye images. (Another scientist) If you are looking for the most stable of the color films that we know about, that’s it. The statement is partly based on practical experience and partly on what we can predict based on existing tests. The life of Kodachrome film is unknown because you see, even at room temperature, it has kept from 1940 to 1970; if we can believe the Arrhenius equations, this goes up very rapidly as you go down in temperature. Now, we didn’t say anything about exposure to radiant energy. Just on the basis of storage, though, it seems that Kodachrome film has some advantages over black-and-white separations, because there would be less film to store. There is the possibility that there could be some problems with contrast because it is not the normal procedure— to take the negative and go on to reversal. With that particular reversal material, you might have a contrast mismatch because your negatives are made for certain printing tech- niques, in conjunction with intermediate steps, and the gammas are adjusted for the total se- quence of films. There may be other problems on going to Koda- chrome that I don’t know about. The marketing men would be the best people to talk to about that. S: Alright. On the point of base materials, we’ve come to the conclusion that you feel that polyester is of no particular advantage? K: Well, it’s more stable, but I don’t think that is really pertinent here. I don’t think you need to go to the trouble. But, if I had a triacetate print and a polyester print of the same thing and I could only keep one, I think I’d keep the poly- ester, but I wouldn’t go to the trouble of making the polyester in the first place. When something goes into the Library of Con- gress archives, you don’t reprint it, do you? For instance, a movie that is made today— you don’t know if that particular movie is going into the archive so it would remain on regular material, would it not? S: The Library of Congress automatically con- siders everything that it chooses to store as archival. Their right to request and receive prints, is found in Copyright Law. But the law presently says nothing about the nature of the materials, except that they be of good quality and identical to the copies exhibited publicly; thus, the mate- rials are of standard manufacture— no special materials. K: Say we did have the capability— although we do not right now— of making a film which had a 100 year dye stability at room temperature, that film, in all probability would be more expensive than our current material. Now, a film lab is not going to use that film just because several of the prints out of a 1 00 or 400 print order are going to be for the Library of Congress. So what mechan- ism would be used to insure that a special film would be utilized for the archival prints? S: The mechanism would be the Copyright Office’s rules for copyright, and would have to be altered to that effect: i.e., the specification that copyright prints must be submitted on archivally permanent materials would have to be spelled out. I think that there is reasonable precedent for this elsewhere. On a practical basis, the Library has been extremely choosy about the prints that it receives for copyright purposes. For example, “2001 ” was rejected 13 times before a reasonable copy was accepted. K: You have another problem. We’re talking about the stability of a certain product. You must consider the product and the processing together, not just the product. If black-and-white film is not washed well, for example, if hypo is left in, then all bets are off. That’s another danger about giving the stability of a product. S: That is a good point. In this regard, do you think that it would be wise to recommend that the Library have as a practice the rewashing or stabilization of all materials received? K: After-treatments aren’t where you’ll actually run into trouble. It’s the actual making of the print. In color, it’s a film process combination which insures that you receive the dye stability to which you are entitled. The manufacturer can only say, “If everything is done right, you are entitled to this amount.” The film processor, if he does things correctly, will insure this. But, if something is not up to “snuff,” then you can run into problems. To illustrate: what if the film wasn’t put through the last stabilizer bath? As far as the immediate quality of the image is concerned, no difference; but, the image certainly won’t last for more than six months or a year. (Dr. West) One more point: when Pete and I were down at the Library of Congress, we saw a gal running a very simple test to see if the residual hypo was down to an acceptable level. If the film isn't right, she throws it in a box and it goes back for re-processing, to wash out the residual hypo. I don't know if this practice is still followed, but we do have better methods now than what she was using. Our silver densitometric method is the method that would be used by somebody follow- ing our recommendations and would be found in our paper about water conservation. In that paper, 38 numerical values are given for all Kodak products that were then on the market — in 1969. Incidentally, and to our surprise, we tested some products for stability under nitrogen compared to oxygen and they were worse under nitrogen than oxygen. S: That’s an interesting point. A number of people have raised the question of gas, pressure storage. K: It’s worse— at least, this is what we found. There are other institutions besides the Library of Congress which store film materials, are there not? S: Oh yes, several in this country, and many more throughout the world. K: I spoke to a Dr. Levenson from England last month who I think is England’s representative. They don’t have too much information to go on. S: There is then, really the question of whether or not any changes in your opinion have occurred since your paper on preservation was written? K: I don’t think so. As far as we know, it’s still valid and we have no more information, really. S: You have recommended the use of hermetically sealed containers. What type of practical container are you talking about? K: That's a problem, but it’s not impossible. You do it with coffees. Yes, vacuum cans, or at least hermetically sealed— you can leave air in it if you wish. S: Do you know of anyone who is doing this? K: No, because no one wants to. S: What about the application of aluminum foil packaging, evacuated pouch packaging? Is this an adequate substitute for a vacuum can? K: (Dr. West) I don’t think it’s a substitute although it may be adequate. The problem is that there are pin holes in those things which cause me to worry. When we do tests, we usually put the material in double sealed bags just to make sure. And of course, they are awkward to handle— they’re bulky, and rough handling can cause the packaging material to break. They are not nearly as satisfactory as cans. S: What about your recommendations for vault storage at 35° F.? K: (Dr. Adelstein) We arrived at that after considerable argument. Lloyd (West) wanted lower and I was worried about the lower temper- ature because of moisture. That’s why, if you get a vault and you could keep it below this RH, you would not be worried about moisture. Of course, I recognize that this sort of thing is extremely expensive, but I was thinking in terms of someone who has a valuable commercial film, who can release it every two years and make a million dollars and can, therefore, afford to invest $2,000 in a room. (Dr. West) Our accelerated testing with deep freeze conditions has been so short in years that we’re not able to make bold statements. (Dr. Adelstein) Although we know that in the rooms the RH can be quite high, and we also know that although the moisture exchange is slower at these temperatures, there is moisture exchange. I guess you are saying that we haven’t had direct evidence. (Dr. West) You can pre-condition the film at 15 to 30% RH and then drop it in deep freeze, but we don’t really know from tests what the humidity of the film is at various time periods. S: Have you come up with any technique for speeding up either the pre- or post-condition requirements? K: The only real way to do this would be to put the film through the dryer section of a film processing machine. You can get your film a good way there in just ten minutes, but that means a fairly long rewind unit. For archival purposes, is that really so important— the time spent waiting until something comes out of vault temperature? S: I don’t think it’s that important going into the archive as it is coming out. The consideration is the accessibility of the material. Ideally speaking, there should be no reason to rush it. But every access situation seems to involve getting it out “yesterday.” K: There is a summary here with respect to recommended limitations regarding humidity. We wish to keep the relative humidity at less than 60% to avoid fungus growth. It should be kept lower than 50% for black-and-white and less than 30% for color films, to avoid hydrolysis. On the other end of the scale, as far as humidity is concerned, if it is too low it may become brittle. For cellulose ester that is less than 15% ; for polyester, 25% . In our recommended storage, in fact, we mention this difference. It is PH 1 .43. In that particular specification, we recommend that with polyester base film you don’t go to quite as low a humidity as you do with cellulose triacetate. The reason for this is that at low humidities there is a greater strain between your emulsion and your base. You have really two very dissimilar materials. Some of the earlier polyester films did not have as good adhesion as you might like. Of course, we’re not writing standards around a particular product, but a class of materials. There are some polyester materials that are not all they should be. To be conservative, as we feel we must be, we said, “Let’s not go below 25% RH.” There is a fair amount of activity going on at Kodak in this area. We feel this is a responsibility that we have. 39 A B C Samples of triacetate black-and-white print films from film exchanges found in cans with unstable nitrate film : A, 1949; B, 1950 ; C, 1951; D, a comparison sample not stored with nitrate film. 40 TREATMENT AND STORAGE To attempt to preserve a silver halide picture which, from the beginning, was improperly processed is effort misplaced. The key to successful photography is not in being able to develop an image, but to fix that image against fading. This was abundantly clear to the earliest research experimenters using silver halides. Today we still face the same task. To insure the permanence of an image it must be fixed, and fixed properly. This act involves not only specific chemical treatment, but also the thorough removal of the byproducts of those chemical reactions. Yet archivists must face the reality that they are often called upon to preserve films of unknown origin or condition. Frequently such films, because of improper fixation, washing, or attack by outside pollutants, have faded or spotted. The question then arises: what to do? There are several possibilities. Gold protection and image stripping are just two of a number of potential remedial procedures. Finally, when the film is right, how should it be stored? On this matter, there is great divergence of opinion and practice, debate, hope, and prayer. What follows is directed to those gut issues of archiving film; along with the guts, you will find some blood. Image deterioration is an inherent problem in photographic materials kept in archival storage. If physical and chemical damage suffered by the photographic image is allowed to continue un- checked, in a matter of time the material will no longer be worth preserving. Fortunately, there are measures which can be taken to prevent such damage, as well as some processes available to the archivist that can re- store deteriorating silver images. PROCESSING Since evidences of image deterioration in stored materials are not usually detected until the mater- ials have reached a dangerous state of decompo- sition, the necessity of careful processing to in- sure archival permanence of photographic mater- ials cannot be overstated. Photographic materials subjected to faulty processing run a serious risk of being destroyed during storage. The processing reguired after development of the photographic emulsion involves two steps — fix- ing, to convert undeveloped silver halides into water-soluble compounds, and washing, to re- move these compounds from the emulsion. FIXING In a fixing bath, a negative emulsion is treated with a fixing agent that not only dissolves the undeveloped silver halides but also forms soluble salt complexes which can be readily removed without staining the silver image, or otherwise reducing its guality. Although various fixing agents can be employed (depending upon the nature of the emulsion, type of processing equipment, etc.), two principal fix- ing agents are ammonium thiosulfate, (NH4)2- S2O3, and sodium thiosulfate (“hypo”), Na2S2C>3- 5H2O. For reasons of cost, sodium thiosulfate is more commonly used in photographic fixation processes. RATE OF FIXATION The rate of fixation depends on: ( 1 ) Fixing agents. Ammonium thiosulfate fixes more rapidly than sodium thiosulfate. Also, am- monium thiosulfate is more easily removed by washing than sodium thiosulfate. However, in the case of color film materials, it may have an ad- verse effect on the dye stability of the materials. Treating the Image ( 2 ) Concentration of fixing agent. Other factors being equal, the rate of fixation increases with the concentration of thiosulfate. However, at regions of higher concentration, an optimum is reached, with the rate of fixation increasing only slightly beyond a certain value. ( 3 ) Emulsion types. Fine-grain negatives fix faster than course-grain negatives, and silver chloride emulsions fix faster than silver bromide emulsions. Emulsions containing iodide fix more slowly than those containing only silver bromide. Thin emulsions fix faster than thick ones. ( 4 ) Temperature of the solution. Fixing time for a given concentration of thiosulate varies with tem- perature. Temperatures higher than 75 ° F. are not advised in the case of acid fixing and hardening baths. 1 Increases in temperature also cause in- creased swelling of the gelatin, an effect which can be mitigated by the addition of a repressing agent. ( 5 ) Agitation. Agitation increases the speed of fixing up to a certain point. It has only a slight effect on fine-grain or thin emulsions. (6) Degree of exhaustion. Accumulation of dis- solved halides, particularly iodide, and silver thio- sulfate complexes greatly reduces the rate of fixa- tion. Also, repeated use of a fixing bath can result in developer carry-over, which raises the pH and dilutes the strength of the solution. Hence, the time require for fixing tends to increase rapidly with use. Controlled replenishment in the course of extended use will help to hold the time of fixation relatively constant. It is difficult to establish proper fixing procedures because the exact time for complete fixation can- not be pinpointed. As a working guideline, the time for complete fixation is generally determined to be twice the clearing time (the time required for disappearance of all visible traces of silver hal- ide). Some investigators 2 have maintained that fixing time is equal to clearing time. They found that thorough washing removed all unused silver from the emulsion even when fixation was stopped at the moment that all visible traces of silver halide had disappeared. WASHING Because of the negative correlation between the keeping qualities of processed photographic film and the amounts of residual chemicals retained in the emulsion, it is important to insure adequate 41 washing of photographic materials destined for archival storage. If processed photographic film is not adequately washed, over a period of time residual thiosulfate reacts with the metallic grains of image silver, causing it to fade or discolor. Excessive thiosulfate retention also produces a colored degradation in the low density area of developed film stored in a humid atmosphere. High temperature and humidity greatly accelerate image density and/or color changes caused by residual thiosulfate. 3 TESTING FOR RESIDUAL CHEMICALS In the past, the Crabtree-Ross test was widely accepted as the standard test for measuring resid- ual thiosulfate in films intended for archival stor- age. A test strip sample is immersed in a solution comprised of mercuric chloride and potassium bromide diluted in distilled water. The sample is allowed to soak, and its turbidity compared with the turbidity produced by known concentrations of thiosulfate. The degree of turbidity is depen- dent upon the amount of sodium thiosulfate pre- sent in the emulsion. This comparison can be done visually, or with a photometer. Any turbidity visible in the solution requires the film to be rewashed. However, subsequent experimentation has put the validity of this test method in question. Inherent deficiencies of the Crabtree-Ross test are: (1) the formation of some turbidity within the film layer, rather than in the solution, which causes low results; (2) interference from traces of dissolved gelatin, which alter the amount of turbidity; (3) attack of test reagent on the silver resulting in residual particles, which cause the formation of additional turbidity recorded as residual thiosul- fate; (4) certain fading agents, such as trithionate and tetrathionate, known decomposition products of thiosulfate present in older films, do not re- spond to the test; (5) analysis must be performed within 24 hours of processing. Modifications of the Crabtree-Ross test overcome many of these deficiencies; however, its inability to measure polythionates and its reliance on tur- bidimetric measurements remain distinct disad- vantages. Recently, two newer methods for quantitatively measuring the adequacy of washing have replaced the Crabtree-Ross test in accepted use. These are the methylene blue method for measuring thiosul- fate, and the silver densitometric method for measuring residual chemicals in films, which to- gether form the basis of ANSI PH4. 8-1971. This standard is recommended as a practical guideline for testing procedures. These two tests hold a number of advantages over previous methods of determining thiosulfate con- tent in that they are applicable to color as well as black-and-white products, afford sufficiently re- producible test results, and are less sensitive to time lapses between processing and analysis. The first method is based upon the reduction of thiosulfate with borohydride to form sulfide ions, which can then be measured colormetrically through the formation of methylene blue. It is rapid to administer, requiring about 15 minutes per sample, and approximately four minutes for analysis. “The sensitivity of the methylene blue method is adequate even for amounts of thiosul- fate well within the archival limit (equivalent to 0.7 g S2O3 — /cm2, specified for black-and-white products. ”4 Illustrative correlation between silver densitometric method and methylene blue method tor measuring thiosulfate. American National Standard PH4. 8-1971 . methylene blue method This material is reproduced with permission from American National Standard PH4. 8-1971 copyright 1971 by the American National Standards Institute. Copies of the standard may be purchased from American National Standards Institute, 1430 Broadway, New York, NY 10018. The methylene blue method measures only the residual thiosulfate, and not the polythionate de- composition products and their complexes which may form as the product ages. For accurate re- sults, samples should be analyzed within two weeks of processing. A simpler but somewhat longer test method is the silver densitometric method, by which residual chemicals are measured densitometrically. One half of the test sample is immersed in acidified silver nitrate, causing certain residual chemicals to produce a yellowish-brown sulfide stain. The entire test sample is then immersed in a solution of sodium chloride which converts unused silver ions to silver chloride. Next, the test sample is immersed in a fixing bath of sodium thiosulfate, which removes the silver chloride. After the sample has been washed and dried, the densities on the stained and unstained areas of the sample are measured. These density differences are re- ported as a measure of residual chemicals in the sample. An advantage of the silver densitometric method is that it measures polythionate decomposition products and their complexes, as well as thiosul- fate, and can therefore be applied to aged samples. Besides the fact that it is relatively insensitive to time lapses between processing and analysis, the test is convenient and simple to administer. The chief disadvantage of the silver densitometric method is that it lacks adequate sensitivity for measuring archival levels of residual thiosulfate. It is not sensitive enough to reliably measure thiosulfate below approximately 0.9 g/cm2. FADING Decomposition of retained hypo, insufficient fix- ing, and attack by external oxidizing agents in the atmosphere can induce the partial conversion of image silver into silver sulfides causing the image to fade or take on a yellow or brown coloration. This results in a loss of image density, and per- haps even complete disappearance of the image. Heretofore, there have been few practical sugges- tions for restoring photographic images that have faded or discolored. If the material is not severely faded or discolored, a relatively simple process of redevelopment by bleaching and subsequent ex- posure to light in the presence of a photographic developer can be applied successfully to regener- ate the affected images. Photographic negatives can be soaked in a sublimate solution and then redeveloped. 42 However, the problem with many such regenera- tive processes is that they do not, in most cases, reproduce the black silver grain color. Instead, the image often displays other colors, stains, and a very high degree of fog. Dr. Edith Weyde reports a successful method for restoring discolored negatives by immersion of the affected negatives in a 0.5 to 1 .0% solution of iodine in alcohol. The iodine bath penetrates the gelatin layer, changing the yellow silver into silver iodide. The treatment is administered for several minutes, then terminated prior to attack on the image silver itself. The negatives are then fixed and washed to archival standards. 5 A new process for restoring black-and-white silver images has been discovered by Dr. Johann Albrecht Keiler of the German Democratic Repub- lic. The process (German Democratic Republic Patent No. 36078) is claimed to make possible the restoration of images previously considered hope- lessly lost. The process involves subjecting the film to a vigorous oxidation and bleaching bath. Finally, the film is redeveloped through a treat- A translation from the German of Johann Albrecht Keiler’s “Process for the Restoration of the Silver Image of Black-and-White Films,” German Demo- cratic Republic Patent No. 36078, (Berlin, East Ger- many, May 25, 1965). Quite unexpectedly, it was discovered that one can achieve a satisfactory restoration of faded or yel- lowed black-and-white films; and this applies to Positive, Negative, Duplicate and the like films, without any color change, stain or fog, even in a situation where the process of yellowing is well- advanced. This is achieved by subjecting the image, depending on the degree of fading, to a strong oxidizing bleaching bath, preferably with a relatively high concentrate, strongly acidic potassium dichro- mate solution. The image is washed, then immersed in a stannous chloride solution that has been acidi- fied with hydrochloric acid. The image is again washed and finally redeveloped. By the normal pho- tographic bleaching process, potassium dichromate solutions are used; however, only in about 0-5% concentration. This concentration is, however, suffi- cient to convert the metallic image silver into silver salts. Of immense importance to this new process is the vigorous oxidation process because it has been recognized that only through this Is It possible to convert the silver/sulfur compounds completely into silver compounds that can be developed. For this reason, the bleaching process is followed by the ment with a stannous chloride solution that has been acidified with hydrochloric acid. MICROSPOTTING Formation of microscopic spots or “aging blem- ishes” has been discovered on processed negative microfilm stored in rolls. Occurrence of microspot formation has been widespread and diverse. Microspots have been observed in films made by different manufacturers, subjected to varying pro- cessing methods, stored in divergent parts of the world under a wide range of conditions. They have been found in films between two and 20 years old, but not in freshly processed films. Although the exact mechanism of attack is not yet fully known, recent investigations indicate that microspot formation is the result of external oxidizing agents transported in the air. Common atmospheric components such as sulfur dioxide, ammonia, or hydrogen sulfide have been found to produce microscopic spots on microfilm under laboratory conditions. 6 Hydrocarbons in automobile exhaust fumes are oxidation step, whose final effect, however, depends on the subseguent treatment with acidified stannous chloride, a process that had not been described previously. The chemistries of the entire process have not been completely resolved; however, all experiments have practically led to a complete re- generation of the silver image, even in the case of such film parts which by visual examination were no longer transparent. Such disadvantages as observed in the regeneration of the silver image by the pre- viously applicable methods are not known in this process. No hard-and-fast rules can be made here as to the length of time for carrying out the various processes described in the baths. This depends on the extent to which the image has turned yellow and the spe- cial properties of the emulsion layer. The same can be said about the concentration and the pH values of the oxidation bath. Experiments with extremely yel- lowed film samples had shown that appropriate po- tassium dichromate concentrations lie between 5% and the saturated solution. Appropriate hydrochloric acid concentration was found to lie about 0.1%. Additionally, it had proved advantageous to add 0.5 % potassium bromide. The stannous chloride bath should contain about 25 % stannous chloride and 1% hydrochloric acid. For every black-and-white film that has to be restored, the optimal concentra- tions of the bath have to be separately determined. The bath temperatures lie around 18° to 20°C. another potentially dangerous atmospheric ele- ment because they can form, in combination, harmful peroxides which will attack silver images. Also, nitric acids contained in automobile ex- haust fumes can produce an acid reaction detri- mental to photographic materials. 5 Materials stored in archives situated in large industrial areas or heavily trafficked urban centers are ex- tremely susceptible to this type of atmospheric attack. GOLD PROTECTIVE TREATMENTS One of the most effective methods of protecting film against attack by external oxidants is the application of a protective layer of gold to the silver image. Gold is much more resistant to oxidation, and other reactive processes, than silver. By substitu- tion of the surface layers of the grains— essen- tially, gold plating— a silver image assumes the resistance and stability of gold. In various oxidiz- ing and accelerated aging tests, treated film samples with gold-substituted images offered outstanding resistance. It is reasonable to assume that test results under accelerated aging conditions would adequately correlate with the effects of extended storage under natural conditions. The gold protective process is a commonly de- scribed method of preserving silver images in photographic materials. Much of the work in this area has been done by R.W. Henn and associates, whose published reports form the basis of this section. Henn bases his observations on gold-treated test samples of fine-grain Recordak microfilm. “A gold content of ten mg/ft2 changes the warm tone of many microfilm images to a more neutral hue. A higher gold content produces a blue-black hue, and a slight increase in density. ”7 (However, the gold protective solution cannot be considered a toning bath in the conventional sense.) “En- largements made from negatives containing the 10-mg level of gold show no change in printing time, contrast, sharpness, or resolving power as result of treatment. ”7 Under electron micrograph readings, no physical changes in the structure or size of the grains are evident when the gold is introduced. The sole undesirable effect of the gold treatment seems to be a slight “softening” of the film. However, if the film is treated in a supplementary formaldehyde bath, its hardness 43 characteristics are almost completely recoverable. The gold protective solution that Henn employs in his experiments consists of: gold chloride (HAu- CI4 • 3 H 2 O, assaying approximately 50% Au, .05g), thiourea, 5.0g, tartaric acid, I.Og, and so- dium sulfate (dessicated) 15.0g, and lOOOcc water to make. 8 Gold chloride in solution yields auric gold, gold ions with a plus three valence. Thiourea reduces the gold ions to aurous gold, having the neces- sary valence of plus one. Tartaric acid controls the pH of the solution, increasing the rapid action. Sodium sulfate inhibits “swelling of the gelatin layer and improves the final physical con- dition of the film. ”8 It is important to note those factors which in- fluence the gold protective process. Time has a direct bearing on the effectiveness of the treat- ment. A linear relationship exists between time of treatment and the gold content of treated films. The process is dependent on agitation. Increasing agitation causes the gold content to rise by a much larger factor than would be expected in conventional development or fixation processes. The gold content of treated films is directly pro- portional to the concentration of gold in the solu- tion. “The composition of the rest of the solution does not markedly affect the rate of gold deposi- tion, provided it is kept acid. ”8 On the other hand, the process is relatively inde- pendent of temperature, type of emulsion, age of the film, or image density, provided that the silver content of the film is substantially higher than the final gold content. Because the solution is very dilute, rapid depletion of gold at the image site occurs. The effect of exhaustion is severe, requir- ing replenishment or a new supply of the solution after a certain point. In preparing the solution, Henn advises that the gold salt be dissolved first, or added from a separate solution. A white or pale yellow sludge of sulfur that forms is a normal product of the interaction of thiourea and gold; the more con- centrated the solution, and the higher the mixing temperature, the more rapidly it forms. The sludge is harmless, but Henn advises that the solution stand overnight before use and the sludge be filtered off to prevent residue on treated film. Based on the fact that silver coverage on the surfaces of microfilm images is about 70 mg of silver/ft 2 , Henn estimates that the quantity of gold required for effective gold protective surface layering would be on the order of eight mg/ft 2 . Tests confirm that a concentration of eight or ten mg of gold/ft 2 is a quite reasonable working level. The gold protective solution may be applied as an in-process treatment in the case of new films, or as a post-process treatment for old films. The quantity of gold absorbed, and the level of protec- tion imparted, are similar in both cases. Because the gold protective process is subject to certain variables, it is important that a simple method for analysis of gold content be evolved. Henn recommends the following procedure: com- pare two samples of film having identical densi- ties (a) before gold treatment, and (b) after gold treatment. Bleach samples in dichromate solution (Kodak Bleaching Bath R-9 is recommended) for 60 seconds or twice the time required to bleach. Rinse, then clear (Kodak Clearing Bath CB-1). Wash briefly, dry. Read the density values of both samples. In the case of the sample which has not been gold-treated, a silver sulfide residue will be present. The gold-treated sample will have addi- tional density proportional to gold content. Sub- tract the density value of the untreated image from that of the treated image. The difference in the two densities is an estimate of the quantity of gold present in the gold-treated sample. Henn notes a linear relationship of 0.01 density unit corresponding to one mg of gold/ft 2 . A density of 0.21 corresponds to the aim level of ten mg /ft 2 . 8 Henn notes that some evidence of residual reac- tivity, as determined by the Crabtree-Ross test, may exist in images following gold treatment. The source of this turbidity is undetermined. Such residual activity may be largely overcome by sub- jecting gold-treated film to an alkaline reducing bath. A formaldehyde bath appears to be the most effective treatment in conjunction with the gold protective process because it not only eliminates residual reactivity but introduces needed harden- ing as well. Also, the formaldehyde treatment offers improved resistance to peroxide attack. There is also some evidence that the gold-plus- formaldehyde treatment imparts added resistance to fungus growth. 8 Costs of gold treatment are contingent upon the cost of material handling (installation and main- tenance of processing machinery such as treat- ment tanks, dryers, etc. plus actual handling costs), and the cost of chemicals. Whereas no accurate estimation for the first cate- gory is possible, chemical costs roughly equate to one cent per foot of treated film. Based on the work of Henn and his associates, the gold protective treatment, in conjunction with a formaldehyde hardening treatment, can be recommended as an effective method of prevent- ing microspot formation, protecting against oxi- dant and fungal attack, and insuring archival permanence of film images. IMAGE STRIPPING This technique seeks to preserve the original image layer from early nitrate films, by transfer- ring it— in its entirety— to a new support. Two techniques are possible. The first seeks to preserve the same “wind” (or emulsion position) as the original; the second reverses the emulsion position. With the first technique, the original film is first conditioned and repitched to a per- foration as close to conventional standards as possible; then it is bonded, emulsion down, to a traveling, pinned belt. This initial bond would be a temporary one, reversible by temperature. As soon as the bond is secure, solvents are applied to the exposed nitrate base. The dissolution of the nitrate base would be either (1) softened to the extent necessary to break the sub-bond between the base and the emulsion, or (2) totally dissolved and washed away. Either alternative is feasible— experience should dictate the choice. In the case of the first alternative, when the sub-bond is broken, the original base could be lifted from the image, leaving the image bonded to the belt. After proper preparation (i.e., wash- ing, resubbing, etc.), a new, previously perforated polyester base would be brought into contact with the image layer. The two would be sealed to- gether by a thermosetting adhesive, or five per- cent gelatin subbing layer. The process would be completed by eliminating the adhesive bond be- tween the image layer and the pinned belt, then washing and drying the “new” film package. The second technique, resulting in a product with reversed emulsion position, would commence with conditioning and repitching the original material. When properly prepared, the original is 44 registered to a traveling, pinned belt, emulsion up. A new polyester base, previously prepared with an optically acceptable thermosetting adhe- sive, is registered, adhesive down, upon the ori- ginal film. Both heat and pressure set the adhe- sive bond between the old image layer and the new base. The two bonded films are now stripped from the pinned belt and passed through a solvent bath, which dissolves the old nitrate base and leaves the image affixed to the polyester base. The pro- cess is terminated by a final wash and drying stage. Neither of the above processes have been actually accomplished; however, the theory of image strip- ping has been pursued throughout the various discussions of this survey in an attempt to dis- cover, before laboratory research begins, whether or not there may be standing reasons why such a proposal would not work. In almost all cases, interviewed researchers in the field have upheld the basic theory, but caution that the work would be of a critical and tedious nature. Because of the critical character of the work, it is felt that the second technique would be prefer- able. This process considerably reduces the num- ber of steps through which films must pass, thereby reducing the possibility of damage to a minimum. All archivists interviewed have stated that they would be prepared to accept an original with a reversed wind, knowing that the new ver- sion retained the original image on the best avail- able archival base. 7 C.S. Neblette, Photography: Its Materials and Pro- cesses, ( New Jersey, 1962), 6th ed., p. 251 . 2 A. Lumiere, L. Lumiere, and A. Seyewetz, British Journal of Photography, Vol. 71, (1924), p. 172. 3 American National Standard Specifications for Pho- tographic Film for Archival Records, Silver-Gelatin type, Polyester Base (ANSI PHI .41-1973) Appendix A, p. 14. 4 American National Standard, Methylene Blue Method for Measuring thiosulphate and Silver Densi- tometric Method for Measuring Residual Chemicals in Films, Plates, and Papers, (ANSI PH4. 8-1971) Forward, p. 4. $Edith Weyde, “A Simple Test to Identify Gases FUJI PHOTO FILM CO., LTD. (This part of the conversation with Shuichi Ogura, Tadashi Nagae, and Shigeru Morishita at Fuji has been placed here because of its discussion of gold substitution treatments.) Do you know of any after-treatments, besides the gold substitution procedure, that would make film impervious to its storage environment? F: There is another method you may know called the “Sodium Sulfide” method. S: For image toning? F: Yes. But it seems that only the most careful conditions under which this treatment is given will improve the image quality. On a practical level, the gold substitution method is best. S: Have you used the gold substitution system? F: Oh, yes. Two years ago, at the World’s Fair in Osaka. At that time, we made “time capsules” which were intended to be preserved for 1 ,000 years. They asked us to prepare several microfilms that would last this length of time. We did what we could, what was possible. We used the gold treatment on these films. But nobody knows what will happen because no one will live until he is 1 ,000 years old! One proposal discussed at this time concerned a copper etching process. This might be better than gold toning of usual photographic film. To do this, you start with a thin, transparent base which you coat with a thin copper layer (plate): then coat the copper with a photo-resist. After expo- sure, you develop the image and etch the copper with nitric acid. After careful soaking, the image Which Destroy Silver Images,” Photographic Science and Engineering, Vol. 16, No. 4 (July - August, 1972), p. 283. 6r.W. Henn and D.G. Wiest, ‘‘Microscopic Spots in Processed Microfilm,” Photographic Science and Engineering, Vol. 7, No. 5 (September - October, 1963), p. 257. 7r.W. Henn and D.G. Weist, “ Properties of Gold- treated Microfilm Images, “Photographic Science and Engineering, Vol. 10, No. 1 (January-February, 1966), p. 15, 21, 260. 