= “<4 = ~e hap 1 titer UP ie Tae way ltt? 4) Lit Limes a ey rive PPARs HE we pepe te LL Rater dial ate dh RRR Eee btn. a oe WASHES ARCOM OTIS EN INOID) WW IP O3 b, OFSPHOTOSEN GRAVIN G —S—T te) ee Ow a. ee oe ee oF " | _ cy 4 ® ii ‘ - 2 ‘ aq 7 nt . a) - ¥ 7 ? . . . Va i . THE PROCESS AND PRACTICE. ~ OF PHOTO-ENGRAVING BY Bera aly (GIRO) ee SMO Uibpe ral Manager, The Walker Engraving Co., N. Y. /.. A GARDEN CITY New Yor«K DOUBLEDAY, PAGE & COMPANY LO24 Ah SeEhA 0 DUG 7 at“ ’ “ : SHUATEIE LU no oy . i) i yy \ seat A842. COPYRIGHT, 1924, BY DOUBLEDAY, PAGE & COMPANY | _ ALL RIGHTS RESERVED. PRINTED IN THE UNITED STATES THE COUNTRY LIFE beet GARDEN CITY, N.Y. First Edition = Iie GETTY RESEARCH INSTITUTE LIBRARY a Vo : ee FOREWORD N ADORING student once asked Whistler what he mixed his paints with to get such wonderful effects. ’ “With brains, madam,” retorted the master. Photo-Engraving is the mixture of brains with chemicals and metal. Photogra- phy and the mechanical processes are but tools in the hands of master craftsmen. It is not only an art supplementary to that which created the original it repro- duces; it is also a service—the service of skill and brains—intelligently applied, to retain or even increase the effectiveness of the original creation. Let five Photo-Engravers endeavour to make five identic halftones from the same original, under identically similar conditions, and there will be a difference in the five plates produced. ‘The difference will lie in the variation in skill of the five groups of men who worked on the plates. Not in the process—not in the camera—not in glass, metal, film or chemical—but in MEN. On a realization of the intricacies of the business, gained at first hand, Hon. Joseph F. Mulqueen, Judge of the Court of General Sessions, State of New York, held that: ““Photo-Engraving is rather to be regarded as an Art—and there is not an item of evidence to sustain the allegation that Photo-Engraving is an ‘Article or Commodity in Common Use.’ ” Like all arts, Photo-Engraving is dependent for its success upon the skill of human beings. This human element must be permitted to function under the best possible conditions. It is of even greater importance than the machinery used, for a dry bearing or broken part of a machine can be repaired or replaced; it is no such simple matter to develop or replace brains. Cooperation between the Buyer and the Photo-Engraver will afford each the opportunity to contribute their best toward the ultimate success of the production. The purpose of this book is to enable the buyer to know all of the conditions under which photo-engravings of various types are produced. It is hoped that it may create a better cooperative spirit, reduce or simplify complicated manufac- turing problems and ultimately result in more satisfactory reproductions. v 2 CONTENTS FOREWORD . CHAPTER i. VIII. LX, XE XII. By Way oF INTRODUCTION . Some early history—Movable types OM aad hbckse aT he Jeeeeent of metal plates—The first photo-engraving—Daguerre, his work—Chem- ical development—The origin of bichromate resists—Origin of the screen— Photographic printing on metal. THe Basic PRINCIPLES OF PHOTO-ENGRAVING . Makinc a Puotro-ENGRAVING The line plate—The halftone plate. # THe PRINCIPLES OF PHOTOGRAPHY LENSES AND LIGHT THE CAMERA MakING a Line NEGATIVE Making a Line Ree Rhoroeaphic wats ue sain Who: ats —Chloride prints. Maxine a Hatrrone NEGATIVE eae aes 3.2: The halftone screen—The exposure—Development—Tint ee lat rite tone positives—Halftone negatives from objects—Dry plate halftone nega- tives—Screen effects—Screen patterns NEGATIVE TURNING AND INSERTING . The use of tint negatives—Stripping Sete Deel ene an extra negatives—Changes in proportion. PHOTOGRAPHIC PRINTING ON METAL . Making a zinc print—Making a copper amen ala beater —Double printing—Painting in solids. ETCHING : Kerrey eee Etching line varie on carne eileen on Berkut ary: copper plates. RouUTING Vil PAGE IO 23 27 30 37 44 55 73 87 102 III Vill CHAPTER XII. XIV. XV. XVI. eV XVIII. XIX. XX. O44, XT GUA CONTENTS HALFTONE FINISHING . Re-etchings—Squared Mleae ap no ane eeseered “as Bleek finishing line, no white—Squared black and white finishing line—Circles and ellipses—Silhouettes—Vignettes—Combination plates—Tooling— Rouletting—Highlight Halftones—Finishing zinc halftones. Layinc TINTs . Patching Tints and Shee CoLour Work . a re Le, en! a Solid zinc line plates for colour Saree nen Day zinc plates ee colour oon —Colour plates from transfers—Hand-cut colour plates—Copper plates for colour work. Process CoLtour WorkK . Making process colour SE een Eire Sion separations—Process plates from black and white copy—Process and Ben Day plates combined— Colour schemes and guides—Combining subjects for process plates. PHOTOGRAPHY OF COLOURS . Colour separations for black and atic Ore nlont separa fon Lae work—The Lumiére autochrome. PROOFING AND PRESSES Proofing a Line SE ealeeatine Halfeonecene overlay Pape anaes proofing—Inks—Other Presses. BLOCKING Flush Recneecon bane tiie. on pIGckse arse a néechinees Routing down the wood—Metal bases. ELECTROTYPING STEREOTYPES REPAIRS AND CORRECTIONS Patching. PREPARATION OF Copy ards one oe Copy for line plates—Tints on Re copies ens for special coarse- screen halftones—Allowances for ““bleed’’—Line copy for colour work — Preparation of copy for halftones—Indicating sizes—Multiple copies for colour plates—Multiple copies for process colour work. SPECIAL METHODS AND OTHER PROCESSES The Mezzograph—Special Screens—Plates from Transparent Proofs— Plates from Halftone Positives—Making Negative Prints from Negatives —Intaglio Plates—Rotogravure. FoRMULAS—BIBLIOGRAPHY—INDEX . PAGE 114 137 158 192 198 214 221 223 226 238 243 LislOF ILLUSTRATIONS FIGURE NO. Reproduction from intaglio plate photo-engraved by Niepce, 1824 . Pigment grains of black water colour paint magnified about 500 times. Silver grains of photographic negative magnified about 500 times . Line plate from simple line drawing. Line plate from shaded line drawing Halftone from photograph Line plate from part of Fig. 5 Line plate from part of Fig. 6 Close up of etched line plate magnified Bote oe times Etched halftone illustrated in same magnification as Fig. 9 . Line plate from crayon drawing . Line plate from crayon drawing, ee iaced Vignetted, silhouetted halftone . Halftone, 120 screen, from shaded line drawing Line plate from photograph Chart of progressive stages of photo-engravings Diagram of light wave vibrations Diagrams of reflected light from one ratte in a panels Plane Diagrams of reflected light from single points in two planes . Unsharp halftone from sharply focussed photograph . The same subject sharply focussed . Process camera stand . Typical process camera Line operator focussing for size at Haron Plate holder with back removed Halftone screen and adjusting mechanism . Diagram of light reflected from a copy . Flowing negative collodion on albumenized Blas ’ Dipping the coated glass in silver bath Placing plate holder containing sensitized glass Peres on Back oh camera for exposure Reproduction of line copy and line negative therefrom viewed by transmitted light . Typical E. C. & R. camera Line plate from a line negative . Negative line plate from a positive of same copy . Reproduction of silver print inked in and one half bleecheds A line plate made from the completely bleached print One copy reproduced in all screens from 55 to 400 A 20 x 24 halftone screen and enlarged view Diagram of light from highlight stop passing ThEOen halfconeys screen Diagram of light from detail stop passing through halftone screen . Tone effects of three styles of tint negatives Photomicrograph of halftone negative before being maa ; Photomicrograph of the same halftone negative after being intensified oH cut ix xX LIST OF IVEUSTRATIONS FIGURE NO. 44. Reproductions of three halftone negatives of the same copy Halftone of 100 screen with dots running vertically and Ranbentalle Halftone of 100 screen with dots running at usual 45° angle. Halftone, 200 line screen dots running at usual 45° angle The checkerboard pattern The same halftone with pattern rediced The same halftone with pattern eliminated A line plate from a section of Fig. 48 Halftone, showing moiré . Same subject reproduced to Sarate hen moiré A very objectionable moiré showing 1 in hatband The moiré reduced to a minimum A diagram of fine lines broken by a Pattrone screen Negative turner’s easel, showing negative flat in position A line plate reproducing the line copy used for Fig. 64 ’ Halftone reproduction of the retouched photograph used for Fig. Gr The halftone negative superimposed on the line negative Removing the outer area of film. ae The halftone negative of the box folded over . All of the underlying line negative removed The completed combination plate ; A silhouetted combination plate Hemonstrrine cliborete nesarive inseruneae The ragged joint caused by fitting together two halftone negatives. A white line tooled at the juncture of the two screens Reproductions from separate halftone negatives, and from these nesatees joned Line plates made from black and white copy, solid and tinted . Five grades of ‘halftone tints . Reproduction of a line copy with ecnne separate ord aati postive attipped on The same line negative with a tint negative and a positive stripped on Line plate from a copy for a border only half of which was drawn . Line plate from the same copy with proportions changed Line plate from the same design with size and proportions Bane Cleaning a sheet of zinc with powdered pumice and water Coating the zinc with sensitized albumen solution ; Whirling a coated zinc sheet to distribute and dry the eoanine The vacuum printing frame . Placing the sensitized zinc in contact ah Heeative in vacuum fear The printing frame swung into position for printing . Rolling up the zinc print with ue ink . Developing the zinc print Diagram showing how the acid resist 1s obtaineds Burning in the zinc print to melt topping powder. A line plate reproducing the line copy used for Fig. 88 Reproduction of the halftone area of ms 88 The combined plate Reproduction of line work needs in ie 92 ; Halftone of photograph used for upper panel in Fig. oe : Halftone from retouched background used for Fig. 92 PAGE EDS OrsIEVUSTRA PIONS VIGURE NO. g2. 93. A combination plate with surprint Reproduction of outline drawing The same drawing with solids painted in on Alace ietiaee ecchine : Halftone reproducing statuary with ordinary background . Halftone plate from same negative with black background. An etching tub Sectional view of the Levy Gd blast Aahtiys peclune The Edgor electric etching machine Enlarged diagram showing acid beginning to een Enlarged diagram showing appearance of zinc plate after first bite Putting the Dragon’s Blood on a zinc plate Tapping the dusted plate Brushing the Dragon’s Blood in one direction After the first bite showing resist The result of the brushing after the eerond bee After the third bite Menta A modern ball-bearing routing machine A close-up of the router head showing the bit The appearance of an etched line plate before routing The same plate after routing The same plate with dead metal removed: Finisher applying the perchloride of iron | A too screen flat tint locally re-etched A line copy reproduced as a 150 screen flat halftone nian The plate painted in . The result of re-etching . ae Finisher burnishing a halftone plate A 100 screen halftone plate with highlight dor locally burnished Reproduction of a halftone plate squared up for beveling The same plate bevelled The printed result A lining beveller Operator trimming the pheclder & Reproduction of halftone plate from negative eter onely pacred up . The same plate bevelled The black finishing line . Detail view of the equipment on Ee Bevellce : The black and white finishing line . Operator scratching a thin elliptical outline Tooling the scratched outline with a graver . Various shapes and finishing lines . A squared halftone from vignetted, retouched Blotter rie The same subject after silhouetting A squared halftone of a difficult subject to be nloverred Reproduction of a black and white line drawing to be used for minors Ries aOR A silhouetted halftone made from a halftone negative with a line negative stripped on A squared halftone of vignetted, retouched photograph. The same subject vignetted and silhouetted . xii LIST OF ILLUSTRATIONS FIGURE NO. PAGE 140.. A graver and cross sections.of different styles 7 "25s oe 141. Lines tooled by gravers called tint tools.mw aes: AS Te eee 142. A typical magazine halftone illustration elaborately rooted prov haiy of Ska | PA Cape 5 aes ete 143. A Roulette . . SN ees ee ee eG em 144. Lines and stipples cut rhe a foulede eRe tar Tree Migs Ea MEEY OS ha 6, hg re 145. A highlighted halftone, Iso screen. . . , RABE 146-153. Samples of Ben Day tints as they appear Parner laid on che Plate a on he nega— TIVE Ma, bo yet, ay ee RS PRS ES ea se ol ara Tg 154. Protomicrerea ph GE Ben Day a ee ee ee ere iss. A Ben Day machine with-film in position. 2 9° . 2). 2 3 2) re 156. Reproduction of line copy of map. 9. > 5 9.9 20. 2 9) 52) =) 1 ee 157. Reproduction of a zinc print gummed out” .7 <5 5 9 ee 158. Rolling up a Ben Day film with special ink po ae 4 a > re 159. Printing the flm on the zinc print’. .. + oe Se) a fl rs 160. Reproduction of the gummed out zinc print ae tint eee oo eo See 161. Reproduction of the zinc print after gum is washed off. . . . 1) 5) eee 162. The finished plate resulting from Figs. 156 to 161 ©. - 4.) 2 92). 2) ee 163. Reproduction of a zinc print gummed to holdiareas. 5 79. 2) . 2) 00 164. The zinc print washed off and Ben Day tint laid > . 2 | =) .) 2 eee 165. The finished plate . . . Sk oe 166. Method employed in patching nev mercn! flrne wea) ay ote 167. Impression of a film and effect of shifting and printing nine times |) = se 168. Line plate reproducing a line copy used in Fig. 169... . « eres 169. The same copy reproduced with heavy highlight dot double pire . « | ge cess 170. Halftone of photograph with a solid background used in Fig. 170. | 5) ee 171. Result of graining the background with a box grain. . s) Sy See 172. Line plate reproducing a poster from crayon drawing used for cine 173 . 2 Sere 173. The same subject tinted with a box grain... OE he 174. Variations in tone obtainable by shifting and doable up a Ben Day it 4S Ee 175. Reproduction of a simple outline drawing used for Fig. 176 . . . | 176. The same subject tinted with a variety of Ben Day films . . . aos ee Bee 177. Reproduction of a line drawing to be used for a set of two-colour dieere sone 3 ee 178. Illustrating all areas routed away except those to printin blue . . . . . . . 4158 179. All areas routed away except those to print in yellow . . . | (2) 30eee 180. The two-colour result . . . reer lll 181. Line drawing to be reproduced i in two plocre 5s . 5 ee 182. Reproduction of the stained zinc after print 1s washed oie Loe 2 183. The stain painted in for the colour\plate . . . | . . . |) 184. The blue plate . . MP 185. The finished colour late Eoined ah black S1ARe Soe 4 a a) 186. The blue plate of a two-colour set. 7 . . =. . «ss 1) 4 187. The yellow plate of a two-colour set -. . §. 2. . . . | (0) 188. Three colours obtained with two printings . . . . 0) | ios 189. Enlargement of two halftone plates printed in the two colon ene . « re 190. Enlargement of three halftone plates printed in the three colour angles . . . . . 163 191. Enlargement of four halftone plates printed in the four colour angles. . . . . . 163 192. The key plate of a three-colour halftone and Ben Day set. . . . . . =. =. =. I64 193. The finished Ben Day yellow plate . .. .. 2. 2 | . 5) 2 2 jer LIST OF ILLUSTRATIONS FIGURE NO. 194. 195. 196. 197. 198. 199. 200. 201. 202. 203. 204.. 205. 206. 207. 208. 209. 210. aes 22: 21%. 214. 78 oe 216. a le 215. 219. 220. 221. 222; 22%. 224. 225. 226. 227: 228. 229. 230. 231. a2: 233; 234. 23%. 236) 2a 7° 238. 2a; 240. 241. The finished Ben Day blue plate The finished black, yellow, and blue plates printed Poe eLher Reproduction of a pen drawing. The finished black plate made on a zinc ihe The finished yellow plate made on zinc stain The black and yellow plates printed in register . The finished red plate made on zinc stain. The black, yellow and red plates in register . The finished blue plate made on zinc stain The four colours printed in register Three-colour process plates made from hand- erlocred drawing si ine colours ’ Illustrating absorption and transmission of coloured light . Silver grain structure of a wet plate halftone negative . Silver grain structure of an emulsion halftone negative . Silver grain structure of a process dry plate halftone negative Silver grain structure of ordinary dry plate halftone negative . A typical process camera equipment for colour work The circular halftone screen and screen holder A flat etched black plate of a duograph set made for Re sie The finished black plate ; The flat plate from the red cena ion erative The finished red plate : The flat red and black plates The finished red and black plates The yellow plate of a three-colour process set flat erched The yellow plate finished The red plate flat etched The red plate finished The blue plate flat etched The blue plate finished . ; Three-colour flat etched plates printed 4 in Perierer Three-colour result from finished plates The finished yellow plate of a four-colour set. The finished red plate of a four-colour set The finished yellow and red plates printed ropehe! The finished black plate The yellow, red, and black plates syrah in Perse The finished blue plate . The finished four-colour set Halftone reproduction made with Prine wet lace from a elec: chee Reproduction of same colour chart made from orthochromatic negative. . Halftone reproduction made with ordinary wet plate from colour painting Reproduction from same painting made from orthochromatic negative The Washington hand press Inking a line plate ; The inked plate in position on caderiee Illustrating the frisket placed over bearers Rolling the bed into position for the impression . xlll 164 164 166 166 166 166 167 167 167 167 172 174 177 E77. 177 177 178 179 180 180 181 181 182 182 184 184 184 184 185 185 185 185 186 186 186 186 187 187 187 193 193 193 193 199 200 200 200 201 XIV LIST OF ILLUSTRATIONS FIGURE NO. PAGE 242,02 Pulling the pressover’ to. make the impression §.). sause ee 244." Removing the-proot fromthe plate. |.) 2 ms. a, ee ee 244.. A*detail view of a halftone overlay) 04>) i ag By os) hy Oe 245. A-vignetted plate prmted with fatimpression 3 22 2. 2 a en 246. Lhe'same subject printed with proper make-ready >) 79) 9 0 eee 247. A make-ready sheet showing two halftones in position. . . . . . » 1, os 248. The overlay folded into position . . PML Ota Me rere 249. -Photomicrograph showing edge of newspaper.” . 2 2 2) 260. Photomicrograph showing edge of super paper © =. © «°° | 2) 9 ee 251. Photomicrograph showing edge of heavy coated paper. . . ~ |. | |) Es 252. Diagram showing impression of 120 screen on coated paper . . . . . | ueeOE 253. Diagram showing 120 screen being printed on rough paper. . . . < | |.) ueeOe 254. A 120 screen being squeezed into rough paper... oR 6 oe. ee 255. Diagram showing 65 screen halftone printed on chitin paper... |. 3 ee 256," Pinning*a proof’ 3" Se” ha eee ee ee 257. Lhe Victoria press 4, 9% 24 tee 206 acketaptess aa op ee 259. Detail view of nailing pothide So ee a ig Se 260. A blocked line plate .. rT 261. A blocked halftone showing Bloeuine evel all aoind owes So 262. Trimming a blocked plate on the tablesaw . . . > | . =) |] une 263. A small halftone blocked ise atoneside .:. » ».. | «| |) 0 2 er 264. Method of “anchoring” or “slugging”. se en 265. Jigsaw used for notching and mortising Rodd blocks PPP 266. Mortising a blocked line plate . . . . . . ©. | | . 4) 2) 0) 267. A blocked line plate mortised .. 1. . 2 2. «6 ee 268. A blocked line plate notched . . . . oe ee en ae rr 269. A frame block with grain running all around pe ee: ME = 270. Photomicrograph showing the dots destroyed by a scratche ri 271. Metal raised up in seratch and new dots partly formed. | | - 7 eee 272. Electrotype of a scratched halftone . 9 2) 2.) | 273. The original scratched plate repaired . . . . 8 a ng rr 274. A diagonal drawn across will indicate sizes in reduecon Pr 275. A Pryorscale with adjustable diagonal . . . . . | 95) 2) 276. Fig. 7. Line plate from part of jig. 5. Enlarged about seven times. the form and tone of an original is what makes the process commercially practicable. The entire surface of a photo-engraving may be inked with an ink roller and when the plate is properly pressed on the paper, the impression transfers the ink from the plate to the paper and makes the printed impression. The original to be reproduced, be it photograph, an oil painting, or a dish of fruit is called the “copy.” It may seem inconsistent to apply to the original a term which would seem more appropriate for the reproduction, but trade terms frequently dis- regard propriety. Copies are grouped into two classes, as are photo-engravings. They are known respectively as “line copy”’ and “halftone copy,” depending upon their suitability for reproduction by the one method or the other, always bearing in mind the mechan- ical necessity for sufficient depth of etching. The appearance of an etched plate is shown in the illustration in figure 9. This is an enlargement of an etched line plate. The flat ridges are the printing surfaces which were protected by the resist. The grooves or hollows were etched out by the acid. It will be clear that the areas of resist must present a sturdy protection to the metal under them, otherwise the acid will undermine them and break down the printing surfaces of the plate. Just how fine and close they may be depends upon the purpose for which the plate is to be used as well as the paper on which it is to be printed, but generally it is not advisable to make line plates of finer subjects than that shown in figure 5. Even this plate 16 THE PROCESS AND: PRACTICE OF PHOTO -ENGEAVING Close up of etched line plate, magnified about 35 Fig. 10. Etched halftone illustrated in same magnification times. pene Due: Both reproductions are halftones, 150 screen, squared, no finishing line. Fig. 9. would not print satisfactorily on rough paper, as it has comparatively little depth in the etched parts. Figure 10 shows an enlarged illustration of an etched halftone plate. ‘The dots appear as tiny hills with flat tops, not unlike the raised castings of a waffle iron. The flat tops of these hills are the printing surfaces which were made with the halftone screen and protected by the resist. “The valleys between the hills were etched away by the acid. Sufficient spacing between halftone dots to permit sufficient depth of etching is regulated by the halftone screens. ‘They are made in various degrees of spacing, some of which will produce as few as 55 dots to the inch and some as many as 400. ‘The 55 screen, as it is called, is coarse enough for use on newspaper, but the 400 is so fine that it can be properly printed only on the finest smooth-coated paper. Both of the illustrations in figures 9 and 10 are shown magnified nearly 35 times, so the actual sizes of the printing areas and the etched depth are naturally micro- .) a 7 a « Lie re a 4 Oe ie HSA tener agar Doe eee WH By a a Ss S > % we & = 3 = ~ ~ IS; %S s Re S S 8 rS S = S do Qs % x 8 aS do, SR, ie) ERY S a i S ~ ~ 3 9S C Fig. rt. Line plate from crayon draw 17 18 THE PROCESS AND PRACTICE OF PHOTO ENGRAVING scopically small features of the plates themselves. When copies are composed of elements too fine or too close to permit proper depth of etching in a line plate, they should be reproduced by a halftone. Line copies which may be entirely suitable for reproduction in a large size may prove unsuitable if too much reduced. Great reduction may bring the elements so close together that they either run together and lose their definition and form, or else they break down and etch away when suitable etching depth is obtained. This is illustrated in figures 11, 12, and 13. The first is a line plate of a crayon drawing reproduced nearly actual size. The grain formation of the copy was produced by eee Hie eae = ap mecgeagem a BAR sf Tice ' (Se oe Wee? ¥ 3 COPS ae ne stem “ Fig. 12. Line plate from crayon drawing re- Fig. 13. Vignetted, silhouetted halftone, 150 duced to one fourth size of copy. screen, from crayon drawing reduced im same scale as fig. 12. crayon on the rough surface of the paper on which the drawing was made. Repro- duced in this large scale it is quite suitable for line work. Figure 12 shows the same subject, reproduced in its entirety as a line plate, but reduced to one quarter the size of the copy. The elements have either closed up or else broken down and etched away. Figure 13 shows the same subject, reproduced by the halftone process in the same scale of reduction as figure 12. The comparison is obvious. Halftone dots have replaced those of the original which were too fine to be held on the plate during the etching process. This subject lends itself to reproduction by the halftone as THE BASIC PRINCIPLES OF PHOTO-ENGRAVING 19 well as the line process because of the irregular formation of the elements of the drawing. Had it been a copy composed of pen lines, its reproduction by the half- tone process would not have been so satisfactory because pure lines cannot be sat- isfactorily reproduced by dots, and they will appear ragged on the edges. The foregoing are not a set of rules, but merely explanations of the principles involved in obtaining suitable reproductions of various types of copies. “They may be disregarded at will, if the results to be obtained warrant such procedure. ‘There is no mechanical reason why a line plate cannot be made from a photograph or other tone copy, nor why a halftone cannot be made from a line copy. ‘The latter is often done for the reasons previously explained, and the result is shown in figure 14. \g y. = ie es “oy — : ah 7 Fig. ee ees facie FE ar om ota ols This is a halftone reproduction of the shaded line drawing used in figure 5. The screen dots appear on the lines as well as between them. Figure 15 is a line plate made from the photograph in figure 6. It has but two tones: black and white. The “halftones” are gone. It is the ability of the halftone plate to produce these “halftones”? which gave the process its name. It must be apparent from the foregoing that it often becomes a difficult matter even for the expert to determine the suitability of any copy for reproduction by the line plate. Line copies vary so greatly in technique that it is impossible to describe 20 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING them all, and experience is the only teacher whose rules may safely be followed. The results to be obtained on the grade of paper to be used are the controlling fac- tors. A plate which prints satisfactorily on smooth paper may be a complete failure on rough paper. Determining the suitability of halftone copy does not present the same problems, because of the provision for halftone screens of varying spacing for use on different grades of paper. Summed up in a few words, this whole matter may be stated as follows: The original to be reproduced must be photographically printed on metal in the form of an acid resist. The elements of resist must be large enough and far enough apart to permit etching the plate to suitable depth. When the elements on the original copy are large enough and sufficiently dis- tinct when printed on metal to fulfil these mechanical requirements, the reproduc- tion may be made by a line plate. If the copy does not fulfil these requirements either because of fineness, close spacing, too great reduction, or because of “tones,” a halftone plate must be used for the reproduction. While these descriptions and microscopical analyses of grains and dots are inter- esting as well as essential for a thorough understanding of the basis of photo- engraving, they are soon taken as a matter of course as one gets more familiar with the process. Copies are considered merely from a standpoint of the suitability for reproduc- tion by either the line or the halftone process, and experience will usually enable one to determine, without hesitancy, which process should be employed. If unsuitable for line reproduction, there is no choice but to reproduce the copy by the halftone process, because that is the only other method used in the photo-engraving process. The process has been briefly described as the art of photographically printing an acid resist on a metal plate and then etching the unprotected parts. The prac- tice, however, is a much more complicated matter, due to the great variety of copies and the results to be obtained from them. The diagram on the following page (figure 16) shows the subdivisions of the proc- ess, and will serve to convey an idea of how complicated it may become. In order that the process as well as the practice of photo-engraving may be well understood, LINE COPY HALFTONE COPY COLORED BLACK AND WHITE COLORED COLOR FILTER COLOR FILTER BLACK AND WHITE LINE NEGATIVE es BLUE PRINTS— OTHER HALFTONE NEGATIVE PHOTO [eae PRINTS NEGATIVE TURNING—INSERTING NEGATIVE TURNING—INSERTING COMBINING NEGATIVES eel Vea LINE—HALFTONE—POSITIVES LAYING TINTS ON NEGATIVES—BLOCKING OUT—OTHER WORK PRINTING ON METAL FROM SINGLE OR COMBINED NEGATIVES COMBINING BY SURPRINTING— DOUBLE PRINTING LAYING TINTS—PAINTING IN—ON PRINTS ETCHING—DEEP ETCHING ROUTING—TRIMMING—TOOLING—BEVELING RE-ETCHING—ENGRAVING—ROUTING—TOOLING—BEVELING PROOFING—BLACK AND WHITE—COLOR BLOCKING—MORTISING—NOTCHING HALFTONE PLATE COMBINATION PLATE LINE PLATE COLOR PLATES Fig. 16. Chart of progressive stages in the production of various types of photo-engravings. 