8 R. W. Henn and Bernadette D. Mack, “ A Gold Pro- tective Treatment for Microfilm,” Photographic Sci- ence and Engineering, Vol. 9, No. 6 ( November - December, 1965), p. 380, 383. is left on the film as copper metal. In this case, the thickness of the copper is much greater than the thickness of silver in the usual photographic image. The copper will keep the image for a longer time, but in this process we cannot guarantee high resolution or make continuous tone. This is why the process was not used for the Osaka project. If the picture is only black- and-white, with no grey shades, and there is no need for high resolution, then this is a practical solution to the problem. S: Have you made this material? F: No, but it would be quite possible to make. S: As part of the gold treatment procedure, we have investigated the use of a formaldehyde after- hardening solution. Have you used this? F: We are not using the hardening method. When we considered the gold treatment, we did not think that the gelatin would be very much affected by age or by the gold treatment. S: We have a tremendous quantity of nitrate film. The procedure in the past has been to duplicate this onto conventional film material. My company has reason to believe that it might be possible to lift the emulsion from the nitrate base and to put it onto a polyester base. Have you ever done any experiments of this nature? F: We have experience with this sort of thing, but our experience has not been aimed at using it for archival purposes. Through our own experi- ments, especially for graphic arts applications, we accomplished this. S: Would you please discuss the procedures you used in stripping the film? F: Our procedure has been to “paste” the emulsion to glass, then remove the nitrate base by dissolving it in ether. We’ve done this, but it was a long time ago. We are all young men, and we don’t know about earlier work. If someone can make an automatic processing machine that could do the work, then it would be practical. Still, dissolving the nitrate base is a difficult task. Also, the very old emulsions have shrunken badly in some sections. This would make the work difficult to accomplish by an auto- matic machine. Especially keeping the image in register with the perforations. S: But you think that the theory is sound? F: The theory is alright. 45 E.I.DU PONT DE NEMOURS & COMPANY (This part of the discussion with Emery Meschter and David Woodward at Du Pont has been placed in this section because of its application to film aftertreatments.) W: For all practical purposes, polyester is completely satisfactory, unless you get into some archival problems where you’re talking about very long-term storage under cycling conditions. Here again, the gelatin, the emulsion, is the limitation, not the base. S: With respect to separation from the base or sheer distortion of the image? W: Yes, and migration of silver. Silver itself is not all that stable, particularly in film. M: For real permanence, I wonder whether you shouldn’t go to some kind of sulfiding or gold toning— at the beginning, and not depend on silver because it takes so little hypo to destroy silver. S: You’re the first person interviewed to even mention gold substitution after-treatments. M: That’s probably because I’m so old that I remember reading about it long ago. This used to be fashionable: gold toning, bromoil toning, all this kind of jazz. W: The first thing to do is to be sure that your processing is careful and that the film is thoroughly and carefully washed. Fresh fixer and a thorough wash after it’s fixed. Otherwise, you leave chemicals that will take away the image. S: While we’re on the subject of gold-substituted images, that reference was primarily from several articles in the SPSE that I think some Kodak people put out for protection against microspotting, oxide attack, and similar situations. Coupled with that is a formaldehyde hardener, with the two together operating supposedly in some form of super-combination. Have you done any work in this area? W: No, not really. That’s not a problem that ever bothered us. It’s people like you that are concerned with the problem. S: l now have a “loaded” question to ask you: one of the possibilities that we’ve been looking into is stripping the image off the nitrate base and transferring it to a polyester base— literally transferring the image. Have you done any work of this nature? What’s your attitude toward the possibility of making it work— from either a chemical or mechanical standpoint? M: There have been two or three: roto film is a stripping process. W: You’re talking about taking existing films, these archival films, and transferring them. I think that your chances of that are slim. M: Would you have to think about it in terms of actually dissolving away the nitrate? W: You’d have to break the bond between the emulsion and the nitrate. S: If you do your transferring first, and then dissolve the nitrate. . . This is the procedure we’ve been talking about: repitch the nitrate materials as closely as possible to a standard, then cement the emulsion to the new base. Sub it to the new base, and then literally either dissolve it away or else dissolve the sub. W: Dissolving away the whole thing I think would be your best chance because if you start fiddling around with the subber, you’re going to distort the emulsion. M: That emulsion is just so thin and so fragile. It probably isn’t over a tenth of a mil in a positive image. W: I think if you got the right polyester base with a good adhesive coating on it. . . There are commercially available adhesives. M: And this would have to be a thermal adhesive rather than a solvent because there would be no way for a solvent to get out. W: It could be a solvent adhesive applied dry. M: But you’ve got to get rid of the solvent before you put this nitrate layer on top of it because then this is what would make it seal. S: Right. I think a thermal adhesive of some sort would be dangerous. But do you think the concept of image stripping has potential? M: I think it would be worth looking at. I don’t know how fast you could do this. I’d hate to try to do this very fast, in terms of feet per minute. S: We’ve got to be able to mechanize it to a rate of about 200 to 250 feet per minute to be practical. Because that’s the ordinary printing rate. W: Dissolving the nitrate would be the slow step. If you’ve got the right kind of tape with adhesive on it, you could laminate it as fast as you want. M: You’d probably have a few little problems with trapped air and things of this sort. W: Yes, but the really slow thing is getting the nitrate dissolved. M: High energy jets, maybe? W: Pretty soluble. At least, fresh nitrate is. You’d have to look to make sure that the old nitrate hasn’t degraded in total length. M: Once you got it on, you could burn it off in sort of a flash fire. W: You know they do have processes for using nitrate, where they actually burn it off. Fairchild makes printing plates, with a little thin layer of nitrate and a stylus that goes across, and this actually heats it. The stylus gets hot and burns out the nitrate. S: It’s an idea. W: It works. But every once in awhile, it sticks and the whole thing goes “fssst.” S: At least they’re dealing with a small enough quantity that it’s not hazardous. That’s something that we’re definitely going to pursue. 46 Storage Conditions Effect of temperature on rate of conditioning of film (Single strip) 0 1 1 I I I I ill II 1 2 5 10 20 1 2 5 10 20 50 100 minutes hours TIME BLACK-AND-WHITE IMAGES ON ACETATE BASE Archivists seem to be in general agreement that black-and-white acetate-base films should be stored at about 50 to 60° F. and 55% RH, whereas scientists have recommended an optimum stor- age condition of less than 0° F. and 1 5 to 25% RH. However, these storage conditions would present difficulties in handling the film if it has to be taken out for either testing or use. A carefully controlled, time-consuming condition- ing process is necessary to achieve proper mois- ture/temperature balance when use environments are not identifical to storage environments. 16mm, 35mm, and 70mm rolls were evaluated to determine how long it would take these films to reach 100% moisture/temperature equilibrium. At a temperature of 70° F., a 16mm roll takes about two weeks to achieve equilibrium, a 35mm roll takes about five weeks, and a 70mm roll about 12 weeks. Obviously, such lengths of time are prohi- bitive for a working archive. COLOR IMAGES ON ACETATE BASE The problem of color film storage is severe. Tradi- tionally, photographic experts have stated that the best way to store color film information is to make black-and-white separation masters. This eliminates the danger of dye fading; on the other hand, it increases the cost of storage due to two factors: (1) the color negatives have to be trans- Effect of relative humidity upon the dye stability of a processed motion-picture negative film at 70° F. Density change determined from an original neutral density of 1.0. fered to separation masters, and (2) three reels of film must be stored instead of one. Further, all three masters must be stored at the same tem- perature and relative humidity to prevent varying amounts of shrinkage and curl between rolls — which would jeopardize the exacting registration essential to reconstituting a full color image. If the original color film material must be pre- served, various experts recommend that the film be moisture-conditioned to a relative humidity of between 15% and 30%, and then placed in her- metically sealed containers at temperatures of less than 0° F. As of 1970, no such containers are commercially available. A compromise is to store the color material in a vault at 35° F., 15 to 30% RH. This has the advan- tage of avoiding the need for sealed cans alto- gether, as well as diminishing the conditioning problems. (Test data on the suitable length of conditioning time could not be found.) The chief drawback is that maintenance of optimum storage conditions requires a rather expensive control system for temperature as well as humidity in the storage area. The control of humidity in the storage of color film is very important. Tests have shown that increasing relative humidity produces rapid changes in the stability of color dyes. Strips of color film have been subjected to two varying humidities at 70° F. Over a four-year period at Effect of width on rate of conditioning of motion picture film minutes hours days weeks TIME 47 60% RH, the density (determined from an original neutral density of 1.0) for blue changed from 0 (ND 1 .0) to -0.04, for green to -0.08, and for red to -0.12. The results for the same period at 40% RH were as follows: blue to -0.02, green to -0.04, and red to -0.08. These tests indicate that increased relative humidity has a detrimental effect upon the stability of color dyes in general and cyan dye in particular. A similar test was performed to evaluate the effect of temperature upon dyes, which confirmed that all dyes tended to fade with increased tem- perature. The cyan dye proved to be the least stable. The higher the temperature, the more acute the dye fading. BLACK-AND-WHITE IMAGES ON NITRATE BASE A primary problem with nitrate film is the emis- sion of nitrogen oxides. Nitrate film cannot be stored in hermetically sealed cans since gases cannot escape and will attack the emulsion and base immediately. Storing nitrate film in unsealed cans still does not solve the problem. Ventilation, per se, to remove the gases is not sufficiently adequate to prevent decomposition. Ideally, nitrate film should be stored at a tempera- ture as low as possible above actual freezing point: 33° to 40° F., with relative humidity con- stant at approximately 50%. This would however make immediate access to the films almost im- possible, and the construction of storage facili- ties extremely costly. Thus a compromise must be made. The major archives report that they store nitrate film at temperatures around 50° F., with relative humidity around 50%. Both values must be controlled very closely. In addition, a constant testing system to evaluate nitrate films for decomposition must be established in order to predict their future life span, or the advisability of immediate copying to safety materials. TESTING METHODS FOR NITRATE FILM In an evaluation of various testing methods used to predict the remaining lifespan of nitrate-base film * , two tests were found to be both conven- ient and reliable— the Alizarin Red Heat Test and the Micro-crucible test. *G.L. Hutchison, L. Ellis and S.A. Ashmore, “The Surveillance of Cinematograph Record Film During Storage, " Journal of Applied Chemistry, Vol. 8 (Jan- uary, 1958), pp. 24-34. The other testing procedures studied appeared to be either inaccurate— as in the case of the Abel Heat Test and tests for acidity, or too compli- cated-such as the Small Vessel Test (Semi- micro) and the Vacuum Stability Test. ALIZARIN RED HEAT TEST This test was simple to apply to a large number of small film samples, and yet was relatively accu- rate in predicting the film’s lifespan. Results of the test generally agreed with the age of the film samples, giving a range of times from 60 minutes and more for new film down to four minutes and less for older films. MICRO-CRUCIBLE TEST Results of this test correlated well with the results of the Alizarin Red Heat Test. It measures the weight loss of a punching of nitrate film after it has been heated, expressed as a percentage of the punching's original weight. RECOMMENDED PROCEDURES Hutchison, Ellis and Ashmore suggest the follow- ing procedures: After a critical visual examina- tion, the subject film should be given the Alizarin Red Heat Test, using not less than two punchings for two separate tests taken from the middle and the edge of the film. If both tests give a figure of 30 minutes or over, sentence the film for re- examination and retesting after one or two years. If under ten minutes, copy the film and destroy it. If either result is under 30 minutes, but not under ten minutes, submit a sample to the Micro- crucible Test. If the loss in weight after 168 hours is under ten percent, sentence for re-examination and retesting after six months. If the loss is ten percent or over, copy the film, and then destroy it. 48 National Film Board of Canada Montreal, Canada AS: Arnold Schieman S: Ralph Sargent Arnold Schieman is the Senior Technical Officer, and Chief of Laboratory Services at the National Film Board. Our first conversation was in Los Angeles, and was followed by a second talk at the Film Board's offices in Montreal. AS: Most of the archive material in Canada is not original. Unfortunately, there are no originals around, and therefore we are picking up prints as we can get them. Canada’s National Archives are responsible for Canadian film heritage— although we at the Canadian Film Board have an interest in preserving films. I think all of this material has got to be put on some kind of archival base support, whether or not it is by duping and getting the best quality from that, and/or, as you mentioned, by trying to strip the emulsion and lay it on another base support. That is an interesting idea to think about. S: I’d like to discuss that. You told me yester- day that you had not done this. That only theoret- ical work had been done. AS: Yes. When I was doing some early research on the possibility of stretching. I use the word “stretching” rather than “de-shrinking”— the makeup of nitrate film seemed such that the emulsion did not shrink. When you look at it, you find very little distortion. A good man who had written on this earlier was Kemp Niver. I think he really pioneered this approach. But, I had to satisfy myself, so I played with it. I believe I mentioned to you the Vacuumate treatment and the Peerless treatment and so on. A Vacuumate machine happens to be in our operation. Being a close friend of the man in New York who is responsible for this process, I decided I would spend some time to really find out what I could about nitrate. I had a roll at my disposal, and I did a fine job of messing it up. I found I could move the base support. S: In reference to the image? AS: Yes. S: Without distortion to the image? AS: Oh, yes— stretch distortion. This was what happened. Suddenly, outside the normal environment of the printing room, I would find that the base had almost moved back, within an hour, to its original state. So, it was very temporary, and I did not think that it was the answer. S: What technique were you using at that point? AS: I was using the Vacuumate chamber. Because his solutions are patented, I asked him if I could juggle the chemistry. Some of the alcohols I tried had higher melting points than the type he was using in his formula. Only recently, we have been engaged in comparing some notes, and hopefully, we will be able to negotiate some- thing. All the research in shrinkage has now swung over to acetate black-and-white. It is not a temporary treatment now. It might be called temporary, but the temporary period is not one hour or one week; rather, the minimum period is now six months. We expect it will go beyond that. The same man is also engaged with me in a process using a coating material. I developed the coating, which I laughingly call “Coca-cola;” it is actually what I call a refractive coating. It is not a lacquer; it does not peel. Lacquer tends to break and crack, etc. For example, at one time Disney lacquered his films for storage; when he brought them out, the lacquer had to be stripped. There is no stripping involved with the present process. You coat the base and emulsion. The results have been very successful. S: It is successful for protective purposes in that it will actually fill in scratches? AS: It will remove emulsion scratches and base scratches. However, it does not require the conventional type of propulsion wheels you have heard about where acetone is used to soften the base and melt out the scratches. Wet-gate was designed to try to remove base scratches. They think it removes some of the emulsion scratches, depending upon the type of spurious mark on the emulsion surface— whether or not it cuts a color. If it is color, I find that— if the scratch penetrates more than one layer, if for example, you have a blue scratch showing the red— you are not going to remove that under any wet treatment or refractive coating. But if the scratch or mark is a straight type, that is, when viewing it straight on you see a line, not a color, my treatment will remove that. Wet-gate will remove most of it, but not all of it. Refractive coating does some other things: when duplicating through an optical source— and I think an optical printer is almost essential for part of the transfer, even with 16mm film— the coating lowers the contrast. 49 I think that in the acetates and triacetates you should try to stretch; this will not destroy the image. I think what has happened in the shrinkage of the acetate types, both the emulsion and the base have shrunk together, whereas with nitrate, the emulsion has pretty much remained the same, as image size goes, even though the base might shrink appreciably. The image seems to slip on the base support. S: This is an observation on your part? Have you done any measurements to see whether or not this actually takes place? Is there any way of detecting whether or not this could be proved? AS: No, but listen to this: there is a Niver printer at Ohio State. Someone named Ron Smith, who has been lecturing there, has been doing some of the duplicating on that printer. The device does not use liquid gate. There is no cleaning up of the image. The film is moved by hand over a light box and registered visually, rather than by registration pins. I saw some results that might shock you. The pictures, when projected, were rock steady. There did not appear to be any spurious breakdown or distortions of the image. That was an observation. I tried to go back to Montreal and do the same thing, only this time, trying to stretch. There was no way of making a direct comparison with the material produced at Ohio State, unless I could get some of the same material and try to stretch it. S: But, this printer was primarily developed to shoot paper prints, was it not? AS: Yes, primarily. But now they are using it on nitrate material, using the light box. S: I should like to return to our discussion of stripping. We have been talking about it quite a bit because it seems that the problems of mechanizing such a process would not be as extreme as they have been made out to be. Our idea is this: using a polished drum, the original nitrate film is cemented, emulsion down, onto the drum. A solvent is then used to dissolve the nitrate base and flush it away. A new subber-puller material is then coated on the image, followed by a new polyester backing. The concept of the drum might be replaced with that of a device derived from the Technicolor IB printer— a pin-belt machine, which would obviate the problems of pitch and register. How do your ideas vary on this? AS: It all started with some early still materials our Archives had. These old stills were completely corkscrewed. I put them through the Vacuumate process, then sent them back to the Archives. The archivist there decided to rewash one of the pictures, but when he did this, the entire emulsion floated on top of the water, with the base sinking down below. His first thought at the time was that this could be applied to nitrate. S: He had released the subbing, then? AS: Yes. What probably happened was that in the Vacuumate process, the subbing was released; the water was just a means of washing it off. It just so happened that he didn’t have anything to lay the image on, because it was one of those old panoramic-type pieces of film. However, it was a second copy of something he had. I didn’t go any further on this because of the problems in Canada regarding fire regulations with respect to nitrate materials. But after you mentioned it, I began to think that perhaps it should be pursued. About the pin register process you mentioned: I wonder whether you should worry about registration of that part. Why not strip the emulsion, and lay it on unperforated mylar film or its equivalent. After it is laid on and set, perhaps it could be put on forms that could be easily molded, then perforated afterwards. S: Here’s another way of looking at it: throw out the idea of the drum and get a pin-belt machine that we could handle this material on, and literally cement directly to the polyester base. Sub the emulsion to that, and then apply a solvent which would knock off the nitrate base. You wouldn’t use a gelatin-type subbing material. You would choose some sort of subbing-puller in combination with the polyester base that would not be affected by the same stuff that the old subber is. Dissolve the base away, and registra- tion is taken care of— presuming that the material is at a reasonable pitch to start with. Of course, this is a false presumption in most cases; and yet, Technicolor has been doing pitching of material for years, especailly for the matrices because they have the ultimate problem with that sort of thing. Also, they have techniques for getting the material into proper registration within certain limits prior to the point where they go for transfer. Today, I would like to know if you are inclined to agree with us that nitrate stripping is possible, and whether you feel it should be pursued. AS: I think so. There is a lot of material that perhaps cannot be saved. Our Norman McLaren work, for example, is hand painted on nitrate film. Obviously, you’re not going to remove that. At some point, it is going to be gone. We are working on a program with the Canadian National Archives whereby the National Film Board is responsible for the processing of all dupe negatives, etc. A lot of this material requires an archival wash, which we are more qualified to do. S: How do you define “archival wash?” AS: We have a chemist who uses an analytical procedure. I think that the residual hypo is supposed to be .005 milligrams per square inch. We have extended one of our processes to include two additional washes. Although we could use hypo eliminators, we don’t at this point because water washes sufficiently. If we are running something through for the Archives in Ottawa, the first thing we do is put through a wedge of the material we are going to use, at the speed at which it will be processed. The chemist then analyzes these results. S: That’s a very quick test. Does he use the drop system with colormetric matching? AS: Yes. We feel it has to be done at the time of processing. It shouldn’t be left around for three or four days. In Washington, it may even be weeks before the material goes back to the lab, and before they start measuring it and so on. We feel it should be done immediately, within hours of processing. The second stage of the film, that is, the dupe negative, is obviously the archival copy that is going to be considered. From this, because of dollar problems in Canada, we produce a reduction print. I understand now that our National Archives is going to swing to Sony cassettes, made from the print which we will supply. They will make a reference copy. S: That will be what the public sees? AS: Yes. That’s one possibility. Another possi- bility is having the dupe negative made from the reduction print. The reduction reference may be 50 kept as a fairly good copy from which you can generate a number of prints. I think you could go to a Metro-Kalvar process. From the print, you could produce another negative which would be on Kalvar and eventually get all the references on Kalvar. S: Have you done that? AS: I am having a Kalvar printer/ processor installed in my place in January. S: A 135-16? AS: No, it’s going to be 16mm only. It has a new head called an “SAR” head— “Steady As a Rock.” There is one at Kalvar that is a prototype. I hope that in January we can give the Archives their first example and let them see its possibilities. We don’t have the printer now. We had one of the early ones. Greg Hoyt of Graphic Consultants had a large collection of 28mm films which he just sold to our public archives. He’s the Kalvar repre- sentative in Canada. There are a lot of things wrong with the printer. Kalvar has acquired the services of Jim Wassland, who used to be with Bell & Howell. He’s a printing man— knows sprockets, etc. With his expert help, I know there’s a lot we’ll be able to do. S: Can you tell me what problems and their solutions you have come across in the nitrate transfer business? AS: We think we’ve solved the problem with the optical printer. S: With tapered pins and the like? AS: Fortunately, we aren’t required to do any printing of nitrate in-house because of the wet- gate application which is now being done right on site at the Archives. Whether the same optical house will continue to do the printing remains to be seen. S: Are you using any continuous contact printing at all? AS: We did on material where it was reasonable. We still run most of our nitrate films on a contact printer, but we can't run them too fast. I have mixed feelings about this nitrate transfer thing. Some people think we should save nitrate in its original state; make dupes but keep the nitrate somewhere. It may last another 50 years. I believe that estimates put life expectancy of nitrate at about 50 years, and we’re running pretty close to that now. A lot of books are full of secret chemistries for treating film. I don’t want to say too much about the process I’m in the middle of right now; however, I will say that it will not be anything that is going to generate some kind of deterioration of the material. There are certainly enough things built into film itself that will take it away. If the film shrinks, what good is it to you? Should you put it on the shelf and let it lay there another ten years? Or should you try to do something now with the stretched copy? Even if you do keep the original around for another ten years in case someone does come up with something, at least you have something now that you can show. That’s the reason I’m going full- blast on this. In fact, we lost most of our library of nitrate in a big fire. S: What happened? AS: We don’t know what happened. Some kind of spontaneous combustion, perhaps. S: Was inadequate vaulting a factor? AS: The vault was not subdivided in the usual sense. Also, because of space considerations, a lot of the material that was on safety was de- stroyed with it. We’ve gone around the world, through letters and personal contact, picking up old newsreels and prints. We’ve produced substitutes from these, copying when necessary. Is that an area I should pursue? I feel I should. S: Do you have a fund set aside for this work? AS: At the Film Board, not as such. This year we have about $35,000 we can play with for old subjects on the shelf. Eventually, under the national film heritage policy for Canada, the public archives will be changed to a federal or national archives. They will be responsible for selecting all sorts of material. The Film Board will fit into the picture for some types of dupli- cation. Nitrate will be a separate program. How- ever, the funds on either side are just so small that we’re going to be years and years behind. Print from scratched negative before refractive coat- ing. Print from scratched negative after refractive coat- ing. 51 CONDITIONS IN THE FIELD Although widely separated geographically, the working archivists interviewed in the following pages all deal in similar situations, with much the same materials, and with many of the same problems. The general procedure in each meeting was to begin by presenting a copy of the specifications for the three archival media, and asking them for their comments. That discussion most usually led to a conversation on their day-to-day problems, and on to how those problems might be solved with new procedures, or new media. 52 National Film Archive London, England L: Ernest Lindgren, Curator S: Ralph Sargent L: Our brief is to preserve a selection of the film distributed or shown in this country irrespec- tive of its country of origin. To preserve what is either artistically or technically considered most important in contemporary judgement. Straight away, let me say that selection is imperfect— all selection is imperfect. There is only one way to be sure of preserving everything that the future is likely to need, and that is, to preserve everything. For financial reasons, this is impossible. I don’t know of any archive in the world that attempts to preserve every foot of film made for the cinema or television. So we must have a selection and that selection is handled by a committee. We are subjected to a further process of selection after we have made our own selection in that, under the voluntary system of deposit that we have here, we don't get all that we select or all that we ask for. This is something that we are hoping to remedy by acquiring powers of legal deposit such as are already enjoyed by books in the British Museum. S: Under copyright law? L: Not under copyright law in this country, under copyright law in your own country. We don’t have the registration of copyright for films in this country. We have in our copyright law an anonymous clause— which has no place in copyright law— requiring publishers to give copies of their books to the British Museum. We do not want a law requiring producers and distrib- utors to give copies of their films to the National Film Archive. S: Why not? L: Because I think that would be drawing the parallel between books and films too closely. Films are more expensive than books. A system of gift would not hurt the major companies very much, perhaps, but would certainly be injurious to the interests of smaller companies. Under a selection process, there would be unfairness between companies producing rubbish and perhaps making a lot of money out of it— and in which we are not interested. Also, other companies might consider that they were being penalized by being required to give films to our archive because they are producing films of such good quality. What we have tried to get is a statutory right to purchase the copies of those films that we want at laboratory cost. In order for this to be effective, of course, we must have money from the Govern- ment to purchase these prints. But I think this is a fair and proper way to accomplish the preserva- tion of film. S: What amount of money would this require? L: Right now, it amounts to about 300,000 Pounds a year. But I don’t think, either, that that is excessive to preserve a national collection of the best and most interesting historical examples of film and television shown in this country. After all, one can pay that for one painting. It only looks a little shocking because we haven’t had to pay it until this moment. If we had the right to purchase what we wanted, the film industry would be happier, I would think, feeling that they were not going to be required to donate copies. We would be free to order precisely what we regarded as being best for preservation. One of the weaknesses of the voluntary system is that the national collection has to take what is given to it. If we had money to buy what we wanted, rather than the statutory obligation of the producer or distributor to send us a copy, we could order what we wanted. In the case of a Technicolor picture, for example, we could have a set of separations which otherwise might not be made. At the present time, we are forced, in many cases, to accept good used prints, and I think it is criminal to spend public money on the preservation of copies which as far as the film industry is concerned are “throw-outs”— that they would not keep. S: Then, are you buying your own pictures right now? L: No, they are being donated when we request them, if the other party agrees. S: Like the Library of Congress, you are being forced to accept used prints? L: Yes. I think that it is regrettable that the Library of Congress collection is in a weaker position, it seems to me, than— by American law — it need be. As I understand their position, film producers, like book publishers, are required, when registering the copyright of a film, to deposit two copies with the copyright office. 53 Under a so-called "gentlemen’s agreement” between the Library and the producer, these two copies which are deposited for copyright registra- tion are handed back to the producer or distrib- utor in return for an understanding on his part that if the Library collection requires the film, the producer will give a good used copy. I think this is wrong. Under American law, the Library of Congress, as far as its obligations to posterity are concerned, comes off badly. What I’m saying is that you should start out with the best possible material. If you start out with less than the best possible material, to that extent, you are failing in the job of preservation. S: To extend that a bit further: there seems to be distinct philosophical differences in the approach that various archivists use in regard to their collections. I would appreciate an elaboration of your attitude regarding the use of the basic collection and how you choose material for circulation and distribution, either for scholarly purposes or for retrospective use. L: You are right in saying that archives vary in their attitudes toward their collections. They vary in their purposes, in their financial resources, in all sorts of ways. Many archives, for example, cater exclusively to the art of the film. Ever since we started in 1935, we have been concerned with acquiring two types of films. First of all, films which are important in the “film as art” form— of entertainment, of expression— films which are important in the development of the technique. On the other side, we have always been interested in films as contemporary historical records, for their content rather than their technique. We have always been interested in collecting newsreels, documentaries, and even acquiring fiction— feature films which we might have rejected as being comparatively unimportant — either reflecting some social sense of the time or social problems, or even being perhaps at the center of discussion or controversy— reasons extraneous to the film itself. Broadly speaking, it is true that the “film as art” area contains mostly fiction films, but not exclusively. So many documentaries, too, fit into that category. It is also broadly true that the part of our collection that we select for recording the life of our time is largely non-fiction, but not exclusively so. In this second area, we have to have the help of experts. In the selection and collection of important medical films, for example, we have to have the advice of doctors. We are also collecting anthropological films, with the advice of anthropologists. S: In 16mm or 35mm? L: Almost entirely in 35mm, very little in 16mm. We have always taken the view that while 35mm remains the standard of the industry, it is important that the archive standard should be 35mm. We do not want to be regarded as a substandard film library. Indeed, where a film was made on 35mm, we should have it on 35mm. Our interest in the motion picture as a record of contemporary history has led us invitably into the area of television. There are differences of opinion as to whether television is an art form or not. I'm not going to tell you on what side I stand! But of one thing there is no doubt, tele- vision is a very rich source of documentary motion pictures— far richer than the cinema ever was. This is why I say that we used to collect newsreels, but are now not so much interested. There is still one company making newsreels in the United Kingdom; however, the treatment of political subjects and so forth on television is so much fuller and richer than it ever was in a cinema newsreel so that our interest in collecting them has fallen off. However, not every archive is interested in television; but we are very interested indeed! We have a television selection committee. S: In what form do you receive your television materials? Are they on film or video tape? How do you handle them? L: We try to get them on film, wherever possible. S: 16mm or 35mm? L: 35mm. S: Is most of this shot on 35mm? L: If it was shot originally on 16mm, we would receive it on 16mm; but if we are having transfers made from video tape, for example, we transfer to 35mm film. In the early 60s, we were in some doubt as to what we should do about video tapes since we had no expertise on our own staff. We called a meeting of representatives of magnetic tape manufacturers, television engineers, and the like. They met under the chairmanship of our archive technical committee. We asked them, quite simply; “what should the National Film Archive do about video tape?” Although these people had somewhat of a vested interest in video tape, they nevertheless came to the unanimous conclusion that we should— wherever possible — transfer to motion picture film. They gave a number of reasons for this advice. One was that they could not foresee the future of video tape. They did not know how long it was going to last, or how it might be changed in the future. They could not look ahead further than another five or ten years, and they based their advice on that. They said that it was highly likely that methods of video tape recording being used at that time would change. If we preserve video tapes, we must have the video tape machines upon which to reproduce them, otherwise the tapes would be useless to us. We would have to employ a staff to look after these machines. If in a few years such machines became obsolete, we would have a big “white elephant” on our hands. They said also that if we stuck with film and had transfers made to film, we would then have a preservation material which, in their view, was more stable than video tape. Also, film transfers would be easier to refer to, and would form a more homogeneous part of the total collection. These were the reasons I remember. With respect to storage of video tape, they said that because of the hazards to which video tape would be subject both in storage and in playing, it would be necessary to have a master video tape which was never used except for making other video tapes to be used for viewing. This was felt to be unnecessarily cumbersome. By 1969, we thought that, in modern technical terms, a long time had passed so we decided to call this group together again to see if they had anything new to tell us. I should say “another” because the individuals in this group were different, although the same interests were invited. An ad hoc committee was called and we faced them with the conclusions of the earlier group eight years previous. We asked them what their views on the subject were, to date. 54 Basically, they confirmed the conclusions of the earlier group. However, they made an exception in the case of color material because color had been introduced subsequent to the earlier meeting. This second group recommended that in the case of black-and-white videotapes, we should continue to transfer to film. However, in the case of color— because the cost of transfer- ring to color film and the problems with getting accurate color reproductions are great— they advised us to preserve the original color video tape and to make an additional 16mm black-and- white reference print. We have followed this advice, to some extent. Of course, we are limited by finances. The archive has two arrangements. As you know, we have two forms of broadcasting in this country: commer- cial, or independent, and the BBC. The commer- cial companies, those under the Independent Broadcasting Authority, give us a sum of money each year to buy all their programs which we select. Three years ago, the sum was 10,000 Pounds a year, at which time we were selecting black-and- white material. Since color means increased costs, they increased the sum to 20,000 Pounds annually. For the first time, we have 20,000 Pounds, and I hope we shall get the same amount for the coming year. This enables us to make copies of all Independent Television productions we want, in the form we want. I’m sorry to say that the BBC is not so cooperative. This is partly due to the way the BBC is financed. ITV gets its money from adver- tisers. The BBC gets its money from the public through the Government in the form of iicense fees paid by the public. The BBC argue that this money is to provide an entertainment service and not to create an archive or to archive TV pro- grams. We think that their view is quite mistaken, and we hope to persuade them to change their minds about this. Guite apart from our own position in this, we consider that the BBC has a public responsibility for preserving those of its productions which are recorded and are of historical interest. Of course, the BBC could discharge this responsibility by having its own archive; but we believe that the most sensible thing, from the Government’s standpoint, would be to do what the Independent Television people are doing: that is, cooperating with the National Film Archive. This is the only preservation center supported by the Government which caters to all needs. If the BBC set up its own archive, it would have to duplicate many of the services which we already provide: storage vaults, technical procedures, and so on. A duplicated and divided national preser- vation service would be more costly and less efficient than a centralized one. S: How much nitrate material do you still have in storage? What are you transferring this to? L: We’ve got about 60,000 reels of nitrate film— 1 ,000-foot reels. Almost as much acetate: about 45,000 reels. S: Is the acetate of mixed types? L: Yes. Most of it was produced since 1950. Before 1951 , acetate was mainly restricted to sub- standard film, was it not? We started to copy onto acetate in 1942 or 1943, so we had a ten-year headstart. S: At what rate are you transferring your nitrate? L: I can only calculate this on the basis of how much money we spend per year. We spend about 42,000 Pounds per annum. That would mean we copy at the rate of about 1 ,000 reels per year. We store our nitrate at a place called Aston-Clinton, about 40 miles outside of London. Our acetate is stored at Berkhamstead. We keep the two collections separate. With respect to materials, we use Eastman 5234 for duplicate negatives. For Fine Grains, we use Eastman 5366. There are two kinds of sound reproduction: one is rerecording in which case we use 7375 or Gevaert ST 6 stock. For printed repro- duction, we use ordinary release positive material. We’re experimenting with two methods of color preservation. One is the preservation of color material in the form of black-and-white separations which enables us to reconstruct the color in some future time. In the meantime, we are concerned only with the storage of black-and- white material. The disadvantage of this method is that it takes up three times the amount of space. We do keep a number of color films in the form of color dye copies; and we therefore reserve one part of our acetate storage area, which is completely air-conditioned, for color. This section can be brought down to a temperature of -20° C. It is unlikely that we shall run it as low as that. There seems to be a difference of opinion on this. When we were designing the vaults, Kodak said that color materials should be kept at very low temperatures to avoid color fading. Whereas on the Continent, Agfa, for example, suggested that -4° C. would be sufficient. Mr. Volkmann of the FIAF Preservation Commission brought representatives from both sides together, and it now seems that Kodak’s original recommendation of -18° C. was based on theoretical considera- tions. We are now inclined to agree with practical experience that -4° C. is sufficient. We shall probably run our deep-freeze store at -4° C. or -5° C. I say “shall” because we have been held up on using this store by problems in the construc- tion of the conditioning chamber through which the film must be passed as it goes into or comes out of the store. This has presented problems. We have actually run the store at -20° C., but not for long periods. S: How do you handle conditioning? Under what conditions do you store color film? L: The film is rewound very slowly, and what will be controlled, I understand, is the humidity of the film. It will pass through a converted ordinary laboratory processing machine and the humidity will be adjusted. I have been waiting for this for about two years, and have yet to see it actually working. I’ve never seen it in actual operation, so the theory as it was originally explained to me has become a bit dim. S: Does it include the use of hermetically sealed cans? L: No. One is faced with two possibilities: either to condition the film and put it into a hermetically sealed can to maintain proper humidity and temperature conditions; or, to maintain conditions in the store. We maintain conditions in the store. We don’t hermetically seal the film cans. S: What about your testing procedures for nitrate? Are you happy with these tests? How do you go about determining the priority of your printing? 55 L: We've found no reason to be unhappy with our tests. They seem to work. Our main test, based on what I believe was originally an American procedure called the Crabtree Test, was adapted for us in this country by Kodak Research Laboratories and subsequently modified by our Government laboratory. The Government labora- tory has a representative on our committee and advises both ourselves and the Imperial War Museum on the preservation of our collections. The test consists of taking a small quarter-inch punching of the film and dropping this into a test tube. Each test tube is fitted with a glass stopper around which is wrapped a strip of prepared filter paper impregnated with Alizarin Red dye. This is moistened with a mixture of water and glycerin to make it more sensitive. It is then put into the interior chamber of an electric oven with a jacket of zylene which boils at 1 38° C. , giving us a temperature of 1 34° C. in the inner chamber. The action of the heat is to drive off the acid gases from the punching which bleaches the dyed paper. When the bleaching has proceeded a certain distance, a time reading is taken. In the original tests which Kodak devised for us, the indicator paper was litmus. The Government laboratory, together with other improvements, suggested the use of Alizarin Red. We find that if the paper is bleached within a quarter of an hour, then we can assume that the film is coming to the end of its life. If we want to continue preserving it, we must dupe it. If the bleaching occurs in a period of more than a half an hour, but less than an hour, we put it aside for retesting in two years’ time. If it is over one hour, we retest it in five years' time. In this way, all nitrate films in our collection are continually passing through this testing process. We keep a technical record card for each film on which results of the tests are entered. The cards are marked according to whether the film has to be duped or retested in two years or five years so that they can be picked out when the time for retesting comes. S: How large is your staff to do this testing? L: We have just about enough staff to get through it in two years’ time. But if we acquire much more nitrate film, then we should increase our staff to handle the load. It’s a fairly simple test. The ovens can take 20 or 30 tubes at one time. The test operator prepares a number of tests and then puts them in the ovens. As the papers bleach, he notes the time. The total of tests takes an hour. The test papers that we use are made from ordin- ary filter paper impregnated by our own techni- cians with Alizarin Red dye on quite large sheets. The sheets are hung up to dry. Then, the large sheets are cut into strips of a suitable size. S: Would you consider the possibility of using a machine that would automate this type of test and perhaps allow you to go at a higher rate with the same number of personnel? L: Yes. S: Have you ever thought of having such a machine designed? L: No. One difficulty would be changing systems. It’s rather like starting a catalogue using a certain system, with thousands and thousands of volumes or films catalogued, and then deciding to change the system! With the test results of all our nitrate films recorded under this system, changing it would cause problems. S: If the results read out in exactly the same way, the only difference being that the test was handled mechanically rather than by hand, would it then be considered reasonable? L: Yes. I only meant to say that because of the difficulty of changing over to a new system, there hasn’t been any great incentive. If a new system were offered to us and it resulted in economies in manpower and time, we would welcome it. It would then no doubt be worth making the change-over. S: Have you used any other tests prior to this one? L: No. When a film comes into the archive, it is examined physically on a rewind and the condi- tion of the film is very carefully described. Apart from this visual inspection, the only test then carried out is the stability test. The only other test we have is carried out on newly processed film: a test for residual hypo. This is the FIAF hypo spot test. A quarter-inch punching of the film is taken and cemented onto a clear base, then put on a dark background. A small drop of test liquid is placed on the sample, and the tester then looks for signs of milkiness in the test drop. If milkiness appears, this indicates that there is residual hypo. S: Is this, then a different test than what we would normally consider a residual hypo test in the United States? L: Let me quote from the FIAF Preservation Report. On page 47, item number 7.342, it reads: It often occurs, however, that the film has been properly fixed, but not sufficiently washed after- wards. In this case a residue of the fixing salt (sodium thiosulphate, also called hypo) is left in the emulsion. This, like other sulphur com- pounds, will in time bleach the image. It is therefore recommended that new films, as they are acquired, should be tested for the presence of any hypo in the emulsion. The test is as follows: In a test tube a solution is made up of mercuric chloride 25 gms potassium bromide 25 gms water to 1 litre Into this solution is put a piece of film (one frame of negative, two or three frames of positive, because of the difference in thickness of the emulsion layer), cut into strips of a suitable size. With even a very low content of hypo (0.05 mg . ) the solution quickly turns milky and turbid. The degree of turbidity depends upon the amount of hypo in the emulsion. It is also possible to cement a punching of film (base down) on to a piece of plain acetate base. When it is dry this piece of film is laid down on the black background and a drop of the above- mentioned solution is placed on the punching of the film to be tested. If hypo is present, the drop becomes turbid within three minutes. This method has the advantage that the film does not need to be cut. Whichever method is used, when the mercuric chloride solution becomes turbid this is an indi- cation that the film must be thoroughly rewashed. There is no exact rule for the duration of this washing, but a minimum of half-an-hour is generally considered necessary. 56 The test merely indicates that there is some residual hypo. If we find this, we send the film back to the laboratory for rewashing. S: I’d like to return to our discussion of the philosophies of film archives regarding their conceptualization of the material they hold. When you get a roll of film from someone, what happens to it? L: If we have only one copy of the film, what- ever that copy is, whether it is a master or whether it is a projection print, we regard it as a master copy. For us, it is a preservation copy and this original is never allowed to be used for pro- jection— not even by our own staff. Very excep- tionally, we might allow it to be run on a table viewer of some kind, but we would regret having to do that. We act on a principle laid down for us by the British Kinematograph Society in 1934 that a copy of a film being preserved should never be used for projection, but only as a master copy for making duplicates for projection. This means that duplicates would have to be made if the film were to be projected, viewable duplicates— whether 35mm or 16mm. We are limited in making these prints by lack of money. If the collection were in ideal condition, then we would have a collection of preserved masters which had never been projected, and a complete collection of viewing prints of these same films for anyone to view. Then, the total archive collec- tion would be viewable by any bonafide researcher or student wishing to study them. Shortage of money makes this impossible. As a result, I know that we have been the subject of some criticism in this country amongst the enthusiasts who would like to get their hands on our films and view them. They accuse us of sitting on a collection of films which we are not willing to let people see. This is simply not true. We want to make this collection as viewable as we can, but we want money for acguisition of films and we want money for the business of preservation. We just haven’t got enough for everything. Being limited, we have always thought it was right to put the emphasis on preservation. If one has preserved a film, then it is potentially always viewable; if one has the money, he can make copies. But if a film is lost, or allowed to deteriorate, this can be irreversible. We therefore accept the view laid down for us by the British Kinematograph Society. It’s not worth wearing out preservation copies just for the fun of viewing them, simply because you haven't got the money to make copies. S: If it were possible to remove the image layer from nitrate film and re-cement it to a new base, would you employ such a process? L: Yes, we would employ any process which preserved the original image and in no way marred that image, allowing us to preserve it intact. We have, from time to time, been urged by commercial interests to employ some process which has been developed either to improve the quality of projection prints or to extend their life. Processes which involve softening the emulsion and perhaps passing the film through rollers in order to fill in scratches have come to our attention. We have always been advised by our technical people to be on guard against such processes. I think you will find the same advice repeated in Mr. Volkmann’s report. If you take an original negative which has scratches on it, a process of this kind may in fact enable some scratches to be filled in; but at the same time, softening or flattening of the emulsion may result in an over-all loss of defini- tion in the picture as a whole. For this reason, we have always been suspicious of these processes, especially those which involve the use of chemicals which the proprietors claim are secret and therefore refuse to divulge. We are quite shy about this because we conceive our responsibility to be taking a film as it comes into our hands in the best form we can get it and continuing to preserve it in that form— not tampering with it. Therefore, if you asked if we would be willing to accept a process which transferred the emulsion from nitrate to another base thereby improving its preservation prospects and increasing its life, I would personally say “yes”— provided that we were assured that what was transferred was kept intact, without loss. If there would be any loss, we’d be against it. S: Once you’ve made a dupe of some nitrate you have chosen to duplicate, do you then destroy that nitrate or maintain it as long as you possibly can? L: No, we destroy it. S: In essence, then, there will be some point in the future when there simply will be no nitrate around? L: That’s right. We shall abandon our nitrate vault at Aston-Clinton, and it will become an acetate store. But this is 20 or 30 years away. S: What are your storage conditions for nitrate? L: Here, I must be historical. At the outbreak of the War in September, 1939, we had a much smaller collection than we have at the moment. It was stored here in the center of London just a few streets from here. When war was declared, the Government immediately issued an order that all inflammable material, and all nitrate film in particular, must be moved out of London at once. So, all the film companies were engaged in a mad scramble to locate places outside of London where they could put their films. We found a temporary home in Sussex, south of London. It was a big stable. Next door was British Movietone News, with Paramount News Film across the street. This was clearly unsatis- factory, so we immediately set about to find something more permanent. It was then, at the beginning of 1940, that we found this site in Aston-Clinton. Not only was our film collection much smaller then, but we had very little money. The archive had been in existence only five years. We found a piece of ground which had a house in front and out-buildings around three sides of the grounds. We moved a caretaker into the house, and we built our nitrate vaults in blocks of twelve, under- neath these out-buildings. Later, still during the War, we bought a piece of ground next door which was once an orchard. Here, we built two new blocks of vaults and also a workroom. The whole thing was a wartime improvision done on very little money and against the wartime diffi- culties of getting material and labor. These facilities have served their purpose. They have enabled us to keep nitrate film under good conditions. The store is not air-conditioned, but 57 the temperature is thermostatically controlled. The stores are heated by tubular electric heaters; in the old stores, there are underground heaters. In both cases, they are thermostatically con- trolled. The buildings themselves are painted white to reflect heat in the summer. In these fairly simple ways, we are able to maintain a temperature throughout the year of between 55° F. and 60° F.— really very steady. We make thermograph records of the temperature, and the graphs are an absolute straight line. The humidity is high. Sometimes, it’s up to about 80% R.H., but of course, it may drop down to about 55% . However, the stores have served their purpose. We had to find a site for our acetate film, and Aston-Clinton was full. We found a piece of ground which is much nearer to London, eight miles nearer. This was a different proposition altogether. At Berkhamstead, we found a very large piece of ground, five and a half acres, with a large house upon it that had fifteen rooms. In 1968, we built a corridor off the house which leads to four acetate stores. At the beginning of this year, 1972, we built four more stores, so we have eight alto- gether, with the exact same capacity as our nitrate store. The acetate vaults are fully air-con- ditioned; one of them is able to run at -20° C. In our workrooms, we do a certain amount of printing. Mainly, this is printing badly shrunken film with which the laboratories cannot cope. Harold Brown has developed a step printer, and copies have been produced on it. As part of the extension to the workroom, we have built four new printing rooms, and we have acquired one printer, and we have another printer on the way. We shall do more and more of our own printing. One reason for this is that the laboratories are becoming increasingly disinclined to handle nitrate material. I think that we will be forced to do it all ourselves. We still send the film out for processing, but we do the printing ourselves. S: What sort of device do you use to measure shrinkage? L: A device we built ourselves. The film is engaged on two teeth, and at a certain number of frames away, the film is engaged on an additional set of teeth. The difference between what the film shows on the gauge and what the standard should be, shows up on a dial gauge and indicates the amount of shrinkage over the length of film. S: What do you consider to be the life of the materials you are now producing? L: I don’t know. I can only judge from labora- tory tests on stability which were made when acetate was first used commercially. These tests showed a curve going along a horizontal path very much longer than a similar curve for nitrate film. What this curve means in terms of years of life, I don’t know. I don’t know that anyone does. In our experience, nitrate film which has been processed well originally and kept under reasonably good conditions can last 50 or 60 years. I should think that the acetate copies we are making right now should last 100 years, or even 250 years. I really don’t know. The assump- tion is that they will last a good deal longer. At the moment, this seems to me to be a basic procedure in order to keep what you’ve got as long as you can— which is what we’ve been doing with nitrate. Then copying, and hopefully copying onto something which is very much better and will last a good deal longer. For us, now this is acetate. When the time comes to copy that acetate, there will be something better still. The intervals between copying should extend over longer and longer periods. It is very much hoped that this will happen because so far, every stage of copying has resulted in a slight loss. It is our hope, as an archivist’s article of faith, that by going this route, copies will eventually be made that will enable film that we now know to be preserved for hundreds and thousands of years. Are you going to produce the material which will enable us to do this? S: It is premature to say. L: I find this an immensely exciting prospect because one of the difficulties any archivist has to face at the moment is the fact that so much of what he is holding is almost comtemporary. It hasn’t yet acquired the veneration of age. This was very forcibly brought home to me when we asked one of our most distinguished historians, Professor Trevelyan, to write the introduction to our first newsreel catalogue. He agreed to do so, but said he’d like to see some of the early news- reels first. We arranged a viewing for him in our theatre. I went back as far as I could. I went back to newsreels of 1896 and 1897 in order to impress the old man. When the lights went up at the end of the screening, there was a silence. He said he was interested, but he asked, “Tell me, what year did you say that particular newsreel was?” “1896,” I said very proudly. “Ah yes,” he said “that was my first year up at Cambridge as an undergraduate.” For him, all this was contemporary material! The boys who are really going to have the most fun are our successors who, in some hundreds of years time, can show film— very full film records, hopefully— of events that go back 700 years. L: Our television film officer says that we have bought quite a number of videotapes, and they are stored in the acetate store under the same conditions as acetate film. This acquisition is comparatively new; we’ve only had them a year or so. I’m perfectly sure that for reasons of staff shortage, that they are just left on the shelf. Whether or not that is the right thing to do, I’m not sure. I’m sure that this is what happens to them. We have no videotape machine which will reproduce, so we have no way of testing them. I would like to say something more about our nitrate stability tests. For us, these tests are a fire safety measure. It helps to insure that we are detecting and eliminating from our collection material which might be liable to spontaneous combustion. It might be of some interest for you to know that in the making of viewing duplicates, we are exploring the use of videotape. We have a recording machine at our storage vaults. We also have two viewers now fitted with television-type screens. This is very experimental and explora- tory. We don’t know how much use of this we are going to make, but it has occurred to us that there will be different types of users of the archive. 58 Some people will want to see only certain films, i.e., there will be considerable demand for partic- ular titles in which case it is justified to make optical copies however expensive that may be. There are other films, however, that will be viewed only occasionally. It has occurred to us that we could put these on videotape for viewing purposes, then wipe the tape and use it again. Although, I understand that the possibilities of using videotape are not quite so great as it is popularly supposed. However, this may be a convenient method of viewing. L: Let me say in conclusion that hearing about your own explorations makes me want to say how important I believe all this to be. I believe that the moving picture is a new kind of language, an extension of human communication similar to such extensions in the past as the invention of writing and the invention of painting— this capacity to record pictures and to transmit across time. We are concerned here with time. I am not sure that the importance of this is fully recognized. One has only to look back on the written and printed word. The invention of writing marks the change of pre-history to history. The fact that people could write things and record them provided a kind of race memory which did not exist before. One also has to remember that this would not have operated unless what had been written, and later what was printed, was preserved. It is a fact that manuscripts preserved in monastic libraries gave the written word a permanence which made it really valuable and extended immensely its usefulness and contribu- tion to culture. I am sure that the same will be true of the moving picture. 59 Cinematheque Royale de Belgique Brussels, Belgium L: Jacques Ledoux, Curator S: Ralph Sargent S: Let me ask you about your vaults. What sort of materials do you store? L: 35mm, 16mm, 17V2mm, 28mm, and a little 70mm. Mainly 35mm. S: How much of that is nitrate? L: Between 40,000 and 50,000 reels of 1000 feet each. S: Do you presently have a program to check these for decomposition? L: Unfortunately not. Not an organized one. It has only begun to trouble me. I was quite arro- gant in the last few years because, in the 30 years of our archive’s existence, we never had any decomposition in our vaults— not a single film. Until last year! Last year, for the first time, we had a copy of “The Lost Weekend” suddenly decompose. It was very sudden. I know because we had shown the film only a year before. It was not a film that had been stored for 30 years without projection. I think that it was on Du Pont stock. It was completely decomposed— just powder. We had a similar thing happen this year with two very old newsreels made in 1917 about World War I. These two newsreels were never really touched, so I can not guarantee when they decomposed. So lately I have begun to worry about the decom- position problem. Even though we are a small archive, and a poor one compared to others, we installed humidity controls at a very early date— 1949. It took me the first five years of my stay with the archive to get these controls— but I succeeded. Our main nitrate vault is underground; it was an air raid shelter which, after the war, was trans- ferred to us. It is made of concrete and was quite humid when we took it over. We did not care about the temperature, since, inside the vault, it only varies between 9 and 14° C. This variation depends on the season, but in any case is extremely slow. We knew that this was not an ideal situation, but were assured that the real problem was one of constancy of temperature. There should not be any sudden changes— that would be more important, perhaps, than lower temperatures. We had no means for doing it any other way. From the humidity standpoint, the vault has remained between 50 and 55% since 1949— nearly 25 years. Up until last year we had no decomposition. S: What about new vaults? L: We have built a new vault because the first one is too small, and we continue to receive nitrate. We found an old fortification (18th Century) with walls two and one-half meters thick —quite isolated— in a town near Brussels, called Namur. It is part of The Citadel. We received it almost free of charge. It had been abandoned for a long time. Although the exterior walls were standing, a good deal of reconstruction had to be done. We have built separate cells for the film. One of the defects of our vaults in Brussels is that the film is not subdivided into small, safe amounts. The present vault is one big room. This is extremely dangerous. At Namur, for safety, we have provided two doors into each cell. One permits entry from the interior of the building, and the other provides entry from the street. At the moment we have finished three cells. The work was finished in June or July. We have installed machinery to control the humidity, not the temperature, but temperature control will be added shortly. We will go to 10° C. I know that the FIAF Preservation Manual recommends lower, but on the other hand Kodak recommends 10° C. If you have to choose between a lower humidity or a lower temperature, what choice do you recommend? It seems like the kind of choice where you ask yourself, “will I lose my left foot or my right foot?” This is the kind of compromise we have to make. Or must we have both? The lowest we can go is 50% RH and 10° C. — because of finances. At the moment we have no hope of keeping color. I don’t think any archive has any serious hopes of keeping color (for any truly archival period)— not at this time. S: What about videotape? Do you keep any videotape? L: No, we do not have the chance. It is not a choice. We do not receive any videotape. There is no production of videotape except for television, and for the moment we have no agreements with the television stations, except for films— movies, etc. 60 S: What are your opinions about the FIAF recommendations? L: For me, the FIAF recommendations are not the Bible! I think that my impression may be a bit silly, but I think that it is more or less realistic. You can make a recommendation for the ulti- mately perfect vaults and condition, presuming that the individual archives can afford them. But what about the archive that cannot? I think that FIAF should give three recommenda- tions, in order of capability: (1 ) the perfect solu- tion; (2) the moderately compromised solution (for example, lower temperature or lower humid- ity); (3) the severely compromised solution— for the archive on a very restricted budget! If you do not make these recommendations, every archivist does what he thinks is best— which may not always be the best thing. S: Have you had any problems with fungus? L: You will remember that the building at Namur is two and a half centuries old. We have refinished the interior of the cells and installed humidity control equipment. We are removing the humidity, but not very rapidly. We have massive amounts of fungus. Our humidity problem is aggravated during rain storms because we have not finished completely caulking the building. Also, when the humidity control equipment cycles, the vault humidity goes up. It will take a long time for the vaults to dry out. We have only recently reached 60% RH. S: What was it before you started the equip- ment? L: Oh, 100% RH. But, by the time we are finished it will be at 50% RH. S: How are you handling the fungus problem? L: We have not had it before; we are waiting to see what will happen. This is a new venture for us. For the moment, it should be enough to brush the fungus off the walls, but what will come after that, we do not know. For the moment we have not put any film into these new vaults. We will have someone advise us on this. The fungus that is in there may only be able to survive in a very high humidity, I think. After a certain time, there should not be any more fungus. I’m not saying that it is not a problem, but that we will just have to wait and see. It is my impression that fungus cannot grow in a humidity of 50% . S: As Secretary-General of FIAF, how do you sum up your impression of the operation of the various archives? L: It is easy to list the archives that a re not doing things properly. Do not misunderstand me, I’m happy to welcome you to Brussels, but to tell you that we do not have enough money to do this or that is probably the answer that you have been getting everywhere. In the Socialist countries the archives are very strictly bound to the general rules of the various governments regarding the priority of their work. Hence it is less difficult for them to get money for their work. I know that the problems for the archives is the same in the Socialist countries as it is in the West— just seen from a different point of view. They may not have a problem with money, but they do have a problem getting supplies and materials. For example, I once had the idea that all the archives should install a Telex— or that we should have a universal computer-coordinated general catalogue. But the problem is that when you come to Moscow, you cannot have a terminal! Gosfilmofond could not buy an IBM terminal for the computer or an ITT terminal for the Telex! We finally come to the same point. We do not have as much money as they do, but still we can do things that they cannot do. I can, for example, buy a small machine for humidity control because they are available everywhere in the West, but in Rumania they cannot get one because they cannot be imported! S: I understand. It’s an interesting point. How do they interpret the FIAF reports? L: Experts from Moscow have participated in the writing of the black-and-white report, and are participating in the preparation of the color report. As you can see, one can be a scientist advising the use of certain things, even if you have problems in getting them. I am not saying that it is impossible to do or get something, just very difficult. I saw a machine at Gosfilmofond which rejuvenated film and I wanted to buy one like it. That was three years ago; I am still trying to find the price and conditions of delivery. I talked to our colleagues in Moscow— who were more than willing to help me— but they said that they were absolutely powerless, that the matter was in the hands of another department. Finally, I found the organization that was in charge and they told me that the model was no longer being produced. They had a better model of whose existence I had not even been told! They said that the machine was not ready for export. All I wanted was information about one machine— just the cost and a date when it would be available! This problem is just as severe for those working within the Soviet Union, also. If Gosfilmofond goes to that same department for a machine that was not written into the plan as a necessity, the department will not construct the machine Gosfil- mofond needs! This is the situation in all the Socialist countries. S: How do you store safety film? L: Nitrate film is the “minority” of our collec- tion. We have a great deal more acetate film than nitrate film. We cannot afford to do for acetate what little we are doing for nitrate, because we have so much more money tied up in rental of vault space for acetate. We have a new vault, located near here, which we have just rented. It’s area is 1 ,000 square meters. We will install air-conditioning, but all we can afford is 70° F.— perhaps a little less than that: 68° F., at 50-55% RH. If we go below that tem- perature, to 60° , 55 or 50, the cost would rise enormously— especially for the volume of film we have. The present total is about four or five thousand cubic meters. We have a list of things that we will need to buy this year. We do not have the money yet, but everything we need must be written down in advance, if we want to get the money from the Government. 