2I 22, THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING some rather technical and complicated descriptions are given, and in some instances they may seem to diverge considerably from the main features being described. That the thread of the story may be more easily followed, a tabulation of the methods and processes described in the various chapters has been given in connection with the outline of the process in the following chapter. ‘These detailed descriptions of what may appear to be irrelevant subjects are quite necessary for a thorough foundation knowledge of the process. ‘The main principles can be explained with- out them, but if one is to be prepared to meet all problems as they arise, the knowl- edge of the detailed technicalities will prove to be of the utmost value. CHARTER IIT MAKING A PHOTO-ENGRAVING THE LINE PLATE (The references in small type indicate the chapters describing special details connected with each subject.) HE first operation in the making of a line plate is to make a photograph of the copy on a photographic plate. This is called “making a line negative.” (See Photography, Lenses and Light, The Camera, Making a Line Negative.) The image becomes reversed when passing through the lens, so the photographic image on the line negative is backward or reversed. The negative film is therefore stripped off the glass and turned over on another glass so that it assumes the posi- tion of the copy. (See Negative Turning and Inserting.) A piece of metal, usually zinc, is coated with a photographic emulsion of albumen and ammonium bichromate, evenly flowed and dried. The line negative is placed in contact with this coated metal in a printing frame. Heavy pressure forces the metal into thorough contact with the line negative and the frame, negative, and coated metal are then exposed to the printing light. The light passes through the transparent parts of the negative and affects the bichromated albumen so as to render it insoluble. The dark, opaque parts of the negative keep the light from the emulsion so it is not affected in those masked parts. (See Photographic Printing on Metal.) Handled in a subdued light, so as to prevent further light action on the sensitive emulsion, the printed sheet of metal is removed from the printing frame and coated with a greasy ink, called etching ink. After this ink has been evenly and smoothly distributed over the entire surface by a roller, the plate is developed by immersion in 23 24. THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING water. This slowly dissolves the soluble albumen, which washes off, taking its ink covering with it. The insoluble parts, with their ink top, adhere to the metal. They will eventually become the acid resist of the plate. The metal plate now has on it a reproduction of the original copy and is called a “zinc print.” The line negative having been turned over, the image on the metal is now backward again, or reversed in position. The zinc print, when dried, is covered and dusted with a resin called “topping powder,” which adheres to the greasy ink. When heated to a proper temperature, this powder melts and becomes the acid-resisting top which protects the surfaces while the exposed areas of metal are etched. (See Making a Zinc Print.) The plate is next placed in a solution of nitric acid which attacks the metal ex- cept where protected by the resist. As it eats the metal away, there 1s always dan- ger that it will eat under the top, as a river undermines its banks. This is called “undercutting” and is prevented only by very careful handling by the etcher, after the completion of the first stage or “bite.” When the plate has the proper depth for the first bite, the acid is washed off and the szdes of the parts now in relief are dusted with another resin powder called “dragon’s blood.” This is melted by heat and forms a resist on the sides of the parts standing in relief, thereby protecting them against undercutting during the next bite. This is re- peated for each bite until the plate has sufficient depth. (See Etching.) In this condition, the plate could be inked and printed, but further work is necessary for commercial use. In order to get greater depth in the larger etched areas, as well as to remove excess metal, the plate is routed. This is done with a routing machine and a milling tool, which cuts the excess metal cleanly away. (See Routing.) The plate is now inked with a roller and printing ink and printed on paper. The impressions from the inked plate on paper are called proofs. After proofs have been made, the plate is ready for blocking on wood or metal and is ready for the MAKING A PHOTO-ENGRAVING 25 printer. ‘This last operation of printing again reverses the position of the subject to that of the copy. (See Proofing, Blocking, Mortising, and Notching.) THE HALFTONE PLATE A HALFTONE plate is made in quite the same way, differing only in minor details. The photographic negative is made from the copy, but through a halftone screen in the camera. (See the Halftone Screen, Making a Halftone Negative, also refer again to Photography, Lenses and Light, The Camera.) The negative is turned like a line negative. (See Negative Turning and Inserting.) The metal, usually copper, is coated with an emulsion of bichromated glue or bichromated albumen. (See Photographic Printing on Metal, Making a Copper Print.) The halftone negative is printed on the metal in the same manner as is the line negative, but the print is developed without rolling up with etching ink. The glue top adheres in the form of insoluble dots, and acts as an acid resist without the use of topping powder. After development, the print, called a “copper print,”’ is heated until the glue becomes a hard enamel, thus producing the acid-resisting “top” for a copper etching. (See Burning In.) The etching is done in a solution of perchloride of iron. The acid etches the metal away between the dots, leaving them in relief where protected by the top. (See Etching.) In this condition it is called a “flat plate.” Like the line plate, it may be inked and printed at this stage, but additional work is required before it will print as a suitable reproduction of the copy. (See Finishing, Re-etching, Engraving, Tooling, Burnishing, Routing, Bevelling, and Proofing, Blocking and Mortising.) 26 THE PROCESS AND? PRACTICE OF PHOTO-ENGRAVING These outlines of the line and halftone process are but little more than a list of operations involved in the simplest type of plates. They will serve, however, as a basis on which the detailed descriptions are made. Beginning with the two groups —line plates and halftones—the descriptions of their making, followed by the more intricate details of their component processes and combinations, inevitably spread out like the branches from a tree trunk. ‘The descriptions lead through all of the major and minor manufacturing operations until all details of the process are ex- plained for the convenience of the student or the user of the process. The first step in the making of either a line plate or a halftone is the negative. The nature of a negative controls the effect of the finished plate in so many ways that its characteristics should be well studied. Somewhat elaborate descriptions of photographic principles have been necessary in order that this subject may be en- tirely clear, and these also involve the subject of light, lenses, cameras, and half- tone screens. Without these descriptions, it becomes a very difficult matter to understand how and why the negative plays such an important part in the process. CHP RE RELY. THE PRINCIPLES OF PHOTOGRAPHY HOTOGRAPHY is, of course, the basis of the photo-engraving process. It means writing with light or, still more literally, drawing with light. It was more than a hundred years ago that Daguerre utilized the action of light on salts of silver combined with iodine. These salts, after exposure to light and development with other chemicals, turn dark. They darken in proportion to the intensity of the light to which they are exposed. This peculiar property of silver salts is still the basis of modern photography. In order to use this property and reproduce an image photographically, this image must be thrown upon the photographic emulsion containing the sensitive salts. This “throwing” of an image is called “projection,” and the result is a “ projected image.’ Projection is done by means of a lens and light. The sensitive photographic emulsion must be protected from all light except that which is projected upon it in the form of the image. For this purpose a camera is used. ‘This is a light-tight box-like structure with the lens in one end and the photographic plate inside of it at the other end. ‘The word “‘camera”’ is the Latin name for “room,” and it may be of interest to know that a room may be used asa camera. It is only necessary that it be light-tight so as to exclude all rays of light except those which are permitted to enter through the lens. The projection of an image is caused primarily by the light which it reflects, but a lens is required in order that this reflected image may be seen. There is a lens in the human eye through which reflected images are projected, thereby giving us vision or sight, and the same result is accomplished in a camera by means of the photographic lens. The property of lenses and the action of light through them, as well as the similar properties of the human lens in the eye, are more fully described in the following chapter, “Lenses and Light.”’ 27 28 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING For photographic purposes lenses are made of glass ground with surfaces of certain accurate spherical shapes and enclosed in a light-tight tube. The nature of the glass and the optical effect of the curved surfaces control the rays of light so that the shape and colour of the image are preserved. Sucha lens, placed in an open- ing in the front end of the camera, and all other light excluded, will project a duplica- tion of an image into the camera. ‘This image will be clear and distinct on a plane parallel with the lens and at a distance from it called the “plane of focus” or the “focus.” The clearness and distinctness of this projected image at the plane of focus is known as “‘sharpness.” When it is sufficiently sharp it is also known as being “in focus.” At any other distance from the lens it will not be so sharp, and it will then be “‘out of focus.” If a glass or other suitable substance, coated with the sensitive silver salts, is placed in the camera at the plane of focus, the image will act on the salts according to the intensity of the projected light. Bright areas of the image will act most in- tensely; dark areas will act less so. After the proper amount of exposure the plate is removed from the camera, keeping it protected from all light, and subjected to the action of chemicals which turn the silver salts dark. This operation is called “development”’ and the chemical solution is called the “developer.” The blacken- ing of the silver salts is in direct proportion to the amount of light that has acted upon them: the brightest areas turning the darkest, and the darkest areas remaining the lightest. Such silver salts in the photographic emulsion as have not been affected by light and subsequently developed must be removed, because they in turn would likewise be affected by any light to which the plate might later be exposed. ‘This removal is accomplished by another chemical solution, which dissolves and removes all of the unaffected silver salts. These salts are called “unreduced silver saamere operation is called “fixing,” for without it photographic images would be valueless except in the dark. The appearance of the developed and fixed image on the negative may now be considered. If it has been made on glass it is examined by holding it up to light and looking through it, and the dark areas will appear opaque, the light areas trans- parent. ‘This is called viewing by transmitted light, and the finished image is called a negative because the values are negative to, or opposite to, the values of the original. DHE SERINGIPUES*OF PHOTOGRAPHY 29 If light is now passed through this negative to paper or any other substance sen- sitized with a photographic emulsion, the latter will be affected only by the amount and intensity of light which is permitted to pass through the negative. The opaque areas will permit the least light to pass; the transparent areas the most; and the new sensitized surface will be affected accordingly. Developing and fixing will give a finished photographic image from the negative. The opaque areas of the nega- tive will appear lightest and the transparent areas darkest, thus reproducing the ’ values of the original. This second operation is called “printing,” and the result Pee positive Ora print.” It is somewhat unfortunate that the word “‘printing”’ is used in this connection, as it may be confused with the printing with ink on a printing press. “‘ Photographic printing” would be more correct, but the term is so cumbersome that it would soon be discarded. It will be assumed, therefore, when speaking photographically, that the word “printing”’ will be recognized as representing the process outlined above and will not be confused with the other mechanical operation. CHAP TE Ray. LENSES AND TIGHS IGHT is the medium which traces the image on a photographic plate, but it must be guided and controlled as is the pencil or brush in the hand of the artist. It is one of the most active forces known and is composed of rays which ema- nate from the illuminating source, such as the sun, electric arc, or other light-produc- ing medium. The rays are formed of waves, not unlike those of the sea in shape, but so amazingly minute that they are measured in ten millionths of a millimeter. As there are about twenty-five millimeters to the lineal inch, one gets down to star- tlingly small dimensions when considering these waves. Measurement is made from the crest of one wave to the crest of the next and the unit is known as the “‘ wave WAVE LENGTH Fig. 17. Diagram of light wave vibrations. length.” The wonder of their minuteness is no more amazing than their velocity, which is one hundred and eighty-six thousand miles in a second. In spite of their small size and high velocity, these waves are readily controlled. They may be refracted, which bends them and changes their direction; they may be reflected or bounced off a reflecting surface, or they may be absorbed. Different mediums such as air, water, and various kinds of glass and crystal have the property of refracting light waves differently. This property of refraction is employed in photographic lenses to refract light rays and bring them to a focus. Reflection is controlled by the nature of the surface off which the light is bounced. Rough surfaces reflect light in numerous directions and diffuse it, due to the angles of reflection from the various rough parts of the surface. Smooth polished surfaces reflect without diffusion. This is what produces a duplicate image in a mirror. 30 LENSES AND LIGHT ay There has been no diffusion due to rough surfaces and the form of the reflected image is not impaired. All substances have a greater or lesser degree of absorbing power. Those which absorb the most light appear the darkest. The impression of black ink from the type used to print this page appears black because it has absorbed so much light. The white paper has absorbed the least and appears white in contrast to the printed type. These three properties: refraction, reflection, and absorption, are the basis of photography and photographic optics, and present a formidable subject when studied in detail. For the purpose of explaining their use as applied to photo- engraving, the technical features have been simplified as much as possible and with the explanatory diagrams, the principles involved will be readily understood. The manner in which different objects reflect light controls the power of vision as well as photography. Light falling on any object is reflected, like a rubber ball bounced off a surface. ‘The variation in the amount of light reflected gives the corresponding variation of tone and colour of the reflecting surface. Reflected light from any object, passing through the lenses of our eyes, creates the sense of vision (79 and we “see” the object. Light reflected by an object travels in the wave form previously described and passes through the lenses in the eyes, and is refracted or bent, so that it is brought to a focus or point of sharp definition on the nerve centre called the retina. The same process is duplicated in photography with the difference that a photo- graphic lens is substituted for the lens of the eye, the camera is substituted for the eye-ball, and the sensitive photographic plate is substituted for the retina. Refraction by the lens and the consequent focussing of the light waves are the essential features which must be understood for intelligent appreciation of photog- raphy. Light reflected from any surface travels from the different points of reflection in undulating waves or ‘“‘vibrations.” These light rays are like the spokes of a wheel, and their wave crests form waves, not unlike the ripples in a still pool, which spread from the point where a pebble is dropped into it. They emanate from every reflect- ing point of the surface, but for explanatory purposes, and to avoid confusion, consideration will first be given to the reflection from one point only. ‘The We THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING A. POINT OF REFLECTION : : “LIGHT RAYS FOCUSSING ABERRATION... : IN DIFFERENT PLANES BO ha we OF SHARPNESS BECAUSE OF CONFUSION LIGHT RAYS REFLECTED TO LENS A. POINT OF REFLECTION : PLANE OF SHARP FOCUS CONFUSION ELIMINATED BY DIAPHRAGM | | "LIGHT RAYS REFLECTED TO LENS LENS Fig. 18. Diagrams of reflected light from one point in a single plane, passing through lens, showing aberration and confusion eliminated by a diaphragm. Actual relative proportions greatly changed for sake of clarity. Reproductions made by stripping a line positive of original copy on top of 150 screen halftone tint negative. diagram above (figure18) shows light rays reflected from a single point designated as “A.” Only a few rays are shown, in order that the diagram may be free from con- fusion. ‘The lens is shown in cross section in the shape of an ordinary double convex lens. ‘The purpose of the diagram is to show how the light waves pass through the lens and what occurs during the operation. The moment these light rays enter the glass of the lens at any point other than the exact centre they are refracted and change direction. ‘This is due to the re- — fracting power of the glass, called its “refractive index,” and it varies with different kinds of glass. The curvature of the lens surface, as shown by the diagram, also aids in this refraction. When the rays emerge from the lens into the air on the opposite side they are again refracted as air is also a refracting medium. Owing to the different angles at which the rays entered the lens through the curved surfaces, they are refracted at different angles and although they are bent so as to meet again, LENSES AND LIGHT 33 POINTS OF LIGHT RAYS FOCUSSING INCREASED REFLECTION . IN DIFFERENT PLANES —~—- ABERRATION __—__ f 1 ' 1 1 Ket be } 1 y POINTS OF : : PLANES OF SHARP FOCUS REFLECTION : : FROM TWO PLANES CONFUSION ELIMINATED BY DIAPHRAGM LIGHT RAYS REFLECTED TO LENS Fig. 19. Diagrams of reflected light from single points in two planes, passing through lens, showing aberration and confusion reduced by a diaphragm. ‘Actual relative proportions greatly changed as in fig. 18. Reproduced by same method as fig. 18. they do not all meet at the same point. The rays which have passed through the parts of the lens nearest the centre meet at a point farther away than those which have passed through the outer areas. The different points where these rays meet are called “planes of focus.” If the rays shown in the diagram represented an image, it would not appear sharp or in focus, because of the confusion called “aberration”’ due to the numerous planes of focus. It therefore becomes necessary to eliminate the rays which have been most acutely refracted by the outer areas of the lens and use only those which have passed through the central area. ‘This is done by covering the outer areas with a b) ’ 3 “stop” or “diaphragm.” A hole in its centre called the “diaphragm aperture’ permits only those rays near the central area to pass. ‘This causes the image to ap- pear sharp or in focus, owing to the elimination of the conflicting images in the other planes. The diaphragm and aperture are shown in the second diagram as is also the effect on the light rays. 34 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING When light is reflected from points at different distances from the lens, this also causes the rays to focus in different planes. This is shown in figure 19, the two different points being designated as “A” and “B.” ‘The light from “B” focus- ses farther from the lens than that from “A,” and creates confusion and lack of definition of the two images. It is not possible to bring both of these points into a technically sharp plane of focus, but a satisfactory compromise may be made by again using the diaphragm. The diaphragm eliminates confusing rays and allows only those which focus in nearly the same planes to pass, and the result is greater sharpness of the combined images “A” and “B.” ‘The plane where both appear sharp is midway between the planes of actual sharpness of each and although it is i tees if, Z ie et ie AME SS i Sau ‘te... halal Illustrating “Out of Focus” and “In Focus.” © Major Hamilton Maxwell Fig. 20. Unsharp halftone from sharply focussed photo- Fig. 2t. The same subject sharply focussed when making graph. Made by making halftone negative out of focus. halftone negative. Both reproductions, halftones, 150 screen, squared, no finishing line. not scientifically sharp for both, it is satisfactory to the eye. Finding this plane is performed by “focussing,” which is described in greater detail in the chapter on pelhet@anicrin The more widely points “A” and “B” are separated, the smaller the diaphragm required to obtain satisfactory sharpness of both. ‘There is a limit to this, of course, and if there is too much space between them, it will eventually become impossible to obtain satisfactory sharpness of both images. If an exceptionally small aperture is used, the refractive properties of the lens become almost nullified because such a small sector of the curved surfaces remains uncovered. In some instances the lens may be done away with entirely and only the small aperture employed. This is called a “pin-hole lens” and the size of the aperture is just about that indicated by its name. LENSES AND LIGHT 35 Lenses are seldom made in the simple form that has been illustrated in these dia- grams. Additional glasses of varying refractive indexes, different curves and mounting of the glasses are employed for lenses of various classifications. These modifications are all for the purpose of obtaining sharpness of the images, correct reproduction of form and colour. We should soon be well away from our subject of photo-engraving if we attempted to describe them all, but certain descriptions are necessary. Photo-engraving lenses are called “process lenses.””. They are made up of many different glasses, ground in different forms and mounted with great accuracy in a tube or cylinder called the “lens barrel.” They are usually made with an adjustable diaphragm called an “iris diaphragm” and have, in addition, a slot in the barrel in which may be inserted the special diaphragms that are essential to the halftone process. A cap or cover completes the lens equipment. Its purpose is not only to keep the lens free from dust when not in use, but it is also employed in making the photographic exposure. A very important feature of all lenses is their “focal length.” This varies ac- cording to the type of lens and is controlled by the curves of the lens surfaces. A long-focus lens gives sharpness of the image at a greater distance back of the lens than does a short-focus lens. As this distance varies according to the distance of the object from which the light is reflected, it is necessary to find some standard by means of which focal length may be measured. Objects at a considerable distance from the lens all focus in nearly the same planes, so focal length is measured after the lens is focussed on a distant object. This distance, however, must be greater with long-focus lenses than with short-focus ones. A lens focussed on an object at a considerable distance and producing an image ‘6 in focus eighteen inches back of the lens is called an “eighteen-inch lens.” The measurement is made from the plane of sharpest focus to the optical centre of the lens. As the object is brought closer to the lens, the plane of focus becomes farther removed, and this follows a definite mathematical formula. It is so definite that tabulations of distances from lens to object and from lens to plane of focus have been worked out for various focal lengths. This formula is employed in actual prac- tice in the automatic focus camera described in the following chapter and will be 36 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING recognized by any user of a Kodak as the focussing scale for different distances to which the lens may be adjusted. The lenses of longer focus are employed for photo-engraving and they are usually of the eighteen-inch length. ‘The size of the image projected by a lens is controlled partly by the focal length, and better definition is obtained in a large- sized image if a long-focus lens is used. An object a foot high, focussed to actual size with an eighteen-inch lens, will be sharp when the lens is thirty-six inches away and the image will also be thirty-six inches back of the lens. If the same object is focussed to actual size with a twelve- inch lens, the distance from the lens to the object and from the lens to the sharp image will be but twenty-four inches. Being but two feet away with the short lens and three feet away with the longer one, the angle of view or perspective will be dif- ferent in the respective images. ‘That of the longer-focus lens will be less violent and therefore more pleasing. If the same object is focussed with the twelve-inch lens, but at the thirty-six inch distance, the image will be but six inches high, or one half actual size, and will be in focus eighteen inches behind the lens. These examples of the difference in action of lenses of different focal length have been given as a guide and only to show how important this factor is. In photo- engraving, photographs are usually made from drawings or other material compris- ing the copy. Ifa copy is too large for reduction to the desired size when the usual long-focus lens is used, then a lens of shorter focus must be employed, which gives a smaller image at a given distance than does a lens of longer focus. Only an outline of this subject has been given, but it will be apparent that it is one of great importance. The elaborate camera equipment used in conjunction with the lens furnishes the mechanical means for obtaining sharpness of focus, prop- er size of the image for the reproduction as well as the necessary device for holding the halftone screen and photographic plate. This equipment is in truth the “eye”’ of the photo-engraving process. It provides the means by which the photographic image of the copy is made which is photographically printed on the metal plate in the form of the required acid resist. CHAR LE RS VI THE CAMERA ARIETY in camera design and construction covers a wide range. In the following description no attempt has been made to describe these different varieties, but rather to concentrate on the general principles of camera design and the function of the various elements. The photo-engraving camera consists of a group of mechanical devices arranged so that all moving parts may be manipulated accurately, without loss of time and in the fewest possible number of operations. It is called a ‘‘Process Camera” to dis- tinguish it from the numerous other types. The complete equipment consists of the camera, a specially designed stand, and the board to hold the copy. As most photo-engraving shops are in commercial buildings where printing presses and other machinery keep the entire structure in constant vibration, proc-. ess camera stands are designed and constructed to counteract this effect. The stand is a long, swinging frame supported or suspended by springs attached to a base, which is on casters to permit the whole apparatus to be readily moved if desired. The copy board is fastened to uprights at one end of the suspended frame. COPY BOARD OUTLINE OF CAMERA IN POSITION TURN TABLE SWINGING FRAME BASE Fig. 22. Process Camera Stand. Illustrating the swinging frame hung by springs attached to the base. The camera, copy board, and swinging frame will vibrate as one unit. docs A silhouetted combination plate, 150 screen. Line negatives of type matter combined with halftone negative before printing on metal. a7, 38 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING The camera also rests on this frame. ‘This arrangement results in one unit, con- sisting of frame, camera, and copy board, being suspended by springs from another unit, and it eliminates the possibility of camera or copy board vibrating separately. When vibration exists, the camera and copy board must vibrate or swing in exact unison or else the negative will not be sharp, due to the motion of the image on the photographic plate during exposure. The design of stands varies fully as much as that of cameras. Coil springs or elliptical springs may be used and sometimes the swinging structure is supported by cables terminating in springs attached to the ceiling instead of being supported by a frame resting on the floor. It is, of course, unnecessary to use this elaborate swinging stand unless vibra- tion is present, but the use of some type of stand is advisable so as to assure proper alignment of the camera units and the copy board. The length of the camera stand is usually from twelve to fifteen feet, which is GROUND GLASS FEAME sufficient for ordinary requirements, "2 wa but in some instances this length is + not sufficient if the copy is exces- | sont sosan sively large or if the negative 1s to tens be made in a very greatly reduced size. The lenses used for photo- engraving are usually of eighteen- FRONT BOARD A : ; Se inch focus and the size of the image FOCUSSING ae WHEEL is regulated by the distance between the lens and the copyee Wits SCREEN DISTANCE ADJUSTING LEVER BELLOWS Perle Te pee Pee RC ee camera base fifteen feet long and an A silhouetted combination plate, 150 screen. eighteen-inch lens, the greatest re- duction which may be obtained is about one seventh. Should greater reductions be required, a lens of a shorter focal length must be used. In some instances, it is impracticable to use a short-focus lens, and the reduction must then be obtained by a double operation, which requires reducing the copy by making a photograph of it, and then making the negative of the required size from the new photograph. The camera itself consists of a front and rear box or frame joined together by a bellows. These front and rear sections are mounted on the camera bed (which THE CAMERA 39 rests on the swinging frame) and their position on the bed is adjustable. This per- mits bringing them close together or extending them as occasion may require, in order to obtain the required size and focus. The