61 We are operating our Brussels nitrate vault at between 9 and 1 4° C. We plan to install a machine to limit the temperature to 10° at 50% RH shortly. This will cost $1 ,400. For our new vault to be maintained at 68° F. and 54% will cost between $7,000 and $8,000, which may be nothing to you, but for us is quite high. If we want to go below that, it will cost three times as much. As the costs rise, other problems must be consid- ered. You have to go much more deeply into the problems of the archives. For example: I am not sure that all the archives have the same problem, but I know that there are some who must raise the question, “how are we acquiring films, and what kind of films are we acquiring?” In our case we answer the question this way: Belgium is not a production country; it is very seldom that we receive negatives. There are very few original negatives in this country because there are very few films made in Belgium. What this archive is mainly preserving are either films of which we made a copy from a negative obtained somewhere else or used distri- bution prints which we receive in many different ways, in varying conditions. I will give two examples: in this country, Fox and MGM came together to save money. They share an office. They found that they did not have enough space to store all the prints they had. This archive did not have an agreement with MGM, but it did have one with Fox. Fox asked to deposit with us 200 or more titles, some of which they were continuing to distribute on a very limited basis. They wanted us to keep the films, but if they had a request, they reserved the right to come to us and get the film they needed. We agreed to this for the reason that this is our main source of acquisition. Most people who think that they will deposit films and use them from time to time, never do and years pass without the films being used. In the case of Fox, it was different because they were really using their films. But I know that this will not go on forever, and that for the majority of films, there will be no request by Fox. Eventually this collection will become permanent. There are used copies, some in very bad condition, some quite new. We are taking a chance by taking everything, figuring that it is better to have one bad copy of a film than nothing. This is one case. The other case concerns a French company called Pathe which disappeared as a distribution company about ten years ago. They refused to hand over copies to us; instead of that they put their films with another distribution company called “Belgarde” which has a kind of vault located in a garden. That was until a few months ago. Then they ran out of space, so they gave us hundreds of titles. In the garden, the films had been preserved without any type of temperature or humidity control whatsoever. The cans had become so rusted you could not even read the titles! These films have to be washed, cleaned, and checked to see if they are complete— but we cannot do all this work rapidly, because we do not have enough people. We are an old archive, but an archive that is old and poor is not in a good position. Our philosophy has been to keep everything possible and hope that perhaps a time will come when there will be enough money and personnel to check all these things, and to junk those of no value. . . the Archivist’s Dream! Then we face the question of whether we should spend so much money keeping films of whose value we are not sure. There are many questions about archives which must be answered before we come to the purpose of your visit— questions that really have nothing to do with preservation problems per se. London, for example, refuses to do business as we do. They will not accept any films which the donor might call back. Once they are given films, the films cannot be taken back. They have no real problem of transferring nitrate to acetate because every year they receive something like 40 or 50,000 Pounds for printing. I have told them that they are printing from prints which I know are bad. Better copies could be found in Berlin or New York— wonderful prints of the same film! So I ask, “why are you spending your money duping films which are incomplete or inferior in quality?” Lindgren’s answer to this is sound. He says that the cost of bringing in copies from other archives and comparing them with his own would be higher than duping the prints he has. So it is not easy to talk about a good system for preserving films in an archive unless you consider the whole process of selection and so on. The case only applies if you have the original negative; then there is no problem. You must keep the original negative in the best condition possible if the film is a masterpiece— and everything possible should be done to preserve masterpieces! But this is only a small percentage of the archive’s problems. When I visited John Kuiper in Washington, his staff said that they were reproducing the sound track on a separate film and they would never make combined or composite dupes because it was better to keep the picture and track separately. They also said that they would never make 16mm prints, etc. About two years later, they were doing all of these things because the amount of film they had to deal with was so tremendous! When we have to dupe a film, we make a com- posite print. The only thing that we are duping more or less carefully are Belgian films because we know that no one else will keep Belgian films. We have to do this, because we are in Belgium. We do not make any selection on the basis of quality. We are rerecording the soundtracks for these Belgian productions. But for films of other countries, we are comparing a lot of copies of the same film. We select the best footage from each and make up a spliced version of the whole film. For example, in some of the color films, one section of color might not be as good as another. We select the best parts from each print of the film and assemble the final version from these parts. We are doing this all the time. I do not know of any other archive that is doing this type of work. I chose this as an impor- tant priority; another archive might not. S: Do you periodically run the films that you store? L: Yes, but only in our own theater. We are not a lending archive. S: What do you do when a scholar comes to the Archive and wishes to see a particular film? L: We have table viewers— four of them, and we let the scholars use these. The tables are made by Prevost and are modified in three ways: (1) two blowers— one on the lamp and one on the film. The lamp can be lit for one hour and shine on the nitrate film for this period without burning the film; (2) for shrunken film we can remove the 62 normal sprockets and put on sprockets that will pass two percent shrunken film; (3) dimmers on the lamp to allow for compensation of uneven print density. S: Is there anything that you would like to add, summing up your position? L: When you ask me what we are doing for safety films, I can only say that we are doing quite little. As I told you, the film is kept at 70° F., 50% RH. On the other hand, if we should have to install something more costly, we will have to go to a process of selection of films that should be kept permanently— those of greater value than others. Now, we just do not know. We are constantly receiving films, and we are con- stantly making new and better copies, especially of those films that are of the most importance. We must come to a system of grading the films— most important, less important, not very impor- tant, etc. Not only based on the quality, but on the state of the film. I mean, an important film in what we might call “State I” or best quality, must be preserved better than any dupes we might have. And so on. All of this, however, takes personnel. We are very short of personnel. It is very nice to design a system, but you need the people to make it work. We do not even have a catalogue of films. We have a kind of system that we have been looking into, because we just could not continue the way we had been going. Last year we hired a girl to begin cataloguing the films; next year there will be four. We brought in, from foreign archives and foreign producers, films that we had in our own vaults— which was really stupid. I used to know all the films that we had in our archive, but now I’m completely lost. There are just too many films coming in. I think that if you really want to get a picture of the work of an archive, you cannot limit yourself strictly to preservation aspects. This is why I have talked about our side problems— you cannot disconnect them. There are problems which simply concern preservation, but if you want to know the difficulties faced by archivists, you have to be aware of all related problems. Temperature and humidity charts from the Brussels Nitrate Vault. Temperature and humidity charts from the Brussels Safety Vault. Nederlands Filmmuseum Amsterdam, The Netherlands V: Jan de Vaal, Curator S: Ralph Sargent Koningshof ( King's Court) 20 kilometers from Amsterdam in the middle of a green area of a small wood is Nederlands Filmmuseum’s Technical De- partment. V: In my opinion, in the United States at the moment, there is, after too long a period of silence, activity— such as the Library of Congress and the attempts of The American Film Institute, together with other institutions such as the Museum of Modern Art, and the Eastman House— that in my country doesn’t exist. I’m not talking about technical problems; I’m just talking about th eidea that material has to be preserved. S: Do you have trouble with funds? V: Terrible. You mentioned Phillips: Phillips is interested only in Phillips. Shell is interested only in Shell. They gave us 1,000 Guilders, but that’s all. About $300. And don’t forget that the only countries where the idea of preservation already existed for a long time were the Socialist countries. America has gone far in this respect also. Because all these institutions are interested— either the small Museum of Modern Art or the great Library of Congress— it’s going on. Maybe they have quarrels and nervous contacts, but they are talking about feature films, documents, etc. and the preservation of these wonderful materials. They are talking about keeping history in good shape. But here, we only have the Government, and the Government has helped us, but still our level is very poor. S: What does your archive consist of? V: Feature films, documentaries, newsreels. S: Do you maintain any nitrate storage? V: Yes, too much. In percentages, nearly 70% . S: Can you give me a rough idea of how many reels that is? V: No, but I can tell you in meters. It’s about eight and one-half million meters. S: And of course, the vast majority of that is black-and-white? V: Black-and-white. I must not think of color at the moment. The only thing we have achieved, with the help of the Government over a five year period, is the building of the film vault— accord- ing to the new “laws” of FIAF. I myself started with the others at the first meetings of the Preser- vation Committee, then gave it over to those people technically concerned. I must say that I am very grateful for this attempt. It is, of course, ridiculous to say to the Govern- ment, “here is a more or less definite plan. We absolutely ought to do this because otherwise we can’t work and the material will be destroyed.” That happened six years ago— after talk, talk, talk. Finally, five years ago, we got the first very small grant. This went on but we could only finish it by taking money out of our own budget every year to build this damn film vault— which is a small one. But still, it is our pride. S: It is not finished yet? V: It’s finished, but we haven’t stored any films in it yet because, as you probably know, when the building is first finished, it is still wet inside. We are now waiting for the moment when we have the right temperature and the right humidity. S: Where do you store your films now? V: That’s a funny story. A real film vault didn’t exist in our country. They had, of course, what they called film vaults, but they were warehouses or magazines. Just before World War II, the Government made impressive, very up-to-date vaults for pieces of art: paintings, etc. One of these was near the village of Castricun, which is about 30 kilometers from Amsterdam. During the War, the Rembrandts, the Vermeers, and the van Goghs were stored in this vault. At the end of 1942, the Germans, who were already in our country as you know, came to the two directors who were keeping an eye on that vault. One was a director of the State museum, the Rembrandt House; and the other was the director of the Museum of Modern Art. They had a little wooden house near the vault, where they lived. They would take turns for a few weeks at a time. They were very serious about this. The Germans told them to get out. They didn’t want the treasures, they just wanted the place. They wanted to rebuild it as a launching pad to shoot the V-ls and the V-2s to England. With great trouble, the two directors managed to transport these paintings to the South of our country. After World War II, they gave it up and we got it. It was quite damaged; the inside was nothing. I still have the vault. S: What sort of temperature and humidity control did it have? 64 V: The temperature is between 11° and14°C. It has a beautiful relative humidity of 55% to 58% . The new vault will have a temperature of 0° to 5° C. And of course, a relative humidity of 55% —which is extremely difficult to reach, and expensive, I assure you. We measure weight in tons, so the new vault will have space for seven times five equals 35 tons. This has already cost us 500,000 Guilders, which is— for us— an enormous amount. When you see the film vaults of East Berlin, you will call us “little animals,” but for us it’s really something great. S: Is this new vault strictly for nitrate? V: Yes, absolutely. As soon as I can get rid of the nitrate by the plan we are going to set up now— a five or ten-year plan to save the whole lot— we hope to use the vault for color. S: What technique do you intend to use to dupe this nitrate material? V: With the very little budget we have, espe- cially since so much of it is going for building the film vault, we first of all preserve Dutch material, of course: feature films as well as documentaries. Documentaries for example, about the terrible treatment of Jews in our country during the War; documentaries about the crisis years during the 1930s— these are the types of things we do. We can really only do these when we can send these materials to a lab. This means, of course, that we have people working on the films, restoring them by hand, cleaning them. Then comes the final point which is to take the film to the lab and request a duplicate negative and a master, etc. There is a surplus of material of that kind which we simply cannot handle yet — because it includes shrunken material, and the like. S: What do you do about material like that? V: Speaking quite frankly, we hope to have the help of The American Film Institute. Like Jacques Ledoux is doing, we are now trying to have our own printing machinery, which is very old appara- tus, reformed into a suitable printer. We’re doing that now, but not with much success yet. However, we’ve got to do it now, or the job will become impossible. S: Because of shrinkage? V: Not only that, but also because of the fact that there is only one lab in Holland which accepts nitrate film; all the other labs say that they can’t do it— because of insurance, and because they would have to invest lots of money in the project— money they would rather put into color film processing. S: They feel that such an assignment would endanger their operations? V: Oh yes. A lab in the Hague with which I have done some work was quite frank. They told me that unless I could give them a definite order, every year, for 50,000 Guilders, they wouldn’t be interested. They have too much money invested in color processing, and nitrate material to them is just too dangerous and too difficult to handle. S: Now you have to put in your own facilities. Do you have the money for it? V: No, we don’t have the money. S: What are you going to do? V: Fight for it, from the Government. Every month, we submit requests, have meetings, invite Government people to listen, send reports. Now there is a little bit more hope. There is a move- ment going on in our country. Representatives of the various municipalities— various cities and towns in our country— have come to the conclu- sion that their local archives are not far enough ahead by merely keeping papers. They also realize that it is a very difficult thing to hold celluloid material. So they have now formed a group and have held several meetings. The results of this were recommendations to the Ministry of Culture and to the Ministry of Science and Education that there should be a central film storage depository, and that the Nederlands Filmmuseum should direct it. There is, in our country as in yours, a National Archive Institute and that institute in our country never, never, never looked after film — but realizes now that as a document of importance, film is undeniable; they must do something with it. They also realize that it is impossible to have nitrate material in their beautiful buildings next to very old precious paper documents. They have asked for a study committee, which has now been formed, with the Governmental groups responsible for this, i.e., the Ministry of Culture, which subsidizes the Filmmuseum, together with the Foundation for Film and Science. The Foun- dation is located in the city of Utrecht, and protects the scientific films to be used in univer- sities. They have a great documentary department and are very interested in film as a document. So, on both sides, something will be done. S: Are you starting to store any television materials— or have you had any requests to store them? V: No. This is also a point that we’ve brought before these committees— that we want to have the help of the television companies. What few programs we have stored have been gotten by chasing after the television people and asking them. They usually say OK, but we must pay the lab costs. S: Do you archive films from other countries? V: Yes, we store the normal Italian, English, and American films as far as we can get them, but we call them reference copies. We are not going to preserve them. An American film has to be preserved by Americans. However, there are exceptions. To give you an example, I heard that the Filmmuseum was the only institution in the world in possession of a copy of Mary Pickford’s “Cinderella.” In this case, we would certainly try to save this film because it is so fragile that we could not transport it. That’s the only thing we can do. We have many films from Italy, but no money for preservation. S: How are you handling paper materials? Are they being stored with the regular national archive materials? V: You mean the stills? The stills— about 900,000 that we have— are stored in Amsterdam. The rarest of them are immediately used to make dupe negatives. If a particular picture is requested and we have to make a negative, the customer pays for the negative. We do have an interesting collection of film posters and therefore, these items are given special attention. Basically we follow FIAF’s system for preserving the posters; but we have already discovered some mistakes in FIAF’s recommendations with respect to preservation of paper. Still, we are in “No-where Land.” We want to do it together with the Museum of Modern Art and the State Museum. I think we have to give an order to a scientific institution to go on with this research because it really is a great problem. 65 S: What do you do about scholarly use of your film materials? Do you have film scholars asking to see specific films? If so, how do you let them see these films? V: First, I have to tell you that by the end of December, this whole building will be ours. We’ve only been here about six months. Before that, we were situated in the Museum of Modern Art which is five minutes from here. In the Museum, people were nice to us, but we did not have enough space. We still have the auditorium of the Museum which we use as our film projection room. Next year, we hope to have our film theater in this building. As the situation stands now, when a film scholar, writer, or film critic wants to see a specific film, there are two possibilities: they can see it in our projection room at the Museum, or if the film is rather fragile, they can see it in our Technical Department, near the film vaults. We use Stenbecks at the Technical Department; seven total. We love them. S: Since you are limited by money, am I correct in assuming that when a request comes in to see a specific film, you are usually forced to let the scholar look at the original of that film, rather than a copy? To put this more simply: do you have a reference library of your holdings— on safety film? V: Yes we have one, but in many cases, because of our critical financial situation, we don’t have projection copies. In those cases, we are happy to say that we have the material saved, rescued— on dupe negatives— but we use then the original nitrate material for study. We wait a long period of time before we discard any nitrate material. S: Of whose manufacture are the materials that you use for duplicating? V: We use mostly American material: Kodak. We are not so fond of Agfa-Gevaert. Their material is greyish and has not got the brilliance of other materials. It is strange that with the merger of Agfa and Gevaert there hasn’t been any observable change in the films. It’s the same with color. You have beautiful examples of American color film — also in 16mm. I can’t say that of Ferrania or Agfa. S: What do you do about testing or inspecting nitrate for aging? V: We don’t. You must have at least one man totally dedicated to that kind of work, and he can only do a couple of films in a certain length of time. We went to England and asked for studies on the BFI testing system. We have copied them and we have still two or three of these beautiful pieces of equipment— they really work; but, we can’t afford to run them. We tested various films and the results showed that this and this reel— four reels, let’s say— absolutely have to be done within half a year. But then, we don’t have the money. So what can we do about them? S: Did you go back, half a year later, and look at those reels? Were they still there? V: They had disintegrated. But before that, we reported our findings to all the people concerned so they knew that they were working on a murder. S: In other archives, I’ve heard of tests being done and the results not tallying with the actual facts of the case. The film will test that it should be printed within six months, and it is still there five years later. V: We’ve had one beautiful example of the opposite. A collaborator of ours once phoned me from the Technical Department to report that he had found a newsreel— Eisenstein visiting Holland in 1929. I was, of course, very enthusi- astic and knew we had to do something. He told me not to worry because we had tested it and the results were fine. Because it was such an inter- esting item, we decided to dupe it anyway. It was a small reel, 200 meters of 35mm film. So we have beautiful copies and there is also a copy in Moscow now. However, after one year, the original was gone completely. Aging test apparatus for nitrate film at the Nether- lands Fiimmuseum. 66 Cineteca Nazionale CENTRO SPERIMENTALE Dl CINEMATOGRAFIA Rome, Italy M: Fausto Montesanti, Curator S: Ralph Sargent M: Of the problems involved in storage and preservation of the two kinds of films, the problem with nitrate material is the most dramatic for film searchers and librarians like myself. Ace- tate is a problem, in some measure, for future generations, because most of the recent prints are not the responsibility of archivists. These ace- tate films are newer productions of the last 20 years, from 1950 on. The biggest problem is how to store and preserve nitrate films. Each film library has to find the best storage conditions for its films. My personal opinion is that the best way to preserve these films is to dupe every nitrate film. The only way to make this possible is to devote large sums of money to duping nitrate films. Even this is temporary. Nitrate films are very dangerous to themselves and the people handling them. For that reason, I repeat, the immediate problem for film libraries is to dupe all nitrate films. It is the only solution as far as I’m concerned. I’m an old man; I’m leaving from this world soon. But I’m leaving with my heart in pieces because I can’t obtain the necessary funds to dupe everything we have. We have a big col- lection of Italian silent films, but no money to dupe them. S: Where does your money come from? M: The Government. S: How much nitrate are you storing right now? M: Oh, we have a lot. We have a five-block house, a very large one. If you are interested, I can show you. We try to store nitrate film in our library in the best possible way, but we are limited by funds. S: What sort of temperature and humidity control system do you use? M: We have no temperature control at all. No money or personnel to institute such a thing. We have only one control. When it is necessary to dupe a film for research reasons or for some cultural activity, we control the film then. S: How do you mean “control?” M: If the film is not destroyed, if it is possible for the print laboratory to make a dupe— this is the only possible control. We have limited personnel in our film library, and none are specialists in this kind of work. We don’t have any chemists, either. S: Then you don’t have any routine method of testing the film for aging or hypo? M: You mean tests like in London? I know what you mean, but we don’t do it. It’s impossible because such a thing takes quite an organization of researchers and personnel. It is impossible for us because of lack of personnel and funds. S: Do you have your own laboratory here? M: No. When we make prints, we have them made in a commercial film laboratory. This was my dream: to have my own laboratory here at the library, my own staff of researchers— to conduct tests as they do in London; but it’s impossible. Under present conditions, particularly here in Italy, the study and research into the history of the movies is not officially considered culturally important. I think it is impossible to have a laboratory here. I am very skeptical that it will ever be possible in Italy to have scholars study on film viewers like in London. At this moment, we have a cultural crisis here in Italy concerning the interest of the younger generation in old films. This is a real problem for film libraries. Young people are not interested in the old films. Only a few people in the universi- ties, some professors engaged in research, such as archeological work— very, very few. The young are interested in Bunuel, Goddard, Losey, Pasolini, Bertolucci— the new ones. There has been a cultural revolution in the last few years which has influenced our work as film librarians. I’m an old-fashioned man and I am saddened and disappointed by this state of affairs in terms of my work. In the last 25 years, I have tried to collect every old film I found on the market, but for what? Maybe when I take them from the boxes, I will find that they are destroyed. Some- times I keep them for better identification, etc. Yes, I have many sad surprises when I find the film destroyed. S: Do you have a lot of decomposition? M: Yes, we have decomposition of old prints and spontaneous combustion fires. Two times we’ve had that. We lost a lot of film— in some cases, 30 films. Here, I’ll draw our vaults for you. Each one is like a cellar, and when we have a fire in one, VOOM! We lose everything in that cellar. 67 S: I’d like to see your vault construction. M: Maybe all my work will be unusable. There is “double talk,” I should tell you. One is tech- nical and the other is cultural. The first one de- pends on the latter. The technical work depends on the cultural work. If the public is not inter- ested in our cultural action like a film library, it is impossible to obtain money for our work on old films. S: Do you ever have public screenings of old films? M: Yes, sometimes. S: Doesn't that generate enough interest? M: No, because the new generation in general isn't interested at the moment. Some years ago, cultural activity was much stronger. Although in the provinces, there is still some public interest. In the big cities where the young people are in a revolutionary mood, the old films are not ac- cepted. The strange thing is that everywhere else in the world I see a very great revival of the Past- in the United States, in England, and in France, but not in Italy. I don’t know why. You have so many magazines about old films, classic films, the old Wild West films— I was very surprised. I receive them all. I’m passionate about this type of work, but I’m one of the few. (The following discussion takes place on location at the vaults. ) S: Are those cans specially made? M: Yes, we make special cans. S: Do you use cores? M: We do in many cases, but not in this case for some reason. We have these cans specially made, but they are not hermetically sealed so the gas can escape. S: Would you say that you’ve run out of stor- age space? M: We wil eventually have more. There will be six vaults, but now there are only five. This is only for nitrate, and it’s very, very full. S: Each cell measures four feet by ten feet. There are two sides to each cell. There are 40 cells on each side of a compartment. When were these built? M: In different years . . . one by one. One was destroyed. The first one was not very good. We began another series of vaults 15 years after. There are five vaults, each with six compartments; 80 storage cells in each compartment. S: Do you have any form of measurement of the temperature swing in the vaults? M: The temperature is regulated by this type of glass, from the circulation of air. We have one for each block house— a temperature recorder. This end vault is impossible to use because of fire hazard. Too near the wall of our compound. S: Which vault burned? M: This one; we remade it. It now has an auto- matic fire alarm. This type of storage for nitrate material is about the best we have. It is not ideal. S: About the only thing the vault doesn’t seem to have is air-conditioning. M: We can’t regulate the circulation of air. It’s a sad situation. (On location at the acetate storage area. ) M: We have no more places. This is the last one we made for storage of nitrate materials. S: How well does your color hold up? Do you have color fading? M: We have only color positive materials, no negatives. Some dupes, inter-negatives, but not originals. I know it's not ideal. Under these con- ditions, I know that in the future this material will decompose. Our problem is money. Hundreds of silent prints will decompose sometime. Again, I say that the best storage system is to dupe. And to destroy the originals. I’m sorry I speak English so badly because there are things I would like to tell you. S: Go ahead and say it in Italian. M: (Italian translation) I repeat, the biggest problem is finances. Trying to convince the authorities to preserve these materials is a hard job. It’s important to preserve them, if for nothing else, as documents of an era. Even if the film is not artistically valid, it is nevertheless important to preserve it as a document of the time in which it was made. If, in 100 or 200 years, films of the 20th century can by found, they would be im- mensely valuable. They would be important for posterity. If we were to discover films of the 17th century, they would be important to us— for instance, a picture of Napoleon, if they had had motion pictures during his time. Even if a film isn’t good artistically, it deserves to be saved for posterity. We can’t really choose, do you think? Or let me ask you: do you think it is necessary to select certain films of the past for storage, or is it necessary to store everything? S: Most archivists feel that it is necessary to choose because there are just too many films to store all of them. Every archive that I’ve visited does have some kind of selection committee that goes through and decides what stays and what goes. They often decide what is to be duped. And if something is to be duped, they decide whether or not the nitrate original should be saved. Usu- ally, there are two committees: one to decide what new materials should be invited for storage in the vault; and the other to decide what old materials should stay, and whether they should stay on safety, or safety and nitrate. M: Maybe the problem of preservation of old materials in the possession of every archive in the world is a problem that would interest UNESCO— the preservation of documents of our civilization, our century. If the archives throughout the world haven’t got the money, maybe UNESCO could find the money and take action to preserve the old films. For example, if the Italian archive has no money to dupe all Italian films of the 1910s and the 1920s, perhaps UNESCO would be interested in the task. S: Have you ever suggested this to anyone at the United Nations? M: No, never. It’s just an idea. Only a big organization with international power can be interested in supplying the funds to save this cultural heritage. It is an urgent problem, because these films are decomposing now. I realize that Technicolor and the newer films are also a problem, but the preservation of nitrate films is the most urgent problem. S: What about your connection with FIAF? If you have an important film that is decomposing, isn’t there some arrangement you can make through FIAF to have it duped? 68 M: Between film libraries, you mean? Perhaps this is a way. But we have hundreds of films! We need big money. Fora program of some years, I think we would need 200,000,000 Lire a year— for a five-year program, let’s say. Our film library gets 50,000,000 Lire a year, and that’s for all our activities, including stipends for the staff. The archive employs ten people. So, from this allow- ance, we can use only a few million Lire for prints and dupes; about two-thirds of it goes for stipends and general expenses. I think that with 200,000,000 a year for five years, it would be possible to save all the nitrate. Without it, it’s the same as if it had already decomposed. It's diffi- cult in our country to convince the authorities of the importance of such a program. S: Do you meet every so often with the Govern- ment people? M: I, personally, do not. The directors, presi- dents and authorities of our Institute do. I am only a curator; I have no official functions. S: How long have you been working? Did you begin the archive? M: I have been here 25 years. When I came, I found exactly 32 films and a house. I now have 14,000 films. In the case of some titles, I have more than one film— negative, dupe, positive copies, etc. S: Are you responsible for searching out and selecting the films that comprise the total col- lection? M: Not completely. I was only a counselor. Engineers and authorities were called in. All the technical equipment was decided upon by the authorities, not the Institute. I have personally chosen many films— in ex- changes with other libraries, on the market, but a lot of films were here for legal deposit. We have a law governing the Italian cinema— not exactly a copyright law. The law says that each film pro- ducer must give one copy of the Italian produc- tion to the library. S: Is this a new law? M: It’s been in existence since 1949. In many cases, we have all the productions of Italian films from 1950 on. Until 1954, the films were on ni- trate. From the mid-1950s on, the law required that they be on acetate. Another law, passed in 1965, stipulates that when an Italian film receives an award from the Government — a cash award of so many million Lire for the producer, director, cameraman, etc. — we must be given a dupe of the film— not only a positive copy, but a negative as well. In the case of black-and-white, a regular dupe; with a color film, we get an inter-negative. We have color separations; the sound track and picture are separate— for the few films which re- ceive such an award. It is a gift to the library. We can print copies when we want. S: What sort of problems do you have with rights— duplicating materials in your collection? M: The problem of rights is not very important as far as the cultural activities of our film libarary are concerned because the Government allows the film library to exhibit any films, including the newer ones, for cultural reasons— and the owners do not protest. The law says that if a film is important from a cultural standpoint, we can show it to the public without payment. This is not only true in Italy, but abroad as well, with Italian cultural institutions in each country— such as an embassy. They are very active about showing films. We send them films by Fellini, Antonioni, Visconti— and many other films. S: When some other country asks for a partic- ular film, is the copy shipped to them from here? M: Yes, copies come from our archive because the production companies don’t always have available prints. Also, they are not always so interested in this type of activity. They are only interested in showing the newer films, like “Un Italia,” which is part of the Association of Italian Producers (ANICA). This Association is com- mitted to showing Italian films abroad— the more recent ones. The film library lends many from the 50s and the 60s. In some cases, the minister of our department can print copies of the newer films for the film library to use in cultural showings abroad. The Government finds the money to make these prints, but not to preserve the past! No one is interested in the past, except archeologists. They all say that the old films have been in the vaults for years and they will remain in the vaults for years to come. What they don’t realize is that in a few years, many of these films will have decomposed. In two centuries, all the films of our century will be lost. S: What you’re saying is that some new tech- nology will take over. Do you think that in the future, transparent film as we know it will not exist? M: I think not, but I don’t know when such changes will take place. I’m not an expert on technology. I do think that future film supports will not be like they are today. In the future, as production increases, how many feet will it take to store materials of one century or two cen- turies? The cinema has only been around since 1890, not even one century, and already we have so many problems! It will definitely be necessary to change film supports in the future. But to what, I don’t know. Perhaps videocassettes? These changes that must come are not part of the distant future, like George Orwell wrote about. The future, for us, has already begun. Film viewer in the Cineteca archives. 69 Notes On Observations: The Italian archive consisted of five major nitrate vaults, each with six compartments. In each compartment, there were 80 storage cells which had hinged, wooden doors— explosion relief doors. All the vaults were overloaded, and the explosion relief doors of each cell were pushed out beyond where they should be— affording no protection for an adjacent cell in the event of fire or explosion. Most of the cans in which films were stored were made of spun aluminum, de- signed in a manner which allowed gas exchange. There were also many steel cans— square and round types— which showed heavy signs of rust. The acetate storage area consisted of three large rooms, each with an undeterminable amount of film stored in it. Films were stored in untaped cans, a number of them steel— all of which showed severe rust. Each can had a label with title and number which corresponded to a card in the library index. 70 Staatliches Film Archive der D.D.R. Berlin, German Democratic Republic K: Wolfgang Klaue, Director S: Ralph Sargent K: We have decided on low temperature storage of color material, and we are preparing a new vault especially for this purpose. We don’t have it at the moment, but we will start construction on the new vault with a capacity for 800,000 tons of film material in 1974. Right now we are doing studies and other preparation work for the new building. It is very complicated and very expensive— much more so than traditional vaults with the temperature and humidity control levels suggested by the FIAF Preservation Com- mittee. Already many difficult problems have arisen. One of the first problems concerns the technical equipment for climatizing the vault. There is no international experience with low temperature and limited humidity storage. Low temperature is no problem; you have it with many other kinds of storage houses. However, in most of these cases, there is no problem with humidity. The problem with storage of color film is that you must have low temperatures and limited humidities (around 30% ). This creates all kinds of scientific and technical problems. We hope we will find a way to solve these problems— together with the Insti- tute of the Technical University— by next year. S: Given those conditions, what will the life expectancy of the films be? K: Nobody knows. There was no practical experience until now. There has been some the- oretical research done, but nothing practical. The basis of our decision is some experiments done in the Soviet Union with different kinds of color material and with different temperature and humidity levels. S: What sort of storage conditions, for example temperature, relative humidity, are you aiming for? K: The vault will have a temperature of -7° C. and a relative humidity of 30% , ± 5% . These were the recommendations of the FIAF Preserva- tion Committee. S: What are your vaults operating at right now? K: They operate at temperatures of + 6° C. , ± 2° C. and a relative humidity of 60% to 65% . S: Is this the recommendation for both safety and nitrate? K: Yes. S: Are you running routine tests to determine the condition of a film and its life expectancy? K: We do not do any aging tests. S: Why have you decided against them? K: Aging tests are useful only if you have the possibility of transferring the nitrate or acetate material. We do not have the capacity to do this. We had to decide on quite another principle for printing from nitrate to acetate. We have more nitrate material in our archive than capacity to store it. Our point of view was that we have to limit nitrate material to our capacity for storing it. We first had to work on selecting nitrate material that can be destroyed or transferred to acetate. Even this procedure of selection will last several years. You have to compare the different material you possess on one film. This is a long procedure which cannot be done only by measuring it on a rewinder. You must see the film. You must do both: check the technical quality of the film, and compare its content to determine which is the most complete version in the best technical condition. S: What type of equipment are you using for these comparisons? K: A special machine that we constructed in our archive. It is primitive, but it works. It is a double projector on a table. We have no other possibilities. There is no machinery for this purpose constructed in our country, and we have no possibility of importing any from western countries. It is too expensive because of currency problems. The archive has enough money, but our currency is not transferable. S: Do you use any equipment to rejuvenate the film? K: We use ultrasonic cleaners and a special machine based on the Debrie wet-gate printer. S: I am under the impression that there is a machine in the Soviet Union which is a descratching, cleaning, preserving machine. Are you familiar with this machine? K: No, I do not know the one you mean. They use different kinds of cleaning and washing machines before they bring the negatives into the vaults. We are not against using them, it is just that there is no available space in the archive to install such machinery. 71 S: Do you think that you will eventually install machinery of this kind? K: Yes, we will have such machinery when we construct new buildings, but this will be the next step in our development. S: What is the quantity of the nitrate you store? K: About 150,000 reels of nitrate. That is more than we have the capacity to store. S: How much acetate do you store? K: Much more. About 350,000 reels. S: Do these figures include color materials? K: Yes, including color. S: Is the bulk of it 35mm? K: Yes, most of it. As yet, I have run across none of the non-standard gauges. I would say that 95% of what we have is 35mm, but this will change very soon because we are getting more and more television material which is mostly 16mm. S: Are you storing videotape? K: Not at the moment. The present decision is to store videotape at the television station. How- ever, this is a temporary decision. It will change in the future, but not in the near future. Videotape is not used for permanent preservation at the moment; it is re-used for television purposes. S: What percentage of color television or color film materials are you asked to store? K: There is a considerable amount of color being done. In the cinema, it is about 70% to 80% , and in television, my personal estimate is between 20% and 30% . S: Have you run into any problems with respect to archiving color television materials? K: Of course, but for the moment we have to face only the problem of color film preservation- films coming from television. This will be the case until independent production of videotape material exists in Socialist countries. When this happens, videotape will also be used for permanent preservation. In our country, most of the videotapes are imported from foreign countries. Even though it is rather expensive, the decision is not to use it for permanent preservation. This will be the case for at least four or five years until such time as there is independent videotape production. S: Since you don’t have low temperature color storage right now, what procedures are you using for storage of color materials? Do you use color separations? K: No, we have not done color separations. In most Socialist countries, the answer would be “no.” We have neither the machinery nor the film material to make color separations. Most Socialist countries have decided on low tempera- ture storage as the means of preserving color materials. As we know from other archives in western countries, it is rather expensive to make color separations. No archive has enough money to do this solely for preservation purposes. In our case, we have so much to preserve— which is especially true for governmental, centralized archives— that to use color separation as an operating principle raises a lot of problems. Not only money problems but storage problems as well, because you have at least four times more material to preserve. S: Do you use any specialized after-treatments on black-and-white or color materials? K: No, but it is foreseen in the future. We do not have the capacity for it now— neither the manpower nor the space. S: Do you know of any specific changes in the recommendations of the FIAF Committee? K: Yes, there will be some changes with respect to the preservation of black-and-white acetate materials. Temperature levels will not be so strict; they are being relaxed. The first version said 6° C. This has been changed to about 1 0° C. to 13°C. However, there have been no changes in the humidity levels; the lower, the better. You should put this question to Mr.Volkmann. He can give you more details. S: Have you ever made any experiments on removing the silver image from the nitrate base and transferring it to an acetate or polyester base? K: No, we haven’t tried this. We have done some experiments on the restoration of the silver image of old film material. This was very suc- cessful. You will see some samples of what we did. S: What do you do about requests for exhibi- tion copies or scholarly use of your materials? K: We have a special fund for distribution materials which is given to cine-clubs and univer- sities. It is limited in number; it is used for regular circulation. In other cases such as study purposes, we use the archive material, the positive print. We do not give out nitrate material. We have very strict rules in our country on this; it is forbidden to use nitrate material outside the archive. It can be handled or projected only in the archive, or transported only by archive cars. Posi- tive prints are given to cine studios, television stations, universities because these materials are not unique. We circulate these positive prints only if we have the negative or duplicate negative of a film in the archive. S: Let’s say that you have an original nitrate positive print, and from it you have already made a safety dupe negative. If someone wanted to look at that film, would you let him look at the nitrate positive? K: He could look at the nitrate positive in the archive. But our tendency is to store only the amount of nitrate material that we can store under our conditions. That number is limited. Alto- gether, we have an over-all capacity for storing 120,000 reels of nitrate material. We have to limit our collection of nitrate material to this figure. This requires a selection procedure. Perhaps in one case, we will preserve this unique positive nitrate print, whereas in another case, we will destroy it and make a new acetate print. S: Are such decisions made by a selection committee? K: Yes. Within the archive, we have two internal selection committees: one for fiction films and one for non-fiction films. I choose responsible people such as the heads of two departments — the fiction film department and the non-fiction film department— and the cataloguers from these two departments and one other collaborator to serve on these committees. These 72 committees include film historians, archivists and cataloguers. This is the procedure for internal selection of materials that the archive holds, but not the pro- cedure for selection of material for acquisition. We have certain theoretical and practical guide- lines for our selections. Selection is not a subjec- tive decision; we try to make it as objective as possible. S: What are some of the rules governing selection? K: I cannot easily tell you because the system is very complicated and it differs for some of the key points such as the content of the film, the historical melieu of the film, the technical condition of the materials, etc. These are change- able. You have to collect experience and then change your principles. S: Is a film’s country of origin a determining factor as to whether it goes or whether it stays? In other words, does this archive tend to heavily stock materials made in this country first, and then materials from other countries? K: Yes. I think that this is the duty of each national archive: to take care of its national production. S: Do you tend to duplicate the archives in Moscow as far as materials manufactured in Socialist countries are concerned? K: No, there is no need to do this because there is such good collaboration between archives in Socialist countries, and also between the members of FIAF. There is no necessity to dupli- cate another archive. In most cases, the archive takes care of just the national production. Then they have specialized collections such as experimental films, abstract films, etc. First of all, I think it is right that the archive should first take care of national produc- tion, not only for fictional material, but non- fictional as well. S: In your acquisition, what procedures do you follow as far as actually getting a print made? Do you have the printing materials sent to you and then have prints made, or do you have them struck off in the particular countries of origin? K: The system that we use in our country is as follows: of each film distributed or shown in the cinema, we get one positive print of the best technical quality. After one year, or in some cases later, we get the negative materials of these films. Of course, we have to respect copyrights and contracts with foreign distributors or producers and in some cases, foreign distributors do not agree to the preservation of their film in our archive. In such a case, it is foreseen in the contract that we cannot make any archive mate- rials from these films. These are the principles for the cinema. For television, we have just started. The decision that there will be one central archive for films and television in our country is a rather new decision made only about one and a half or two years ago. There will be a selection of material from tele- vision, and it will be done by the television stations. S: I must plead ignorance here because I don’t know how your television system works. K: There is one central television station with two channels. A third channel will follow. There- fore, it is rather easy to make the selection of films which should be permanently preserved. Nevertheless, there are problems. Even with only two channels, much is produced and there must be a selection. It is impossible to collect every- thing. (The following discussion takes place on location at the vaults . ) K: We keep original negative material under the best conditions and we move all the positives to a provisional hall. S: Don’t you need to run this equipment when you’re working with negatives? K: Yes, it is necessary, but not at the time when you move the materials because if it works, you must have a climatization point when you take the films out of the vault and bring them upstairs. All the films you remove from the vault must be climatized to the outside temperature. But to remove large amounts of material, it is better to stop climatization so that all the films in the vault are climatized before you bring them out. The reason we did not continue with it is because the possibility for climatization is limited. You can bring about 200 reels for climatization in this room. S: This is your conditioning chamber? K: Yes, for climatization of the film. If the system works, all the films you remove must be put in here for six to eight hours and then the temperature is regulated depending upon the temperature outside. This is our system for storage of acetate materials. The film is stored here according to a numbering system. Each one of these vaults holds 120,000 reels. This is why we are making changes. This is the space assigned to negative materials and we have no space to continue with negative acquisition. We had to take out positive material and move it to the provisional hall. S: What is your attitude about sealing cans? K: We think it is useless. There should be a possibility for gases to escape. Over there is a duplicate positive material. We used to mark the cans with the title and the number of each film, but we’ve stopped marking the title. Now there is only a number on each can. Let me describe our cooling system. From a central cooling system comes a liquid of -18° C. to each vault and it is here that this liquid cools the air in each vault. Twelve times an hour there is a complete change of air inside the vault. When you remove or renew the air, 10% to 20% fresh air should be pumped in. The percentage can be regulated. It depends upon conditions outside. We have a fresh-air replacement of 10% to 25%. The liquid is -18° C. when it flows from the central cooling system, but then gradually increases to -1 0° C. , cooling the air to a temperature of 6° C. This is the temperature we need for this vault. There are 20 of these cells, with about 1 ,000 reels of nitrate film in each cell. In each of these boxes, there are 11 reels of film. This is a special construction of the archive. This is asbestos between these boxes. S: Have you ever had a fire? K: No, but we’ve tested the system. If some- thing explodes in one of the boxes, there is no influence on the others. The door is opened by 73 the pressure; and this pressure closes the other doors. If the temperature rises to about 30° C. , the climatization system automatically closes down. The channels for air going in and out close, and an automatic alarm and sprinkler system are activated by a severe rise in temperature. It is necessary for the preservation of nitrate film. The walls are made of stone, covered with plaster. The building is electrically heated. Fresh air pumped into the vaults is filtered by oil filters. These are for dust only, and not for gases. Nothing more is necessary in this territory because we have no industry surrounding us. This is the central cooling system. Four compressors are working continuously with one in reverse in the event of a breakdown. Here is the liquid at a temperature of -18° C. It is pumped here to the four vaults. S: How long has this whole assembly been here? K: It was constructed between 1963 and 1966. This is the provisional hall for storage of films. It will not be used after construction of the new vault is finished. This is for a limited period of five years. We must have this because there is no other place where films could be stored for pre- servation purposes. This is all acetate material, no nitrate. The conditions in here are not as carefully controlled as in the other vault. We have equipment for removal of air and for climatiza- tion. We blow in warm air during the winter so that nothing will freeze. It is most important not to go lower than 0° C. In the summer, this system removes air and cools it. It is rather new so we have not had too much experience with this system. However, in the hot summer period, we had a temperature of about 15°C. to18°C. inside. The temperature is about 8°C., with 65% relative humidity. This is very good for the moment, but it depends upon conditions outside. S: Are these all relatively new films in here? K: Yes, most of them are new films. We had to take a lot of acetate positive material out of the vaults to have some space for negative materials. We will store only positive material in here and any new acquisitions of positive material in the next three to five years. According to our program, it is foreseen that our new vault will be finished in 1976. S: Will the new vault be specifically for color? K: Specifically for color, but it can be used for other kinds of material. S: But is it going to be large enough even to take all of this? K: Yes, it will be. This new building will have a capacity equal to all four vaults you saw, combined. It will have a capacity for storage of about 300,000 three-hundred meter cans. This place will be used to repair all the machinery that we have here. Some of the space will also be used for storage of machinery not presently in use, empty shipping boxes, etc. These necessities were not foreseen in the past, and we have needed such facilities very badly. When this archive was constructed, a printing department was not foreseen. The room upstairs for developing was foreseen for some restoration process. The cleaning and washing of films and all printing was done in a commercial laboratory outside the archive. However, we had very bad experiences with this commercial laboratory. They did not make good quality archive material because they were not familiar with archive materials and problems. Therefore, we decided to undertake the printing ourselves, and do it in the archive. Hence, it is done in a very traditional way. We are not satisfied with this work. We hope to construct a completely new laboratory with a much greater capacity than we have now. S: When you are printing shrunken films, can your operator adjust the printer for pitch changes? K: Yes, the man working it can quickly adjust it. S: How does he know how far off he is? K: This is measured by his colleagues doing the preparation work for the printing. S: How many different places in a roll are checked? K: Three places. S: Do you find a sizable shift in shrinkage from the heads and tails of the film versus the middle? K: It varies considerably. It depends sometimes upon how strongly the film was wound. S: Do you store your films on cores? K: Yes, we do. S: Many archives do not. What is your reasoning for this? K: Practical reasons only. You can easily use the roll again. It is dangerous if you do not have it. You can scratch the film putting it in. I heard a rumor about this. Because the chemical compo- sition of the cores is not well known, no one knows if it has any influence on the film. I think one museum in London had certain experiences with the cores and they felt it did have some influence on the film. I don’t know what their final decision was. S: What about wooden cores? K: They were produced in the past, but not anymore. This is always a problem with archives. We can use only those things which we can get easily and cheaply. For example, if we renew boxes, we use those from commercial laboratories that once held raw stock which we get without paying. There are better boxes, plastic and such, which can be specially made for the archive, but they are not economical. S: What do you do about copying tinted and toned prints? K: Let me show you some samples. S: Are these new? K: It is done the same way as the National Film Archive does it. I think they have had the best experience doing it. These are experiments to demonstrate that it can be done. S: Have you done it routinely? K: No, we haven’t done it routinely. It is printed in black-and-white and then tinted. S: Have you done any toning? K: No, but we can do it. We’ve postponed it until we have more time. S: If you make a dupe negative of a tinted and toned original, how do you go back through the 74 dupe negative to determine where the colors should go? Do you keep cards? K: No. I think it must be checked after the printing process. That is the reason why we haven’t done it. It must be checked and a decision made about what parts should be colored. S: You are not using color materials to do it on? K: No, we do not use color material for tinted films, but we use color material for hand-colored originals. This is very useful and successful. At the moment, all color printing is done outside the archive in another laboratory; we print black- and-white only. The commercial laboratory is not so interested in doing hand work or work of a noncommercial nature. Therefore, we’ve postponed it, but after we enlarge our laboratory we will have the capacity to do our own printing of color material. We did some other experimental work with silver image regeneration. We have a patent on the process, developed in our country. Until now, it has been done in an experimental way, but it is possible to do it with machines. S: Has the patent been granted? K: Yes. It is a patent in the names of Dr. Keiler and Dr. Polakofsky. S: Does it look even on the screen? K: I haven’t seen it on the screen, but my col- leagues have. Some experiments in color film regeneration have been done in Rumania. I can perhaps show you some examples, but I cannot explain the process. It is not a routine procedure. However, it is possible that it works in a routine way. If we do not have copies of the article in the Technical Film Review with the description of the machine, I will send you copies or complete bibli- ographic information. (N.B. The previous discussion concerned a process that reconverted silver sulfide back into metallic silver in the case of films which had faded badly, usually because of improper washing or excessive hypo retention. In the frames which were mounted in cards, the results were quite good. However, there seemed to be a bit of non- uniformity in the images, but this might be due to the fact that these tests were done by hand rather than by machine. ) K: Next year, we are going to patent a method of binding escaping gases from nitrate film by a chemical emulsion, to lock them in. S: A D.D.R. patent? K: Yes, and an international patent. It was just finished. It won’t be published or sent to the patent office until next year. The work on this is being done by a collaborator of the archive and his colleague. S: Have you seen this new system work? With nitrate binding? K: Yes, we studied it for a year. S: Under accelerated storage conditions? K: Under our storage conditions. We don’t know how it works under other storage condi- tions, but I think it will be useful under all con- ditions. S: Can you speculate how long it would extend the life of the material? K: Nitrate is the most dangerous material in the archive. Everything must be done to postpone the process of deterioration, but there are not so many possibilities. You can rewind the film, or you can move the film to a certain area. But in a big archive, you have the problem of capacity. You can clean the film, wash it, and try to bind escaping nitrate gases so that they have no influence on the film materials or on the cans, and so on. This is the idea of this patent, but I cannot say more at the moment because I am not a specialist. HERBERT VOLKMANN (The following interview takes place with Dr. Herbert Volkmann, the retired Director of the archive whose title is now ‘‘Collaborator. ” He is also the Chairman of the FIAF Preservation Committee. ) S: Have there been any changes in FIAF’s published report with respect to the preservation of color materials? V: There have been some minor changes; but at the moment, I don’t believe I can give you any answers to this question. For nearly three years, 12 scientists in seven countries have been working on this. We will publish the first part, concerning preservation of color films, next year. Therefore, I cannot say anything on the new process before publication of our work. I published a study of preservation in 1963. Are you familiar with it? S: Yes. V: Most parts of it are still valid. That con- cerned black-and-white film; now we are working on the problems of color film. Next year, I believe we will finish magnetic tapes, videotapes, etc. With respect to discs, however, I have not seen an expert who could give me some, new scientific reasons for preserving materials at certain, specified temperatures. You know Kodak’s recommendations regarding original color film. I don’t agree with these. Many scientists have doubts about Kodak’s recommendations. Kodak gave a temperature of -18° C. I believe that this temperature is much too low. It is not necessary to have such a low temperature. Look at this diagram: here is the temperature, and here is the time in which the film will expire. You get a curve like this. If the temperature is 25° C., the life of ordinary film might be 20 years. As you decrease the temperature, you increase the life of the film. However, if you store color film at temperatures of -2°C. or-20°C., there is no real difference. S: What about relative humidity? 75 V: I would say that the highest possible relative humidity is 60% for black and white film; 50% is much better. If you keep color film, the relative humidity should be between 15% to 30% , with -5° C. as the highest possible temperature. S: This is sizably different from Kodak’s recommendations. V: Yes, but we know that Kodak shows a temperature of -18°C. not because it is neces- sary, but because it is 0° F. This is not a scientific reason. Of course, you realize that a temperature decrease of even a few degrees costs hundreds of thousands of Marks more for building storage requirements. S: How do you feel about specialized treatments to test for archival permanence, hypo elimination, and the like? In your preservation study, you recommend a certain test for checking whether or not hypo had been eliminated suffi- ciently. V: I am against hypo tests because they are much too time-consuming for the archive. You can begin one year, and end 100 years later. In that time, all the silver in the films will be destroyed. You may have an original negative comprised of some 200 to 800 pieces of film, each of which would have to be tested. In Moscow, they tried to solve the problem. They built a desk that was nearly 20 meters long, and they took a punching from every piece of film. However, they were able to do it because they had a lot of people. Ten people were on the desk, every two meters. It took them so much time that it was impossible to do this with thousands and thousands of films. The Russian archive is the greatest in the world. We have 900 to 950 tons, they have much more. So you see, it is impos- sible for such a great archive to conduct such tests on all its films. The only solution is to treat every film that comes in as if it had too much hypo and therefore rewash it. They have developed excellent machines for this. The first machine went into operation 30 years ago. Two years ago, they got a new machine which was six meters long, which is much too long for such a machine. Now they have a new machine which is four meters long, and this is perfectly adequate. S: At what speed do these machines operate? V: I don’t know about their machines, but our machines go at speeds of 300 meters per hour. We have little machines. Our machines are only one and one-half to two meters long. We espe- cailly wanted this size and no larger because we had not enough room for bigger machines at that moment. Do you know how much film one ton comprises? Four hundred reels, each with 300 meters of film. There are 1 20,000 meters in one ton of film. Before we built our new archive, we had our film in another old building without air-conditioning. It laid there for five years, and over 40% of it got sticky. S: Was this safety film? V: This was both nitrate and safety film. We had one big store of nitrate film and one of safety film. Therefore, we had to wash the films care- fully and slowly, so we got these machines. In Moscow, they have very high-speed machines. If you try to wash sticky films at too high a speed, the emulsion will be torn from the base. Therefore, we have a lower speed. S: Do you use waxing on these films? V: No. S: Any type of after-treatments? V: No. None of the FIAF archives wax their films. Until recently, it has never been clear whether or not there was some danger in waxing. Yes, there is some danger. It has not been inves- tigated until now. An archivist must be concerned, not with years, but with hundreds of years. Until we are sure that there is no danger to the films, we will not wax them. We have warned every archive that waxes its films or puts chemicals in their boxes that such procedures might be dangerous to the films. Therefore, we recommend that they abandon this until it has been clearly determined that such practices are not harmful. S: Do you know of any archives which are putting camphor in the cans? V: Last year, some archives told me they were putting camphor in the cans. I hope that none are doing it now. It is a dangerous and rather limited method of preserving film. We know that camphor decomposes over a period of time, leaving a powder with very sharp edges. If you should move the film, take it to the laboratory or to the projection room, the sharp edges of the powder might scratch the film beyond repair. S: What about sealing the cans? V: You can seal the cans containing triacetate films, but not those containing nitrate films. It is forbidden to do it with nitrate. S: Right. You have no feeling one way or another about sealing cans that hold acetate film? You don’t believe that there’s any advantage to it? V: No. Sealing is said to protect the film from dust. You can do it, or you don’t have to do it. S: What I had in mind was prevention of loss of solvents and plasticizers from the base, and moisture exchange. V: Moisture exchange is hampered by the tapes. There is no danger of moisture exchange if you have air-conditioned block houses at relative humidities of 50% . If the film lies in this block house for months or even years, it will stay at 50% RH. If it comes from outside, it may have a relative humidity of 70% from the outer atmosphere, but when it goes into the block house, it will exchange to 50% . It might come in at a level of 40% , but it will also exchange to a level of 50% . There is no danger if you have air- conditioned block houses. In such cases, there is no need to seal the cans with tapes. It is quite another story with nitrate film. There you have nitrate gases, dioxides, that will destroy the film if you cannot take off these gases. S: With the tests that you’ve done so far, what sort of lifetime have you gotten, or do you expect to get, for original color materials? V: Maybe 20 years, in a vault with, let us say, 20% RH. S: With no detectable change in color? V: Yes. 76 S: What is your predicted lifetime for black- and-white film under the conditions you specified? V: Under these conditions, and provided that the film is not removed from the block house more than every five years, I believe that it would last for 80 to 1 00 years— I hope. S: Without any detectable loss of image density or a sizable amount of shrinkage? V: Yes, without loss of image density or shrinkage. It will not shrink if the relative humidity is between 50% and 60% . S: Have you investigated polyester bases? V: Not until now. We have looked at polyester base only for Super 8, but not for 35mm or 16mm. For 16mm and for 35mm, we have no polyester base and have made no tests on it. However, as far as film is concerned, polyester base is one future. It is only a question of time how long we will have film and how long we will be able to show films in the way that we show them now. Many new media will come. Some technology has already come too soon. For example, the storage of information using lasers is something that belongs to the future, some- thing which we can overlook for the moment. To preserve color in films is, I believe, ridiculous. However, we have no other possibilities, so we must do it. It is much better to store color in an electronic way. There are many possibilities for this which will come to public attention in the next five or ten years. I believe that in 20 years, there will be possibili- ties to show film in theatres and in our homes by other means. Already we have television. There will also be other means of storage. All the block houses we build now for the storage of color will be used to store vegetables, in 20 or 30 years! But it is necessary to build them now. If there should be new media to which we will eventually transfer our material, we still need to preserve what we have for those 20 or 30 years until such media are available. For seven years, we have been copying our nitrate film onto acetate. We still need to continue for ten years more. S: Right now, can you say anything about your recommendations for archival storage of television images? V: Not now. We began already, at a meeting in Copenhagen in 1971, but we have not finished. S: The reason I ask is because the manufac- turers of videotape to whom I have spoken all believe that it is not an archival material. Or, that if it is in any sense, it is an extremely temporary one. I was interested to know your opinion regarding (1) its use archivally, and (2) if it cannot be used archivally, what techniques you would use to preserve the images. V: Film producers are of the same opinion. I cannot say exactly, but I believe that the best temperature is about + 6° C. to + 8° C. In principle, videotapes are the same as optical film. There is a base and a so-called emulsion: binders and oxide coatings. There are at least three parts. If your temperatures are not constant, these parts will burn together, and the result, I don’t doubt, will be somewhat dangerous. S: How can print-thru be prevented? V: Print-thru is very great at the first winds of videotape. It is not so great if you have only a sound track because the sound track is much thicker than the video track. S: By that you mean magnetic film? V: Yes. S: I am concerned about print-thru for video- tape. V: Yes, there is no print-thru with the picture but there is with the sound. S: Has the question of “trimer bleed” come up in your discussions? This is a by-product of the base that oozes through the oxide, which over a period of time will cause the material to become unplayable. I have been told that one of the problems of storing videotape is that certain batches of the material— and there is no way of predicting which batch— will produce undesirable by-products which collect on the surface of the oxide, and will jam the heads when the tape is replayed. V: Yes, I have heard of it. We will not discuss it until Spring of next year. This year, we will finish the color study, and next year we hope to finish the discussion of magnetic videotapes. S: In all cases, has your archive worked with existing materials— film types which were made for the general market— rather than something made specifically for archival use? V: We have worked only with those for general market use. We made some tests on special materials, but most of them were made in Moscow. S: How about making changes in the material? Was there nothing they felt important enough to warrant it? V: No. S: What about vesicular images, bubble images rather than silver images? Have you done any work on storage techniques for this type of film, film like Kalvar? V: Nothing. I don’t believe it has any great future. I believe that the inventions made in laboratories in the last five or ten years are quite a departure from any of the old media such as film. In 20 or 30 years, we will have very different media. I am glad, because if we do have the media which I believe are coming, we will not have many difficulties preserving the new materials. S: Do you have any faith in aging tests for nitrate? V: Such tests are impossible for a great archive to do. I know that the London Archive does it, but it is not a great archive. A great archive does not have the capacity to punch every piece of nitrate film. We had 350 tons of nitrate; we now have between 210 and 220 tons of it. We have at least 20 million meters of nitrate film. It would be impossible to make these complicated tests. Also, these tests are not exact. I am of the opinion that every nitrate film in your possession is in danger. For more than 20 years, cinema films have been on triacetate. Therefore, we will treat every nitrate film as if it were in the last stages of decomposition, and we copy every nitrate film we have. We destroy the nitrate films which have no special importance, but we store those which are of special value— either documents or feature films. 77 After we have copied every nitrate film to triace- tate, we will still have perhaps 100 tons of nitrate film which would fill one block house. We will keep it as reference material as long as possible. It is better than the material from the cinema that we have on triacetate. Of course, we must have special protection against fire. We have no fear that if one film burns, the other films will burn too. We made quite a few tests, burning one box containing 11 reels next to several other boxes, but only the one box burned. So, we don't have that problem here. In Canada, however, I believe there was some problem with this. In West Germany, there was a very great problem. In three days, two great storage houses of nitrate films blew up. That was in 1968. In 1960, there was a great fire in the Cinemateque Francais. Many reels of nitrate film, films from all over the world, were burned. Some of our films were destroyed in this fire. S: Was it caused by spontaneous combustion? V: Yes. They had 4,000 reels of nitrate film which, when seized by the sun’s rays, exploded. All 4,000 reels were destroyed. In Bulgaria, there was a very great and tragic fire in which some lives were lost. There are many fires in Brazil and in the United States. S: But you apparently don’t have that problem. Because your vaults are properly designed, and you store things properly. Also, since your vaults are located in rather remote areas, there is little danger to anyone’s life in the likelihood of a fire or explosion. In summary, you are saying that all nitrate must be treated as if it were about to decompose at any moment, and it should be copied as fast as possibie? V: Yes. 78 RECOMMENDATIONS (FOR SECTION ONE) 1 . Without question, polyester is the best available film base material. Its inherent strength, physical and chemical stability, and its freedom from plasticizer loss will allow the archivist greater freedom of choice in the operation of his vault. It will permit less stringent storage and handling conditions— while at the same time extending the useful life of the film. Polyester shifts the burden of preservation from concern about the base to concern about the image. It is recommended unequivocally that all new photographic moving image materials intended for archival use should be ordered on polyester base. 2. It is recommended that archivists strongly urge the manufacturers of silver halide motion picture products to accelerate their efforts to find a substitute for gelatin as the key binding agent in film. Along with the usual performance criteria, such a substitute must take into account such archivists’ concerns as the binder’s invulnerability to attack by fungus, air-borne pollutants and other deleterious chemical and physical agents, and the ability to withstand the test of time in terms of durability and adhesion. 3. Films newly acquired by an archive should be rewashed.* If such routine rewashing is precluded by either the archive’s resources of manpower or money, it is recommended that all films be tested for determination of residual chemicals. The best available tests to determine the adequacy of final washing, as well as possible means of predicting the fading potential of photographic materials in archival storage, are the methylene blue test and the silver densitometric test. *Before rewashing color films, consult the manufac- turer for recommendations regarding washing and restabilization of the color image. 4. While, when possible, the FIAF recommendation should be followed for storage of nitrate and acetate materials, frequently individual archives must modify these figures to produce conditions which are manageable within the archive’s resources. For this reason, when an archive feels it must deviate from the FIAF standards, it is recommended that: First, the archive give priority to consistency in its archival environment regarding temperature and humidity, even at the expense of some increase in those factors. Second, should there be a choice between control of temperature and control of humidity, that, within reason, humidity be the first consideration. Third, new vaults should be constructed away from industrial areas, and areas with air-borne pollution, even at the sacrifice of convenient access. 5. Gold protective treatments applied to silver films, in conjunction with formaldehyde hardening baths, appear to be an excellent means of insuring image permanence — even under relaxed conditions of temperature and humidity. Money should be sought for research into the exact procedure necessary to make such treatments to motion picture films routine. Further, investigations should be pursued on the various proposed methods for restoring faded and discolored black-and-white silver images. Dr. Edith Weyde’s iodine bath restoration technique, and that of the German Democratic Republic, hold much promise in this area. 6. It is a given principle for archivists that the preservation of the original image should be the foremost priority in an archivist’s scheme of things. Unfortunately, it is also a given fact that nitrate images will, one day, surely decompose. One technique has been cited in this book which might successfully prevent the otherwise inevitable result: image stripping. Research aimed at the development of practical stripping techniques should be undertaken. This concept seems promising, even within the cost parameters given, and, if successful, would indeed save the original image— while transferring it to a far more durable and long lived base material. 