bellows provides the necessary light-tight flexible connection between these two sections. ‘These boxes are con- structed of either wood or metal, substantially and accurately made, and are fitted to the camera bed absolutely vertical to it and parallel to each other. ‘The front section has an opening in the centre of its face about 10 x 10” into which the board carrying the lens is inserted. ‘his lens board is removable to permit the use of different lenses if necessary. Lenses of different focal lengths are usually of differ- Fig. 24. Operator focussing for size and sharpness. Squared and vignetted halftone, 150 screen. ent sizes, and the use of separate mountings and lens boards provides a convenient means of changing them. These boards fit snugly in the opening and are held rigidly in place by metal clamps, providing a light-tight joint and firmly securing the lens against any possibility of its separate vibration. Size and focus are obtained by moving the camera toward or from the copy, at the same time adjusting the distance between the lens section and the rear sec- tion. The whole camera and its bed slides or rolls on a truck mounted on the 40 THE PROCESS AND: PRACTICE OF PHOTO-ENGKAVING swinging frame, which permits the regulation of the distance between the copy and the lens. The setting of the distance between the lens and the photographic plate is accomplished by moving either the front or rear section. In some types of cameras only the rear section is movable, while in others both sections may be adjusted. These adjusting operations are accomplished by a means of conveniently placed hand wheels, operating gears or spiral screws, the design and construction of which vary in different types of apparatus. Means are also provided for moving the lens either horizontally or vertically, which is sometimes necessary in order to obtain the desired position of the image on the photographic plate. The purely mechanical details of all these controls are important only in so far as they insure the correct movement of the front and rear sections of the camera so as to permit of the necessary adjustment for focussing and yet keep all the elements parallel . with each other and the copy board. The copy board is hung on a copy board holder which is fixed at one end of the swinging frame. The holder is also made adjustable so that it can be kept true with the camera. Having the three elements, sensitive plate, lens, and copy board, in exactly parallel planes is of prime importance, as otherwise the photograph of the copy will not be correct as to size or shape. Copy boards, which are usually around 30” x 40” in size, are made in various forms. The simplest and least desirable 1s in the form of a wooden board on which the copy is either tacked or pinned, with resulting holes. A better form is that of a board filled with equi-distant holes into which special clamps fit, which hold the copy without damage. Copy holders are also made of a wooden frame with a hinged glass front and also on the principle of the vacuum printing frame, an apparatus which is fully described in the chapter on Photographic Printing on Metal. The rear section of the camera is designed to hold a frame and ground glass for focussing and a plate-holder containing the photographic plate during exposure. It is of the utmost importance that the photographic plate be placed in exactly the same position with relation to the lens as was the ground glass on which the fo- cussing was done. Spring catches or wedge holders on the camera back engage with and hold the ground glass and frame firmly in position. After focussing, this frame and glass is removed and the plate-holder fitted and secured in its place. This holder is equipped with duplicates of the catches and holders on the ground- THE CAMERA 41 glass frame and as a result its position and that of the photographic plate co- incide exactly with that of the ground glass on which the image was focussed. The plate-holder is a shallow box with a removable sliding front and a removable or hinged back. The sensi- tized plate is held in place by two honi- zontal bars which are movable so as to Fig. 25. Plate-holder with back removed, showing sensitized plate in position. A silhouetted and vignetted halftone, 150 screen. take large or small-sized glass. The bottom bar is fitted with clips against which the plate rests and these clips are usually made of silver, but for economical reasons, aluminum, though not so good, is frequently used. Originally, the halftone screen, which must be used very close to the sensitive plate, was mounted in the plate-holder. This method, however, was found un- desirable and modern cameras carry the screen in the rear section of the camera, in a carefully built mechanism which is operated by a handle on the outside. When the plate-holder is set in position on the camera and the front slide re- moved, the movement of the handle carries the screen into the plate-holder to the desired distance from the sensitive plate. Accurate setting of the distance between the screen and photographic plate is essential, and very fine adjustments and indicating scales are provided on modern cameras to permit of proper regulation of this distance. The screen- carrying mechanism is arranged to take screens of varying sizes, up to the capacity of the cam- era, and this mechanism is made adjustable so that it may be corrected to be al- ways parallel with the sensitive plate. In the early days of photo- engraving cameras as small as 8x Fig. 26. Halftone screen and adjusting mechanism in rear section 10’’ were used, but in the modern camera. A silhouetted and vignetted halftone, 150 screen. 42 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING development of the art it has been found that cameras smaller than 17” x 17” are not economical. Process Cameras, as they are called in the trade, are always built on square measures, so as to permit say a 14” x17” plate to be taken either horizontally or vertically in a 17” x 17’ camera. Most photo-engraving shops have at least one 24’’ x 24” camera, and a 31” x 31” apparatus is far from unusual. There are quite a number of cameras 36” x 36” and 40” x 40” in daily commercial use, and one camera has been built to make negatives 60’’ x 60’... A camera of this size is mounted on a stand twenty feet long. The camera and stand unit which has been described is for black-and-white work. For process work in colour, or when negative turning cannot be employed, there 1s a turn-table added to the truck on which the camera rests. This permits the camera to be swung to a position at right angles to the length of the stand. ‘The lens is Fig. 27. Diagram of light reflected from a copy, passing through lens in camera to ground-glass or sensitized plate. Note reversal from top to bottom. A line plate with halftone tint negative surprinted, 150 screen. then fitted with a prism or reflecting mirror and the negatives are made with the camera in this position. Needless to say, the truck must be fitted with suitable locks, as once the camera it carries is focussed, it must be immovable until the ex- posure is finished. The diagram which has been used to show the side view of a complete photo- engraving camera equipment has been sectionalized to illustrate the course of the light reflected from the copy passing through the lens to the ground-glass or photo- graphic plate. The matter of illumination is one of great importance, and it is essential that the copy be brightly illuminated with a white, even, steady light. To produce this THE CAMERA 43 result the electric arc has been found to be the most satisfactory. Daylight can of course be used, but it is not even and constant as is the arc light and its use would limit photographic work to certain hours and eliminate it on dark days. Modern demands are such that the twenty-four hours of the day are employed and conse- quently arc lights are, of necessity, the standard illuminant in practically all shops. The foregoing description of a photo-engraving camera is intended only to describe the requirements of the apparatus. The various makes of cameras repre- sent many different forms of mechanical contrivances to accomplish the desired re- sults. In fact, a room may be used as a camera; it is only necessary that means be provided whereby the necessary mechanical operations may be performed. Most notable among the special apparatus is the Automatic Focussing Camera which employs the mathematical formula covering the distance relations between copy and lens, and between lens and photographic plate. These distances vary with the amount of reduction or enlargement, as well as with the lenses of different focal lengths. There is a scale on the camera bed to which arrows or pointers on the lens section and the photographic plate section may be set. ‘The size of the copy is measured and compared in a tabulation chart, with the size itis to be. This comparison gives a number, sometimes arbitrary, and sometimes a percentage of the reduction. The numbers on the camera scale correspond with those in the table, and when the pointers of both sections of the camera, as well as of the camera truck itself, are set to the corresponding numbers on the scale, the reduction will be of the correct size and sharply focussed. CHAPTER VII MAKING A LINE NEGATIVE HE technique of making a line negative follows certain rules of optics and photography, but the practice varies with different subjects. So many conditions must be met and overcome that it takes years of experience for a line photographer to become thoroughly proficient. The description of the process must necessarily be limited to the general pro- cedure under normal] conditions. Different operators employ special methods to meet unusual conditions. Mechanical equipment and manufacturing conditions vary in different establishments, so the following outline of the method must be taken as representing only the principles of the process and not as a description of universal practice. 7 The copy is placed in position on the copy board and fastened securely. It must be carefully flattened out, as any parts which bulge or protrude will be closer to the lens than the remainder of the work and this may result in distorted outlines in the negative. The copy board, being marked with centre lines, offers a guide for the placing of the copy so that it will focus in the centre of the photographic plate. The arc lights are adjusted to illuminate the entire copy evenly, and the subject is then focussed for proper size and sharpness. ‘This is done by moving the camera to its proper position on the main bed, then slowly moving the focussing section forward and back, until the image showing on the ground glass is sharp and of the proper size. ‘The element of size is an important one from a commercial standpoint, and great care must be taken to assure correctness in this respect. Subjects repro- duced for use in advertising space must be absolutely accurate in size, especially for the publications which charge for space by the agate line. There are fourteen agate lines to the inch, and an error of even half a line may involve a considerable additional outlay for space. When properly focussed, the lens is capped and the movable sections of the camera are locked in position with set screws or clamps, which are part of the camera equipment provided for that purpose. 44 MAKING A LINE NEGATIVE 45 Glass is used for the base on which the photographic solution is flowed. It should be clear, and free from flaws, bends, or curves. An uneven surface would be just as liable to distort the image as though the original copy were not flat and all in one plane. If the usual wet-plate collodion process is to be used, the negative glass is sensitized just before exposure is to be made. Since they are exposed while wet, they cannot be prepared in advance or they might dry out and lose their sensi- tiveness. aca iverslass is cut in standardized sizes of 8’ x 10”, 10’ x 12’’, 11’ x 14”, 14” x 17”, 16” x 20”, and 20” x 24”. It is thoroughly washed in a nitric acid solu- tion to remove all dirt, old film and grease, and then flowed with a thin solution of albumen. ‘This is to form a base upon which the subsequent photographic solution is flowed. ‘The cleaned, albumenized glass is stacked in racks, available as required by the line photographer. The operation of cleaning and albumenizing the glass is known as “glass wash- ing,’ and though seemingly insignificant, is in fact an important step in the process. Lack of care and cleanliness in this, the first stage of the process, may mean a spoiled negative later on. To sensitize the negative glass it is flowed with “negative collodion.” This is a solution containing ether, alcohol, gun cotton, ammonium iodide, and cadmium chloride. Coating the glass with this negative collodion is an art acquired only after a good deal of practice. The collodion contains all of the chemicals necessary for the photographic work except the silver, and it is absolutely necessary that it be owed in such a manner as to be of even thickness over the entire sur- face. If thin at one end or thick at another, too little or too much of the necessary chemicals deposited in these places will result in a negative of uneven density and values. Different operators employ different methods for flowing the solution, de- pending upon conditions and the size Fig. 28. Flowing negative collodion on albumenized glass. of the glass. Vignetted halftone, 150 screen. 46 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING As the solution is flowed on, it dries very quickly due to the rapid evaporation of the ether and alcohol, and the glass must be constantly rocked back and forth so that no excess coating will form on any part. When the collodion has dried, the glass is held in a hard-rubber rack, shaped like an inverted “Y’’ and immersed inthe silver bath. This bath is an earthenware or glass tank, in a light-tight box, filled with a solution of distilled water and silver nitrate. Unusual care is employed to keep the silver bath free from foreign sub- stances which might harm it. Even the hard-rubber dipping rack is kept constantly in the bath when not in use, to prevent harmful foreign matter lodging upon it which later might be transferred to the bath. This immersion or “dipping” causes a deposit of silver to form on the collodion, which, in conjunction with the other chemicals contained in the negative collodion, - produces a light-sensitive photographic “‘ emulsion.” This is called a “wet plate.” Though it is light- sensitive, it is not sensitive equally to all colours of light. Deep yellow or red light does not affect it ex- cept during very prolonged exposure, so a deep yel- low light may be used in the dark room for illumi- nation during this and subsequent operations. The sensitized plate is removed from the bath and the excess solution allowed to drain off. The bars in the plate-holder are placed in the proper position to hold the plate, and strips of blotting paper are placed on the lower bar in a trough provided for that purpose, so that any further excess moisture draining from the plate will be absorbed. The plate is then placed in Hig. 29. Dipping ihe coated glasrin the holder between the bars and ‘held inegiaceraeene silver bath. Silhouetted, vignetted halftone, 150 screen. front by the silver clips and at the back by a spring fastened to the rear section of the plate-holder; the action of this spring being just sufficient to hold the glass firmly against the clips. This is to assure the proper posi- tion of the glass in the plane of focus. The plate-holder is fastened to the back of the camera by means of the wedges and clips previously described, which brings the sensitized surface into exactly the same position as that of the surface of the MAKING A LINE NEGATIVE 47 ground glass, on which the image had previously been focussed. The diaphragm or stop of a proper size is inserted in a slot in the lens barrel provided for that purpose and the removable front slide of the plate-holder is pulled out. There is a light trap in the plate-holder which springs shut as soon as the slide is removed, preventing any light from entering at this point. Removal of this slide uncovers the plate in the camera and exposure is accomplished by removing the lens cap for the required amount of time. The size of the diaphragm used and the amount of exposure vary with conditions, such as the nature of the copy, the amount of reduction, and the desired character of the negative. Un- der ordinary conditions with a dia- phragm aperture of one fourth of an inch, exposure would be about two min- utes. The lens having been recapped and the slide replaced, the plate- holder is removed to the dark room for development of the plate. The plate is removed from the Fig. 30. Placing plate-holder containing sensitized glass . f plate on back of camera for exposure. holder and developed by flowing with Squared and vignetted halftone, 150 screen. a developer consisting of iron sulphate, acetic acid, and distilled water. This blackens the exposed silver very quickly. Unreduced silver still in the emulsion is cut with water and cyanide of potassium. ‘This eats away all of the unaffected sil- ver which represents the black areas of the copy, the white areas having been turned black by the developer. This treatment with cyanide is the “fixing’’ process for wet plates. As the line negative is not required to have tone values, but simply areas of clear transparency or opaque black, it may be intensified to accentuate the opacity of the black areas by using a solution of bichloride of mercury, lead oxide, or copper and silver. Either of these solutions deposits an additional metallic structure on the silver structure already existing and intensifies its density. Clearing of the trans- 48 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING parent areas may be accentuated by “cutting”? with an additional solution of cyanide and iodine. After cutting and intensification are finished, the negative is finally blackened to increase further its density with a solution of sodium sul- phide, familiarly known as “stink” because of its obnoxious odour. Many troublesome difficulties arise in this photographic process. Chemical conditions cause the silver bath to deteriorate and “go bad.” ‘Temperature and humidity affect the sensitized glass or developer, or both. All such must be met and overcome by a thoroughly efficient operator. ‘“‘Fog”’ is one of the greatest troubles encountered. Its effect may be due to any of a number of causes such as impure chemicals or stray light in the dark room or camera. It produces an effect on the negative as though the entire sensitized surface had been slightly exposed to light. No areas appear clearly transparent after development, and it may even affect the qualities of the opaque parts. It dims the whole image just as though it were seen through atmospheric fog, from which it gets its appropriate name. From the foregoing, it will be apparent that line copy must be clean black and white to permit getting the opaque black and transparent clear areas in the nega- tive. If the white areas of the copy are not clean or if they are of toned paper such Fig. 31. Reproduction of a line copy and line negative therefrom viewed by transmitted light. Note opaque and transparent areas as compared with copy. A combination plate, vignetted and silhouetted, 150 screen. MAKING A LINE NEGATIVE 49 as buff, gray, or other colours, they will require a longer exposure to photograph them sufficiently to make them opaque on the negative. This increased exposure may affect the character of the lines of the drawing. Likewise, if the lines of the drawing are not clean, sharp, and black, they may photograph with a tone on the negative. To avoid this, less exposure may be required or excessive cutting of the negative with cyanide and iodine, either of which may also tend to affect the char- acter of the work. ‘There are so many details relating to the nature of the copy that a special chapter has been devoted to these features. It is not out of place to refer to them briefly at this point, however, when the method employed for making the negative is fresh in the mind of the reader. After the line negative is finished so far as development, intensification, and cut- ting are concerned, it should be dried in a heated oven. This protects the wet film from dust particles and also hastens the drying. The negative is now ready for the next step in the process, which may be the making of a positive or printing on paper or metal. As the making of a positive is somewhat similar to the making of a negative, let us consider that feature before starting the investigation into printing on paper and metal. MAKING A LINE POSITIVE Any photographic print from a negative is positive, inasmuch as it is the op- posite of a negative in values. When such prints are made on transparent bases such as glass they are called “positives.”’ In more technical words they are “dia- positives,’ because their values are shown by transmitted light, which passes through them. If they are made on opaque bases such as paper, metal, or any other substance which reflects light, they are called “prints.” Line plates are often made which are negative to the copy; that is, all whites are reproduced as black and all blacks as white. To accomplish this, the plate is printed from a line positive instead of from a line negative. There are two methods of making line positives on wet plates from line nega- tives. If the positive is to be the same size as the negative, the latter is put in the plate-holder on the bar used to hold the sensitized glass, the film side toward the back of the holder. A negative glass, sensitized as for a line negative, is also placed in the plate-holder directly behind the negative already placed in the holder. 50 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING The film side of this glass is toward the front and, as it is wet, two thin strips of blotter are used to separate it from the negative. ‘This brings the original negative and the sensitized wet plate almost in contact, face to face, in the plate-holder. The plate-holder is placed on the back of the camera, just as though an ordinary exposure were to be made. A piece of white paper is placed on the copy board and illuminated with the arc lights. Exposure is then made in the usual manner. The light coming into the camera through the lens creates a new image of the negative upon the sensitized plate directly behind it. The new exposure is developed in the usual manner and when finished is a transparent positive of the original negative. — It is necessary that the light entering the camera should pass through the lens, to avoid diffusion. Light is so easily reflected that, even in passing through the narrow space between the original negative and the sensitized glass, it would be- come diffused were it not for the control effected by the lens. Diffusion would re- sult in a hazy outline to all the black areas on the new positive and it would appear unsharp. If the positive is to be made on a dry sensitized surface like photographic printing paper, 1t may be made by contact printing (see description, page 52) and then a lens is not necessary to control the light. PLATE HOLDER LENS BOX KITS TO CARRY NEGATIVE Fig. 32. Typical E. C.&% R. Camera. Used for Enlarging, Copying, and Reducing. Line positives may be made in this type of camera by photographing a line negative held by the kits in front section. Can also be used with halftone screen if required. A combination plate, silhouetted, 150 screen. The other method is to photograph the original negative. It is placed in a frame, like a picture frame with no back, in front of the lens, just like an ordinary copy. This frame, however, is placed about two feet in front of the copy board. A piece of white paper on the copy board, illuminated with the arc lights, reflects light through the negative in the frame. It is focussed for size and sharpness and ex- MAKING A LINE NEGATIVE 51 posed as if it were the usual type of line copy and the finished result is a line positive. This method produces the same result as making the positive in a plate-holder, but it has the advantage that the size may be changed when being focussed. Line plates made from positives have become known as “ positive line plates”’ or “reverse line plates.” ‘This is unfortunate, as the names are confusing and not en- tirely correct. They are “negative line plates’? because of the negative values as compared with the copy. Plates to be made opposite to the copy, with the left reproduced as the right, are made by another method explained in the chapter on Negative Turning. These _ Courtesy American Writing Paper Co. Fig. 33. Line plate, made from a line Fig. 34. Negative line plate, made from negative. a positive of same copy. In specifying line plates from positives, the area of black background should be clearly indicated. are also erroneously known as “reverse plates.”’ They are “reversed’’ plates. Care must be taken to avoid confusion between these “negative plates”? and “‘re- versed plates.” While the wet-plate process is quite generally used for making line negatives and positives, it is not the only method employed. Any suitable photographic plate may be used. As has been explained, the wet plate is sensitized just before exposure, but ‘ there are “process dry plates”? manufactured which are well suited to the process. The photographic emulsion varies in dry plates of different manufacture, but the photographic principles and results remain unchanged. The emulsion is coated by special methods on glass, flexible film, or paper. When on glass they are called “dry plates.” They may be obtained in the standard sizes 52 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING up to 20” x 24”’.. Those for which the flexible base is used are called “cut film.”’ The base is similar to transparent celluloid. The flexibility of this base permits its being rolled, and sensitized film is supplied in rolls if desired. These rolls are not unlike the roll film used in the ordinary hand camera or “ Kodak” except that they are obtainable in the larger sizes required for commercial work and are sensitized with a special emulsion. The paper-base films are also supplied in standard sizes as well as in rolls. Flexible film in cut sizes and rolls is gradually coming into use in photo-engrav- ing. Special cameras and methods are being developed to use this material in place of the wet plate. When used for photo-engraving, dry plates and films must be made with a special “process”? emulsion. ‘This is quite thin as compared with the emulsion used for ordinary photography, and gives a clean, sharp image, so necessary for suc- cessful metal printing and etching. From a standpoint of general practicability, the wet-plate process seems to be the logical choice under present-day conditions, but what the future will bring forth in the use of dry plates, films, or other substances, time only will tell. PHOTOGRAPHIC PRINTS PriINTs may be made on a variety of photographic papers, from either line nega- tives or positives. Trade demands often require some kind of print as soon as a negative is finished and usually blue prints are made for this purpose. BLUE PRINTS BLUE-PRINT paper may be obtained already coated with a ferro-prussiate photographic emulsion. The paper is placed in contact with the negative in a printing frame and exposed until the image is clear and distinct. It is then washed in water which turns the image blue and also washes away any unreduced emulsion, thereby performing the operations of development and fixing at one time. When dried it is a dark blue positive image of the negative and is reasonably permanent. The printing frame used for this purpose is the ordinary type of photographers’ frame with a removable back and metal springs which force the paper into contact with the negative. MAKING A LINE NEGATIVE 53 The emulsion of blue-print paper is comparatively slow and may therefore be handled in subdued daylight without fogging. The exposure necessary depends upon the character of the negative and the intensity of the light. SILVER PRINTS SILVER prints are somewhat similar to blue prints except that the photographic emulsion on the paper consists of a silver salt instead of iron chloride. The paper may be obtained already sensitized and it is printed the same as a blue print. De- velopment is also done by washing in water, but the unreduced silver must be removed by means of sodium hyposulphite familiarly known as hypo. The re- sulting print is black or a very dark brown, and is more distinct than a blue print. Such prints are liable to fade if kept exposed to light. Silver prints are sometimes called salt prints or bleach prints. ‘They are commonly used as a basis for pen and AU EMA UN LEU nnd tnodacatinne ote HATAAUTTCH ETRE! STMNNNOCOCLUO CUCU ALO samtiead no Fig. 35. Reproduction of silver print Fig. 36. A line plate made from the inked in and one half bleached. completely bleached print. Reproduced by a squared halftone plate, 150 screen, no finishing line. ink drawings with waterproof ink, and are then bleached out. This method offers a quick and accurate means of obtaining a working basis for pen drawings. From negatives of rough pencil sketches or other material the silver print affords a basis on which a new drawing may be made and if waterproof ink has been used, the print may be bleached in a solution of bichloride of mercury which will completely 54 THE PROCESS AND PRACTICE ZOF PHOTO-ENGRAVING bleach out the original photographic image leaving only that of the ink-drawn lines. Blue prints may also be used for this purpose and may be bleached as readily as silver prints. A solution of either sodium sulphite or sodium bicarbonate may be used as a bleach. ‘These solutions are not poisonous as ts bichloride of mercury. These papers are known as “printing-out papers.”’ ‘The image is printed until visible in full strength and is then fixed. CHLORIDE PRINTS PHotroGRaPHic papers with silver-chloride emulsions of much greater speed than blue-print or silver-print papers are known as “developing papers.’ Unlike the ‘“printing-out”’ papers, the image 1s invisible until developed. In this respect they are similar to photographic plates. There are a number of these papers obtainable in standard sizes and rolls, all sensitized. Owing to their relative sensitiveness they may be printed by ordinary electric light or other suitable illuminant, but development and other operations must be carried on under dark-room conditions with an orange or subdued yellow light else they will fog. Exposure is made in a printing frame, using either daylight or artificial light. The latter is to be preferred because of its constancy, which enables the exposure time to be judged more accurately. With an incandescent bulb, a line negative may be printed in about five seconds. ‘There are a number of efficient developers suitable for those papers, every manufacturer furnishing special formulas for the © purpose. After development, the image is fixed with hypo and the prints should then be thoroughly washed. Hypo remaining in the print will cause it to fade. Chloride prints, when made from a line negative, offer no particular advantage over silver prints except that they are more permanent. ‘The processes of develop- ment, fixing, and washing consume considerably more time than that for the blue print or silver print. ‘These prints have come to be known as “velox” prints. This is due to the fact that “ Velox”’ is a trade name for one of the many grades of paper obtainable, among which are also Cyko, Azo, Haloid, and many others. CH Ab be Ray 111 MAKING A HALFTONE NEGATIVE HE general procedure for making a halftone negative is similar to that employed to make a line negative, the main difference being in the use of the halftone screen in the camera directly in front of the photographic plate. The image on the halftone negative must consist of the dot formation which will eventually produce the variations of tone on the halftone plate. By photographing through the halftone screen, the necessary dot formation is produced in the halftone negative. THE HALFYTONE SCREEN THE halftone screen is a very accurately made grating or mesh which consists of two pieces of clear, finely polished glass, each piece being about one eighth of an inch thick, and ruled with parallel lines. ‘These rulings are first cut in a special resist and the lines are then etched into the glass and filled in with an opaque substance, and then both pieces of glass are cemented together with balsam, the rulings on one glass set at exact right angles to the rulings on the other. This produces a grating of crossed lines, leaving transparent square apertures. ‘The area of each aperture is approximately the same as the area of the intersection of any two black lines. This relation can vary slightly in different screens but the correct relation is 50 per cent. black and 50 per cent. transparent. Halftone screens are made of optically clear glass and it is quite essential that they be free from any imperfections which might distort the image or in any other way prevent its perfect reproduction. In the early days of the process, bolting cloth and fine wire mesh were used, but not in quite the same manner as in the modern method. Practically all the modern halftone screens in the world have been made by the process developed and perfected by Max Levy of Philadelphia, and are known as Levy Screens. Screens must be handled with great care, to prevent the highly polished surfaces being scratched or damaged, as well as to avoid any possibility of the glasses be- coming separated. While they are cemented together with balsam and bound with 55 200 line 300 line 400 line Fig, 37. One copy reproduced in all screens from 55 to 400. 56 MAKING A HALFTONE NEGATIVE 57 a metal frame, heat or a sudden jar may cause the two glasses to separate, and the screen must then be reset. Screens vary in size and in the number of rulings to the inch. The usual num- Pam@ortulities to the inch on different screens is 55, 65, 85, 100, I10, 120, 133, 150, 175, 200, 300, and 4oo. ‘The choice of the screen to be used depends on so many different conditions that they have been described in detail in Chapter XVIII. It has been shown in the enlarged illustration of a halftone plate (Fig. 7) that the dots vary in size. ‘The accompanying illustration of a section of a halftone screen shows transparent apertures of equal size. An interesting feature of the process 1s that dots of varying size may be obtained through a screen having uniform aper- tures. In making a halftone negative the copy is placed on the copy board and focussed in the usual manner. ‘The wet plate is coated with collodion and sensitized with silver in much the same manner as that employed in the making of a line nega- tive, the principal difference being in the addition of strontium iodide to the collo- i ¢ ¢ dion. K 5 Once sensitized, the plate is placed in pincer ocd oe? o¢¢ 9% the plate-holder, but before the exposure ooo 5% 69 is made the distance between the screen N 2 and photographic plate must be most ac- Fig. 38. A 20x 24 halftone screen and an enlarged view showing the opaque crossed lines and transparent square curately adjusted as the success of the halftone negative depends to a large ex- is aoe ee ee ticincd ene tent upon this adjustment. plate, 150 screen. Halftone cameras are equipped with a device for moving the screen and adjusting its distance from the wet plate. The distance between the screen and plate is known as “‘screen distance,’ which varies according to the screen rulings. It is based upon an exact ratio as shown by the table given herewith. 58 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING It will be noted that the distance is greater for the coarse screens than for the finer ones. SCREEN DISTANCE TABLE, PENROSE DIAPHRAGM NO. II, CAMERA EXTENSION 18” SCREEN 20082175 tC Omiet sane E20 SCREEN DISTANCE | #/,,7 | 5/457 | ©/,9 | 7/so" | ®/gom The device which holds the screen and controls its position is operated by a lever on the outside of the camera. ‘The screen is usually set so close to the plate that it can be moved into position only after the plate-holder slide has been drawn. The outside control lever permits this and also enables the operator to move the screen well forward and out of the way of the plate-holder when the slide is replaced and the plate-holder removed. A fine adjustment which may be locked in position provides a gauge for the screen setting, making it unnecessary to readjust the dis- tance for every exposure unless a new screen distance is required. After the proper setting of the screen distance, consideration is then given to the diaphragm in the lens. In ordinary photography the use of this diaphragm is merely to obtain a greater degree of sharpness or depth of focus, but in the halftone process it is used to obtain the proper variation in the size of the dots. If a photograph were to be made through a screen or grating which was in con- tact with the photographic plate, the resulting negative would simply be cut up by crossing lines and the squares or dots between the lines would be uniform in size but they would vary in intensity according to the intensity of the copy. This would be of no use to the halftone process which knows no means of printing these little squares in varying intensities; they must be of uniform intensity but of varying size. It is the screen distance which makes this possible because the light is given an op- portunity to spread while passing from the screen to the photographic plate. The degree of spreading is controlled by the intensity of the different areas of light, the size of the diaphragm used in the lens and the screen distance. THE EXPOSURE Tue following description is typical of the process but is in no sense to be taken as a standard. Exposure, stop, screen distance, and methods vary with different MAKING A HALFTONE NEGATIVE 59 copies and conditions and the details of the following operations are given merely as a typical example under normal conditions. ‘lhe operator having placed the plate- holder on the back of the camera with the sensitized wet plate in position, draws the dark slide and then sets the screen to the proper distance. The stop in the lens is then set for what is known as a highlight stop. The size of the opening in this stop will vary according to the fineness of the screen used but tor a normal subject with a 120-line screen it would be about 4 inch in diameter. With this stop in position and the screen distance properly adjusted, sufficient exposure is given to photograph only the brightest parts or the highlights of the picture. Under the foregoing conditions this would be about one half minute. The PHOTOGRAPHIC PLATE HALFTONE SCREEN LIGHT FROM HIGHLIGHT STOP Fig. 39. Diagram of light from highlight stop passing through halftone screen, forming overlapping circles of light on a photo- graphic plate. Reproduction made by stripping a line positive of original copy on top of 150 screen halftone tint negative. diagram above shows the effect of rays of light passing through the diaphragm and then through the screen to the photographic plate. It will be noticed that as it reaches the plate, it is larger in area than the aperture in the screen through which it has passed; this takes place over the whole area of the picture wherever there are any highlights, and it produces a series of overlapping dots of light. Following out the principle of photography which has already been explained in Chapter IV, these dots of light become black in the negative after exposure and development, leaving smaller transparent areas between them. It will now be clear that these small transparent areas become the small black dots in the highlights in the picture when the finished plate is printed on paper. During this exposure the middle tones and shadow tones of the copy also pass through the screen toa certain extent, but as they are less intense than the highlights, they do not affect the plate to an appreciable extent in the short exposure given. 60 THE PROCESS “ANDOPRACTICE OF SPHOTOAENGRAVING After the highlight exposure has been completed the lens is capped and a smaller stop called the “detail stop”’ is inserted in place of the highlight stop. This aper- ture would be about } of an inch in diameter. The cap is then removed and an exposure of about one minute Is given with this stop to photograph the middle tones of the copy. The diagram shows the conditions for this exposure as they were shown for the highlight exposure, except that the beam of light has been narrowed down by a smaller stop and consequently projected through the aperture in the screen in the form of a cone with a smaller base. The effect of this operation is to produce dots of light which are not as large as those made with the highlight stop and which do not overlap. When developed and printed they will appear as small- PHOTOGRAPHIC PLATE HALFTONE SCREEN LIGHT FROM DETAIL sToP Fig. 40. Diagram of light from detail stop ee through hauhbae screen and forming small circles of light on photographic plate. Reproduced by same method as fig. 30. sized white holes in the middle tones of the picture. They appear clearly in the enlarged illustration of the halftone plate which is shown in figure No. 7. A third exposure is then made with the shadow stop. ‘This aperture would be about ss of an inch in diameter and the exposure would be about two minutes. The details of the shadows reflect so little light that this longer exposure is necessary, and if they are very dark they may produce no effect at all. Smooth graduation of tone from shadows to middle tones requires that there be at least a fine shadow dot in the negative. If suitable exposure does not accomplish this, then dots must be forced into the shadows by other means. This is done by “padding” or “flashing” or ‘“‘papering.’’ A piece of white paper is placed over the copy and an exposure given of about forty-five seconds with a very small stop. ‘This is called the “paper” stop and the aperture is only about ;¥ inch in diameter. This forces a fine dot into an otherwise solid area. Papering is sometimes localized in small areas by using a MAKING A HALFTONE NEGATIVE 61 small piece of paper on a wire handle. ‘This small flashing sheet is kept in motion in front of the required dark area during a part of the shadow-stop exposure. Simi- larly a small black piece may be used to hold back some small, excessively light area, during the highlight exposure. ‘These operations must all be practised with great care and judgment or they will produce false effects. All exposures for highlight, middle tone, and shadow are made without moving the plate in the plate-holder and without changing the screen distance. The question will now probably arise in the mind of the reader as to what is done to the highlight dots first exposed while the succeeding middle-tone and shadow exposures were being made. The highlight exposure produces large dots on the negative, and the succeeding exposures smaller dots. These do affect the first or highlight exposure, but being smaller, they do not affect the size. The subsequent exposures intensify the centres of the dots first exposed somewhat after the fashion of a nickel placed on top of a quarter and a dime placed on top of the nickel. In general, this is what produces dots of varying size through a screen of uniform apertures, and were this the only controlling factor there would be but three sizes of dots. In actual practice, the varying intensities of the highlights, middle tones and shadows of the copy affect to a marked extent the size of the highlight, middle- tone, and shadow dots. During the highlight exposure the more intense highlights of the copy have the effect of spreading the circle of light produced through the screen. This spreading is called “‘halation.”” Although this circle of ight has a sharp, well-defined shape, its light is reflected by grains of silver on the rim of the circle to other silver grains which lie outside the circle. These outsiders are consequently affected and the circle will continue to spread as long as the exposure lasts. Halation is therefore also depended upon to help produce the variety of dot sizes in highlights, middle tones, and shadows during the various exposures. If the ex- posure is properly timed for all stops, the result will be a finely graded halftone negative with all the delicate details of the original copy. If, however, the expo- sures are incorrect for any or all stops, or if the screen distance is not properly set, the tone values in the halftone negative will be incorrect and give a false render- ing of the original copy. Halation plays such an important part in this dot formation that it may be used 62 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING to produce very well-graded tones when only one sized stop is used. Negatives so made require different manipulation during development, but the “one-stop” method is worthy of mention if only to demonstrate the many variations to which the process is susceptible. In the chapter on Lenses and Light, reference is made to the pin-hole lens, and it is interesting to note, in analyzing the action of the halftone screen, that each aperture in the screen acts like a pin-hole lens. ‘These screen apertures, or if we may call them, for the moment, pin-hole lenses, actually make tiny photographic reproductions of the different sized diaphragms used during the exposures. ‘This peculiarity of the halftone screen is employed to produce halftone negatives with odd-shaped dots. By proper variation of the shape of the diaphragm, halftone dots may be changed to the extent of elongating them so that they will join and form a series of straight lines. This is called a ‘one-way screen.”’ ‘The following diagrams show enlargements of a few different kinds of halftone negatives together with the shape of the diaphragms which were used to produce the odd-shaped dots. DEVELOPMENT Tue development and finishing of a halftone negative are as essential to the suc- cess of the process as is the proper exposure. After the first development, which yl” Y y Fa 4 V3 yi i Wy Uf g fs Be Wl Ulli ll lle Uy las Mlle oe a Fig. 41. Tone effects of three styles of tint negatives. The apertures in the black circles represent the shapes of diaphragms used to produce the odd-shaped dots shown in the enlarged sections. The reproduction is a tinted copper line plate, tint negatives being stripped over line negatives of the stag’s head and combined with line negatives from drawings of the diaphragms and enlargements from the tint negatives. MAKING A HALFTONE NEGATIVE 63 is practically the same as for line work, the dots are more or less crude and indefinite in shape, this crudeness being due principally to halation. Halftone operators must be able to judge whether or not the relation between the various sized dots is correct and finish the negative accordingly. Dots which may be too large can be reduced in size by cutting with a solution of potassium cyanide and iodine. ‘This eats away the silver grains around the edge of the dot where they are less intense and acted upon more quickly, and thus reduces the area of the dot. Dots which may be too small or indistinct may be increased in size by intensification. The negative ts flowed with a copper sulphate solution which causes a copper deposit to form on the ’ silver grains of the dots. ‘This intensifies the less intense “halation”’ edges of the dots and increases their opaque area. After thorough washing, a further intensi- fication by means of a silver nitrate solution blackens the dots to create the desired degree of opacity. Two illustrations are shown—one of the halftone negative when first developed Fig. 42. Photomicrograph of halftone negative be- Fig. 43. Photomicrograph of the same halftone fore being finished, magnified about 40 times. negative after being properly intensified and cut. The magnified halftone dots in both these figures correspond in position and may therefore be compared. Both reproductions are halftones, circles, 150 screen, no finishing line. and which shows the rough edges caused by halation. With it is shown a reproduc- tion of the same negative after proper intensification and cutting. Thus, by skilful manipulation in the hands of the operator, the halftone nega- tive is built up in some parts and cut down in others and finally brought to a condi- 64 THE PROCESS “AND, PRACTICE OF PHOTO{ENGRAY ING tion of proper relative values throughout. Many pitfalls lie in the way of these operations, and only the most skilled operators can produce even passable results. It is a simple matter to make a negative, but that is not the problem. ‘The negative must be of such values that it will reproduce the copy after passing through the various operations which follow. So many varieties of tones may be obtained by manipulation of stops and finish- ing operations that examples of them will prove interesting. The three illustra- tions which are shown herewith were all made from the same copy. ‘Their titles describe the means employed to obtain the varied results. When the halftone negative is finished it is dried in a heated oven as is the line negative and it is then ready for subsequent operations. © H. A. Strohmeyer. Courtesy Country Life in America. Fig. 44. Reproductions of three halftone negatives of the same copy. Photographed through detail stop, highlight stop, and shadow stop. These plates have not been re-etched and show the variety of results obtainable by means of the different diaphragms. Blue prints or other photographic prints may, of course, be made from halftone negatives as from line negatives, but great care must be exercised in handling them so as to avoid slight scratches which would impair or destroy some of the dots and consequently affect the perfection of the negative. MAKING A HALFTONE NEGATIVE 65 TINT NEGATIVES SOMETIMES it is necessary to make what is called a tint negative, consisting only of even-toned areas of the halftone screen. These are usually produced by making a halftone negative of a piece of white paper, the tone of the tint being regu- lated by the size of the stop and length of exposure. A tint of half colour would be made with‘a detail stop, a dark tint would be made with the shadow stop, and a light tint with the highlight stop. By means of the slotted stop tints may be made with the dots joined producing the one-way screen effect, which has been shown in fig. 41. The use of these tint negatives is more fully explained in the chapter on Negative Turning and Inserting. HALFTONE POSITIVES Just as it is possible to make positives from line negatives, so it is also possible to make them from halftone negatives. The photographic method is quite the same and the result is a transparent halftone image or halftone “‘diapositive.”’ One use for halftone positives 1s in intaglio plates which must be printed by the process of inking and wiping. ‘They may also be used for certain types of colour plates which are more fully described in the chapter on this subject. HALFTONE NEGATIVES FROM OBJECTS Copy for reproduction is usually flat like a drawing or painting or a photograph, but objects are quite often reproduced direct. A great many factors govern the method of direct halftone reproduction, the principal one being the suitability of the object from a purely photographic standpoint. In order that this direct method may be more intelligently described, it will be necessary to consider the usual style of copy as compared with an object. Drawings and paintings may, of course, be eliminated from our comparison be- cause they form a class by themselves. They are ideas or ideals, executed by an artist. Photographic copy, however, must be considered as representing a different class. Ifa photograph is made of a landscape, a building, or other object, the result in no sense represents an ideal. It is a photographic image of the original and any imperfections in the original or in the composition of the view appear in the photo- 66 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING graph. Unless these imperfections are to be reproduced, it will be necessary first to ‘ correct them. This may readily be done by what is known as ‘“‘re-touching,”’ which is fully described in the chapter on The Copy for Reproduction. No matter whether this retouching be slight or extensive, it enables a change or alteration to be made which would not be possible were the same object to have been photo- graphed direct by the halftone process. The principal factor, therefore, for determining whether or not an object is suitable for reproduction by this method is whether or not it is free from imper- fections and suitable to be reproduced just as it is seen by the camera. If the object is not too large, it may be secured to the copy board or set on the camera base. Large objects, or those which are not suited to be posed in this manner, require special methods and -handling. Still another factor is the shape of the object. If it is shallow, it offers much greater possibilities than if it is thick. Thickness requires stopping down to a very small lens aperture if critical sharpness is to be obtained through the entire depth of the object. This is a matter which leads into the realm of a different class of photography from that employed in photo-engraving, but the difficulties caused by this necessity for stopping down will be apparent when the function of the dia- phragm employed in making a halftone negative is recalled to mind. ‘Thick ob- jects, therefore, present a difficulty in the employment of the direct halftone method which may in some instances be so serious as to make its use impracticable. The matter of colour offers a stumbling block more often than any other factor. The wet plate, as has been explained, is not equally sensitive to all colours, and it, therefore, does not reproduce colour values of an original in the same relative tones as are seen either by the eye or by the special colour sensitive photographic plates which should be used for their reproduction. Finally, the matter of illumination must be considered. Few objects can be properly illuminated by the intensely brilliant arcs employed to illuminate the usual halftone copy. Either the intensity of the light casts offensive double shadows or creates objectionable highlights. If less intense illumination such as a diffused light is employed to produce the proper light and shade values of the original, it may then be so weak as to make the exposure too long for the direct halftone method. The emulsion of the wet plate is slow enough under the most brilliant light conditions MAKING A HALFTONE NEGATIVE 67 and if extraordinarily long exposure is required, there is always a chance that the wet emulsion will dry up during exposure which would impair the photographic properties of the sensitized plate. The use of an object as original copy is the exception rather than the rule and the objections to its use have, therefore, been described and explained before enter- ing into a discussion of the points in favour of the process. A reproduction direct from an object is one step nearer to it than a reproduction of a photograph of that object. This is naturally a point in its favour, as there is always a loss in reproduction even though that loss may be slight. It may, there- fore, be considered possible to employ the direct process under the following con- ditions: The object must be of a size and shape which will permit posing it before the camera. Its nature must be such that it may be properly illuminated. Its colour should be neutral; that is, of tones of black and white, and it must be free from im- perfections except those which are to be reproduced. Comparatively few objects fulfil these requirements, a most notable exception being flat silverware. Even this is usually prepared especially for direct halftone photography, by giving it a dull mat finish to obviate disagreeable reflections. Book pages containing illustrations, if they are not in colours, also belong to the class which is suitable for direct work but the outsides of the books themselves present greater difficulties owing to their shape and colour. No set of rules or specifications can very well be drawn, whereby the suitability of any object for direct reproduction may be determined. As in so many other steps of the process, it is a matter which is governed by conditions, and in nearly every instance a different set of conditions will be encountered. Some establishments specialize in direct work and when the objects lend them- selves to this method of reproduction, the results are usually far more accurate and pleasing than when photographic copy is first prepared. DRY-PLATE HALFTONE NEGATIVES HALFTONE negatives may be made on process dry plates or films, but the difficul- ties presented are a little more complicated than for line work. ‘The size of the halftone dot is usually a smaller area than that of any part of a line negative and Is consequently more difficult to produce in the sharp, well-defined form required. 68 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING The wet-plate image is on the surface of the collodion and consequently of very slight thickness. Dry emulsions of even the process photographic plates have a tendency to be thicker. The silver grains combined with the other necessary chemicals are in a gelatine base and the tendency is for the silver grains to be in layers rather than in one flat, thin surfaceimage. Thick emulsions will produce dots with “fuzzy” edges. Halation also tends to cause a lack of clear transparency be- tween dots. Therefore, dry emulsions, either on plates or films, must be of the thin- nest possible structure and designed to give clean, sharp dots with equally clean transparent areas between. Otherwise the halftone negative will be lacking in the quality necessary. Many suitable makes of process dry plates are on the market and they are being used for different purposes and in conjunction with specially designed apparatus, according to the requirements of the subjects. A special characteristic of the dry-plate emulsion 1s that it can be made so as to be sensitive to colours. Wet-plate emulsions are also made which are colour- sensitive, but it 1s not practicable to use them in the photographic equipment employing the usual wet plate. Both the wet and dry colour sensitive emulsions are usually employed in special equipment for colour work in one form or another and are more fully described in the chapter on Process Colour Work. SCREEN EFFECTS THE success of the half tone process depends largely upon the deception of the eye. In most instances halftone dots are small enough to be practically invisible. It has been found that visibility of the individual dots 1s materially decreased when the angle of the screen is 45 degrees off the vertical and horizontal. Reduced visi- bility at this angle may be due to the fact that our eyes have become accustomed to illustrations made with the screen running at this angle, but whatever the reason, a variation of this angle has the effect of causing greater distinctness of the dots. Figures 45 and 46 have both been made with Ioo-line screens to demonstrate this peculiarity. In the former it is shown running vertically and horizontally and in the latter at the usual 45-degree angle. Halftone screens are usually made with the lines running at the 45-degree angle, and it is advisable that this angle be retained whenever possible. For decorative effects the screen is some- times intentionally run vertically and horizontally to simulate texture and some MAKING A HALFTONE NEGATIVE 69 2 classes of copies lend themselves particularly to reproduction with the screen at this angle. The resolving power of the normal eye is said to be 200 elements to the lineal inch. Figures 45 and 46 have but too dots to the inch, so each is quite distinct upon close inspection no matter what the screen angle may be. Figure 47, how- Fig. 45. Halftone of 100 Fig. 46. Halftone of too Fig. 47. Halftone, 200 line screen with dots running vertt- screen with dots running at screen, wih dots running at cally and horizontally. usual 45° angle. usual 45° angle. ever, has been made with a 200-line screen and represents the limit of the eye’s re- solving power. The dots will probably be quite invisible unless examined with a magnifying glass. SCREEN PATTERNS SCREENS are denoted by the number of single lines to the lineal inch and, of course, the number of dots produced by the crossing lines of the screen is the square of the lineal measurement. A Ioo-line screen produces 10,000 dots to the square inch; a 400-line screen, 160,000. Screens are so accurately ruled and the dots in the plate are so uniformly spaced that peculiar patterns are produced when one screen conflicts with another. Ifa copy happens to be a halftone reproduction, as is often the case when pages from books are reproduced, the new halftone negative with its screen will conflict with the screen of the copy. The effect will vary, depending upon the mesh of the two Pere nemancethe result is called-a “pattern, or moire: A typical screen pattern is shown in fig. 48. It is caused by the screen in the copy conflicting with the screen in the halftone negative made to reproduce it. The checkerboard effect is most pronounced where the two series of dots overlap most closely. As they overlap less and less, the patterns become lighter and less 70 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING visible until another row of dots is encountered and the checkerboard pattern is then repeated. An enlargement of this figure shows the manner in which the dots overlap and conflict. Patterns can usually be materially reduced by changing the screen angle, so as Fig. 48. The checkerboard pattern Fig. 49. The same halftone proof re- Fig. 50. The same halftone proof re- caused by crossing a roo line halftone produced with roo line screen rotated to produced without pattern by using 150 screen with a halftone proof of 100 screen. reduce pattern to a minimum. line screen rotated about 5°. to cause the dots of the new negative to fall in the open spaces between the dots on the original copy. This angle can be determined by a close inspection on the ground glass, when the copy is focussed through the halftone screen. The copy is rotated until the image appears as free from pattern as possible. Some cameras are equipped with screen holders in which the screen itself may be rotated, making it unnecessary to adjust the copy at the necessary angle. Fig. 49 shows the pattern reduced ma- terially by rotating the screen and fig. 50 shows it nearly eliminated by using a finer screen at a suitable angle. Screen patterns are also caused by the conflict between | the screen of the halftone negative and fine lines on the copy. Fig. 51. A line plate from a section of fig. 48, enlarged to Jf these lines are very close together, as, for example, in a steel show the screen formation which ; : ; causes the pattern. engraving, they will form a pattern with the halftone screen but it will be quite unlike the checkerboard pattern which has been illustrated. It will be more like the “moiré”’ of a piece of watered silk. It is produced in the same MAKING A HALFTONE NEGATIVE 71 manner as the checkerboard pattern but is unsymmetrical because of the lack of precision and regularity of the lines in the copy which conflict with the halftone dots. This unsymmetrical pattern also appears in reproductions of ribbed materials like hat bands, stockings, or underwear, and it is often very difficult to eliminate it. Changing the screen angle will lose the pattern in some places, but it may appear again in others, in which case the only way out of the difficulty is to try a coarser or Courtesy Grolier Society. Fig. 52. Squared halftone, 120 screen, made from a steel Fig. 53. The same subject reproduced with 120 screen rotated engraving. The motré pattern is noticeable throughout. to eliminate the moire. finer screen, or make separate negatives at different screen angles and combine them. There is no rule by which the elimination of this unsymmetrical pattern can be figured out, as it will vary with subjects of different characteristics. The effect of reproducing lines by means of halftone dots creates what is called ‘fa saw-tooth edge,” and this effect varies with the nature and shape of the line. 72 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING Courtesy Crofet = Knapp Fig. 54. A very objectionable moiré showing in the hat- Fig. 55. The motré reduced to a minimum by rotation, band as a result of the 120 screen conflicting with the ribs of but it 15 still apparent in some places. A much coarser or the silk in the ribbon. finer screen would have to be used to eliminate this entirely. The reproductions are both squared halftones with the backgrounds painted in solid before being etched. This is noticeable in curves, particularly if they are small. A typical example of this effect is shown, and the reason for the saw-tooth edge will be evident upon ex- amination. The foregoing are but a few of the many peculiar screen effects and considera- ~ tion should be given to this matter when the halftone process is to be employed. When using a coarser or finer screen, con- sideration must be given to the paper on which the plate is to be printed. ‘This may limit the choice of screen fineness, in which event there is no choice but to re- duce the pattern as much as possible and be content with the result. In some cases where a very pronounced disagreeable pattern appears, the copy may be photographed slightly out of fo- Fig. 56. A diagram of fine lines reproduced by means of aso screen squared halfione. Note the breaking up of both cus. [There are a number of ways of do- the curved and straight lines where they are crossed at certain . angles by the halftone screen. ing this and! 1t-is 2 practice which must Inspection with a magnifying glass will show the dot for- : : mation which causes this effect. be employed with care and judgment, else so much definition will be lost that the effect of reproduction will be materi- ally impaired. CHA Rae. NEGATIVE TURNING AND INSERTING HE human element plays the most important part in photo-engraving, so much so that mechanical appliances used in the process may be considered only as accessories. Negative turning and inserting depends on manual skill entirely. It is in this operation that the delicate films of line and halftone negatives are prepared for the printing and etching process. No small amount of this preparatory work consists of combining negatives, either halftone, line, or both, to reproduce plates complete in one piece from numerous copies. It has been explained that a wet-plate negative consists of a piece of glass, a thin solution of albumen, a coating of negative collodion, and a delicate photographic image of silver salts on its surface. It has also been explained that photographic images are backward on the nega- tive, and this reversal is corrected by turning the negative over on glass before it 1s printed. As this requires removing the thin collodion film from the negative glass, it must be strengthened and the delicate photographic image on its surface protected. After the negatives are taken from the drying oven, they are coated with two films in addition to the original film of negative collodion. The first film to be added is a thin solution of pure rubber dissolved in benzole. It is flowed in the same manner as that used for flowing the glass with negative collodion. ‘This film of rubber dries quickly owing to the rapid evaporation of the benzole; and the second film is then added. This consists of “‘stripping”’ collodion. It is a solution of alcohol, ether, gun cotton, and castor oil. Owing to the presence of alcohol and ether in this solution, it is necessary to insulate it from the original film of negative collodion by means of the rubber film, otherwise the second collo- dion film would soften and might dissolve the film of negative collodion and de- stroy it. The original film is in this manner protected and strengthened so as to permit 73 74 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING its being removed from the original negative glass. After the stripping collodion has dried, which takes place quickly, owing to the evaporation of the alcohol and ether, the negative film is cut with a sharp knife well outside the limits of the work area and is then immersed in a weak solution of acetic acid. This dissolves the thin albumen film on which the original negative collodion was flowed, and the negative with its two additional films floats off or may easily be removed from the original negative glass. Even though the original film has been protected and strengthened, it is still so delicate that it must be handled with the utmost care. After it has been stripped off the original negative glass, it is turned over and mounted on a second piece of glass, usually about $inch thick. Ifthe negative is a small one, it may be lifted from its original glass and mounted directly on the new one, but if it is a large negative, it is usually supported by means of a thin sheet of wet paper. Newspaper may be employed for this purpose and, when thoroughly soaked, it is placed on top of the film which has been loosened from the glass and the paper and negative are both lifted off together, the paper acting as a reinforcement to the delicate film. The glass on which the negative is to be mounted is kept wet and the film is very care- fully flattened out on this wet glass and pressed down into contact with a rubber “squeegee”’ or with the moistened edge of a piece of blotting paper. During this operation the film may easily be wrinkled or the corners may turn under, or it may be stretched out of shape. It would be absolutely unsuitable for the processes following were it to show any such evidences of careless handling. The prime purpose of negative turning is of course to reverse the image, thereby correcting the reversal which took place through the lens. Advantage is also taken of the fact that a number of negatives of similar character may be put down on one piece of glass to be printed and etched at one time. ‘This is worth mentioning as a manufacturing procedure but is unrelated to the technique of the process. The bench on which the negative turner works is like a transparent drawing board. It is a frame with a large plate-glass centre and an electric light under- neath. The frame has an accurate steel square fastened across the top and one side used with a T-square for aligning and squaring up negatives when turning and setting them up. The light underneath permits the negative turner to see through the negative films. NEGATIVE TURNING AND INSERTING ais The heavy plate glasses on which negatives are turned or mounted are called “flats.” They vary in sizé ac- cording to the size and number of neg- atives to be turned on them. There are occasions when nega- tives are combined to produce a plate larger than the size of the available Fig. 57. Negatwe turner’s easel, showing printing frame. ‘This is a very unusual negative flat in position. occurrence but when it arises unusual methods are employed to surmount the difficulty. Such flats are clamped into contact with the metal, for the purpose of making the metal print. In cases where even this method is found inadvisable, the negative films may be stripped directly on top of the sensitized coating on the metal. They are oiled to prevent their adhering to the sensitized surface. In ordinary practice, halftone and line negatives are turned on different flats, but in many instances plates are made which are combinations of line and halftone and in such instances the line and halftone negatives are combined on one piece of glass. This may prove a simple or elaborate operation depending upon the subjects to be combined. Negative turning does not present great mechanical difficulties. Skill and care are the essentials. All negatives must be turned over, unless the final result is to appear backward, or reversed in position. If such a result is desired, which is quite often the case, the negative is stripped in the usual manner but ts not turned. Combining negatives or inserting one into another is a more difficult operation. There are simple as well as complicated subjects and it would be out of the question to try and describe them all. Conditions vary with every different copy, but the principles involved do not change. Negative inserting is just what its name im- plies. It means that one negative must be inserted into another, just as though two original drawings were cut and fitted together to make one. The negative turner’s skill has been developed to such a degree, by reason of tne extraordinary demands which have been made on this branch of the work, that im- possible or impracticable results are often expected. A typical example of a simple inserting operation is shown in figs. 58, 59, 60, 61, 76 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 62, 63, and 64. Two copies were supplied. A line negative and a halftone nega- tive were made and coated with the usual strengthening films of rubber and collodion. A faint outline of the halftone subject was indicated on the line copy, to show the position to be occupied by the halftone negative when combined with the line nega- tive. Both negatives were stripped and turned on a flat, the line negative being squeegeed down first and the halftone negative laid on top of it. The proper posi- tion for the halftone negative was determined by laying it to fit the faint guide oe ae Sa HE : a Yad yo | : 1 y a a {= le : a ee a ie Af bs 7 2 ¥ ¥ y : 3 ae pty ‘eo 1% as _ = ry wis A. Fig. 58. A line plate reproducing the line copy Fig. 59. Halftone reproduction of the retouched photo- employed to produce the finished result shown in graph to be combined with the line work shown in the pre- fig. 64. ceding figure. lines showing on the line negative. This would have been a difficult matter had not the light under the negatives permitted the operator to see where the halftone negative was to fit. It must be remembered that nearly the entire area of the line negative is black opaque film, the only transparent parts being the lines of the copy. The guide line, being transparent, afforded sufficient indication of position to permit placing the halftone negative in position. Position being determined, the halftone negative was squeegeed down tight. The negative turner then cut through both negatives at one time with a very sharp pointed knife. The parts of the halftone negative not required were then moistened and removed, leaving the remainder of the halftone negative in position but as yet unfit for printing owing to the black film of the line negative underlying it. This halftone section was then moistened and part of it lifted, permitting the removal of the line negative film under this part. After this part of the halftone negative NEGATIVE TURNING AND INSERTING 77. Fig. 60. The halfione negative superimposed on the line Fig. 61. Removing the outer area of film of the half- negative in exact position, both negatives being cut by the tone negative, leaving the reproduction of the box itself in negative turner. position. Fig. 62. The halftone negative of the box folded over and Fig. 63. All of the underlying line negative removed and half of the underlying film of line work being removed. the halftone negative of the box inserted. All four reproductions squared halftones, 150 screen, from actual photographs of the inserting operations. had been squeegeed back in position, the other part was moistened, lifted, and the remainder of the line negative under it removed. When finally flattened back in posi- tion the halftone was accurately inserted into the line work, in the space provided for it by the guide lines. It will be apparent that this particular subject does not represent an extremely difficult example of the Courtesy American Safety Razor Co. process. Figure Ga. however, is not so simple. Fig. 64. The completed combina- tion plate resulting from the foregoing A careful inspection of the joining of the halftone negative turning and inserting. 78 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING and line areas and reference to the method just described will convey some idea of the care and skill necessary to produce such a result. In a similar manner, it is of course possible to combine halftone negatives, but in this operation, consideration must be given to the fact that the screen of one negative will not join cleanly where it is cut and fitted into another. A homely com- parison of this would be in cutting a wire fly screen and fitting it into a hole in an- other. A somewhat ragged line will appear where the two screen negatives join as Courtesy Harper’s Bazaar. Fig. 65. A silhouetted combination plate, 150 screen, demonstrating an elaborate example of negative inserting. Each area of halftone was inserted in the line negative by the methods illustrated in figs. 60 to 63 inclusive. NEGATIVE TURNING AND INSERTING 79 illustrated in fig. 66. In such cases it is usually advisable to cut a white line in the etched plate at the point of joining, as shown by fig. 67. Sometimes it is inevitable that halftone negatives must be joined, as in the case of a plate to be made which is larger than can be photographed on one negative. It is out of the ordinary but still not unusual, and there is no choice but to join the negatives. Panoramic views, sometimes made in halftones six feet long, are made in this fashion and the extreme of the negative turner’s skill is demanded to match Fig. 66. The ragged joint caused by fiting Fig. 67. A white line tooled at the juncture together two halftone negatives. of the two screens to clean up the joint. up the sections accurately. Cutting of the negatives is usually done along irregular lines and where possible, along definite outlines in the picture so that the joint, even though ragged, may be concealed. Fig. 68 shows an example of this joining along appropriate outlines and the joint will not be indicated other than by stating that it does exist. Whether or not the reader can find it will indicate to a certain extent how far the skill of the negative turner goes. The style of the finishing edge of a halftone must be provided for when the negative is turned. If the plate is to be finished with “no line,” sufficient screen background is allowed to remain on the negative so that the plate may be bevelled to shape, letting the screen run up tothe edge. (See Chapter XIII.) Finishing lines or borders vary. If a simple black line, or “hair line”’ as it is called, is to be used, the negative is cut down in size until the screen area corresponds 80 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING © Cross &F Dimmitt Fig. 68. The two upper illustrations are reproductions made from separate halftone negatives of the two ends of a panoramic photograph. The lower illustration has been made from these two negatives joined. The three reproductions are squared halftones, 150 screen, no finishing line, and have not been re-etched or manipulated in any way to hide the jount. with the size of the inside dimensions of the border line. All screen film is removed beyond this edge. The negative will then print, leaving solid metal around the edge of the screen area. The bevelling machine is then used to cut this solid metal away until it leaves only the hair-line finishing edge required. Thus, any halftone, whether it be square, oval, or circular, to be finished with such a line, must be prepared in the negative-turning operation. The screen tint must be cut away to leave solid metal when it is printed. Negatives are cut to oval or circular shape by using a thin celluloid gauge or templet, which is laid on the negative in proper position and furnishes a guide for the knife cut. These gauges are cut to the desired shape and size with a special machine. Some styles of borders or finishing lines are too complicated to be cut in this manner. It is then necessary to have drawings made of such borders and make line negatives of them, and insert the halftone negatives. NEGATIVE TURNING AND INSERTING 81 THE USE OF TINT NEGATIVES Tue making of a tint negative has been described in the chapter on Making a Halftone Negative. It is used to produce a smooth, even tone consisting of half- tone dots of a uniform size. ‘Tint negatives may be made to produce either light or dark tones, and they are nearly always employed to produce a screen effect in areas which are solid black in the copy. This process is known as “‘tinting”’ or “screening.” It is seldom necessary to employ this process on halftone copy, because the necessary screen effects can usually be obtained when the halftone negative is made. With line copy, however, screen effects in the blacks are readily produced by this method. An example is given in figure 69, the copy for which was a black-and-white line drawing. The effect produced was caused by stripping a tint negative on top of the line negative. In order to under- stand this process it must be remembered that the white areas of the copy were opaque on the line negative; the black areas being represented by the transparent parts of pig. 65. Line plate made trom a black-and-white copy and same subject reproduced by stripping a 100 screen mnenetne tit mecative is stripped on top of it, it will only slight halftone tint over the line negative. the negative. These opaque areas act as a mask and print through the transparent parts of the line negative, all the rest being effectually masked out. The desired tone of the tint must, of course, be known before the tint negative is made and it is usually specified as go per cent. dark, 50 per cent. dark, or whatever other tone is required. ‘This illustration is of a simple subject, but the tinting process is applicable to any line negative. Fig.70. Five grades of halftone tints from highlight to shadow. These reproductions are all squared halftones, 120 screen, and were made by photographing white paper, using diaphragms of suttable sizes. 82 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING The reader may wonder why the same result could not have been produced by making a halftone negative from the line copy. Had this been done, the halftone screen would have appeared in the surrounding whites as well as in the blacks, there- by requiring considerable additional work in the later stages of the process to cut this screen away. Tint negatives cannot be stripped on top of halftone negatives without producing a pattern. For this reason any areas of a halftone copy which are to show screen should be so prepared in the copy that the desired screen effect will be produced when the halftone negative is made. STRIPPING POSITIVES Just as it is possible to produce a halftone screen in a solid area of a copy, so it is also possible to produce a white area. It is only necessary to strip on opaque film instead of halftone film. For this purpose a positive is gen- erally used and is stripped over the underlying negative, whether it be halftone or line. An occasion for the use of this method arises when white lettering or other form of design is to be shown on the darker background of either the line plate or a half- tone. The method of procedure will, of course, vary with different subjects, but it is usually employed when one copy is supplied for the background and a separate copy for the part to be reproduced in white. A typical example of this method is illustrated in fig. 71, in which both copies and the finished result are illustrated. The first copy is the principal drawing, or background. ‘The second represents the lettering to appear in white. A line negative was made of No. 1 and a line negative and line positive were made of No. 2. The positive was, of course, opaque in the areas represented by the black of the copy and all the other areas were transparent. When stripped on top of the line negative, the positive masked out all the areas which appear white in the finished plate. The same result would have been obtained if the lettering had been drawn in white on the original copy, but for economical reasons it is often advisable to pre- pare the copy in the manner shown. A tint negative as well as a positive may be stripped over a line negative and the result will be as shown in fig. 72. The tint negative was stripped NEGATIVE TURNING AND INSERTING 83 BOND Fig. 71. Reproduction of a line copy, a separate copy of lettering and the result obtained by stripping a positive of the lettering on top of the line negative. over the background and the line positive was then stripped on top of the tint negative. The same method may be employed in stripping a positive over any halftone negative. The black areas of the positive mask out the screen and produce white areas in the finished plate without screen. There are, of course, many varieties of effects which may be produced by strip- ping a negative or positive over another, and when this method is to be used, the characteristics of the negatives and positives must be considered. The superim- posed negative will print through only the areas of the underlying negative which are transparent. ‘The black areas of the positive will only be effective when stripped over transparent or tinted areas. In some instances separate drawings for white let- tering or designs are made with the lettering or design in white on a black background, rather than in black : on a white background. When this is done, it is Courtesy Clucts, Peabody & Company, Inc. 2 Fig. 72. The same line negative with only necessary to make a negative of such a draw- = 120 screen halftone tint negative stripped over the background and the positive of the ing and then proceed with the required superim- lettering stripped on top of that. posing. The drawing having been made white on USERS G SON tab ai Ai black, it becomes unnecessary to make an additional positive from the line neg- ative. The foregoing description of stripping positives over line and halftone negatives has dealt entirely with the production of white areas. Black areas cannot al- ways be produced by the process of negative stripping or inserting. ‘This will be clear when it is remembered that black areas on the plate are transparent areas on 84 THE PROCESS AND (PRACTICE OFSPHOTO-ENGCRAY ING the negative. Inserting a transparent area would simply mean cutting a hole in the negative in the form of the black area to be added. In some instances where a line negative is to be combined with other negatives, it can be cut and fitted if the out- line of its design is not excessively complicated. If, however, a considerable amount of black area like type matter is to be added to a line plate or halftone, it is usually advisable to surprint it. ‘This is an operation performed when the negatives are printed on the metal. DUPLICATING WITH EXTRA NEGATIVES REPEATING patterns in design afford an opportunity to use duplicate negatives to complete a plate from a copy represented by but one section of such a pattern. ITO?) oy SSUES AOC pone eh ak seer —as| Sai ZPD SS OKO. JES. S \eae SS ASS DO DWE OWEN Et SEI Ch) =) De ——a |; ye alia SF eX Bone w= Fa) OX DBO Dic3} a a =s3 aN Sr SE 7 >) en aut =) UG ia re) ro © Weed Sse WN, ("3 14s % Vi Sa eda He RENE S Courtesy Winemuiller & Miller. Fig. 73. Line plate reproducing a copy for a border, only half of which was drawn, but made into a complete border by setting two line negatives together, reversing one of them to complete the design. This method is quite generally used to reproduce elaborate borders and similar copies. When two halves of a completed subject are identical except for reversal NEGATIVE TURNING AND INSERTING 85 of one of them, it is only necessary that one half be drawn. Two line negatives are made, one being turned in the usual manner and the other set up alongside of it in position, but not turned. This causes the necessary reversal of one half and when properly joined, the design is completed. This method may be used with any copy which lends itself to repetition to form a complete sub- ject, whether the individual elements to be repeated are halves, quarters, or smaller divisions. It becomes merely a matter of making enough negatives to complete the design. This same method may be employed with halftone negatives, but consid- eration should be given to the difficulty in joining the screen tints cleanly. It is advisable that copy for halftone reproduction be complete, unless the nature of the design is such that the joints between screen negatives may be made incon- spicuous. It is essential that an accurate diagram or guide be provided to show exactly how repeated negatives are to be placed, and care must be taken to see that the parts to be repeated lend themselves to this method. In event of any doubt as to the manner in which a repeated design will work out, it 1s well to have a sufficient number of blue prints made from the line negatives and set these prints up in the form of a guide, which can readily be followed by the negative turner. CHANGES IN PROPORTION Line drawings are often used for making plates of different proportions. ‘This applies, particularly, to subjects such as borders. Proportions are changed by cut- ting the negatives and fitting them together to the new size and on line plates the joint can usually be successfully hidden. Borders or designs of decorative forms sometimes offer difficulties when set up in changed proportion; because of the possible necessity of cutting through some essential feature when setting the negatives up to the new size. Consideration must always be given to this possibility when the negatives to be combined consist of any form other than plain straight lines. Changes of proportion are also effected by making extra negatives and setting them up. This becomes necessary when a border is to be pieced out instead of being cut down to a new size. 86 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING Conditions change day by day and the foregoing have been given as typical in- stances of the work in this department. The department of negative turning and VeQ ERs OE SaaS Ne OOS Neopets narra elernaceh el: 2% Lae SSS PTC) cS ams ae D3 OO! SGI ] NG —_ — iad? —~y ts we A, > WA << 2 PEAS) ce Ss owe. P= Se ¥ [es a Fd 2: px Fig. 74. Line plate from the same copy as used for fig. 73 but proportions changed. One extra negative was used to repeat the design but a section was cut out of each side and the remaining areas moved together and joined. The removed sections are shown within the border and show how the design was cut at a point where the continutty of the scroll work would not be destroyed. GE ae = BNC OTe ge ii nt H war = PSE ALC)? 