7. Archivists should urge the development of a hermetically sealed storage can for acetate-based motion picture film; and along with it, the necessary equipment for utilizing such cans. This type of can could significantly inhibit plasticizer loss, prevent moisture exchange and attack by fungus, and eliminate the effects of air-borne chemical pollutants. Indeed, the adoption of a hermetically sealed can might have profound effects on conventional vault construction by controlling at their source these four of the most insidious enemies of stored film. 80 SECTION TWO: New Approaches The vagaries of manufacturing and preserving silver images have led a number of inventors and research laboratories throughout the world to search for alternative light-sensitive systems. In this section, attempts are reviewed to discard liquid chemical treatment for the development of silver images, replacement of silver by various other light-sensitive compounds, and development of those compounds by liquids, gases, heat, and cold. And too, we cannot overlook developments in electro-optical image storage. In the last few years, a variety of such systems have come and gone— been promoted and fawned over. Whether or not any one of these techniques will survive on the commercial market only the future can tell. Yet, for our purposes, emphasis will be placed on those features of each system which seem to lend some potentially useful asset to the archiving world. Indeed, this is intrinsic to the charter of this book: to examine new approaches and new technologies. A photo-micrograph of vesicular structure in Kalvar film. 81 Vesicular Films and Dry Processes DRY SILVER In recent years, numerous companies have worked on developing photographic processes which are completely self contained chemical and photographic entities. In the case of silver based dry products, the application of light, heat, and cold is sufficient to produce images capable of fulfilling many of the criteria for image quality expected of wet silver processes. From an archi- val standpoint, these products are too new to have established themselves as proven, workable systems. Moreover, because of their basic construction, most by-products of the exposure, development, and fixation processes of dry silver remain in the material which presents possible hazards to the archival life of the image. 3M Company and East- man Kodak Company have been active in the development of dry silver processes. DIAZO Diazo processes depend upon the decomposition of diazonium salts, under exposure, to render positive latent images which are made visible by coupling reactions to final dye images. As such, these final images do not have archivally perma- nent characteristics. In terms of resolution, diazo processes can potentially produce images of higher quality than silver images because diazo images have no grain structure per se. Diazo processes can be either wet or dry, but in all cases, the result is a dye image. A major fault with all diazo materials is the shape of their characteristic curves. No manufacturer has yet been able to produce a diazo film that has a sufficiently linear “straight line portion” to its transfer curve. For this reason, the sensitometry and densitometry of silver and diazo processes do not match, and diazo prints from silver negatives characteristically show grey scale distortions which severly limit the quality of diazo prints. VESICULAR Production of images by density is not the only method of achieving photographic results. Tech- niques which involve a shifting of the refractive index of a material can be employed to produce images of highly acceptable quality. To illustrate: think of a refractive image as one made up of a multiplicity of prisms, each with a differing geometry. The prisms representing bright areas of the picture would most closely approach a refractive index of one; whereas the prisms representing darker portions of the picture would have a higher index of refraction. When light is transmitted through this multiplicity of prisms, it is bent and scattered at various angles, depending upon the content of the original scene. The rays representing lighter areas are bent least, and continue to travel forward, toward and through the projection lens; the rays representing darker areas are bent more and only a portion travel forward through the lens, allowing less light to get to the screen. Actually, practical systems based on the above theory gain their point for point shifts in index of refraction by forming bubbles within their image layer and sealing these bubble shapes with a deformable matrix. It is from this formation of various sized bubbles, or vesicles, that these pro- cesses derive their generic name: vesicular photo- graphic systems. DRY DIAZO VESICULAR Though not the sole manufacturer, Kalvar Cor- poration, and its subsidiary, Metro-Kalvar, Inc., are the leading exponents of vesicular images produced by dry diazo techniques for motion pic- ture and television use. Kalvar prints are made by ultraviolet exposure through normal silver nega- tives. Upon exposure, the diazonium salts de- compose, releasing varying quantities of nitrogen gas. This gas is trapped within the saran matrix of the image layer, where, with the application of heat, expansion takes place, producing gas cells (“bubbles”) which deform the matrix. Upon cooling, the deformation of the matrix is made permanent. The final steps of the Kalvar process involve fixing the image by decomposing the remaining, unexposed diazo material and allowing the nitrogen thus produced to escape. Kalvar material gains a permanent image, on a polyester base, free from image elements and residual chemicals which could later deteriorate or be attacked by chemicals that easily destroy conventional silver images. Unfortunately, there are drawbacks to the above method. Kalvar images are still diazo images in 82 the sense that they exhibit the classic diazo trans- fer curve. In addition, it is difficult to produce as great a brightness range with these materials as is possible in the case of silver materials. Another major disadvantage of Kalvar materials is that they require ultraviolet exposure for efficient printing, and it is difficult to sensitize them to blue or red light. Green-sensitive films have been manufactured for laser recording applications, but considerable energy is required to make the expo- sure compared to the energy requirements for the exposure of silver halides. A final difficulty inherent in all vesicular systems is that the gamma or contrast of the resultant image is always dependent upon the projection optics used: the higher the f-stop number of the lensing, the higher the gamma. The one exception is Type 63 Kalvar film, made as a direct contact duplicate negative material. This application ob- viously requires no lensing and therefore the gamma characteristics are more closely fixed; but the material would still be affected by the co- herence of the printing light source. SILVER VESICULAR Though the phenomenon of producing vesicular images in silver materials has been investigated by various researchers for some time, only recent- ly has any practical solution to the question of permanence been discovered. The leading worker in this field today is Dr. Edith Weyde of Agfa-Gevaert, Leverkusen, West Ger- many. The Agfa-Gevaert “W.B. Process” is based upon her work. This is a processing system for the production of vesicular images in silver-image films, based upon silver as the catalyzing agent in the decomposition of hydrogen peroxide. The gas produced by this reaction permanently changes the natural and synthetic binder structure, caus- ing ruptures and vesicles which accomplish the basic requirement of altering the index of refrac- tion of the medium. Though it is possible for the bubbles of gas to escape from the film if it is accidentally wetted, Dr. Weyde has developed a protective layer to keep them trapped permanently. Even if the gas should escape, the permanent rupturing of the natural and synthetic matrix has occurred, and an image— which can be made visible by the use of Schlerin Optics— permanently remains. A number of important advantages are inherent in the ‘‘W.B. Process”: (1) The system requires one-tenth the amount of silver required for equivalent silver density sys- tems. (2) Graininess is considerably reduced because vigorous development is not required— in fact, W.B. images can be produced from negatives in which the silver image is not visible to the naked eye. (3) Because silver is being used as the sensitive medium, all normal sensitization techniques can be employed and the material can be made to have densitometric and sensitometric characteris- tics identical in every respect to normal silver- image films. (4) Gelatin need be used only to the extent that it is required to act as a protective colloid for the silver halides; it need not be the total binding agent. In fact, films made specifically for the ‘‘W.B. Process” have contained as little as 25% of the gelatin normally found in silver films. (5) The size and characteristics of the bubble image may be altered during processing to either enhance speed or diminish grain size. (6) The image can be regenerated repeatedly if, for some reason, the initial bubble image is lost. (7) The matrix image is always permanent, even if the catalytic silver image is lost. A print from an underexposed negative before bub- ble intensification by the W.B. Process. Print from the same negative after bubble intensifi- cation. 83 Kalvar Corporation New Orleans, Louisiana K: A. Tulsi Ram Elvin Potter Vernon Wagner S: Ralph Sargent A. Tulsi Ram Vernon Wagner S: Let me ask a few basic questions which are not answered by the published material. The first question has to do with a concern of the archivists about corrosion. Corrosion has been observed on reels and cans used for storing Kalvar materials. What can you say to this point? K: We recently found that this problem occurs, and are presently working on a film that will eliminate it. We hope to have it out next year. It will not outgas and we feel that it may show a little improvement in its actual lifetime stability, as best we can predict, compared to the film we are producing right now. The problem is something that has been overplayed; but it is true, especially with Type 16. It does occur. S: One of the questions raised last night had to do with using the Kalvar Model 135 printer to duplicate nitrate materials. There was the question of safety . . . K: At the moment, we have no answer. It is our belief that the heat at the printer head of a Model 135 would not be sufficient to present a safety hazard to the operator dealing with nitrate; however, there is also the question of the effects of UV radiation on nitrate, and whether or not this would have any detrimental effects on the archival qualities of the material. There is no question that the Model 135 will run nitrate material; that is, pass it through the head. The speed of the machine is rather low, however. It does not exceed 100 feet per minute. This could be changed of course, all it takes is money. S: What about the spectral sensitivity and emulsion speed of various Kalvar materials? When we talk about encoded color processes such as EVR or ABTO one of the requirements of any of these media is the ability to reconvert the archival image to a conventional photographic image. With Kalvar materials, the primary problem, it seems to me, would be getting the initial master most efficiently from an original color image which has not been separated into its primary records. This is not a problem with EVR since the original transfer would be by electronic means, but in the case of ABTO the transfer would be by direct optical means requiring a pan- chromatic receiver emulsion. Dr. Ram talked about a green sensitive film which could be exposed by lasers. I questioned whether or not it would be possible to sensitize Kalvar materials to red or blue. K: That is further down the line. We have a proposal before our Board of Directors (and they have okayed it, but we have not come up with the money to finance it) to put a program into research to up the speed of Kalvar film. In these proposals we have included plans to sensitize the emulsion to red and blue. This has never been done before; we are looking for a breakthrough, so we can’t make any promises. However, we do have some definite ideas about how to proceed. S: Then, from a practical standpoint, there is no usuable sensitivity in the red and blue regions of Kalvar film? K: There is some blue sensitivity, but no red. S: Are there any special storage conditions which would render the vesicular image even more stable? For example, pressurization tech- niques, etc.? K: No. We recommend the storage conditions of PH 1 .43, the ANSI specification for storage of other than microfilm. The unique quality of Kalvar film is that the image permanence increases with age. Our paper on development, presented at the New York convention of the SPSE two years ago, relates the development of vesicular films and in particular, our films. It discusses some of the characteris- tics which render Kalvar films more stable than ordinary materials. Although this paper is not primarily concerned with stability, the under- standing of the development process and the stability that can be achieved through proper development, is pretty well described. S: Has there been experimentation with Kalvar films in electron beam recorders? Do you know of any work in this area? K: There has been some work. The problem with the process is that it is very slow. The tech- nique involves the total flashing of the material and the use of the electron beam recorder to selectively develop the image. From our stand- point, the process is presently impractical. S: Have you used lasers for exposure? K: We have exposed and developed Kalvar film 84 with lasers, but not with laser kinescope recorders. Right now UV laser technology is not up to the point where I would say that practical speeds could be possible. At Coherent Radiation Labora- tories we exposed Kalvar film at a speed of about 30 feet per minute with their Model 53 Argon laser. The technology is progressing to the point where these lasers are getting bigger and more reliable. You can focus laser light down to a point, because laser light is parallel; laser light can be made brighter than its source. So, with a kinescope recorder, it might be possible to get a raster bright enough to record at 30 feet per minute. That’s technology today. There is no doubt that the technology of lasers will advance. S: Alright. Say that the technology of lasers stands still. How does Kalvar fit in? K: Okay, you could use either the green sensitive film or the ultraviolet film. I think right now we would prefer to use the green sensitive film, although we don’t know. It is not a product yet. It will be a product in the future. S: Have you done any work using Kalvar materials as intermediates from which silver prints are made? K: We have a film that we specially developed for this, our Type 63. It was meant to be an inter- mediate film for printing to silver by contact. It has a printing gamma of 1 .0 to white light. This would not be good film for direct viewing; the D-min is too high, but it works very well for printing back to silver. This is a product we make for the Navy every three or four years. We’ve made it before, we can make it again. S: What do you consider the brightness range and latitude of the material to be? Is it directly compatible to silver print stock? Is there any loss in Delta D or exposure scale? K: It is around 1 .6 Delta D, which is not as good as Kodak’s 5234, but is usually adequate to cover most of what is required. S; In the past there were problems of emul- sion adhesion with Kalvar film. Have you done anything about this? K: In the type of film we are talking about for this application, I don’t think you would have any adhesion problem at all. We are talking about non-degradable Type 15. Earlier Kalvar films were unsubbed. In other words, there was no subbing layer between the base and the emulsion layer. Any future films that we make, especially the non-degradable kind, the kind that will not give off acidic fumes, will be subbed, of necessity. We have films now which we can provide even without subbing, which are coated on “treated” bases which show remarkable adhesion. The treatment is given to the bases by the manufac- turers. There are quite a number of suppliers now. We’ve successfully made materials which I can show you that you can’t pull the image off in any way, shape or form. We have graphic arts products now which can be used with very highly adhesive tapes; tapes which do tend to weld. We have a product, Type 43, for the graphic arts specifically designed to meet these problems. There are certain other problems, such as editing applications, but we are prepared to furnish materials on existing products which have excellent adhesion for the particular problem that’s required. S: Let’s talk about improving emulsion speed. What’s the story there? K: There again, we have ideas. We’ll shortly have a film that will be about ten times the speed of our current films. We’ve already delivered it to certain special customers. We have a couple of kinks to work out in the process; but the film itself is perfectly acceptable. The production of it is difficult; it is not the easiest thing to make. We have a couple of hurdles to overcome before the material is a product for mass consumption. We can print at 500 feet per minute with older materials, right now. With the new material, we will be able to print at 2500 feet per minute. S: Or you could drop the energy requirement so that, from the standpoint of nitrate transfers, the exposure energy would be at safer limits? K: Good point. S: Another point is that there is always a problem in dealing with older films. Differential shrinkage in older films causes registration geometry to swing wildly within a roll. Many of the films that are being duplicated right now to safety material are workprints that were made by the studios from 1915 on. From shot to shot, the pitch changes drastically. This is a problem then, for the printer operator. It is not one of those things that ordinary continuous contact printers can readily handle with great facility unless the total roll is within certain specifications. Therefore, more and more material must be printed using a stepping printer which operates at a lower speed and is more oblivious to the geometry of the originals. The connection to Kalvar is that Kalvar has historically taken more energy to effect exposure than normal duplicating films; amounts which make the use of a normal step printer and Kalvar film impractical and dangerous. If the speed of the Kalvar material were greatly increased, the dangers would be lessened. K: There is also the problem of timing we have encountered in silver motion picture processes. I think that the MetroKalvar duplicator has some kind of light control for changing lights for different shots. But in conventional Kalvar printing, the light remains constant; the negative has previously been timed and corrected. S: Have there been any changes in the develop- ment techniques for Kalvar films? K: We’ve tried all sorts of things; developing with laser radiation from the Carbon Dioxide laser; and in one special application, for EVR, we’ve developed in hot water. S: To get more uniformity? K: Yes. We could not get a drum uniform enough to develop EVR film. It has to be developed under conditions that are not really full development. We tried underdeveloping this particular film to get the right gamma character- istics, exposure range and resolution, and we ran into mottle. We could not get it by either polishing or roughing the drum, or anything else. We finally solved the problem beautifully by just dunking the film into a hot water bath— followed by an air knife. The temperature of the water was about 210° F.— a little less than boiling. 85 In the case of water development, development occurs through the emulsion side. When the development energy takes effect on the emulsion side, approximately one-tenth the energy is required compared to the application of heat to the base side. The resident time is very important to the photographic property. It is important to the stability of the image as well; and it relates to glycerin development which we feel is the ultimate in delivering development energy. In our paper on developing, there is a chart which shows the crossovers, for instance, a half-second of glycerin vs. a half-second on a standard hot roller developer. It requires much lower temperature in glycerin for the same resident time than it would on a standard hot roller developer. In the case of Type 1 0 film, for example, if you are developing on the standard hot roller at 240° , for one-half second, the time roughly transports to 205° in liquid development temperature. 240° standard development temperature comes out to .13 calories per square centimeter in glycerin. This is what we got for Type 10 and Type 16. Type 1 7 is about ten times faster than regular Type 1 0 film. This is a motion picture film. S: Have you used these liquid development techniques on volume machines of any kind? K: Yes. We have a regular processor. It’s speed limitation is about 60 feet per minute. That is just as fast as the machine will run now; it is not as fast as we could run it. That is the speed we’ve gotten to right now with liquid development. There should be no problem with going at any speed, really, because we can immerse the loop more or less, or wind the loop any way you want it to control immersion time. The film comes out perfectly dry. You never know the liquid’s been there. An air knife takes all liquid off. When the film reaches the clearing station, it is completely dry. S: What sort of new printers do you have? K: The 500 feet per minute printer is quite a step forward. It has highly uniform development, not liquid, and is a non-sprocketed machine. It could be applied to a sprocketed material. In this printer we have quite a bit more exposure energy which is quite well collimated. S: What about the use of strobe exposures? K: We had a film that could be exposed by one flash of light (it was actually developed by one flash of light, but development was actually an exposured development and fixing step, all in one.) It can be done this way, but we haven’t made any system based on this. S: I was skipping around in my head about various ways of printing and I was thinking about step contact or step registered prints— contact registered prints, and of using a strobe as the light source rather than continuously operating arcs. K: You mean like a photo-flash lamp? Well, we’ve looked into this possibility. In fact, we were thinking about making a roll to roll printer similar to our Type E equipment. In that equipment we had a film which was exposed by an ultraviolet lamp, just like our other products and then given a flash development in which case, during flash development, we perform a direct image process similar to our Type 51 film process, with the exception that here the first exposure, the flash, causes the image to diffuse, be re-exposed and developed all in one instant. S: To get a direct image? K: Right. We got a direct image. That had certain drawbacks because the development energy that was applied in the reversal and in conjunction with the product in the reversing, did not provide enough exposure latitude (D log E) to compete with diazo. It had about 1 .2 to 5, maybe 1 .4 D log E maximum. This could be varied a bit, but was still a problem. Also, we did not have the marketing distribution for all these small satellite installations which use aperture card material. That is why this technique never got off the ground. We know that we can expose the film within a very short period of time. There is a military application where a strobe lamp is used to expose our film. They use the material in a 70 mm format to make three color separation positives. They expose it in milli- seconds from previously prepared separations. The color is reconstituted by additive projection, through color filters. So we know that it is physically possible to make a machine for this type of processing of sprocketed film, but we’ve never had enough commercial interest to really develop it. The machine, here at the lab, that uses this tech- nique is not used to make the initial exposure, rather to give the film an over-all flash exposure which diffuses and develops the original exposure. But the instrument I mentioned regarding color separations is a very sophisti- cated application that has been in existence for about ten years. S: What about Kalvar’s stand with color? How far away do you think it is? K: I don’t know because color will require a real breakthrough. The diazo compounds that we use get more thermally sensitive as you go further into the visable spectrum, so that the shelf life of the film becomes critical. We have made a red sensitive diazo, but we have not made a film out of it. It is that unstable. S: You don’t get enough storage to even get the emulsion on the film? K: That’s right. S: Any leads on that? K: Yes, we think we have some, but we don’t have the money to do it right now. We wish that it would be possible to predict when it might be possible to make a red sensitive diazo. No one has yet been successful in doing it. But we do have ideas. S: As part of this, do you believe that ultimately you would be able to produce a monopack color film, if it becomes possible to produce sectrally-sensitized diazos? K: With vesicular photography, the vesicular image is either there or not there. It’s not a color process, nor does it seem to lend itself to color. We’ve gotten color out of it in two cases: one was the ABTO system; the other was EVR. S: ABTO seems to be a basically inefficient process for direct projection. K: That’s a good point; let’s talk about it for a minute. Using the ABTO system with conven- tional silver films, only about 2% of the light gets into the first diffracted order. With our film, properly developed, we can get almost 50% of the light into that form. 86 Boeing did some work with our film on making more efficient diffraction gratings. With one of their gratings you can look at an incandescent source, let’s say, and hardly see the source. The source is just about blotted out — the zero order is almost eliminated. This violates the laws of physics, but the grating is there for you to see. All the light is in the diffracted orders, and if you work out the mathematics of it, about 50% of that light is replaced diffracted order. S: In our specifications for archival media, we've asked that there should be no requirements for conditioning of the material to changes in environmental temperature or humidity. K: There is no need for that because we have tested our films from -100° C. all the way up to 212° F. and we found that proper development meets most of the requirements. This is covered in the development paper. About the brittleness of polyester, there is one thing important to note: silver gelatin becomes brittle at low temperatures; we don’t have that type of problem at all. The coating that we use is a flexible themo-plas- tic material, even at -100° C. to + 100° C. If we go down to a liquid nitrogen temperature of -196, we still maintain flexibility and find that the material does not craze. We have exceptional quality in that respect. S: We have been toying with the idea of using a packaging system such as yours. I’d like to know your experience with the packaging techniques that you use. K: We used the aluminum pouches and we found out that they were really unnecessary. We went to a polyolefin pouch. With one particular product that had a sensitivity to moisture which has now been eliminated, we went back to the aluminum pouch temporarily. S: On a routine basis, do you find the aluminum pouches to be the most effective type of temporary storage technique to prevent humidity change? K: I think a complex laminate containing aluminum is the ultimate in packaging material. S: To meet our requirements for the material taking the least amount of space, how thin a base is practical for this application? K: We can go all the way to a .7 or 1 .0 mil base. S: Have you been doing this with perforated materials? K: We have. For the EVR films. We perforate it to run it through our printer/ processor, then we strip off the perforations. S: But you have not actually made a film for projection on conventional motion picture pro- jectors, that has been this thin, have you? K: No. We have done it on our printer, but not on a projector, but I don’t think that the printer is entirely different. On some projectors this might cause problems. But as far as the processors are concerned, we have tension isolation even in development so that we can maintain the dimen- sional properties in the end product for thin base films. On the Micro Publisher 500, for example, we can balance the dimensional change so that we can get what we want. This we can do here in New Orleans, but with some of the existing equipment at Metro-Kalvar in Los Angeles, we probably could not develop two mil film satisfactorily. S: Is there anything further you wish to say in regards to the aging properties of Kalvar materials? K: Kalvar film basically contains a polymer. It is this polymer which contains vesicles producing the image. On natural aging, the strength of the material increases with the evolution of HCL gas. You have talked about the corrosion problem. What happens to the film when the gas is released? It leads to conjugation. If you think of a long chain of polymer molecules which are singularly joined all the way, the chain will have one particular strength. But if you introduce double bonding, the strength of the matrix increases. The release of HCL by the emulsion leads to conjugations of double bond formation; this leads to an inherent increase in strength. This is a highly temperature-different reaction. If you increase the temperature, the reaction proceeds very rapidly, whereas if the film is kept at room temperature, the reaction proceeds at such a slow pace that even to find an increase of .01 ND, will take almost as long as 200 to 300 years. The effect of this conjugation is seen by measurement when you plot temperature as a function of the storage sheer moduli (G Prime). Supposing one point is -100° C. and another is + 200° C. Say you heat the polymer all the way from -100 to + 200° C., there will be a time when the polymer transforms from a rigid glassy state to a viscous elastic region, and then to a flowing state. But if you cool the polymer, generally if there has been no conjugation, or if there has been any deterioration of the strength of the material, then there will be a lowering of the moduli. In the case of Kalvar film, two very important things happen. First, the moduli of cooling increases two or three positions on the temperature chart, with a shift in the glass transition temperature. Second, most Kalvar film will lose its vesicles at around 55° C. over a period of time. With nonnatural aging, the temperature at which these vesicles can collapse increases to as high as 1 1 0° . Based on these two phenomena, we can conclude that: the strength of the polymer at the surface of the vesicles increases with its age as it eliminates HCL gas. What this shows is that, supposing we have film produced today, and you measure the thermal resistance of the film you would expect the polymer to flow at such and such a temperature. But, if you hold the film for 10, 20, or 30 years, you will not find the flow transition at the same temperature. It has moved to a higher temperature. This is unique to the Kalvar material. No other polymer exhibits this effect. This is one of the reasons why samples of our Type 10 film, manufactured in 1954 tested then for thermal resistance (60% resistance at the end of four hours at 55° C.) today show 100% resis- tance when subjected to the same conditions. The strength of the image has improved because of th eslow reaction. S: Is there any way to speed up the reaction? K: There are ways to speed it up, but we don’t want to do that because 55° C. is a fairly high temperature to occur in normal storage. If we had a polymer which might flow at room temperature, then we might consider enhancing or catalyzing the reaction. But we would like the reaction to act as a natural phenomenon because at 55° C. the polymer has got capability to flow, capability for image formation and capability to produce a 87 single D log E curve— benefits of which we do not want to be deprived. If we made a catalized polymer, we would not have the same photo- graphic performance as when the polymer had a glass transition of 55° C. What it comes down to is a desire for the ability to resist stress as opposed to suitability for archival storage. Our experience over the years in applications requiring a material to resist stress has shown that with normal processing proce- dures, we haven’t really experienced any use problems in viewers, printers or projectors. Under archival storage conditions— which are more controlled than normal working areas— the stress factors would be lower still. S: You were talking earlier about a film which would have no HCL leakage. What would its archival characteristics be? K: What we are trying to do is to change the matrix so that it will have a fairly high modulus of cooling, right from the beginning; a saran in which the vesicles will not flow until the material has reached 100° C. or so. We won’t require an increase in strength with age for such a material. Remember, however, that with the present matrix, we have been able to produce motion picture films, graphic arts films, electronic video recording film, microfilm and several types I haven’t even mentioned. Though we are not totally satisfied with our present matrix formula, it has done well by us. If you are talking about the HCL problem speci- fically, we have a variety of ways to overcome it. Relating to the storage standard, PH 1 .43, it would take almost 600 years before one could detect any HCL contamination by our present film. In addition, Kalvar film itself will not be attacked by the direct application of the vapors of concentrated hydrochloric acid. At the moment, however, it is recommended that normal silver materials, diazo, and vesicular films not be interfiled. This prohibition is a part of the ANSI standard. In fact, no other material can be interfiled on a permanent basis with archival silver. The standards just don’t allow this because silver is so over-sensitive to minute quantities of anything. I think what it comes down to is this: you mentioned the storage and the conditions of storage— whether it is this film or an improved version that does not release HCL, we are looking for storage at probably 90° F. or less. That’s going to be the main criterion: 90° or less. The relative humidity really isn’t going to make an awful lot of difference. For the number of years you are looking for, and response— photographic fade, other factors— this is really what it would come down to: we have to be afraid of high temperatures, whether we increase the glass transition temperature or not. Our film is going to be more susceptible to extreme high temperatures than silver or diazo films. That’s the one thing we have to fear: high temperatures. Not 110° F. now, but those times when the film might be put on the hood of your car at 190° F.; the film is not going to take it. We might be able to show that in certain instances it might be able to take 200° F., but it’s not going to take it like silver. Given these temperature considerations, Kalvar film shows itself to be very durable. Take silver, for example, you can scratch it with eight grams of material on the stylus, using the ANSI stylus scratch test. It takes almost twice as much weight to mark on Kalvar film. The required weight goes up with the age of the Kalvar stock. When you are talking about archival quality, you require a film which is not going to deteriorate its image by natural aging. We can vouch that images on Kalvar will not deteriorate in 600 years. That’s the prediction we have now based on the HCL elimination; it keeps on constantly increasing. We have no way of checking what the absolute life of Kalvar images will be. This is why we don’t have an accelerated test. The problem in establishing such a procedure revolves around the indeterminate natures of polymeric flow, actuation energy, and temperature. There is no linear relationship between these factors. In effect, you can't apply silver tests to Kalvar. They just are not the same materials. S: Is there no way to simulate a glass transi- tion within a given period of time? K: No. S: What about the possibility of bubble loss? K: It is impossible for migration to take place. This is because the cell wall increases its strength with time. The cell wall is the most rigid part of Kalvar film. We have tried to collapse the cell walls by subjecting the film to very high pressures. We have gone all the way up to 5000 lbs. and have found no loss of density at all. We could go higher than that, but the device we were using was not able to exert more than 5000 lbs. of pressure. You cannot destroy the vesicles by external pressure. The scratch tests were done by the American Standards Testing Bureau. They did fading tests, viewer scratch tests— 4800 passes in a normal microfilm viewer— and then compared the film to traditional silver and diazo materials. After 2400 passes, which simulates 150 hours of viewing, they found no loss of density, no loss in image quality. Another surprising thing which we found, that we had not realized before, was that even though our material was on a polyester base, our film showed less accumulated dirt after all these passes, than the other films. We had expected more accumu- lation because of static electricity; in fact, we found that the other materials tended to self-generate powder. Something was coming off the other materials that wasn’t coming off ours. We are looking into this further. This is fairly significant. Of course, any time film breaks down physically, powders or the like, it contributes to scratching. But our films just don’t powder. Since these tests we have had reports from our customers verifying this. We can not document what keeps this from happening, but we have some theories about it. In summation, the American Standards Testing Bureau report said, “On the basis of our testing of a limited number of film samples described herein, we submit that the commercially processed Kalvar Type 1 03 film is equal to or superior to silver, and superior to diazo products intended for similar applications.” 88 EASTMAN KODAK CO. (This part of the interview with Lloyd West and Peter Adelstein at Eastman Kodak has been placed In this section because it deals with vesic- ular images. ) S: Dr. Tulsi Ram, at Kalvar, said that you were presently working on a standard for vesicular films and that it might be ready in a year or so. How is it progressing? K: First of all, that standard ANSI is working on is not necessarily aimed at the question of archival use of vesicular and diazo films. A lot of people think that those materials are not archival. What we want to do is find what their behavior is, and if they are not archival, how good are they? We have, in committee, defined other levels of stability such as long-term, medium term, and short-term. Archival is defined as 200 years or more. We are now distributing test films and trying to find out what the behavior of these products is. There are some difficult technical decisions to make, unlike the standards that have been written for silver gelatin films and polyester and cellulose ester base— because the variety of materials used to make vesicular and diazo films is very, very wide: all types of binders, coated mostly on polyester base. How do you determine whether the binder is stable? You just can’t use the mushiness test which we use for gelatin. There are all kinds of problems of this nature. I would say that if we have a document in five years, we would be doing very well. This is not because of inactivity on the part of the Committee. The Committee is a very diligent one; they meet twice a year, generally for two days at a time. There is a lot of activity going on. Vesicular and diazo is a field in which we don't have any background at all. Vesicular films are only ten years old; diazo films have been around longer, but no one ever considered them for this type of application and there is no information available. It’s a much more difficult problem than with silver. We had the Brady plates to fall back on for silver, but we have nothing for vesicular or diazo. So, I don’t think that a one-year prediction for the standards is a valid one, or realistic. S: Do you think that Dr. Ram is being optimistic in saying that his materials are of archival quality? K: I don’t know. I’d like to see some results. He has published two papers from which there is data up to ten years, but that’s all there is to go on. I just don’t know. Vesicular films from several manufacturers are being tested by the ANSI committee. I think that there are eight labora- tories participating in the study. So something is going to come out in the wash. As of yet, however, we haven’t started the tests on these materials. One of the difficulties in testing a vesicular film is how do you predict what is going to happen? This is a tremendous problem. With dye work, we use these Arrhenius equations— accelerating temperature and then extrapolating down to room temperature. If chemical kinetics apply, then straight-line extrapolation should hold. Of course, we are not really doing a completely true chemical analysis, I guess we all agree, because there are many things going on there, but at least there is good chemical reasoning behind this approach. The very fact that the points all come up in a straight line gives us some confidence. If they all came up in a curve, we’d shrug our shoulders and say this is a very complex reaction. So that’s why we do have a little bit of confidence that what we are saying is true. But when you are talking about vesicular film, how do you accelerate the reactions? It’s true that the manufacturers kept the stuff around for ten years, but is that going to tell us what will happen in 30 years or 100 years? And if you increase the temperature, which would seem logical— to do the same thing to vesicular that you do to silver— you run into another problem. That is, the binder softens and you lose the bubbles. The vesicular manufacturers tell you that that is a ridiculous thing to do because no one is ever going to heat it up to 1 30° F. That’s terrible storage. Of course the binder will melt. But if it stays at normal temperatures, it won’t; they are absolutely right. It’s the type of thing that prevents you from using the ten-year keeping data and applying it to 100 years, without supporting data. S: What about diazo? Can’t you do accelerated tests on that? K: On diazo you can. Even with vesicular we can heat it mildly and we are planning to— 70° , 80° , 90°,100° , 110° , and maybe 120° . S: There is a certain appeal to vesicular film — at least in theory. There is nothing left to be attacked. But there are a lot of problems, we feel, from the standpoint of the H & D curve and the over-all exposure latitude. And of course, the question of whether or not the material is archivally suitable. 