7O8Ghic = —auar =p Y ES, a 23 Va a ees Fig. 75. Line plate made from the same design with seven additional negatives set up and joined. inserting is the assembling room of the photo-engraving business. If the required assembling and joining is not done in this department, then it will be necessary to do it with the plates themselves. Surely, the cutting of metal plates is more diffi- cult than the cutting of the thin collodion films of the negatives. Grp RE Xx PHOTOGRAPHIC PRINTING ON METAL ALFTONES and line plates are usually made on copper or zinc. It is customary to use zinc for line plates and copper for halftones, but under certain conditions halftones are made on zinc and line plates on copper. Other metals such as brass, steel, aluminum, or silver can be used. Zinc and copper sheets are specially rolled for the photo-engraver’s use. The metal is practically pure and is rolled with great care and accuracy to supply sheets which are free from imperfections and which are of a uniform thickness throughout. The usual thickness is 10 of an inch and is called 16-gauge metal. The sheets are supplied by the rolling mills in practically any desired size to fulfil trade require- ments and are highly polished on one surface. Uniformity of thickness is of extreme importance, because when zinc and copper plates are mounted together on the same wood base any variation in thickness would result in an uneven printing surface. Both copper and zinc may be obtained in thicker sheets for use on special bases, if desired. So-called “patent bases” used by many printers require plates 3,5, or about 11 points thick. (‘‘ Point” is a measuring unit of the printing craft, 1 point=,4, inch.) To meet such requirements copper and zinc are rolled in sheets of this thickness, and are known as “heavy metal.” In the early days of photo-engraving, zinc was the only metal used. Halftones as well as line plates were made on zinc and it was not until a suitable resist was evolved for it that copper came into general use. The choice between copper and zinc to-day depends largely upon the subject and the nature of the plate to be made. The metallic structure of zinc is tough and somewhat fibrous, while copper is more ductile or “velvety.” Zinc is less costly than copper. It etches more rapidly than copper and it is customary to use it for line work. When used for halftones it 1s usually for the coarse-screen variety. Halftones of fine screens and fine line work are usually made on copper. Some of the technical features relating to the use of 87 88 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING copper and zinc are more fully explained in the chapter on Finishing in the descrip- tion of “‘re-etching.” It has been explained that negatives are turned on “‘flats’”’ which are of different sizes, depending upon the number and size of negatives mounted on them. The metal sheet on which a flat is to be printed is cut sufficiently large to allow a working edge beyond the outer limits of the negatives. MAKING A ZINC PRINT THE photographic operations having produced a negative of the original copy and the required negative turning or inserting having been accomplished, the next operation is to make a_photo- graphic print from the negative on the surface of a sheet of zinc. A sheet of zinc is¢cuthresto. required size and the polished side is thoroughly cleaned with finely powdered pumice and water to re- move all traces of dirt or grease. It is dried and then coated with a photographic printing solution made up of distilled water, albu- Fig. 76. Cleaning a sheet of xinc with powdered pumice and water. men, and) potassilim | Righsgiis A squared and vignetted halftone, 150 screen. by flowing the solution on the metal in much the same manner as in coating negatives. To hasten drying and to distribute the solution evenly over the entire surface of the metal, it is whirled and slightly heated. There are a number of devices which may be used for this purpose, the essential feature being a means to hold the plate so it can be whirled. A pair of metal clamps hung on a swivel bearing will hold the plate securely and when spun around on the swivel, will afford the whirling motion required to dis- tribute the solution. Rapid whirling will spread the solution in a thin coat- ing, which is to be desired for certain classes of work. The metal is usually suspended, coated side down, in a cylindrical enclosure, which catches the excess solution thrown off the plate during the whirling operation. A small heater PHOTOGRAPHIC PRINTING ON METAL 89 about three feet below the plate will afford sufficient heat to dry the coating in a few moments. The metal now has a coating of bichro- mated albumen which is sensitive to light. The degree of light-sensitiveness of this coating is much less than that of the or- dinary photographic emulsion, and the metal so coated may be safely handled in subdued daylight if not unduly exposed. Care must be taken that the sensitized metal does not become “fogged,”’ so it is not usually coated until just before it is to be printed. The principle of the printing operation is not unlike the ordinary photographic method of making prints on sensitized pa- per. The negative must be pressed into contact with the sensitized surface of the metal and then exposed to light. Fig. 78. Whirling a coated zinc sheet to distribute and dry the coating. Fig.77. Coating the zinc with the sensitized albumen so- lution. Metal printing requires a special type of print- ing frame to force the metal and nega- tive into the closest possible contact. The older types of printing frames were very heavy and cumbersome. They had a heavy plate-glass front, an inch or more in thickness, and pres- sure was exerted from the back by means of crossbars and wooden screws. These screws were later replaced by lever hooks. ‘This method resulted in somewhat uneven pressure, and a slight speck of dirt or dust between the heavy plate-glass front and the glass of the go THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING negative flat usually resulted in breaking one or both. For large work, such frames sometimes required the strength of a couple of husky operators. The modern efficient and easily operated type of printing frame is a “Vacuum Frame.” It consists of a wooden framework supporting a piece of quarter-inch plate glass about 30” x 40” in size. Another wood frame is hinged to this and sup- ports a thick rubber blanket which has a rubber beading all around its outer edge, which comes in contact with the plate glass when the hinged section is closed on it. When the two frames are clamped tightly together, the rubber beading forms an air-tight joint with the plate glass. A small hole in the rubber blanket connects with a tube leading to an air suction pump driven by an electric motor. The whole frame, consisting of the two wood sections, plate-glass front, and rub- ber back is supported by pivots in the centre of the two ends, and mounted on two uprights. This arrangement allows the frame to be swung to any desired angle where a locking wheel holds it securely in position. Preparatory to printing, the frame is swung to a horizontal position, the hing- ed back opened up, and the negative flat laid in the centre of the plate glass. It is cleansed with a broad camel’s-hair brush and the sensitized side of the metal laid on top of it. The hinged back is then closed down, securely clamped, and the air pump started. Since the rubber beading has made an air-tight joint be- tween the plate-glass front and rubber Courtesy Repro-Art Machinery Co. Fig. 79. The vacuum printing frame. back, the suction pump is enabled to pump out the air between these two sections and to create a vacuum inside the printing frame. This causes the atmospheric pressure of more than fourteen pounds to the square inch to exert an even squeeze over the entire surface, both PHOTOGRAPHIC PRINTING ON METAL QI front and back, forcing the metal and negative into proper contact. This pressure, while greater than that produced by the old type of frame, is so uniform that there is lit- tle or no possibility of breaking the glass. When the closest possible contact is obtained between negative and sen- sitized metal, the flat is ready to be printed by exposure to light. The frame is swung to a vertical position with its glass front toward the lighted — Fig. 80. Placing the sensitized sinc in contact with the negative electric arc. Daylight will answer, fea. a but the electric arc has been found to be more suitable because of its intensity and uniformity. The length of exposure required for printing line negatives depends upon the intensity of the light, its distance from the printing frame, the character of the negative, and the relative sensitiveness of the coating on the metal. From three to five minutes is usually sufficient, when the electric arc is used. It is important, at this point in the description of the process, that reference be again made to the appearance of a line negative. The black, opaque areas of the negative represent the white areas of the copy. The transparent areas of the negative represent the black areas of the copy. The light from the printing lamp passes through these transparent areas and in these areas only acts on the bichro- mated albumen. ‘The action of the light on the bichromated albumen so exposed is to render it insoluble in water. All other areas of the sensitized metal, being protected or masked out by the areas of opaque negative film, are not exposed and consequently are unaffected by the light. It is essential that correct exposure be given. Under-exposure will not create a sufficient degree of insolubility while over-exposure will cause a spreading effect, similar to halation. After sufficient exposure, the light is extinguished, the frame swung back to a horizontal position, and an air valve in the back opened to allow g2 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING Fig. 81. The printing frame, negative and sensitized metal swung into position for printing. air to enter the vacuum. Otherwise it would not be possible to open the frame. The back is opened up and the printed metal plate removed to be developed. It is still light-sensitive and must be handled accordingly. It is next covered with etching ink. This is applied with a leather-covered roller and the operation is called “roll- ing up.” Etching ink is similar to lithographic printing ink; it is a greasy oil ink and repels water, because of course oil and water will not mix. When thoroughly rolled up, the plate is placed in water which slowly dissolves the soluble albumen. Although the etching ink tends to repel water, the coating which has been rolled on is not so thick but that water reaches the soluble albumen and the dissolving action is stimulated by gentle rubbing of the surface with a wet cotton wad. In this manner all the soluble albumen is removed, carrying away its covering of etching ink also. This operation is called “‘developing the print” and the finished result is a “‘zinc print” with an “‘ink top.” This zinc print consists of a photo- graphic reproduction of the black areas of the original copy, composed of a thin film of albumen covered with a thin film of greasy ink. The white areas of the copy are represented by the bare metal from which the soluble albumen and ink have been removed. This ink image on the metal will Fig. 82. Rolling up the zinc print with etching ink. eventually become the acid resist and later the printing surface of the finished plate, so it will be useful to recall the various stages as shown by the following: Black on copy=transparent on negative=insoluble albumen with ink top on metal=acid resist = printing surface on finished plate. PHOTOGRAPHIC PRINTING ON METAL 93 White on copy =opaque on negative = soluble albumen washed off met- al=area attacked and etched away by acid=area of plate which does not print. Great care must be exercised in de- veloping these prints, as even though the albumen adhering to the metal is insol- uble it is so only to a degree. Too energetic development may rub off some of the delicate parts of the work and ruin Fig. 83. Developing the xinc print. the print. ‘The film of ink adhering to this albumen on the metal is sufficient to enable the quality of the print to be judged, but is not an impervious resist for sub- sequent etching operations. LIGHT FROM PRINTING LAMP NEGATIVE OPAQUE AREA OPAQUE TRANSPARENT ~ AREA AREA SENSITIZED METAL ETCHING INK ROLLED ON ENTIRE SURFACE SOLUBLE AREAS WASHED OFF BARE METAL INK BARE METAL cee NA SU SEIS NS STR PTTL RTE SCI gee eos ae ee ee oe TOPPING POWDER ADHERES TO INK AND BECOMES RESIST WHEN PROPERLY HEATED BARE METAL RESIST BARE METAL Fig. 84. Diagram showing how the acid resist is obtained. The reproduction is a copper line plate with a box grain on the areas representing the sheet of metal. 94 THE PROCESS AND PRACTICE OF PHOTOSENGRAVING The resist is completed by adding a resinous powder to the ink top and melting it. ‘This resin is called “topping powder.” It is a very pure, white resin powder, ground to a dust, which when brushed gently over the entire surface of the print adheres only to the ink top. The powder must be made to adhere uniformly and completely to the ink image but must be brushed absolutely clean from the other areas. The whole plate is then heated but only enough to melt the topping powder. Too much heat may cause the ink and powder to spread, thereby thickening the | finer lines of the image. | Doowlititc heat will fail to produce the required acid-resisting qualities. Uneven heat may cause the metal to buckle or twist out of shape. When properly applied and “burned in,” as the melting op- eration is called, the areas which are eventually to become the printing surface of the plate are effectually protected by an acid resist. All other Fig. 85. Burning in the zine print to melt the topping powder. areas are exposed bare metal, which will be etched out in the next stage of the process. This is the method for making a zinc print with an ink top, whether the negative be for line work or halftone. The whole procedure, in a word, is to print a photo- graphic image on the zinc and reinforce it with the melted resinous topping powder. This resist must be strong enough to resist acid action and protect the printing sur- face while the surrounding metal is etched down. MAKING A COPPER PRINT THE making of a print on copper differs from a zinc print only in the photographic solution used and the developing method. The metal is cut, cleaned, and polished and then flowed with the sensitizing solution which consists of distilled water, glue, and ammonium bichromate. | The metal is whirled, dried, and printed in the same manner as a zinc print, and the action of the light through the transparent parts of the negative creates a PHOTOGRAPHIC PRINTING ON METAL 95 condition of insolubility of the bichromated glue just as it does with the bichromated albumen. ‘The print is developed in water, but without rolling up with etching ink. The soluble elue washes away and that which has been made insoluble adheres to the metal. While still wet, the developed print on metal is immersed in a violet dye solution which dyes the adhering glue, producing a visible image by which the quality of the print may be judged. ‘The operation of dyeing is not essential, but otherwise the print would be so indistinct as to make it very difficult to judge whether or not it had been properly printed. After drying, this copper print is placed over a gas flame and heated sufficiently to bake the glue, which produces a hard enamel which is called ““enamel top” or “glue top.” This is the resist for the copper print and the operation ts called “burning in.” Either line or halftone negatives may be printed on copper in this manner. Copper is usually used for halftones and very fine line work owing to its finer texture. Zinc is usually used for halftone plates of the coarser screen varieties. The enamel top used for copper may also be used for zinc prints, but its use requires more than ordinary skill and care. The principal difficulty is in getting the solution to adhere properly during the burning in and etching. If every step from the prepara- tion of the solution right through the flowing, drying, printing, developing, and burning in, is not just right, the enamel may come off in spots and ruin the print. When properly applied and used, it offers a fine resist and will yield a clean, sharp print. The ink top is not used on copper as it offers no advantages over the enamel top. There is no mechanical difficulty to prevent its use, however, and in some isolated instances in the manufacture of extremely complicated plates it has been employed. THES COLDS IOE A PATENTED photographic sensitizing solution which can be used on either zinc or copper has recently been placed on the market. It is called “the cold top,” because it requires no heating or burning in. Before being sensitized with this solution, zinc must be placed in a chromic acid bath which gives the surface of the metal a mat finish and enables it to hold the sen- sitizing solution better. It is coated and printed in the usual manner and is de- 96 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING veloped like the glue top, but in a special developing solution instead of plain water. The dye is incorporated in the developer and when the print is completely developed it is allowed to dry naturally or it may be whirled to hasten drying. When dry, the metal is etched without burning in or topping up. ‘This avoids the bending and warping caused by the heat necessary to burn in a print. The method has not been in use for a sufficient length of time to warrant definite statements as to its advantages. SURPRINTING INSTANCES often arise when it becomes necessary to combine subjects by a process of double printing, when it is impracticable to combine the negatives. If the combining consists of superimposing one subject upon another, it is called “sur- printing.” The most common use of this process is when type matter, lettering, or other design is superimposed on top of a tone area. Only lines and areas which are to print as blacks or solids can be surprinted. Whites are obtained by the use of positives in the stripping and turning operations, as has been explained. Surprint- ing 1s effective only when it is done on a tone area like a halftone tint or an area shaded by means of line work, as the superimposed print is solid and will show only when on a lighter background. The process is simply to make a print on the metal from one negative, develop and dry it, then sensitize the printed metal again and print the second negative on top of the print from the first one. The operations may be performed on either zinc or copper and by using either the ink or enamel tops. Line work may be surprinted on other line work or on half- tone work, but halftone negatives cannot be surprinted on halftone prints because of the resulting screen pattern. Halftone negatives can be surprinted on line work, but the screen tints will show only in the open areas not already made solid by the first print. This latter is tinting the whites of the subject and is the opposite in effect to tinting the blacks by negative stripping. One of the greatest difficulties in surprinting is the placing of the negative in proper position for the second print. The metal being opaque, it is impossible to look through it, as is done when superimposing negatives. Furthermore, being sensitized, a strong light cannot be employed. The surface of the metal is com- PHOTOGRAPHIC PRINTING ON METAL FRAN KLIN c— Closed Cars —> Franklin sells more closed cars in proportion to total output than any other maker in the world. The percentage is more than double the average of the industry—Franklin, 75% ; the industry, 35%. Franklin closed cars handle easier, ride better, and cover more ground in a day than other closed cars. This difference in road ability is clearly marked by the overwhelming margin of popularity. Perfect cooling under all conditions with the new Franklin air-pressure system, Powerful New Six Motor Beautiful Body Designs r luggage = man top, trunk. Finished in Royal Blue removable sliding windows, Fig. 86. A line plate reproducing the line copy used to produce the finished result shown in fig. 88. paratively bright, however, and by using a magnifying glass it is possible to judge the position with relation to the under- lying print. If very exact registration of the second print is required, guide marks are put on the copy before the negatives are made or during the negative-turning operation. ‘These are accurately placed on both negatives, and it is then only necessary to see that they register in the double print. DOUBLE PRINTING DovuBLE printing is accomplished by the usual surprinting method, and it is employed as a means of combining sub- Fig. 87. Reproduction of the halftone area to be combined with the line negative from fig. 86. FRANKLIN c~— Closed Cars ——> Franklin sells more closed cars in proportion to total output than any other maker in the world. The percentage is more than double the average of the industry—F ranklin, 75%; the industry, 35%. Franklin closed cars handle easier, ride better, and cover more ground in a day than other closed cars. This difference in road ability is clearly marked by the overwhelming margin of popularity. Perfect eooling under al! conditions with the new Franklin air-pressure system. Powerful New Six Motor Beautiful Body Designs The Sedan The Coupe The Brougham The Demi-Sedau A new four-door type, seating Anintimate personal carthatseas = A for tuwn Chased cat com pen car five paseengers, A great car for tour four when required. Folding auxil- and ing, and for anyone in the family ary eat, rear hamper, recejtacle doors, Pu {to drive. back of driver, Kk. Fi Courtesy H. H. Franklin Mfg. Co. Fig. 88. The combined plate. The line negative was first printed on the metal which was then re-sensitized and the halftone negative surprinted on top of it. O7, COMMUNITY PLATE “Prerced Seroe:All” ber 15/ Jn Blue Velvet lined Gift Bor Tor the Serving of Fish, Tarts and Pastry ADAM DESIGN Fig. 89. Reproduction of line work used to produce fig. 92. Fig. 91. Halftone from retouched photograph employed to re- produce the serving knife and background of fig. 92. COMMUNITY PLATE! Fig. 90. Halftone of photograph used for the upper panel in fig. 92. This was inserted into the panel on the line negative and the combined negatives were then printed on the metal. T— Ty AT —> rT Es a 7 FOV eS | WW y Be wus FZ y in Ae Vs 4 Povced Served!’ aS : : ey hm Bine Cctoetstined — Gift Box wT een ; x use Cosa sea a ; Courtesy Oneida Community, Lid. Fig. 92. A combination plate with surprint, 150 screen, showing the combining of three negatives by inserting and double printing. PHOTOGRAPHIC PRINTING ON METAL 99 jects when negative inserting is impracticable. It is used to print the second nega- tive into or around an area of the first print instead of on top of it. There are of course examples without number, but a typical instance is when the nature of the negatives is such that they cannot be inserted by negative stripping, as in the case of dry-plate negatives. Dry-plate negatives are not usually stripped, and then inserting is possible only by the double printing method. The process is also employed when the character of the subject is such as to make nega- tive inserting impracticable. A typical subject is shown in figs. 89, 90, 91, 92. Separate negatives were made of the line and halftone copies. The halftone nega- tive of the photograph was inserted in the upper panel and the combined negatives were printed and partly burned in. The metal was then sensitized a second time right over the first print and the second negative of the background and pastry knife printed in exact register. After development and while still wet, the second print was scraped off where it overlapped the first print. This was done with a sharp wooden point like a toothpick. Unusual care had necessarily to be employed both to assure complete removal of the surprinted image as well as to avoid scraping away too much, which would have made an imperfect joining of the two subjects. The two prints were then fully burned in and the plate etched. This procedure is typical of the complicated technique involved in double printing. When prints on either zinc or copper have been completed, they are coated on the back with shellac, which, when dry, is an acid resist and protects the reverse side of the metal during the etching process. PAINTING IN SOLIDS Parts of line copies represented by outlines are sometimes required reproduced as solids. This is accomplished by painting in all such areas on the metal print before it is etched, using a resist of asphaltum and turpentine. When possible it is advisable that these areas first be painted solid on the copy, as it can be more readily and accurately done on the copy than on the plate. This is especially ad- vised if more than one plate with such solids is to be made from the same copy, as it avoids repeating the painting in on each plate. However, when the requirements are such that the copy must be kept in its original outline form, the painting in is too } THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING done on the plate. If occasion requires, a duplicate copy may ‘be made by using a photographic print of the original and the necessary painting in may be done on the duplicate. Painting in of solids is often done on halftone metal prints before they are etched, It produces Lt produces Fig. 93. Reproduction of outline draw- Fig. 04. The same drawing repro- Ing. duced with the white areas inside the lettering painted in on the plate with acid resist before etching. as even though such areas may be solid on the copy, there will usually be fine shadow dots in them when the halftone negative is made. When solids are to be produced in halftone plates, consideration should be given to the nature of the subject. Solids — do not blend smoothly into the halftone screen formation of the lighter tones and Courtesy Groesbeck, Hearn & Hindle. Fig. 95, Squared halftone, 150 screen, reproducing photo- Fig. 96. Halftone plate from the same negative but the graph of statuary. background painted in with acid resist before etching. PHOTOGRAPHIC PRINTING ON METAL 101 consequently should not be attempted unless there are definite outlines which can be followed. Reproductions of statuary lend themselves particularly well to this treat- ment and solid backgrounds may be painted in on such subjects, as they present well-defined outlines up to which the backgrounds may be painted. Portraits, on the contrary, do not lend themselves to this treatment because of the soft, indistinct nature of the outlines. The delicate tracery presented by hair offers such an indefi- nite outline that a solid background painted up to it would produce a harsh, patchy appearance. Solids are painted in on either zinc or copper prints with a resist of asphaltum dissolved in turpentine. It must be applied thick enough to provide a thoroughly impervious resist to the acid, yet it must follow outlines with absolute accuracy, and under the best of conditions it is a tedious operation as the medium does not flow freely like black ink. After it has been properly applied, it is heated to burn it in. CHARTER X] ETCHING FTER the line or halftone negative has been photographically printed on the metal in the form of an acid resist, the next operation is to etch the plate. This lowers the parts not protected by the resist and produces the relief necessary for printing on paper. Nitric acid is used for etching zinc and perchloride of iron for copper. Electroly- tic etching has also been found efficient and this method is being rapidly developed. As the solutions and methods are different for the two metals, the processes are ex- plained separately. Etching may be done by subjecting the print to the action of acid in a tub or bath, or in an etching machine. There are a number of etching machines operating under different mechanical principles, but all of them aim to produce the same final result. Some machines spray the acid on the plate by means of compressed air; others splash it by means of whirling paddles, and others agitate the acid by means of brushes; the main principle being to agitate the solution in such a manner that it will become mixed with the proper amount of oxygen and also permit the plate to be freed from the par- ticles of metal as theyearee: renee away. Electrolytic etching employs no acid. An electric current passing through a special chemical solution disintegrates the metal in much the same manner as the metal anode is disintegrated in an_ electroplating bath. The oldest method is with the tub ‘Fig. 97. An etching tub with electrically operated oscillator. ee A squared and vignetted halftone, 150 screen. or tray. The metal print 1s placed in an 102 ETCHING 103 FUMES Bac, Seer engl SSEp Alz St ea Courtesy Repro-Art Machinery Co. Fig. 98. Sectional view of the Levy acid blast etching machine. A view of the exterior of the machine shown in the upper right-hand corner of the illustration. A squared haljtone, 150 screen, with one extra halftone negative inserted. acid solution, face up, and the tub is rocked; the acid immediately begins to attack the bare exposed metal and it is necessary to brush it constantly to free the plate from the particles which are etched away and to prevent air bubbles from forming, which would cause the solution to etch the plate unevenly. The tub may be rocked by hand—an unnecessarily laborious operation—or it may be connected with an oscillating device which will rock it automatically. The etching machine employ- ing the splashing method is filled with a large quantity of the etching solution in which a number of paddle wheels are rotated so as to splash the solution against the plate. The acid blast machine pumps the acid through porcelain nozzles and sprays it against the plate. The solution in the electric machine is agitated by com- pressed air. The position of the plate in the etching machine may be face up, vertical, or face down, according to the design of the machine. 