89 Agfa-Gevaert AG Mortsel, Belgium W: Edith Weyde A: J. Van Rintelen P. Luyten Ing Johannik R. Verbrugghe S: Ralph Sargent A: It is probably true that the difficulties encountered with storage of silver images is due not to the poor archival properties of silver but to poor storage conditions and poor developing procedures. S: What we are looking for is a method to loosen up the requirements for the proper storage of silver images. If we can’t find some new material which will allow this, then to specify exactly how the existing material should be treated to insure its longevity. The purpose of my trip is to determine whether or not there is any new or developing technology that will better the over-all picture for archivists. Our purpose is somewhat different from that of FIAF's Preservation Committee. They must work within the status quo regarding existing mater- ials. Our purpose is to push ahead, if possible. A: If you are talking about materials other than silver materials, you should always be aware of the speed required. For example, Kalvar is too slow. S: Not necessarily. We can work with Kalvar. They have developed a new emulsion which is about 100 times faster than the old one. They have also been able to sensitize it to green. Essentially, the only thing they have not yet been able to do is to get a stable red-sensitized resin. They are talking in the range of .01 joules per square centimeter, but they may be able to make it faster. However, one appealing thing that they have been able to do is to make a vesicular emul- sion which can be used as a direct contact printing intermediate to silver, without having to go through optical printing. My past experience with vesicular images has been that it was always necessary to do some form of projection to get the image up to the proper gamma. With this new type of emulsion they said they were able to make its gammas correct for contact printing. This is unusual for vesicular materials. Is there an inherent possiblity in your process to do likewise? A: Yes, I believe so. We could arrange to get different gammas for our process. W: Here you see a silver image with an emulsion of 1 .0 grams of silver per square meter. This is computer output film with silver images. One side is intensified and one side is not. There is only a very small amount of silver. S: The question of real interest is what happens if the material is immersed in water? W: The bubbles disappear. However, the bubbles have changed the structure of the binder; and though you cannot see a picture, when you use Schlieren optics, you can see a picture. When you use materials other than gelatin for this film you can see the structure with the eye. As you can see, this part is the silver image. This black part has been intensified by bubbles. This part was washed out. You can see the structure. But in this structure, the silver is also here and so you can restore the bubbles. S: By reperoxiding it, or just by the optical system used? W: You treat it with hydrogen peroxide. You can do it repeatedly; and, you can do it in many different ways. A: Silver catalyzes the reaction; it can be repeated over and over. S: What is the long-term stability of this process? A: When the film is not drowned by any silver- consuming inundation, the image can be re- stored. As long as the silver is still there, you can always rejuvenate the image. S: Is this process actually being used anywhere? A: No. This particular version is of high sensi- tivity so it could only be used in situations that require such. S: You talk about using binders of different chemical compositions to enhance the shifts in index of refraction. W: Yes, the silver is held to the film by other materials. A small amount of gelatin is used only to suspend the silver. S: What type of base are you using? W: Triacetate and polyester. S: Could this technique be applied to existing films that have faded? 90 A: It would depend on the type of film. With some variations in treatment, you could do it. But one insurmountable problem is that of fog. The fog level will go up. A: Basically, it depends on the signal-to-noise ratio. If the signal-to-noise ratio is poor, the amplification will tend to produce poor results. When the fog is not silver, there is no problem. Actually, our printer has done several tests on this. We can do it with microfilm, and with computer output film — a number of films will work with this system. S: I was wondering about continuous tone images because most of what I had seen was line copy. I take it that these are continuous tone prints? A: Yes, except this series. Continuous tone is no special problem. We get good consistent results, an even field. There is an interesting problem in Sweden. The Swedish have license plates on their cars which have numbers in reflecting color. When the police take a picture at night, they can see only the reflecting number, but not the car. We have made tests with this film to intensify the picture so that they can see the car. But when we intensified with bubbles, the reflecting numbers became undecipherable because of over-exposure. So we intensified the whole picture, and then, using water, we destroyed the bubbles in the license plate area; so now, both car and plate can be easily seen. S: Are the police there using this now? A: Possibly. They intend to, anyway. S: There is a great deal of grain here. What causes that? A: The amplification works on both the picture and the grain. W: On the negative, you see no picture— only the license plate. A: Actually, it is amplification of the noise and of the signal. S: The amplification is enormous. Would the same effect occur if you were using the low silver version of the film at normal speeds— as far as grain size is concerned? A: If you have a very high speed film with, let’s say, a very high noise, you have enhancement of the noise and the signal at the same ratio. But when you are enhancing very, very small particles of grain, the noise buildup is not great. Nor- mally, such negatives are underdeveloped which means that you do not see anything. The silver image is below the threshhold for visibility. If you enhance this, graininess should be markedly less than in a normal silver system which has the same sensitivity. The color of the bubbles can be changed. You can have tiny bubbles, changing the color to yellow, for example, so that the over-all noise is lower. W: You can make very large or very small bubbles. A: It is easier to have small bubbles with fine low grain noise. There are a number of ways of making the bubbles. The size of the bubbles, and their color, depends on the film and the process used. S: When you say “color” of the bubbles, do you mean the over-all image color itself, the shade of the image? A: You know how you have big silver particles that are a certain color and that you can change the color depending upon the size of the silver particles, to yellow, brown or black? Like silver images, bubble images have characteristic colors. W: Very small bubbles are also yellow. A: If you make copies, the bubbles will disappear. We also have ways of changing the signal-to-noise ratio in making copies, depending upon the color of the bubbles. The speed of the system that Dr. Weyde has proposed is higher than the normal speeds on the market. W: That is right. You can intensify the speed of the film about 20 DIN to about 30 DIN— a factor of ten. A: I don’t know if this is of paramount t importance to you. Maybe for the original, because you were speaking about an original also. S: No, not necessarily. We wouldn’t propose to use this in a camera. Even in that case, if we 'were to use a material like this, we would ulti- mately pick a compromise point that would give us the best over-all signal-to-noise ratio versus the curve shape we want, and something that was of sufficient speed to make the machine run efficiently — but no more. Do you have a patent on this process right now? A: Yes, we have many patents. Yes, the process is covered. S: It seems that it is one of those processes that would be hard to protect— except if you made it as a special material. A: It is a process; I suppose anyone could do it. S: Have you tried any accelerated aging tests on this? A: We are putting a lacquer coating on the film to protect it which works very well. W: Additional protection can be afforded by packing the film in polyethylene bags. S: It’s good that you mention this. One of the things I have been investigating is the possibility of hermetically sealing the films in containers. This would amount to the same thing, would it not? W: Yes. A: But the film should be conditioned before it is packaged. I remember that some years ago we had some trouble with films made for the graphic arts because the film was not at equilibrium with the temperature and humidity of the outside air. Hence, there were a lot of things coming out of the film which degraded it. We had to make some holes in the packages to allow the gases to escape and evaporate. It’s interesting that this subject came up. We were remarking this morning about some films that had been stored in the Munich archive which had been wrapped in paper. There was also the matter of pollution from automobile exhaust fumes— peroxides, formaldehyde, nitrogen oxides. The films had been stored in boxes with 91 phenolic dividers which had been processed with Formalin. Out of the Formalin came formalde- hyde gas which damaged the negatives. But when the films were stored in polyethylene packages, they survived much better than when they were stored in paper. S: What about polyethylene packages? A number of scientists have said that such packages may be good for several years; but in the long run, the plastic is porous and acts as if it weren’t there, i.e., that ultimately the packaging will allow enough exchange to produce a dangerous situation. A: Dr. Weyde made tests for two years under different conditions of humidity and temperature, and the difference between the unprotected control samples and the protected test samples was very great. S: What about the use of an aluminum polyethylene laminate for such a package? A: You don’t need it. Moreover, using only polyethylene, you can examine what is in the package without opening it. S: Have you done any Arrhenius projections on your W.B. films to know how long you can expect the image to survive? A: We have put it in the sun for one week at 35° C. and 90% R.H. S: This system survives that? A: Yes, it is stable. But the ultimate archival quality depends on the care taken during development. S: Then we have established, first: that it is not necessarily important to retain the bubbles themselves, what really counts is the shift of index of refraction of the binder material. Is that correct? A: Yes. The second point is that you can always rejuvenate the bubbles as long as the silver image is intact. A third point is that the film can be sensitized in any normal manner that silver might be. 92 S: What about cost or manufacturing capability right now? If we were to lay out a specification for a particular type of film stating that we wanted a process that would give us a curve shape of Kodak 5234 in a determined quantity, could you come up with production schedules and cost figures required to make it? A: An estimation, anyway. It depends actually on our marketing department— but we could make an estimation. Edith Weyde 3M Company St. Paul, Minnesota 3M: Daniel Pendergrass James Gergen David Morgan S: Ralph Sargent 3M: We're looking at markets and products, so from our standpoint there are three different markets that might be of interest to us, correct? One, a long-term archival storage medium; two, a second-grade duplicating medium for circulation use among various libraries; three, a very low-cost, short-term use medium of some kind. S: It must be projectable. 3M: Both must be projectable? S: Yes and no. In the case of second-grade materials, if we are talking about a system similar to EVR, television projection equipment would be required. However, we would like to avoid this because there are so many installations through- out the country and throughout the world that are already equipped with 1 6mm or 35mm equipment. Therefore, materials that could be projected on standard motion picture projection equipment would be much more suitable and less expensive. This will probably be the case for at least the next ten years, in spite of the fact that Sony has come out with a low-cost television projector. The unavailability of video equipment in the second category may be what shoots down the idea of using some sort of television technique. In the third category, I think some form of storage system based on present commercial television standards is an excellent possibility. When I talk about the master material, let me say that we haven’t determined specifically that it must be a film image per se, or a magnetic image. It could be either one of these or a third type which we aren’t aware of at the moment, or a groove, if it were to be a disc. But, some form of film system may well be the only thing that can economically fit within the requirements of Category One, unless there is substantial proof to the contrary. 3M: Is it for certain that you’re going to have any one material for any one of these markets? You may have several different materials used in each of them. S: Obviously, because of gamma requirements, there will most likely be two materials for Category One if it happens to be a film material that is developed in a conventional sense. 3M: What are your specific objectives for the first part of your study on the archive material? Can you speculate on what might do the job? How are you ever going to get any kind of agreement on something like that? 3M: You’re talking about more than just the stability of the film base, I gather? S: Oh, yes. This is the first time that there has been any agreement among archivists that a serious problem does exist and that the time is at hand to take collective action in finding the solutions. Archivists are concerned that safety base, triacetate, and other such materials that they are presently using do not really meet what they want to consider archival specifications over a long enough period of time. Eastman Kodak, for example, seems to feel that their color reversal intermediate materials are archivally permanent for a period of 25 to 35 years when kept under absolutely ideal storage conditions, but there is no way of proving this. Even if it is true, 25 to 35 years hardly seems worthwhile considering the tremendous effort involved in transferring. The sheer bulk of the material alone is enormous. 3M: In that case, it seems you’re almost immediately restricted to something that has had a history of 100 years for a recommendation like that. 3M: We yearly change our formulations on our binders, and we’ve changed our backing several times. We honestly don’t know much about the properties of these new materials. Some of these backing materials we’re considering haven’t been around for more than five years. No one has any samples of them. 3M: How can you make any guarantee? Nitrate base again? S: Exactly. That’s what the archivists say. The only thing that has been proven to last that long is nitrate. However, this doesn’t satisfy the problem. The black-and-white nitrate situation is self-evident; we don’t have to say much more about that. I should indicate that we have certain things under study back in Los Angeles that we are thinking of doing with nitrate, other than printing it off. However, soon nitrate will not be our only major problem; archivists are now saying that color is the nitrate problem of today, with video tape on the doorstep. 93 3M: I contacted Photographic Products, but they also have nothing to offer on this long-term archival storage question. This has not been our goal in that division. It’s been pretty much consumer-oriented, copies for home movies and the like— really not even much professional movie-copying concern. 3M: Actually, we’ve done quite a study on all the Kodak Fine Grain materials so we’re quite familiar with them. S: So you can quickly see the speed or sensitivity that is involved. 3M: Most of them are quite slow. S: Yes, that’s true. For example, your Dry Silver film, 784, would have been the perfect speed for this sort of material. It has sufficient sensitivity to work in this application. 788 is not fast enough, nor would it have any other characteristics to recommend it unless there has been a radical change in this material. What has happened to work on those types of materials? 3M: Work on 788 has gone on and we now offer it as a microfilm duplicating film. We have a number of versions of it, but they’re not significantly different. We offer the 788 as a positive-acting microfilm duplicating film. It has diazo speeds and requires a good deal of energy for exposing, but it’s not any slower than other diazo materials. S: Did it improve beyond the point where we were working? 3M: No, the sensitivity is approximately the same; it requires about a joule to expose it. We have a negative-acting film; I don’t know if that was even around when we were talking to you. This one is a very slow Dry Silver film with a very high acutance. It works on the same equipment that the diazo film does, but it goes negative— so it’s a negative-pos or a pos-negative. That film is offered also as part of a system where you normally use the same equipment to expose and develop both the negative and the positive. 3M: What is the gamma capability of those materials? 3M: The gamma on the diazo material still runs about 1 .5 to 2. The gamma on the negative- acting— actually, we have two versions of it: a 796 kind where the gamma is about 1 .2 to 1 .5 and we have the high-contrast version for microfilm where the gamma is between 2.0 and 3.0. So we do have the capability on the negative-acting film to go anywhere in the gamma ranges you're talking about, but that would be a special deal. The numbers I gave you are what they are today. The negative-acting Dry Silver film could be made in a faster version, in other words— similar to the 784. 3M: Of course, the 784 has progressed. It is substantially faster than it was: about 100 times faster than what it was. We have three films we offer: a 7841 which is gamma 1 .0 and the resolution is a bit lower on it because we do not use an anti-halation layer; a 7842 which is also gamma 1 .0, but it has an anti-halation layer and the resolution on that is very good, up around 500 or 600 lines per millimeter; and we have another version still called 7842 Special and it has all of the desirable characteristics of a high acutance film, and it is about 1 00 times faster than the 784 you saw, but the resolution there is over 900 lines high contrast, 400 lines low contrast so it is an exceedingly sharp film. A film like that could be used for high-quality duplicating on a fairly rapid photographic system. We can expose that film on commercial printers at over 100 feet a minute, and we process it at over 200 feet a minute, if you’re looking for that kind of output. But the greatest concern is the archival characteristics of these materials. It would be extremely difficult for us to give a projection. We have done some Arrhenius plottings on these materials and they looked to be really good, but we don’t know how you’d ever convince anybody that this film would last 25, 50, or 100 years. We have about five years of experience on that film; and in a file, under just normal office conditions, we have been unable to detect any change. Other than that, we wouldn’t want to be in a position to make any statements. S: One of the samples of 784 we printed at that time I happened to have out in sunlight for a year, or a year and a half. I haven’t put it back into the densitometer to check it, but visually there appears to be no change whatsoever. 3M: That’s good. We made a good deal of progress on the sensitivity of Dry Silver film. We have a 759 that is being used now by a number of people to record from a CRT. We have one application when they’re using about ten ergs to expose it, and the actual exposure time is about 1 /10th of a microsecond— so we’re getting into that area. S: It’s getting pretty fast. What about its use in electron beam recording? 3M: That business has grown very nicely, and we’ve learned a lot about manufacturing it so we have a real good electron beam recording film. The sensitivity is up about 20 or 30 percent from what you knew. S: For kinescope purposes or strictly as data storage? 3M: We’re using it strictly as an electron beam recording film so the optical sensitivity hasn’t really been adjusted much because we’re still using the same form insertions. The fact is that we cannot because the machine is fixed. It’s a zenoflash. There hasn’t been any point in doing anything about it. Now that film is from ten to 100 times slower than the 759 optical, so the 759 is the best film for that type of application. S: What is going to happen with the material? Where are you planning to go with it? 3M: We’ve had the most success with remote sensing: weather satellites, communications satellites— where rapid access is important. This is obviously where it fits best, and this is where we’ve had the most interest and success. When we try to sell it as a high-quality duplicating film people see it and test it and say it’s as good as the wet material, but they have engineered out their problems with wet processing so they’re not at this point ready to dump it and go dry. They will all go to dry when they replace that system. 3M: They have that mill ion-dol lar line ready-built and installed, and they have to use it. 3M: We have had real success where rapid access is the number one priority. This may be ship-borne, this may be air-borne, this may be data coming in from a satellite where people want to use the information right away and not take the time to process it remotely or separately. This is where we’ve been very successful; and that is a big business, of course— developing. Kodak still has almost all of it, but we are making progress. We’re working with a lot of people and it looks like that’s where our big application is. As the 94 years go by, and people have to replace their existing systems because of the pollution of city water supplies, and ammonia, etc., and the increase in restrictions which will be imposed, we feel we’re in a good position because the material is non-polluting. At least it is to the best degree we can measure, and as far as outside consul- tations have shown. It has no noxious emissions, no liquids to dispose of. We think we’ll be in a good position to compete therefore. S: What about hard figures like D/min and D/max? 3M: Sensitometrically, there really is no problem anymore. The D/mins on our film are in the neighborhood of 0.1 and the D/max can be anything up to 4.0 or 5.0; but normally we offer 2.5. On the diazo, it’s still around 2.0; we haven’t made any effort there. With respect to gammas, we can do anything from about a 0.7 to 10.0 so that sensitometrically, there really isn’t any problem, other than sensitivity. We can just about reproduce any type shape curve that exists today. S; What about spectral characteristics? 3M: The spectral response can be totally panchromatic; in fact, we offer one film that is totally panchromatic. The absolute energy required is essentially equal from 700 nanometers to 400 nanometers. It even goes a little lower than that. We can also selectively separate the light to the blue, and the green, and the red pretty efficiently now. I would say nearly as good as the color films are able to do it, so that is no problem. In fact, we offer one blue-sensitive film; we offer a green-sensitive film; and we offer a red-sensitive film, at the present time. You can find them by numbers. S: What about attack by outside influences, chemical attack, air-borne pollutants, etc.? 3M: The fact that we’re not hydroscopic and we’re not even soluble in anything that is carried by moisture vapor or water vapor would lead you to think that we have an edge in that respect. We’re strictly a synthetic material: we’re not going to start growing fungus or anything of an organic nature. S: What about attack by various solvents? 3M: We’re prone to being dissolved by solvents. We use vinyl-type resins which are considered to be pretty tough; but, I guess if someone started putting alcohol, ketones, or hydro-carbons on these materials, there would be a problem. 3M: If you deliberately want to dissolve them, you could because they are plastic. S: What about oxides of nitrogen? 3M: We have no indication that there would be any problem. S: Have you done specific tests? 3M: Nothing that would give you any long-term results. We’re still changing and developing the formulas. People in the laboratory feel we’ve just started. We really have some tremendous capabilities. We haven’t done a great deal of study on the long- term effects of environment at all, other than when we have a formula that is relatively standard in which case we start some rather normal long- term aging. 3M: The markets we’ve really concentrated on would be the ones that you’re calling Category One— the relatively short-term use application. S: Categories Two and Three, actually. 3M: Where the visual information is available very quickly and isn’t going to be used very long in most cases. S: Right. Now to pop the big question: do you think you are going to have a Dry Silver color film? 3M: No question about it. We’re well on with our research. I say that there is no question about it being feasible; but whether it will ever become commercial, or when it will, I have no idea. S: Do you see any indication at this time that it would be basically more stable than existing color? 3M: We have the capability of going dye bleach or generating colors with the classical system, but I would know even less about long-term stability of color than I would about the other. 3M: I guess one of the things you ought to consider in color for the longest term storage would be our electro-color system in which we plate out— electroplate essentially— dyes on zinc oxide base. Here you have the capability of choosing the dye; you don’t have to choose the dye based on the chemistry of the color process. You can now choose the most stable color dye available. S: We’re not concerned with necessarily storing the film in color; it can be a separation, and of course at the moment, common practice is to use separations for this sort of thing. 3M: That’s true. One consideration with the Dry Silver films is that you don’t remove or destroy any of the chemicals on the sheet, so once you make this record with your exposure and your heating, there are things that could be done to regenerate that record in the years to come. You still have that capability because of the by-products and the oxidation products. It’s a very complicated chemistry and we haven’t done anything in that area. S: After it has been developed, what is the sensitivity of the material to heat and environmental storage conditions? 3M: That is probably one of the more sensitive areas in that once the material is exposed to light, it becomes sensitive all over so any subsequent heating near its development temperature can cause the material to darken. On a long-term basis, this is not necessarily the case. These materials do tend to desensitize as they are stored, and we may be in a much stronger position than I thought we were when we began this program. Again, we haven’t any good documentation, and we haven’t the numbers to say that it happens after this period of time under this condition. But, we know that with materials that have been laying around for three or four years, you can heat them and nothing happens. S: You don’t know what the mechanism is? 3M: Yes, we know what the mechanism is, but we haven’t made any deliberate effort to control, define and document its performance in the long run. S: One of the things that this survey hopes to determine is that with a certain amount of money and interest on the part of someone else, can people be spared to check into this sort of thing? What this request is really talking about is a method of very carefully controlled shelf life or some alteration to the material so that after its 95 initial jolt of heat, it would automatically desensitize the rest of the way. A fixation process of some sort. 3M: We have indications that this too is feasible; actually, it’s more than an indication. In the laboratory, we can do some things, but the time and effort needed to make those commercially available has yet to be committed. At this point, we’re not into it that far. S: It’s interesting that you are coming along on this. 3M: Was your question that if there were separate funding for specific studies, would there be an interest on our part in doing them? S: Yes. Would 3M be interested in pursuing this? 3M: Sure, because we’d be responding to a need there. Right now we are responding to the needs of the immediate access market. You’re talking about a different need for the material. With special funding, we would study it and could make special materials. 3M: It might even be feasible that because of the nature of our process, you could go through some fairly unusual post-treatment of light or heat or something and still be dry. That would give you a capability that doesn’t exist today. Again, we haven’t pursued such a possibility because the way the business is going with rapid-access, there’s no requirement for it. Since we’ve had the most success with rapid-access materials, that’s where we've put our effort. Whereas if we had some big incentive to go in another direction, we could very well perform. S: Have you tried these films in laser recording? 3M: Yes. One of the films we offer, 7869, is specially red-sensitized for the helium-neon laser; but the film is pretty much panchromatic. When we added the red sensitivitiy, we just kept it panchromatic. We do have people using the argon laser and the helium-neon laser for recording material. The laser has plenty of power; if you can record from a CRT, obviously you can record from a laser. About this other application where you want to use these materials as use materials for projection, etc.: I think our capability today better fits that application than it does the long-term archival storage application. Mainly because we just haven’t pushed our efforts in that direction. 3M: We simply wouldn’t have the supporting data to justify putting it into an archival situation. Arrhenius plot studies would have to be made because of the short time these products have been available. We have done some Arrhenius plot studies particularly on the microfilm use papers where the question has come up. Color Separation Systems 96 There are two basic approaches to the creation of color separation records for archival storage. The first relies on the separation of the color informa- tion into its primary records as totally separate frames. These frames can be isolated to separate rolls of film representing red, green, and blue, or they can be placed sequentially upon a single roll. Many designs exist for the place of these total frames on film of varying gauges. The second approach to color separation depends upon subdividing the original image into a finite number of analytic units and recording these units, within one frame, on a space-sharing basis. This is the essential idea underlying such sys- tems as Kodak Keller-Dorian Kodacolor and Agfa Lenticular color processes. These obsolete sys- tems are severly limited in their horizontal resolu- tion and suffer from inherently poor efficiency. A derivative of the second approach is typified by systems such as ABTO and RCA Focused-lmage Holography. Both of these systems depend not only upon space-sharing for the storage of color information, but also upon the angular displace- ment of the subdivided records to create a diffrac- tion grating. By such techniques, separate rec- ords can be integrated within the space normally reserved for one record; then, separated by the use of spatial filters. A proposed modification of the ABTO system, for archival applications, would use a grating encoder of 200 lines per millimeter. Coupled with a high resolution microfilm, such as Kodak’s AHU micro- film, such a record would be of sufficient resolu- tion to meet Archival Category One. In RCA Focused-lmage Holography, the diffrac- tion grating is produced by the use of lasers. This technique, when coupled with certain elements of RCA's HoloTape system, offers an extremely at- tractive solution to many of the existing archival problems; the final archival image would be in terms of a nickel strip, which could be used to emboss vinyl replicas, or make ordinary color prints. Such applications of ABTO and RCA focused- image holography techniques are still experimen- tal, and have not been applied to the 35mm mo- tion picture field. At the present time, the only systems which can fulfill the requirements for Category One archival materials are those based upon the classic methods of full-image color sep- aration. The question then remains how to obtain the most efficient use of materials and techniques at hand for the production of such separations. 70MM SPECIAL COLOR SEPARATION SYSTEM The 70mm special color separation system, as proposed by Linwood Dunn of Film Effects of Hollywood, is a coalescense of traditional color separation theory and practice put into a form which allows optimum compaction of the various picture and sound records. Three color separation images are oriented side by side on a four-sprocket 70mm frame. Four- sprocket pull-down has been chosen since it makes possible efficient 1:1 contact printing of the sound track. The picture images are printed by optical means 18% smaller than the standard 35mm format. Equipment would be specially de- signed to allow wet-gate printing of the original film, through special optics which would expose the three separation images simultaneously. Sound track printing could also be handled on the same machine. Retrieval would be accomplished in the same manner as exposure, but in reverse, combining the three images by superimposition through their respective narrow-band color sepa- ration filters. The major advantages of the 70mm special color separation system are: 1) The 70mm film specifications, the emulsion coating, and the processing are all standard. 2) The images are almost their full size. Compar- ing the resolution of separation raw stock against that of the camera negative film, reduction of image size of 18% followed by a subsequent enlargement should produce little, if any, loss of picture information. 3) The increase in bulk, over a conventional color composite print held for storage would be less than 25%, if the separation film is manufactured using a three-mil polyester base. If manufactured on a four-mil polyester base the increase would be roughtly 35% . In either case, when the 70mm color separation film is compared for bulk against comparable records on separate strands of con- ventional film, the reduction in bulk would be significant. 4) The single film format will obviate the image shrinkage, distortion and general instability of three-strip systems. Also, with all of the picture and sound information on one film, there is no chance of loss of one of the film units, or of mis- synchronization. This proposed system is a straightforward ap- proach to the problem— giving due consideration to resolution, placement, maximum utilization of the material, volume, and cost. For all practical purposes, the techniques employed are proven and reliable. To put such a technique on a pro- duction line basis would require only the con- struction of high-speed equipment, and not the development of new, basic technology. Proposed format for 70mm color separation system. cd a a a CD a t 4 0.288 SOUND TRACK 18% REDUCTION a CD CD CD a a 97 98 NEW TECHNOLOGIES For the scholarly study of moving images, as defined in Category Three, certain features seem desirable— ease of viewing, still-frame capability, the ability to access different parts of the material quickly, and low cost, portable equipment. Each of the systems discussed in this following section— some magnetic, and some hybrids between electronics and film— offer many of these features. While it might be possible to adapt some of these technologies for archival storage, their use for distribution and study purposes will certainly depend on the general availability of the equipment, which in turn will be a function of their success in the marketplace. Peter C. Goldmark San Diego, California G: Peter Goldmark S: Ralph Sargent Peter Goldmark, formerly the President and Director of Research at CBS, is now head of Goldmark Communications Corporation, and a consultant and technical advisor to the London-based EVR Partnership. Dr. Goldmark, who headed the CBS Laboratories for 35 years, developed Electronic Video Recording (EVR), as well as the long-playing record, and the field sequential color television system. A section of a nickel master from the RCA HoloTape system. S: We are looking for three different things: in the first case, a top-quality image storage medium to which any existing motion image can be transferred— something in which the losses of transfer and storage are absolutely minimal. The second category is for an image presentation to groups of 50 or 100, with a moderate or small- sized motion picture screen. The third category requires an image closely approximating that of the normal television screen size such that an individual can scan a film, stop it, back it up, and do whatever he has to do to examine it. Do you have any thoughts with regard to any of these three areas? G: Well, in one phase of EVR, we’ve done work which is little known. We recorded on 16mm film for broadcast purposes. That was called “Beaver”— BEVR: Broadcast EVR. The object was to create a very high quality image suitable for broadcast; one that could match 35mm. That was done by using the same type of film base material we used for the consumer EVR. EVR film has a special silver halide emulsion capable of very high resolution. Illford makes the film. The film reso- lution is in no way a limiting factor. The limiting factor in the case of BEVR was the bandwidth of the system. Vertically, we did not exceed the normal 525 lines because we wanted to stay with broadcast standards, but we could have easily accommodated 1000 lines. There are a number of ways to get higher resolution. There were two images: one for the Y, or luminosity channel, and the other one for the chroma. The 16mm image was split in half so that we had a 300 mil x 5mm frame for the Y channel, and an equal one for the chroma channel. Well, in that five millimeters we could get 500 lines resolution. When I say TV lines, I don’t mean where they disappear, I mean, we had at least 30% response, modulation. Now you know how the system works: the colors were encoded on the right hand side. On the left hand side we had the analog of the Y, or luminosity. On the right hand side we used several different types of color carriers, and color encoding schemes. S: With a pilot? G: Yes, with a pilot. In the earlier version, we used a 2.8 megacycle color carrier with a 1 .4 color pilot. In later versions we used a 2.9 color carrier and a 1 .8 pilot— neither of which were good enough but were used because they derived from the 60 Hz system we were on. Originally we worked with decoders but later we directly hetero- dyned the color carrier up to the NTSC 3.58 color sub-carrier frequency. Now let me extrapolate from that: we have to differentiate here between color resolution and absolute resolution. When we reconstitute a good color picture, we would not be satisfied with the color resolution one would get on the average color receiver, which is way below standards for the I and Q signals— only half a megacycle for each. Normally, the I is supposed to be wider than the Q. The I carries those colors where you can see high resolution, and that’s supposed to be 1 .5 megacycles. That’s one reason we started out with a 2.8 color carrier. At that time the higher color resolution was noticeable on studio monitors which were set up and fed directly. Of course, as soon as you went into a home type receiver, and the receiver decoded the signal, the signal went down to a half a megacycle, so the resolution was wasted. For a professional, high quality reproduction, you would want to go even higher perhaps. I think it’s advisable to increase the color resolution in proportion to the number of scanning lines. In other words, if you do 900 lines, then say, you would take your color resolution to two megacycles. That is, the I signal to two megacycles. Now the film was triacetate. We had some polyester. The results were equal. S: Was the polyester thinner? G: No. The base thickness was 2.8 mils, the same for both materials. We finally settled on triacetate. S: Why? G: Because Illford was making it in higher quantities and it cost less. Another reason was static. The polyester was apparently less hydroscopic than triacetate, and therefore tended to build up heavy static charges. We developed an anti-static treatment which did work, but was a little messy and not permanent. In any case, the triacetate did everything we wanted it to do. 99 In terms of image quality or treatment, the choice between the two made no difference. S: Did you find with the polyester that there was a higher coefficient of surface friction compared to triacetate? Or did you run into any problems of that nature? G: We have not made coefficient of friction measurements, however we have made static measurements under given humidity conditions. In any case, we found that polyester figured three times that of the triacetate. That was about as far as we went. We also tried diazo film. S: But this was an ammonia developed diazo material, was it not? With a dye image? G: Aqueous ammonia, yes. We also tried one type that developed in alcohol vapor. That process seemed to disappear from our work after a while. We have done regular work on diazo in other areas— data storage for example. So we know the diazo processes inside and out. S: Did you try the Kalvar materials? G: Very much so. We had an on-going project for years, up to the time when I left CBS Labs, with Kalvar. They developed an extremely fine structure signal film which did pretty much everything we asked with one possible exception: we did not think it was uniform enough. I think that this was due to the fact that they did not have enough production to average out their variations. By the way, that was not tried on the high resolution broadcast version, only on the home version; on the home version we were able to get 400 or 500 TV lines on a studio monitor. On a home receiver we got 250 TV lines resolution, because of the receiver’s front end. S: With the small system? G: With a small image. The Y image was only two and a half millimeters wide. S: Outside of the uniformity problems with Kalvar, did you find any increase in the resolution of the system using Kalvar? G: It did not come up to the very fine standards of the lllford film. It just barely made it. S: Was it better than conventional diazo? G: No, no. Conventional diazo is the best. You see, the kind of resolution we’re talking about, even 500 or 800 TV lines— you can get easily with the silver halide or diazo films we were working with. The question is one of granularity, or the “noise,” of the material. The noise was measured in stationary frames with various wedge scales so we measured it at a half density of .3 density and ten millidensity units was peak-to-peak grain of the lllford “very fine” film. The diazo was about one third of that. The reason there was any noise at all was because there was a threshold level you just couldn’t get beyond. But, ten millidensity units of the lllford was at least 12 to 18 db below the minimum modulation. S: And the Kalvar wouldn’t come close to that? G: Kalvar didn’t go that low, I think— but I can get these figures for you. S: You stuck strictly with silver halide-type emulsions to make the original recording. In this case we’ve just been talking about the prints, correct? G: Right. S: What about the scratch characteristics of the film within the player unit itself? What sort of life did you have for a print within the player? G: We have to talk about the broadcast player or the home player. With the home player, extremely good. Better than any other— simply because the film moved continuously and was designed to ride on the two magnetic tracks. Unless something were to happen to get into the ways of the picture gate, the life of the print would be very long. S: Did you ever see how many passes you could do? G: Oh, yes. Most tests went up to about 500, then we just stopped. The commercial people average 100-150 passes. There were other factors in relation to dirt— dust and handling dirt with the magnetic material. We developed ways of cleaning: cassettes which had a leader with a cleaning characteristic. We made a tremendous number of studies, some which used adhesive, some which were abrasive— had a sort of rubbing characteristic or combination of actions. The life of the material is fantastic. Now, on BEVR film we used standard 16mm projectors and the life was equivalent to a black- and-white 16mm print; much better than a color print, of course. We used an absolutely standard projector— 16mm — no changes on it. However, the changes were on the vidicon. We had two vidicons— with a split field lens— a single lens, and then a mirror split— panchromatic mirrors split the image into two. S: Did you stay with a magnetic sound track on that version also? G: Yes. S: So did the broadcast version of EVR go at 24 frames or at 30? G: Twenty-four frames per second. It was a two-three projector. S: Eastman or something like that? G: It was an Eastman. The picture quality was fantastic. S: Are you familiar with the RCA experiments on holography? Do you have any idea where they are right now? G: Not really. S: Any attitudes toward that type of system? G: I was always very impressed with the elegance of it. The practicality, I don’t know. I was a little familiar with some work we had done in another area that had to do with pressing very high resolution images. To make hundreds of thousands of pictures uniformly is a little scarey. We lost 50% of the images; we couldn’t do it well. I’d like to see RCA’s system work because it’s so darn elegant. I completely discount their claim to be able to do this with meat wrapping tape. As a matter of fact, I have seen some of the plastic they used with images and it’s far from meat wrapping. Their base was not much thinner than the photographic base used for diazo. Simply because in a hologram some of the occlusions and deformations of a hologram will react to discrepancies in the material. S: Have you done any work with any of the thermoplastic or photopolymerization materials? 100 G: A great deal on the first. In fact, the fellow who developed the technique, Bill Glen, was in our lab and is still. We worked a lot in that area trying to apply it to EVR. It is perfectly possible, as a matter of fact to create detraction images. It’s a little harder to get them as clean and as uniform as you can get with straight photographic procedures. S: As we begin to do a good deal of background work on this study, one of the things that is becoming clearer is that if we could eliminate a surface image layer and really build the image right into the base, into one strip, we would avoid a great many of the problems which have historically cropped up with photographic materials. So there is a certain distinct appeal in thermoplastic recording. G: But thermoplastic recording is a surface effect. As a matter of fact, the image layer is a very sensitive one— more so than its photograph- ic equivalent. There are two ways of doing it. Either you coat a cheaper base— which still has to be photograph- ically first class, otherwise you get detraction, and a piece of dirt will show up not as something dark and light, but as a star , right then and there! Or, you can coat a base with a layer of material that is particularly useful for pressing, for the deformation. So these bases are coated, and without question, the surface is more sensitive to scratches and anomalies than anything else I know. S: Have there been experiments that you’re aware of which have worked directly with a base material alone? G: Yes. There are recording systems where the base material itself is deformed. It’s a G.E. material— it’s a polycarbonate. It has a trade name: Lexan. You are limited in resolution by a carrier because to get color it would be the same thing as in EVR— you still need the carrier so wide and you have to think about the side bands and all that. Whatever the maximum resolution the medium has, you’re always lower than if you use photographic reproduction. S: I’ve been going over the RCA Review articles about high definition return beam vidicon cameras. A scanning technique of this type, something that compares favorably to high resolution conventional photographic technique, might lend itself to transduction of existing photographic images to electronic form. Any comment? G: If you talk about the return beam vidicon in real time, it’s not a good system to choose because it sticks and lags severely. S: Is there no way to get around the capacitance effect? G: No way that I know of. I think you’d be better off with a flying spot scanner. With a flying spot scanner you can count on 1000 lines. And if you’re reproducing a color film, there are now phosphors which can do a good enough job. You have to make up your mind as to the type of scanning device: whether you’re converting at 24 frames or something higher. You know, if it doesn’t have to be done in real time, a flying spot scanner can do a very careful job of putting the image down. S: What sort of technique did you use to pick up the image for EVR— conventional film chains? G: In most cases if we got motion picture film, we used a three-vidicon film chain which was more or less conventional, except we “massaged” the unit to get first rate performance. But essen- tially, it was conventional. S: Did you use devices such as combed aperture correctors to improve the picture prior to recording? G: We used an image enhancer; we developed such a device and put it on the market. It did both horizontal and vertical aperture correction and color correction. It was more a question of cleaning; that type of correction must be applied at the recording. What was important was to get absolute minimum noise pickup; to come out with a flat frequency response of, say eight megacycles. We were using plumbicons to keep the lag low. Vidicons aren’t very good at low light levels. We also had to get exceptionally good registration. Normally the Y signal is derived by matrixing the three RGB signals, in which case you must have proper registration, or you lose definition in the Y signal. So the amount of detail in the picture naturally depends on the quality of the registration of each color channel to the other. We didn’t use 4-V cameras, so what we did was to mix the highlights, then use the green signal for the signal up to two megacycles. The results between using a conventional Y signal and one derived from the green channel were almost indis- tinguishable. Now you’re right, if one wants much higher resolution transfer from the original; I know of no vidicons of any kind that are going to do much better than what they’re doing now. S: Well, you came up with a successful flying spot scanner for the EVR player. Did you actually get eight megacycles resolution from that system? G: Before we turned over the prototypes to Motorola, we checked the optical system out completely. We were able to see down to 500 lines, using a high quality studio monitor. That’s better than eight megacycles response. Later, in the production machines, when you played the signal into a normal TV receiver, black-and-white, you still could see comfortably 400 lines. On a color set, there was nothing past 400 lines, because of the color dot structure. Now, this was a three-inch economy flying spot scanner. It had an aspect ratio of one and one- half inches in width to two inches in height, using a forward scan. We “chased” the film with the scan. We ran the system at 60 frames, but you could run a high resolution system at 24, optically equalized, and take your time. You would also use a ratio of three by four and use a horizontal dimension of two inches. S: What sort of phosphor did you use? G: We used P-16, simply because it matched the spectral response of the photomultiplier. It also allowed for the use of an extremely simple lens, requiring no corrections. You want the whole system to match, to get the best efficiency. If you scan a color film, there are now very good phosphors with enough red response to do the job well. I saw this in England, in a three inch tube, where they were scanning Super 8. As far as resolution is concerned, it’s a question of the gun and the magnetic deflection systems. The color phosphor is no problem; it’s a zinc oxide compound with something added to give more red response. 101 S: Maybe we should look a little closer at re- producing techniques. There seems to be no problem of getting the original signal onto some form of material, but there is a question of what to do once you’ve got that. First of all, G.E. has a new small size color projector. G: TheTalaria! That was also designed by Bill Glen. It’s a poor man’s Ediphor! I’ve worked with the Talaria for a while and found it to have limited resolution, because it has one surface within which several carriers are created. One carrier is the line structure of the image; another carrier modulates the line for the I information and another modulates the line for the Q information. You have problems with side bands and beats. But, it gives a very satisfying picture at 525 lines and no higher. The laser recorder would be a very good system. We built one; it’s probably the best laser recorder in existence. It uses a red and a blue-green laser (an argon-iron laser split into the blue and the green modes). We have produced kinescope recordings with that recorder which are the best I’ve ever seen. The resolution is tops because there is no problem with lasers getting a fine spot. So, I’m quite relaxed on being able to assemble exposed color film to standards that you have requested. S: But of course, you were using conventional motion picture projectors to project the image, correct? G: Right. But if you want to use an electronic signal and project it on a large screen, then you have to use an Ediphor to get the very best picture. I’ve seen some of our EVR pictures projected with an Ediphor, using the chroma and Y picture re-encoded. I saw this in Europe using a 625 line system and the results were tremendous. The Ediphor does a good job. As a mater of fact, we developed for the Air Force a 900 line Ediphor for data display and we know that there is no problem getting high resolution. S: That’s a very expensive machine, however. G: It’s not for the home! S: Well, this is the problem: there has been a proposal for funding regional study centers of motion pictures and videotape. Now it’s presumed that each one of these places would have access to a central file of archival materials. If these materials are stored in some form of elec- tronic format, they’ve got to be capable of being shown on a screen of a reasonable size, say, six by eight feet. G: The Talaria would do a good job there because a good 525 line picture is not bad. S: The pricing is about $38,000 or so is it not? G: About. S: It seems to me that a specialized installation would be quite feasible (using a Talaria or Ediphor) if there were a limited number of these regional centers, but if the Archive Advisory Board is going to say that the #2 rated materials are now going to have to be shown in every theater and place they choose, I can see where we’d be in trouble because we couldn’t come up with the equipment to make this feasible: portable equipment, etc. G: Well, from how far away would this material be piped? S: That hasn’t been settled. It might turn out that the material will physically be shipped around to various regional sub-archives, if the material were in a compact enough form. The other alternative would be literally to pipe it around using Telco connections. G: Or satellites! S: Yes, satellites. . . but that extends the idea further than we have contemplated. G: I’m working on such a project right now. S: In any case, the centers would call up whatever information they wanted transmitted to them. Following the simpler, more accepted methods of getting information around however, has brought our attention to the business of video discs, because of their incredibly small volume displacements. But for the moment, let’s return to display devices. What about the TV monitors themselves: the color tube. That would be a rather major undertaking to redesign for high resolution purposes, would it not? G: Well, we are working now on a new high resolution color TV system. First of all, there are tubes now available with unlimited vertical resolu- tion. The Trinitron is a good example. But we’re only half way there. The horizontal resolution is fixed. I think that the Trinitron can be made finer; I also think that the conventional three-dot color tubes that we know can be made with a finer dot structure. But the current standards of broadcast are limiting the construction of the tube. S: The present, run-of-the-mill tubes have, at the very best, a 400 line cut-off, do they not? G: Yes. But there is something that should be appreciated. From where the average person watches, even with the very best studio monitors, you want to see between 250 and 300 lines, very clean and enhanced. There is such a thing as the “apparent sharpness” and the “absolute sharpness.” S: RCA has been making noises about creating thin-film picture display devices. Have you seen any of this? G: No, I haven’t. I haven’t read anything as far as color goes. The only thing I’ve heard relates to black-and-white. And then there’s the question of half-tones. The business of half-tones is axio- matic when you speak of color reproducing systems! You have been talking about the archival storage of images. At the beginning you were talking about transferring a 70mm product. How is the transfer going to be shown? S: It’s hard for me to see any of the electronic systems we’ve discussed as being a replacement for the large format, direct photographic projection system. When we’re talking about display for a very large audience, on a large screen, I wonder if you can afford to go through an electronic step. Is it not possible that the losses would be so tremendous that the retrieved image would suffer greatly? G: Well, as you say, it is viewed by an audience, and the audience is not supposed to allow for intermediate steps. That’s very hard. But I’m not so sure it can’t be done. If the audience sits at a distance of five times the screen height, then the minimum angle of perception would be one minute of arc. This could be handled by an electronic system. S: But in the case of a 70mm exhibition the audience sits much closer than five times the vertical distance. Even the middle of the theater 102 is no where like being five times the distance. The height of a cinerama screen can be on the order of 30 or 35 feet; the front of the audience may not be more than 50 feet away. Of course, this is the most severe example of what I’m talking about. G: Well, good vertical resolution of 750 TV lines would be adequate. We can forget about the current color system because the subcarrier would limit the upper bandpass. I would say 750 lines vertical and 500 lines horizontal— a total bandwidth of eight megacycles would handle 70mm requirements very well. S: Well, that’s certainly within the capability of the Ediphor projector. Now, to reconstruct back to a conventional, projectable image— my presumption is that you’d make prints. G: Yes, I am assuming now that with a laser recorder or an EBR color recorder one has produced the color negatives needed. S: One of the continuing problems for archivists has been the fugitive nature of color materials. Whenever they ask how to go about making these materials permanent they’re told to make three silver separations. This makes for three times as much material, requires three times as much storage space, and produces three times the frustration. G: I’ve wondered how bad it’s been. S: What I am driving at is this: whether or not one could make an analog Y film and encode the color information as an additional portion of the frame. In any case, retrieve from that encoded film a direct, optical Y image printed onto the subsequent film, with the encoded color information decoded and “washed in” over the top of the Y image. Would this be a possibility? G: Do you mean doing the whole job optically and not electronically? S: I think that there would have to be an electronic stage. But that the primary detail was in a strictly photographic sense copied direct from the storage medium. G: That was done. We actually made Y pictures photographically by using dichroic stripe filters which derived the correct proportion of each of the three primaries. The chroma could also be derived and encoded by special filters. Then with film made with these filters, we could play directly into an EVR system and reconstitute the image. At one point we made pictures through the filters in a camera and came up with a black-and-white film which could then be shown directly through an EVR player. We proposed a motion picture camera of this nature as a means to avoid the use of color film. In any case, the answer to your question is “yes,” there is a way to do the whole thing optically. S: Did this camera actually create the carrier frequencies? G: Yes. But we never did build a motion picture camera. We only took still pictures. S: Well, this seems to be to be one possibility for the storage of color materials. One thing we skipped was “video-discs.” What do you know about them? G: For the one I know about, the Tel-Dec system, I’ll tell you what is claimed, and I’ll tell you what I’ve seen it do. They claim to be able to make five minute sequences of high resolution. I’ve seen two and a half minute sequences which had reasonable quality, but nothing like the quality you’re talking about. They usually showed close-ups. Allowing for further refinements, I would say the system has possibilities. But I’ve never heard of anyone having seen any sequences longer than two and one-half minutes. They are using frequency modulation for the recording. The wavelength, peak to peak, is one micron. Of course, as the groove travels towards the inside of the recording, the wavelength decreases. It’s one micron on the inside and two and a half microns on the outside. That’s one of the big problems of the system: radius equali- zation. For what we’re talking about, this is not satisfactory. S: Well, for the #3 category the videodisc might be a good solution. In #3 I think standards of 200 to 250 lines might be considered tops. G: Well, they told me that they get 30 hours, but that they have to repeat the life test because they did it on one and the same record. And it’s their suspicion that the worn-off diamond particles are being distributed into the grooves and accelerate the destruction of the stylus. So they are now re-doing the life tests. I think that their way of making the stylus will probably change. You know that crystals, when cut to very small dimensions, possess stress characteristics quite different from those of larger cuts. To make small stylii of this type will require special orientation of the crystal structure, which will probably mean that the diamonds will have to be “grown” synthetically. I have a feeling that they will lick it, however. S: When was it that you saw this? G: Four months ago. S: Are you familiar with the work at Stanford on videodiscs? G: No. S: In the SMPTE Journal they published an article about their photographically generated videodiscs. G: That one I do know. S: Has anyone taken up that work? G: Photographically generated videodiscs have quite a number of problems. I see nothing to them that represents an advantage over other systems. Before we decided to go into cassette video, we had long deliberations about what way to go. Our first approach was test out discs and the other was to check out cassettes, in two parallel projects. We had some very exotic discs and the results were very interesting. But after we saw all the problems and other limitations we decided to go the route of the cassette. One of the problems with discs is that you have to record on each groove an equal number of picture elements per revolution. The eccentric- ities cannot be controlled to perfection, so the elements from groove to groove must match, if the pickup device intercepts the eccentricities. There really is no way to control eccentricity to zero. That’s why the Germans chose the method they did, of two fields per groove: that covers you. S: Do you think that it will be another five or ten years before the disc becomes a reality? 103 G: Well, I think that it’s going to happen within the next year and a half. But the playing time will probably be in the area of five minutes. S: That’s not really a viable solution for us. I was hoping for something in the area of 1 5 minutes. G: Well, they are working on a changer, using two turntables. Their disc system has a little box in which there are 12 of these discs. An arm reaches in and takes the first disc out, in the meanwhile the second disc is removed and put on another table. The machine uses a cue to change from the first disc to the second. While the second one is playing, the first is put away and the third is taken out. It’s plausible, but very messy. S: Visions of mechanical nightmare! Why not use a larger disc? G: I think the reason has something to do with aerodynamics. In the beginning they talked about a 12 inch disc, but as the project went along they talked more about a seven inch disc. They’ve only shown an eight inch disc. Nobody’s ever seen the 12 inch disc. S: In any case, I think it’s a system we should look out for. G: I think it’s coming. S: The final area we should discuss is video- tape cassettes. What is your attitude about them? G: I saw recently the Phillips machine and was very impressed with the quality of the picture. They maintain that the material is good for many hundreds of plays. But I don’t know what it looks like after 500 plays. I wouldn’t be so concerned about tape deteriora- tion as a result of playing, it’s a question of what happens to the head as a result of running the tape. S: What about the Sony system? Have you seen that? G: Yes, it’s good, but not as good as Phillips. I found the Phillips quality better, only because they had designed it for European standards and the Sony is designed for American standards. 104 I don’t know any more about the Sony. I know nothing about the archival qualities of either system. For archival storage, with today’s technology, I don’t see any fundamental reasons why a magnetic tape couldn’t be used. With an expanded format, you could handle the needed bandwidth. The noise level is good enough. If you scaled the whole system up, say to four inch tape, you could easily do the job. S: It seems to me that there is a question of technological “overkill.” Perhaps this isn’t the most efficient way to go about solving the problem. Do you agree, however, that present-day magnetic videotape recording (two inch) has gone just about as far as it can go? G: Yes, but there is one thing that I’ve just thought of: even if you doubled the tape to four inches, there is a question of the head resonance. You’ve got to have some wind in there and I just wonder how high you can go and still operate below the resonance of the head. It’s quite a problem to the designers to pump in enough energy. But on the other hand, there has never been any need to try; perhaps it can be done. I would keep myself open. You know, there is one possibility: you may want to derive an intermediate product, prior to whatever form you wish for release. S: Exactly, and I think that that has been the thrust of our discussion today. It’s just very hard right now to pick out what the best technique is going to be. Non-Magnetic Video Recording Systems The following section sets out to examine modern techniques for recording scenes photographed by television cameras onto media other than magnetic tape, and also to evaluate the potential use of new systems and materials for rerecording, and storing, filmed material. CBS SYSTEM OF ELECTRONIC VIDEO RECORDING The CBS Electron Video Recording System (EVR) uses electron beam recording to place video and sound information onto photographic material; playback is accomplished by means of a flying spot scanner. Recording: Program material input to the EVR is converted into a color television signal which is separated into its luminance and chrominance components. Both signals are enhanced by verti- cal and horizontal aperture correction, and both are gamma corrected to ensure the over-all sys- tem gamma approaches unity. For color, two electron guns are used. The lumi- nance information is recorded on the left-hand side of the film track, and the chrominance is recorded on the right. Synchronizing windows run between the information tracks. The gun chamber is moveable, and can be indexed to record four dual tracks across 40mm film. In the chrominance frame there is a carrier signal, the freguency of which is an integral multiple of the line scan freguency. To provide a reference carrier for demodulation of the color signal, an unmodulated pilot signal, of a freguency half that of the carrier, is also recorded in the chrominance information area. As the phase relationship between chrominance and pilot carriers is always accurately maintained, nonlinearity, raster size changes, film shrinkage, etc. will not interfere with proper demodulation of the chrominance carrier. A one field delay line permits video sampling between two successive fields. A sampling gate combines both fields in an EVR frame so that it contains the full line 625/525 information during a 1 / 50 or 1 / 60 of a second interval. During record- ing, the electron beam recording the luminance signal is wobbled vertically between adjacent lines at a 14 mHz rate. Wobble phase is adjusted so that video information from the delayed and undelayed signals are recorded on adjacent lines. Printing: A multi-head, wet-gate printer has been developed by Ilford for EVR. Running speeds range up to 200 feet per minute. Using multiple heads, 16 color programs (including sound) are generated every time the master loop is passed through the printing machine. A special diazo film (positive, unity gamma, on a 2.8-mil triacetate base) has been developed for use in the EVR. Its transfer characteristics are: useful D max = 1.76, useful D min = 0.18, average gradient = 0.90. Replay: A three-inch diameter cathode ray tube scans the film through an optical system and the resulting modulated light is converted by photo- multiplier tubes into luminance and chrominance signals. The cathode ray tube scans each picture once per television field. To accomplish this, the film is pulled past an optical gate at the same speed as the film drive recording speed of five inches/sec (50 fps) for Europe, or six inches/sec (60 fps) for the United States. The luminance and color tracks are scanned through a dual optical system which forms two adjacent images of the cathode ray tube raster. Two light pipes then transmit the modulated lumi- nance and chrominance images on the film to two photomultipliers. R.F. Link: The output of the player is fed to a television receiver via its antenna terminals by means of a miniature television transmitter oper- ating on an unused VHF channel. Double side- band video modulation is employed. RCA HOLOTAPE RCA HoloTape is an experimental laboratory re- cording system aimed at the low cost consumer market. The total system is a sophisticated amal- gam of technologies involving elements of holog- raphy, record pressing, electron beam recording, nickel plating procedures and vinyl pressing, yet the ultimate product is a very inexpensive pre- recorded vinyl tape. Recording: A color video signal is injected into an encoder which separates luminance and chromi- nance. The chrominance information phase and amplitude modulates a two mHz carrier. As an aid to subsequent demodulation, a one mHz unmodu- lated pilot frequency is added to the chrominance carrier. Using a 3M Electron Beam Recorder, a 16mm film is prepared in which even alternate frames are luminance information and odd alternate frames are chrominance information. This technique is very similar to the CBS method of EVR; however, the RCA frames are stacked, rather than side-by- side. The 16mm film is the final photographic master from which holograms are made. Cronar tape, one-half inch wide, is coated with 105 photoresist, and wound on reels to be moved through the apparatus necessary to make a series of Fraunhofer-redundant holograms. This type of hologram exhibits certain important and valuable traits during reproduction: (1) images reproduced from Fraunhofer holograms appear to remain sta- tionary, even though the medium moves; (2) high redundancy makes the hologram immune to dirt and scratches. Laser light exposes the photoresist-coated Cro- nar, and softens the photoresist in proportion to the intensity of exposure. Treatment of the resist in a special developing bath removes the softened portions, leaving a relief image of modulated grooves at an average depth of 0.1 micrometer, and an average distance of one micrometer apart. The roll of holograms is then plated with nickel, which, when stripped away, bears the impression of the master pattern. Vinyl tape copies of the nickel master are made by embossing. Replay: To replay the vinyl copies, a laser beam reconstructs the pictures from the holographic recordings. The virtual image is converted to an electronic signal by a specially developed camera tube called a Bivicon. This tube is essentially two vidicons working within one glass envelope; one half of the tube gets the luminance information, and the other half the chrominance information. Subsequent amplifiers, encoders, and modulators produce an RF signal which can be fed directly into any ordinary home television receiver. A scanning electron micrograph of the surface of a hologram recorded in photoresist. The grooves run- ning from lower left to upper right are about one pm apart and 0. 1pm deep. Holographic recording and playback of TV programs. RCA 106 RCA Corporation DAVID SARNOFF RESEARCH LABORATORIES Princeton, New Jersey F: R. E. Flory H: W. J. Hannan L: M. Lurie S: Ralph Sargent S: With focused-image holography, why do you use holographic techniques at all? H: Don’t be fooled by the name. It might be better to call them “focused-image non-holo- grams.” In any case, the focused-image hologram was really invented back in 1898. Then it was called a refraction chromascope or a modulated phase grating. It is a form of diffraction photog- raphy. F: The ABTO system is generally very similar. But ABTO uses optically generated phase gratings. In focused-image holograms, the grating is generated by the laser; and as such, it is a limiting case of the well-known process of diffraction photography. S: Why couldn't you take an ordinary photo- graphically generated image and convert that image into a tanned relief image and then make a nickel master from that? F: We could, but it turns out that focused- image holography has far greater resolution and many other beneficial features. L: For example, we don’t need a laser to read them out. White light is perfectly satisfactory; we’ve even used strobe lamps. H: You don’t even have to call them holograms. The final product isn’t the classic hologram. L: It’s just like a motion picture image, or a schematic variation of it. Focused-image holography bears a very close resemblance to a motion picture system. At the time we were developing HoloTape, we were looking for what was supposed to be a very simple, low-cost, rugged system— in other words, a consumer player for the home. For this applica- tion, there are advantages to using Fraunhofer holograms. Namely the fact that you don’t need the intermittent pull-down and the synchroniza- tion. And Fraunhofer holograms are far more inde- structible. Focused-image holograms are images. If you scratch them, you see the scratch. You don’t have that problem with Fraunhofer-redun- dant holograms. In fact, that was the main reason for using Fraunhofer holograms. The laser readout was a very small price to pay. H: Back in the days when we were comparing Fraunhofer holograms against focused-image holograms, we ran both hot and cold. On Mondays and Fridays, we were all for focused- image; and on Tuesdays, Wednesdays and Thursdays, it was the Fraunhofer system. It turned out to be more or less a draw. F: Yes. For our application, I think that’s definitely the case. L: I think we would all probably agree that if we were going to make a professional quality system— professional quality in the equipment and in the handling of the tapes— we would probably lean a little more heavily toward the focused-image hologram— on a larger format. H: I think if you were talking about archival storage of high-resolution photography you’d have a better shot at it with focused-image holography because with Fraunhofer holograms there is a resolution limitation, imposed by how flat you can maintain the surface of the replicant, and other considerations. S: If we were to talk about either focused- image or Fraunhofer holograms as relief modulations in the surface of metal in terms of Category One materials, in which case we’d be talking about 1200 line pairs, can the system be pushed that far? F: We could give you the resolution and the stability, but not, I think, any reduction in cost or bulk. S: Yes, but the real trick in this system is that it’s the only one we’ve come across so far that’s going to deliver the image in a metal, supposedly indestructible, form. F: That's what I had in mind. We were saying earlier that probably the focused-image form would be recorded with a laser because of the ease with which we can get the resolution, but it then could be played back with white light. But, it would have to be a physically large image to be easy to work with. The working resolution would probably be like camera negative film. But, it could give you the stability of the metal and maybe in a high volume operation, with a lot of development, could be as low in cost as 25