104 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING aoe co. Courtesy Edgor Company. Fig. 99. The Edgor electric etching machine. Squared halftone, 150 screen, no finishing line. We shall not attempt to enter into a discussion of the merits of the various types of etching machines except to state that machine etching is faster than the tub method, owing to the more thorough agitation of the solution, which permits the necessary amount of oxygen to mix with the acid solutions and also frees the plate of particles etched away. ETCHING LINE WORK ON ZINC THE acid etching solution for zinc consists of water and nitric acid. Line work etched on zinc usually requires at least four separate etchings or “bites” in order to obtain proper depth. In the general description of line plates, it has been explained how necessary it is to prevent the acid from undercutting the plate and it is after the first bite that this must be most carefully watched and prevented. ETCHING IOS A great many conditions govern the etching operation. The governing fac- tors, however, are the character of the work, whether fine or coarse, the strength and temperature of the bath, and the nature of the metal. With a normal subject in an acid blast, the first bite would last from one and a half to two minutes. If etched in em ACID ATTACKS BARE METAL e > *{ BARE’METAL > °c ° ¢ RESIST 2) 4 f) , e . Cols Zanes Fig. 100. Enlarged diagram showing acid beginning to etch unprotected areas of zinc plate. AFTER THE FIRST BITE PROTECTED AREAS NOW IN SLIGHT RELIEF BARE METAL RESIST BARE METAL Fig. tor. Enlarged diagram showing appearance of zinc plate after first bite. The reproductions are copper line plates with a box grain laid on the areas representing the metal plates. the tub, the bite would continue at least five minutes as the tub method does not etch as vigorously as the acid blast machine. If the subject is a very coarse one, the first bite can be deeper, as any deterioration of the lines is less apparent than if the subject were delicate. When the first bite is completed, the protected areas are in slight relief and their sides are exposed to the action of the etching solution, and must be protected to prevent undercutting during the following bites. These additional bites are called “deep etching.” Protection to the sides of the areas now in relief is afforded by a powder called “dragon’s blood’”—a very finely ground resin of a deep red colour. The operation of applying this resist is called , , , Fig. 102. Putting the dragon’s blood on a zinc plate “brushing up” and “burning in.” The aiershe fot bee. 1066 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING plate is covered with the powder and while held ver- tically is sharply tapped on the lower edge by strik- ing it against the powdering bench. This jars the plate and tends to cause the dragon’s blood to fall from the bottom of the etched areas and rest against the sides of the relief areas. It is then brushed with . a wide camel’s hair brush in the same direction as Fig. 103. Tapping the dusted plate to drop the dragon’s blood against the sides of the re the powder fell when the plate was tapped on the a bench. Proper brushing can be done only by the most experienced operators, as it is essential that the powder should be packed against the sides of the relief areas but brushed absolutely free from the bot- tom areas since these are to be etched to a further depth. After brushing in one direction, the plate is heated, which melts the powder and forms the neces- sary resist against one side of the relief areas. As all sides must be similarly Fig. 104. Brushing the dragon’s blood in one direction to protected the operation must be done pack it against the sides of the relief areas. DRAGON’S BLOOD RESIST PACKED AGAINST SIDES OF RELIEF AREAS AND BURNED IN BARE METAL RESIST BARE METAL Fig. 105. After the first bite. Showing the resist powder packed against the sides of the relief areas. AFTER SECOND BITE RESIST AGAIN PACKED AGAINST SIDES OF RELIEF AREAS BARE METAL RESIST BARE METAL Fig. 106. The result of the brushing up after the second bite. Both these figures are reproduced by the same method as employed for figs. 100 and Tor. ETCHING 107 four times. Burning in after each one-way brushing is necessary to prevent any powder being brushed off a protected area during succeeding brushings in the other directions. When the four-way brushing has been properly done all sides of relief areas are protected and no powder remains in the bottom of the etched areas. The plate is then givena second bite. In the acid blast this might last from ten to fifteen minutes, depending on conditions; it is again powdered and burned in four ways and given a third bite; then a final powdering and burning tn, four ways, and the fourth bite. Thus an ordinary plate will require sixteen brushings and burnings in, AFTER THIRD BITE POWDERING AND BURNING IN IS REPEATED FOR EACH SUCCESSIVE BITE BARE METAL RESIST BARE METAL Fig. 107. After the third bite. Each bite into the metal must be brushed up and burned in to avoid undercutting. together with four separate bites, in order to give it suitable depth. Should the metal be 11-point zinc and extra depth required, it might be necessary to give the plate five or six bites. Ifthe tub method is used, the amount of time required for each bite will be two or three times as long, depending again on the nature of the work, the strength and temperature of the acid, and the nature of the metal. Some zinc is tougher and more fibrous than others and this necessitates a variation in the strength of the acid and the length of time necessary for each bite. On plates where large areas exist between lines, it is customary to “stop them out” with asphaltum dissolved in turpentine, which when burned in 1s also an acid resist. It is simply painted on with a brush up to within a quarter of an inch of the lines of the image. This procedure saves acid and keeps down the temperature of the etching bath. A certain amount of heat is developed in the bath during the etching process and the greater the amount of metal to be etched away, the more heat will be developed, and the more acid will be consumed. These large areas are therefore stopped out and are finally cut away mechanically in a subsequent opera- tion called ‘‘routing”’ which is described later. 108 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING ETCHING HALFTONES ON ZINC FINE-SCREEN halftones on zinc, and fine-line work, are not of course etched as deeply as the more open, coarse subjects. A halftone of 120-line screen would not require more than one bite as in its deepest part it is only necessary to make it about zoos Of an inch deep. Line work of equal fineness need be etched no deeper. Subjects which comprise both fine and coarse textures require special treatment. The fine work is etched to a suitable depth in one, or possibly two, bites, and then completely covered over with asphaltum and protected during the remaining num- ber of bites required to deepen the rest of the plate. Coarse-screen halftones on zinc, such as 85-, 65-, and 55-line, require two bites and sometimes three, because of the greater space between the areas which require greater depth. No matter what the subject, whether it be line or halftone, if more than one bite be necessary, the sides of the relief areas must always be brushed up and burned in before the next bite. After completion of the etching of zinc plates they are cleaned and the top or resist removed. ‘This is done by scrubbing them out with benzole, lye, and acetic acid. ‘This effectually cuts the ink and melted resin, which, if allowed to remain in the plate, would impair its printing qualities. ETCHING COPPER PLATES Except when the electric machine is used, copper plates, whether they be line or halftone, are etched in a solution of perchloride of iron of a strength of from 30 to 40 degrees Baumé. (The strength of the solution is tested at a temperature of 70° F. by means of a Baumé hydrometer used for determining densities of solutions less than that of water.) The difference of time required in the tub or acid blast ts about the same as in the zinc process. Halftones of 120-line screen may be etched to the full depth required in about two and a half minutes in the acid blast. If they are coarse-screen subjects, they will require more than one bite just as similar sub- jects do on zinc, and must accordingly be brushed up and burned in by the usual four-way method. ‘This applies to line work on copper as well, but the etching time for these subjects is longer than it would be for similar subjects on zinc, owing to the nature of the metal and the fact that the perchloride of iron does not act on the copper as vigorously as does the nitric acid on zinc. ETCHING 109 If the copper plate has been given but one bite, requiring no four-way powder- ing, the scum which forms during the etching is cleaned out by means of a solution of acetic acid, water, and common salt. ‘This neutralizes the action of any acid that may remain in the etched valleys of the plate, preventing any further action on the metal. The glue top, which is a hard enamel, is permitted to remain on, as its presence is required for subsequent re-etching operations. If the plate has been given more than one bite, the melted “dragon’s blood”’ must be cleaned away from the sides of the lines just as on a zinc plate. As on zinc plates, it is customary to paint in all the large areas which may more easily be removed by the routing machine. Combination subjects of halftones and line work, or those of fine and coarse textures, must be etched first for the fine work which is then stopped out and protected, permitting the subsequent deep etching. After completion of the etching, zinc or copper plates are known as “flat plates.”’ This name is given them because the tonal qualities have not yet been worked up to the point where they may be considered a faithful reproduction of the original, and ‘“‘re-etching and finishing” is nearly always required. additional work known as Before flat plates are passed on to the finishing departments, they must be judged for proper tonal values. As they are relief plates, they may be inked and printed on paper for the purpose of obtaining proofs for inspection, but this has been found to be inadvisable. In inking an etched plate for proofing, a certain amount of ink finds its way to the sides of the dots and it is difficult to remove it. As subsequent re- etching is usually required, especially on halftones, the ink remaining on the sides of the dots would act as a resist, causing the plate to re-etch unevenly and imper- fectly and possibly undercut. As a substitute for proofing the etched areas are filled in with powdered white chalk or magnesia. ‘This is dusted into the entire plate and then rubbed off the surface, and as it adheres in the etched areas, which later will be represented by white paper when the plate is printed, it offers a satis- factory means for demonstrating the tonal qualities of the plate. Removal of this chalk is a simple matter, as it can be washed out with a stiff bristle brush and water. When any plate is cleaned out with water or a cleaning solution, it is dried at once by heat so as to evaporate any particles of moisture that may remain and cause damage. The foregoing descriptions complete the story of one division of photo-engraving 110 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING which includes the making of line and halftone negatives; their turning and combin- ing together, printing and flat etching. Practically all of the subsequent operations described in the following chapters are “‘finishing’’ or other steps subsequent to the making of the flat plate. It is during the foregoing operations which result in the flat plate that all com- bining should be done. Once the plates are printed and etched, it is very difficult to change them other than to the extent required in the various finishing operations which are to be described. Colour work is not in itself strictly a finishing opera- tion, but most of its processes are subsequent to the operations previously described. Separate chapters therefore have been devoted to this subject under the titles of “Laying Tints,” ‘Colour Work,” and “ Process Colour Work.” GHARTER X)] ROUTING FTER a line plate has been etched, it is nearly always necessary to rout away excess metal. ‘This is for the purpose of deepening the plate and also to remove those areas previously stopped out before etching. In a sense, routing is an addition to deep etching, to obtain greater depth than that given by the four bites. There is no mechanical difficulty to prevent plates being etched to the full depth, requiring no routing at all, but there is a very good manufacturing reason why this is not done. It might take several additional bites to get a depth equal to that obtained by routing. This would necessitate brushing up and burning in for each bite; operations which would add an hour or more to the etching time required. ‘This additional depth can usually be obtained in less than fifteen minutes by routing. The routing machine consists of a metal base supporting an iron table above which swings an arm carrying a high-speed cutting tool driven by an electric motor and geared by means of pulleys and belts to revolve, in the latest models, at a speed of about 20,000 revo- lutions per minute. The plate to be routed is tacked on a wooden board somewhat similar to a draw- a 5 » 2 ) Courtesy John Royle & Sons. Ing board, which in turn is clamped securely Fig. 108. A modern ball-bearing routing machine. Vignetied and silhouetted halftone, 150 screen. to the iron table on the machine. ‘The rout- ing tool is guided by the operator, known as a “Router,” by means of a long steel arm and a handle. The long arm is guided by the operator’s left hand and rests on a wooden bar across the front edge of the table. “The purpose of this bar is to regulate the depth of the cutting. This bar may be moved up and down by means of a foot lever. When it is raised it lifts the routing tool above the surface IIt 112 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING of the plate, so that it may be moved from one area to another without danger of damage to any part of the surface. When the bar is depressed and locked in posi- tion, it lowers the cutting tool to the depth required, preventing it from cutting en- tirely through the metal unless it has been adjusted to doso. A screw adjustment on top of the router head permits setting the cutting tool to any required depth— either that of the regular routing depth, or to allow it to cut all the way through the metal in order that large areas or other excess metal may be re- moved entirely. As the arm which carries the cutting tool is jointed to permit moving the cutter to any de- sired position, the extra handle, di- rected by the operator’s right hand, is a necessary guide in addition to the long steel arm. The chuck which holds the tool has three short metal blades like those of a propeller or fan which, at the high speed generated, effectually blow the metal chips away from the immediate area being routed. An incandescent light attached directly to the arm of the machine close to the cutter, and Fig. 109. A close-up of the router head showing the bit cutting away the dead metal of the plate. shaded from the eyes of the operator, affords illumination for the work. The operator skilfully guides this cutting tool over the areas of the plate which are to be routed, cutting the metal away to the desired depths or removing it en- tirely. Different sized tools are employed for large and small areas. The larger sizes up to 4” or 7%” in diameter are used for what is known as “rough routing.” Obviously these cutters of large diameter cannot be used in the smaller-areas or in corners, and after the principal parts of the plate have been rough routed, the cut- ting tool is changed to one of a smaller size and the fine, close routing is done. Some ROUTING 113 Fig. 110. The appearance of an etch- Fig. 111. The same plate after routing, Fig. 112. The same plate with the dead ed line plate before being routed. The but with dead metal still remaining. metal removed. dead metal around the etched parts result- The reproduction 1s a squared and sil- ing from these areas being painted in before houetted halftone, 150 screen, with two etching. extra negatives set up in position. of the finer tools will operate in a space ;4”’ in diameter, but it is seldom necessary to rout in the smaller areas. The depth of etching is usually sufficient when the printing surfaces are less than 74”’ or even }” apart. Of course, great care must be exercised by the operator in close routing because the slightest slip of the cutting tool will cause it to plough through part of the work, possibly ruining the entire plate. In order that the router may have a clear guide to work by, the etched plate is blackened in the etched areas and polished on the printing surface with a charcoal block. The contrast between the polished surfaces and the blackened etched area offers the operator an excellent guide to be followed. Work of a very technical nature, such as the reproduction of shorthand characters, foreign languages, technical diagrams, and other similar work, is usually etched to the full depth required and then routed only in the larger areas in order to avoid the possibility of routing away some inconspicuous but essential feature. There is always a certain amount of excess metal surrounding the outside areas of line plates. These areas are the result of stopping out the plate up to within about 4” of the work before it was etched. This dead metal is called ‘‘ bearers”’ and is often permitted to remain on the plates especially if electrotypes are subsequently to be made. For a further description of this feature, refer to the chapter on Electrotyping. CHA TEE Rad Ut HALFTONE FINISHING HEN halftone plates come to the finishing department they are simply flat etchings; the direct result of printing on metal and etching. They are reproductions of the original copy, to a certain extent, but it must be remembered that when a halftone negative is made the screen appears over the en- tire area of the copy. Even the pure whites are represented by the fine dots of the screen. The amount of finishing done after the flat etching depends upon the na- ture of the plate, the purpose for which it is to be used, the technique of the copy, and the paper on which it is to be printed. ‘There are so many variations to the style of finish of halftones that it is necessary to divide them up into classes or groups and explain the process of finishing each group separately. RE-ETCHING No MATTER what the ultimate finish, nearly all halftones require re-etching. This is done by applying the perchloride of iron locally with a brush. The effect of this operation is to etch the plate a little deeper, but in doing so it also reduces the size of the dots, thereby decreasing their printing surface. The action of the weve, acid applied in this manner is slower > 2 and less vigorous than that of the acid in the blast-etching machine and it can consequently be controlled to a greater extent. When the halftone negative is made, the dots in the highlights are purposely made a little larger than it is intended they should be in the finished plate. This permits etching the plate pre atasas elEehes8 nicl oa Fig. 113. Finisher applying the perchloride of iron locally to in the first flat etch to a suitable re-etch q halftone. Squared halftone, 150 screen, no finishing line. depth, at the same time avoiding the 114 HALFTONE FINISHING 115 possibility of too much decrease in the sizes of the dots. They naturally decrease in size to a certain extent during the etching and were they made of the proper size for the fin- ished plate at the time the negative was made, they would be too small by the time the plate is sufficiently etched. ‘This would result in loss of general tone and detail in the highlights. It is, therefore, usual to allow the highlights to come a little stronger in tone and re-etch them as required. Fig. 114. A roo screen flat tint locally re-etched. Examination with a magnifying glass will show the decrease in the sizes of the halftone dots as the tones for, highly perfected as is the method of mak- grow lighter. Middle tones also may require re-etching, ing halftone negatives, it does not always yield etched plates corresponding precisely to the tone values of the copy. The operator who finishes the halftone plate is known as a “‘ Finisher.’’ His work bench is equipped with the necessary easel on which to rest the copy, and his first step is to inspect the chalked up plate and compare it with the original. If the areas requiring re-etching are broad in treatment, it may only be necessary to apply the acid with a brush in the areas desired. This is done without removing the chalk from the plate, because it serves a very necessary purpose of preventing the acid from spreading. ‘The etched areas of the plate being like little valleys between hills, would readily cause the acid to run and spread into areas which it should not be permitted to enter. The time allowed for the action of the acid depends, of course, on the size of the dots and the nature of the subject. Usually it is less than a minute; seldom more than two minutes. At the expiration of the proper amount of time, the acid is washed off with water and the plate scrubbed out with a stiff bristle brush and a neutralizing solution of acetic acid and salt. It is then in- spected with a magnifying glass to determine if the dots are of the required size and shape. When the areas to be re-etched are small, or are confined or bordered by sharp, well-defined areas of another tone, it is usually necessary first to stop out all of these 116 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING Fig. 115. A line copy reproduced as a 150 screen flat halftone plate. The result of re-etching the areas which were not painted in and protected. Fig. 116. The plate painted in exposing only the areas to be re-etched. other tones, in order to define sharply the areas to be re-etched. Such would be the case in a landscape with sky showing through trees. If such a sky required re-etching, it would first be necessary to stop out with asphaltum the trees, branches, and leaves before applying the acid. This same prin- ciple applies to the re-etching of re- productions of fabrics like plaids or patterns in dress-goods. In fact, it is necessary on any areas where the spreading of the acid solution would encroach on areas other than those requiring re-etching. On some sub- jects this stopping out or, as it is HALFTONE FINISHING LET, sometimes called, painting in, may require hours of labour simply to prepare the plate for an etching operation requiring a few minutes. If the nature of the subject is such that areas cannot be stopped out with a brush and asphaltum and still retain the character of the original, a crayon pencil, sometimes called lithographer’s crayon or lithographic touche, may be used. The use of this medium permits a rather free, sketchy treatment in the stopping out, and when the plate is heated, this substance melts and becomes a resist similar to asphaltum. There is a point in the tones of a halftone where the separate highlight dots become large enough to touch and join at the corners. ‘This is called a “connected dot.”’ It begins in the middle tones and the dots become more firmly connected as the tones grow darker. “Tones composed of connected dots cannot be successfully re-etched to a great extent, as the connected dots cannot always be cleanly separated. When the acid breaks them apart by etching away the connecting corners, they do not separate uniformly and the result is a series of irregular, ragged dots. It makes the tone appear dirty. | After the necessary re-etching, the plate is inspected for the quality of its shadow tones. It is good practice to hold the necessary amount of colour in the shadow tones when making a halftone negative, as it is usually better and more simple to lighten them if they are too dark, rather than to darken them if they are too light. They can be darkened, however, by burnishing. ‘This is a method of rubbing the surface of the plate with a flat, dull-pointed steel instrument not unlike the ordinary paper cutter, slightly lubricated with paraffin. This burnisher may be used to rub down the shadows or any other tones of a halftone, thereby spreading the printing surfaces of the dots, which will naturally result in a darker tone. Charcoal or Scotch stone is used sometimes to burnish, as it has a tendency to grind off very slightly the printing surfaces of the dots, there- by increasing their SIZe, due to the Fig. 118. Finisher burnishing a halftone plate, showing the bur- 5 nishing tool and the method of holding it. fact that they are wider at the base Squared halftone, 150 screen. 118 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING than at the top. Great care and judgment, however, must be exercised in any burnishing operation, as it can very easily be overdone. Spreading the dots or grinding them off makes the printing surface of such areas lower than that of sur- rounding areas. Properly done, this difference is so light as to be unnoticeable; but overdone, it will produce a plate which will be very difficult to print, due to the lowering of the printing surface. Finishing operations, which govern tonal values, should be practised with great judgment and discretion. The ideal flat plate is one made from a negative which has in it all the values of the copy, for a plate is at its best when it is a true photographic reproduction. The necessity for re-etching and burnishing should be reduced to a mini- mum as these operations are corrective rather than creative. No finisher can be expected to produce, by hand, the subtle changes in tones or the fine details which are nearly al- paemarmmapemmriminsmans ties SNAG obtainable photographically. dot, locally burnished to produce the darker tones shown. “Get it in the negative” should be the slogan of the self-respecting photo-engraver when quality is the consideration. In fact, this also works for speed as well, for the less the finishing required, the faster the plate can travel toward completion. Elaborate finishing operations are, of course, essential on silhouetted or vig- netted plates, as explained in the following pages, as no photographic means have yet been discovered which will replace the necessary hand work on such plates. The nature of the copy, exceptional requirements, changes from the copy and special printing qualities for super, dull-coated, or antique papers, all demand special finishing. While the screen fineness, suitable for various surfaces of paper, aids materially in obtaining proper printing qualities, special finishing is always necessary. A plate which will print properly on the highly finished coated papers will appear heavy on super or dull coated. Re-etching of both highlights and shadows is re- quired and if vignetted, the edges must be graduated with exceptional care. The : HALFTONE FINISHING 119 reasons for the gain in colour, when halftones are printed on other than coated stock, are more fully explained in the description of proofing. Many users of halftones believe that “deep etching”’ will produce better print- ing plates for the uncoated papers, and that it will obviate filling up of the plate. Proper etching depth for various screens is given in the technical formulas in the back of this book. Filling up should be avoided by keeping the plates well cleaned out during the printing run, and if they are of the correct standard depth to begin with, they will print properly on the stock for which they are made. SQUARED HALFTONE WITH NO FINISHING LINE AFTER the necessary re-etching and burnishing has been done, the halftone is ready for the next finishing operation, to produce the desired exterior finish or the shape and size to which the printing area is to be cut. The most common finish for a halftone is that known as “squared, no line.” ‘This means that the plate is to be squared up, in a square or rectangular form, with the screen running to the extreme edges of the printing surface. To produce this finish the plate is placed on a squaring table, which is usually a flat board with an accurate steel square at the top and one side. A steel T-square is then used as a guide for marking the exact shape and size desired and a cutting tool Fig. 120. Reproduction of a_ halftone Fig. 121. The same plaie bevelled up Fig. 122. The printed result plate squared up with a drag, preparatory to the centre of the squaring lines cut with from the squared-up plate shown to bevelling. the drag. in fig. 121. These are the operations required to produce a squared halftone with no finishing line. wo THE PROCESS ANDS PRACTICE OF PHOTO-ENGRAYVING called a “drag’’ when drawn along the edge of the T-square tools a thin, clean line into the metal to about the depth of the ordinary halftone etching. In the accompanying illustrations a reproduction has been shown of a halftone plate chalked up but unfinished on the edges and showing the squaring lines tooled with the “drag.” In this condition the plate is ready for the operation known as bevelling. That is done on a machine consisting of a steel table mounted on a pedestal to which the plate is clamped after having been accurately adjusted to a guide. The accurate setting of the plate in the bevelling ___, Courtesy John RoyleS Sons. machine is, of course, essential, as, if the gaugeeaoniae Fig. 123.. A lining beveller. : This machine is used to bevel straight edges 1g not aligned accurately with the thin outline cut by as shown in fig. 121. The lining tools also reproduced in fig. 128 are shown at the the “‘drag,” the edge of the plate will not be squared pple FSO up accurately. The usual method is to set the guide so that the cutters of the bevelling machine will cut to the centre of this outline, which gives the operator a little latitude, even though it is only to the extent of the width of the thin line which was first cut on the plate. This guide is hinged so that it may be removed after the plate has been set in position, and the whole table, with its plate clamped on, is moved by means of gears operated by hand, so that it will travel under a set of rotating cutter blades which chip the metal away ina channel or groove up to the thin line cut with the “drag.” The bottom of this groove is on a slant or bevel and at the outer edge is cut nearly through the thickness of the metal. This operation is repeated for each side of the plate to be bevelled and when finished the plate appears as shown in fig. 121. The excess metal beyond the groove cut by the beveller is the dead metal or “bearers” and should be left on if the plate is subsequently to be used for electrotyping. Bearers are also advantageous in the proofing operation explained further on. Any edge may be bevelled so long as it is a continuous straight line. Some subjects have certain parts of the work extending beyond one or more straight sides or edges. Such plates can sometimes be bevelled up to within a quarter of an inch of projecting work, but the rotary action of the cutters makes it HALFTONE FINISHING 121 inadvisable to approach any projection more closely. In such a case the fin- ished edge is continued up to the projection by cutting the fine white line with a graver and then using the routing machine to cut away the excess metal. A more complete description of this method is described under the heading of “Sil- houetting.”’ After the necessary bevelling has been done, the plate is trimmed. This opera- tion is made necessary because the cut- ters of the bevelling machine usually produce a slight burr, just a trifle higher than the remainder of the plate, on the extreme edge of the printing surface. This burr must be trimmed off, else it would print and would have a tendency to prevent the screen directly alongside of it from touching the paper, thereby producing a somewhat irregular, broken appearance on the edge of the plate. The plate is trimmed by hand, using a chisel-like tool, and the burr is deli- Fig. 124. Operator trimming the shoulder off a silhouetted plate : ter it has been routed. cately shaved off, leaving a clean, sharp ais printing edge. As the bevelling tool has cut so nearly through the metal, the “bearers” may be removed by simply breaking them off. SQUARED WITH BLACK FINISHING LINE—NO WHITE Hatrtones to be finished in this manner must first be prepared in the nega- tive turning room as has already been explained in the chapter on Negative Turn- ing and Inserting. An etched plate which has been so prepared is shown in fig. 125. The wide black border around the halftone area is solid metal, produced by cutting away the halftone negative, permitting the border to print solid black. The usual finishing line for plates of this class is called a “hair line.” The re-etching and necessary finishing are, of course, performed in the same manner as for any halftone, and the bevelling machine is again employed to cut away all of this excess metal in 122 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING e oh ay sisecestes : Sanaa ra ped = By i HL ae Fig. 125. Reproduction of a halftone plate Fig. 126. The same plate bevelled but Fig. 127. The black finish- made from negative previously squared up to leaving enough solid metal around the ing line produced by the meth- produce a black finishing line. halftone area to produce the black fin- ods illustrated in figs. 125 and ishing line. 120. the border except for the width of the hair line. To do this requires extremely accurate adjustment with the gauge on the machine. If properly set, the result will appear as in the finished illustration shown, after the trimming away of the burr thrown up by the bevelling blades. If this finishing line is to be wider than the usual hair line, it is only necessary that it be so specified and an indication given of the width of the line required. This width is usually in- dicated by the point system employed by printers. There are 72 points to the inch and the well-equipped engraving shop has gauges of different point thicknesses by means of which such lines may be measured. It then only becomes necessary to set the plate in the beveller the proper distance from the gauge and cut the line as required. SQUARED BLACK AND WHITE FINISHING LINE Tuts finish is similar to that described in the preceding paragraph, except that a fine white line appears between the black outline and the halftone area. To produce this, the plate is bevelled in the usual way to produce the black line and then an ad- ditional tool on the bevelling machine is employed to cut the white line. Machines equipped with this additional tool are called “lining bevellers.”” The point of the tool is like a graver or in the form of a sharp “V.” It is fastened to the bevelling machine in such a position that it may be moved on its pivot and brought into con- HALFTONE FINISHING 123 tact with the surface of the plate directly inside of the black line. Held in this posi- tion, the table and plate are moved by the gears as in the operation for bevelling, but the bevelling tools are not operated. This movement of the plate under the V-shaped tool causes it to cut a thin line between the black outline and the halftone area quite similar to that cut by the “drag,” in the previously described squaring-up opera- tion. This is, of course, repeated for all sides of the plate and the points where the Fig. 128. Detail view of the equipment used on the lining beveller to cut straight white lines. white lines join at the corners is subse- quently trued up by hand with a graver. It is possible to produce a number of variations of black and white lines by means of the bevelling machine and the liner. Multiple black lines may be produced by cutting the required number of white lines in the solid metal, allowing the black areas to show between. This may be done with a multiple tool or with separate operations of the single tool. It is customary to produce unusual border effects by means of separate drawings and line nega- tives, rather than by means of the lining beveller. Unless it is known beforehand exactly what effects can be produced with this machine, it is rather difficult to It is much = draw up specifications for special finishing lines. | safer to have them drawn first where their appearance can be better judged before they have been made a part of the finished plate, and this will also eliminate the possibility of spoilage in attempting to cut too complicated finishing lines with this machine. CIRCLES AND ELLIPSES (Bees Fig. 129. The black and white finishing line shown on this plate was produced as shown in fig. 127 and the white line was cut inside of the black with the lining tool on the beveller. FINISHING circular or elliptical plates with outlines pre- sents a more complicated problem than squaring up plates. Finishing with no outline simply requires cutting the plates to the desired shape. Inthe case of either a circle or an 124 THE PROCESS AND PRACTICE OF PHOTO-ENGRAW ING ellipse, a piece of celluloid is first cut on a special machine so designed as to cut the shape and size accurately. This celluloid is used as a guide for outlining the plate. It is laid on the halftone in the desired position, and then a scratch line is cut into the metal, carefully following the outline of the celluloid guide. This line is not so deep as the one cut by the drag used for the squared plates, and it is therefore necessary to deepen it with a graver. ‘This, of course, is a free-hand operation and the skill of the operator is depended upon entirely to follow the faintly scratched outline. A compass may be used to scratch the outline for a circle but its centre point may damage the plate unless it is placed in the low metal between dots. As the bevelling machine will only cut straight lines, it is impossible to use it for circles or ellipses and such plates must therefore be routed. ‘The router must guide the cutting tool with extreme care and cut away the excess metal right up to the out- line tooled by the graver. ‘The plate is then trimmed to take off the shoulder whicn remains after routing up to the centre of the tooled outline. Plates to be finished in circular or elliptical shape with a thin black finishing line must be prepared in the negative-turning room in the same manner as that employed for squared plates. The circular or elliptical celluloid guide is used for this purpose and the negative turner follows the outline when cutting the negative. The opera- tion of cutting down the resulting solid black border on the plate to the width of the required thin black line is one requiring more than the ordinary amount of skill. It is essential that the line be of even thickness throughout and as the work must be done without the aid of a mechanical device, it is obvious that the engraver’s Fig. 130. Operator scratching a thin elliptical outline on a half- Fig. 131. Tooling the scratched outline with a graver to deepen tone plate following a celluloid guide. it, preparatory to routing. Both reproductions squared halftones, 150 screen, no finishing line. HALFTONE FINISHING 125 hand must be steady and his eye be accurate for this work. Although mechanical devices are. not usually applicable to such plates, the method employed by the engraver simulates a mechanical operation as closely as possible. The plate is supported on a leather cushion or pad which is quite hard and almost spherical. The graver is held rigidly by the engraver and the plate is slowly turned using the pad as a pivot. It is remarkable how true a circle or ellipse a skilled engraver can cut inthis manner. ‘The excess metal is routed away the same as though the plate were made with no finishing line. Making these plates with a black and white finishing line is not usually at- tempted by the hand-tooling method. It is quite difficult enough to cut the outer edge of a finishing line but when a white line is added inside, it is almost impossible to keep the black line of uniform thickness. It is advisable, there- fore, with an ellipse or circle with a black and white finishing line, or in fact any finishing line other than the regular black, to make a drawing of the border line, reproduce it by a line negative, and set the two together. This produces clean, accurate results which fully warrant the slight additional time required for the extra operations. Machines have been designed and built for the purpose of cutting circles and ellipses either with or without lines, or with black and white lines, but their adjust- ment is complicated and for that reason they are not in general use. Another method of producing very successful results in elliptical, circular, or even squared plates, finished with no outline, is to make a line negative from a black drawing of the size and shape desired. ‘This negative stripped on to the half- tone negative automatically blocks out the halftone to the desired shape and etches in that form without requiring any further outlining. The one etching bite given a halftone is sufficient to outline the extreme edge of the plate and it becomes neces- sary only to rout it to the proper depth and trim it. In instances where a large number of halftones of uniform size are to be made, either singly or in groups, it is most economical to resort to this method. Only one drawing is necessary for each shape and size. Stripping on the required number of line negatives from such drawings completely masks out the plates to the required size and shape. Various shapes and styles of finishing lines obtainable by this method are illustrated in eats 2. 126. THE PROCESsFAND ERACTICE OF SPHO VO ING Rian LING eo o2o e Fig. 132. Various shapes and finishing lines produced by combining line and halftone negatives. The upper illustration shows a line reproduction of the required line drawing and lower illustration shows the result of combining the line and halftone negatives. SILHOUETTES IN PHOTO-ENGRAVING, the word “‘silhouette’’ implies cutting the plate to follow the contours of the copy when they are other than straight lines. Detailed specifi- cations for this method cannot be given because they will vary with each different piece of copy. A typical example, however, is shown in figs. 133 and 134. The flat plate was finished in the usual way. It was then outlined with a graver. The operation was similar to that employed in outlining an ellipse except that the irregular outlines of the copy were accurately followed. The plate was then routed and trimmed as usual. | It will be clear that the operation of outlining, routing, and trimming on some silhouetted subjects will involve a great deal of work. ‘This is particularly true, for instance, in reproductions of furniture. In order to cut the background away it is, of course, necessary to outline every single detail and then rout up to the out- line as close as possible. It may be that some corners will be too small to permit the entrance of the routing tool and in such cases the metal must be cut away by hand. On complicated subjects, where absolute accuracy in outline is to be retained, it HALFTONE FINISHING 127 Fig. 133. A squared halftone from a vignetted, retouched Fig. 134. The same subject after silhouetting. photograph. The entire halftone area shown was outlined by hand and the plate then routed and trimmed. is common practice to paint in the whole area to be held, using the asphaltum re- sist. The plate in that condition is then etched to the point where all the remaining exposed dots are permitted to undercut. ‘The acid eats right under the enamel top and the dots finally break away, completely silhouetting the subject. Still another method sometimes employed is to prepare two copies, one of the subject to be reproduced and the other made from a photograph of it. The parts to be held are painted in solid black on the supplementary photograph and the remainder bleached out. ‘These supplementary copies may be made by employing the blue-print or bleach-print method, which has already been explained. ‘The usual halftone negative is then made from the original copy and a line negative from the supplementary copy. When the latter is stripped over the halftone negative, it blocks out all areas to be removed. ‘These areas do not print and con- sequently etch out clear white. It will be seen that this method is similar to the one sometimes employed for producing squared, circular, or elliptical plates by over-laying one negative with the negative from a specially prepared copy of the desired shape and size. It is illustrated in figs. 135, 136, and 137. In producing silhouettes by this method it is, of course, essential that the sup- 128 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 2 SARA: peer _ FEUD ERUBBEEEDD! Fig. 135. A squared halftone of a diffi- Fig. 136. Reproduction of a black Fig. 137. A_ silhouetted halftone cult subject eventually to be silhouetted. and white line drawing from which produced by stripping the line negative aline negative was made and stripped over the halftone negative, producing over the foregoing halftone negative. the accurate results so necessary in a subject of this nature. plementary drawing and the negative therefrom register with the original precisely, otherwise the resultant silhouette will be inaccurate. VIGNETTES VIGNETTED halftones blend gradually from full tones through succeeding lighter tones until they appear to merge with the paper on which they are printed. The style, shape, and technique of the vignetted areas depend quite naturally on the style of the copy and how it has been treated. It is not practicable to at- tempt the vignetting of a halftone plate unless the copy is suitably vignetted to pro- duce the basis for the graduated tones in the plate. The halftone dots of a vignette must grow gradually smaller until they fail to print and the tone appears to merge with the paper. If the vignette on the copy is properly blended until it merges with the white background it will produce a corresponding blending in the plate. Even then, dots will be produced over the absolutely white areas of the copy into which the vignette has merged, and they must be cut away to complete the proper appearance of the vignette. HALFTONE FINISHING 129 Fig. 138. A squared halftone of a vignetted, retouched Fig. 139. The same subject vignetted and silhouetted. photograph. The plate to be vignetted is re-etched and burnished as usual, except for the vignetted edges. ‘The limit to which the metal is to extend beyond these edges is indicated by the engraver who tools a fine white outline in the plate following the contours of the vignette. Local re-etching is then done on these edges permitting the acid to work from the outside or lighter areas inward toward the darker areas. The graduated sizes of the dots produced by the graduated tones of the original are thus somewhat accentuated until those dots on the extreme outer edges of the vignettes are very fine. ‘This operation is one which, under no circumstances, should be car- ried to an extreme, because if the dots are permitted to etch down to a needle-point, they will have so little printing surface that they will punch into the paper rather than print on it. Strange as it may seem, they will produce a darker tone because of the fact that when plates are inked for printing, a certain amount of ink rests on the sides of the dots as well as the printing surface and when such dots punch into the paper the sides print also, and the effect is that of a very much larger printing dot. Of course, this blending must be done with great skill in order that the changes in tone will follow precisely those of the original copy. If the vignette of the original is sketchy or composed of sudden changes of tone from dark to light, the vignetted edge of the plate must be quite similar. 130. THE PROCESS 7ANDSERACT IGRSO RAP HO TO IN Gey Ui The success of a vignetted plate depends as much upon the manner in which it is made ready for printing as upon the way it has been re-etched. These features are described and illustrated in the chapter on Proofing. The necessity for properly vignetting the copy before the plate is made is spe- cifically referred to because of the common tendency to order vignetted plates made from copies which have not been prepared for this purpose. In the case of a very light background, vignetting may sometimes be done on the plate, although it has not been previously done on the original, because all the dots are sufficiently small to start with to permit of the gradual blending. The result, however, will never be so satisfactory as if the original had been vignetted in the beginning. An attempt to vignette darker tones from unprepared originals presents a very great difficulty owing to the nature of the dots. An inspection of the middle tones of any halftone well show that the dots are so large they actually join at the corners. Re-etching these dots to a very fine point requires separating them or breaking down the joined corners. When this is attempted, the result is usually a ragged or mealy looking vignette, because in breaking away the dots break unevenly and do not print like the smooth, well-blended tones of the properly vignetted subject. After these plates have been properly outlined and vignetted, the excess metal is routed away and the shoulder trimmed off just as if the plates were silhouettes. COMBINATION PLATES In THE chapter on Negative Turning and Inserting, the method of combining halftone negatives and line negatives has been fully explained. Now that the vari- ous styles of halftones have been described, it will be apparent that it is possible to combine line negatives with any of them. The halftone area of a combination plate may be finished either squared up, vignetted, or silhouetted, or all three of these finishes may be combined on one plate. The nature of the copy controls this entirely and it is only necessary to consider that a combination plate may consist of any or all of the various styles of halftones com- bined with any or all kinds of line work. Re-etching, burnishing, and other finish- ing operations are performed on a combination plate as on any other plate. It may be necessary, however, to protect the line work during the re-etching operation, as further application of acid to this part of the plate may destroy the lines or at least HALFTONE FINISHING 131 impair them. After the necessary finishing has been done, the combination plate is routed and trimmed in the usual way as may be required on the halftone and the line areas. A typical combination plate is illustrated in fig. 65. TOOLING Too Linc is an operation which may be required on any class of plates, whether halftone or line plates. Its name really describes it, for it is nothing but the cutting of grooves in the plate to produce white lines, or to cut away printing surfaces to produce white areas. Should these areas be large, they are outlined and routed as has been described. Tooling is done with the V-shaped graver, and the width of the line tooled is controlled by the shape of the tool and the broadness or narrowness of the angle formed by the V. (The shapes of the bodies of different gravers and other tools are illustrated in fig 140.) Tooling is used for a variety of purposes. It is employed to produce the white line sometimes used to clean up the joint between two halftone negatives. Fine white lines or lettering in the copy which may be partially obscured by the halftone screen may be tooled pure white in the plate. A style of tooling technique illustrated in fig. 142, which is an inheritance from the days of the woodcut, is sometimes employed on halftones with most pleasing results. This is known as ‘* woodcut tooling” and there are but few among even the most competent finishers left who are skilled in this method. The effect produced by tooling fine lines right into the screen of the halftone plate is similar to the finely cut white texture lines of wood engravings. The combination of the existing texture of the plate itself with these beautifully engraved woodcut lines is a happy one indeed. ‘Tooling of this nature should not be done, however, unless the halftone be especially made for this purpose. The area to be tooled must be held slightly darker in tone than were no tooling to be done, in order to afford a suitable foundation for the tooling. Should this area consist of very fine dots, the effect of the tool running through them is but to cut away these fine printing surfaces in the grooves produced by the tool, leaving on every side other dots so fine as to fail to give the amount of contrast necessary to obtain the effect of the white line. Furthermore, the opening up of a white space between very fine dots causes them to 132 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING uve YV09 Fig. 140. A graver and cross sections ae, some of the different styles employed. A silhouetted combination plate, 150 screen. sink very deeply into the paper in the printing operation, producing the effect of a heavy edge on either side of the tooled line. ROULETTING A ROULETTE, as its name infers, operates on a rotary motion. A hardened steel wheel or disc, on the perimeter of which lines or other patterns are engraved, rotates on Fig. rat. Lines tooled by gra the little steel shaft fastened into the handle of the tool. ers called “tint tools.” Pressing the edge of the disc with a rotary motion on the surface of the plate cuts the pattern of the roulette into the plate. These tools are made with various patterns and are used to soften lines, break up joints, blend repaired areas, in fact, for a number of purposes where a single tool would not an- swer. Examples of a variety of rouletted effects are illustrated in fig. 144. It is customary to call a halftone by the name which has been given to its finish- ing edge. Thus, a squared-up plate is known as a “squared halftone” or “squared plate.” The silhouetted halftone is called a “silhouette.” If it 1s partly squared up and partly silhouetted, it is still known as a “silhouette.” A vignetted halftone is called a-“vignette.” If partly silhouetted and partly vignetted, it is called a “vignette and silhouette,” even though some areas may be squared up. HIGHLIGHT HALFTONES Hicuiicnt halftones, or as they are sometimes called “ Hilites,” get their descrip- tive title from the fact that the halftone screen is eliminated from the highlights. They are used to reproduce pencil, crayon, or charcoal drawings, similar to that illustrated infig.145. They are also known as “ Fac-similes,” “ Drop Outs,” and “ Blow Outs.” HALFTONE FINISHING 133 Courtesy Cosmopolitan Magazine. © Internetional Magazine Co. (Cosmcpolitan Magazine). Fig. 142. A typical magazine halftone illustration showing the result of re-etching, vignetting, silhouetting, and elaborate hand tooling. Hand tooled by Edward Del Orme. Many subjects reproduced without screen in the highlights are simple vignettes or silhouettes, and the term “Hilite”’ is often applied to them erroneously. It would be more appropriate to call such plates “ Highlighted.’’ So much confusion has resulted from the various names and methods applied to this style of reproduc- tion that one scarcely knows when to use one term or another. Based on technical methods of manufacture a halftone is a “Highlight”? only when it is made by a truly photographic highlight process. ‘This requires a halftone negative in which the highlights are completely blocked out. Blocking out of the highlights must be 134 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING Fig. 143. A roulette. The pattern is cut into the hardened steel wheel on the shaft. A silhouetted halftone, 150 screen. done photographically.* If they are opaqued out by hand the plate will not be a highlight in the strict sense of the word. Highlight negatives are extremely difficult to make, and so few copies lend themselves to this method that the highlighting process is more generally employed. ‘The neg- ative may be “high” in the sense that the highlight dots are extremely fine and may then be opaqued to block them Fig. 144. Lines and stipples ; cut in a copper plate with q OUt entirely, or the areas of lines and tones to Desheldamia roulette. The numerals indicate fee ae ae be painted in on the flat etched plate. ‘The highlights may | then be etched away in the same manner as is often em- ployed to make elaborate silhouettes, which has been explained. ‘Tooling may also be employed to remove the highlights in small areas, or, if large enough, highlight areas may be outlined and routed like a regular inside silhouette. Highlighted plates are also made by stripping line negatives over halftone negatives to block out the highlights as has been done around the outer edges of fig. 137. FINISHING ZINC HALFTONES IF HALFTONES on zinc have been made with the enamel top, they are finished in the same manner as copper halftones, but if they have been made with the ink top, they cannot be re-etched unless a new top is put on them. No plate should be re- etched unless the top or printing surface of the dot or line is thoroughly protected, otherwise the acid eats into it and destroys the printing surface of the plate. The enamel top produces a resist which withstands the various finishing operations per- mitting the proper re-etching of the plate, but not so with the ink top, since this is cleaned off after etching. Therefore, zinc halftones so made, while they may be *On October 3, 1893, a patent was granted to F. J. M. Gerland covering the making of halftone negatives or the making of two negatives, to be superimposed one on the other, or any other method to yield perfect highlights without destroying the values of the middle tones. Courtesy Vernon Howe Bailey. Fig. 145. A highlighted halftone, 150 screen, from lithographic crayon drawing. This plate was produced by making a “high” halftone negative, painting in all the areas to be held on the plate after it had received one flat etch, then re-etching the remaining areas until the dots were etched away entirely in the highlights. The plate was then locally re-etched, routed, and trimmed. 135 1336 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING burnished, silhouetted, routed or tooled, cannot be re-etched until they are specially prepared for this operation. If a new top is to be put on a plate it is called “rolling up” or “topping up.” A layer of the usual etching ink is rolled up with a stiff leather roller on the top of the printing surface, and great care must be exercised to see that it does not run down the sides. Topping powder is then dusted on the plate and after having been care- fully brushed to remove the traces of powder from the bottom of the etched areas, it is burned in. This topping up is a very delicate operation and one which is not always successful. Plates are sometimes spoiled as a result of the top adhering im- properly and permitting the acid to attack the printing surface. Topping up and re-etching apply to line work as well as to halftones. When the enamel top has been used on copper or zinc, line work may be re-etched to thin down any lines which are too heavy, but if the ink top has been used, a new top must be put on it before any re-etching can be done. Tooling on line plates is employed to remove imperfections caused by the peculiarities of the original copy. This is a subject which is fully explained in the chapter on Copy for Reproduction, as the operation can be avoided by proper prep- aration of copy. CHARTER XLV LAYING TINTS HE use of tints made with a halftone screen or by other means is constantly increasing. ‘The use of the halftone tint negative for this purpose has al- ready been explained. (See page 81.) Halftone negatives of any required tone value may be stripped over line negatives, thereby producing the correspond- ing screen tint on areas formerly solid black on the copy. It has also been explained that halftone negatives may be used for the purpose of printing tints on open areas by employing the surprinting method or by actually inserting the halftone negative into the desired area before the metal print is made. ‘The peculiar characteristics of some subjects and the demand for tints or textures different from those of the halftone screen led to the development of a tinting process which to-day is familiarly known as the “ Ben Day Process.” It was developed by the late Benjamin Day and although there are now other tinting processes, the use of the words “Ben Day,” to describe these methods, has become almost universal. In order that the principle of this tinting method may be entirely clear to the reader, let us repeat that the necessary amount of relief to produce a photo-engrav- ing of proper printing quality is obtained by protecting the printing surface with a resist and then etching around it. It has been explained that a resist may be printed photographically or applied by hand with a brush. Such a resist may also be applied by transferring by pressure from a previously prepared inked surface. The basic principle of the Ben Day and other tinting processes is in the prepara- tion of special surfaces known as tinting films. These films are made in the form of relief plates, but of a transparent and somewhat flexible composition. They are supplied in various textures such as halftone dots, stipples, grains, lines, and many others. The textures being in relief on the printing surface of the film may be rolled up with a special ink somewhat similar to the etching ink previously described. They are then printed by pressure on the surface of the metal to be tinted. This operation transfers the ink from the printing surface of the film to the metal and is 137 || A | He . HU HA Mar VN Co EE il iil “en mE i ia = i Y ]/ j/ ]/ Mi Do yey j i 7 ome “a — aa a No. aes to i 634 x Not suit im a No. 9. A | in) a i io 9%. No. 442. 774X7%- No. 431. 7X7. { ee + ™ a : ~ ee : ° cask RTS x ea aN SSS ‘o Tg T : SS No. 308 8x6. No. 602.—4% x 4%. ~ ak : ZS | 20. Ss M 212. No. No. 208. BA 74%4X7 Fig. 148, Samples of Ben Day tints as they appear when laid on the plate. 40 I ‘% 6xK % vy pu Fie ev YoxyY ‘gfh °ON Yo— bos Cc v *SOZIS plate. d on the appear when lai Samples of Ben Day tints as they Fig. 149 141 No. 301.—914 x 124%. SEX (Ay abe AIAN 3 See WY YIN Fig. 150. No. 304.—5 x 6144. FLAN UY | IZAGACNWIAOA { y Hh ANY nil RIN AAO NC! . if it yy) i (i) (7 ie ey q! PEI i ee y Zi LA ANG ct LO \ RUE CA Seine TERS No. 310. No. 322.—634 x II. No. 322. Hil 7 VA a RS “fs; MOO US acaqg a Vi No. 328—634 x 11. No. 320.—0%4 x 144. No. 330.—9%4 x 14%. Yj Yj No. 328. Hii No. 330. [im Samples of Ben Day tints as they appear when laid on the plate and on the negative. Mame indicates film laid on negative. 142 SSSe SEN speqenegre Ls of 'aVaValaGa ata idtetetetty ky 2 tack Psd bd bd be- bt be h “eae "e "sa aaa "a: PST S27 See {.°."s-a' a2" ee A (NUN ‘A7ata-e eee a catacacatacara’: No. 335. il No. 336. Mil Feet tee? sirisign ee RCo Srp i Paerat a beat ass SAAR o*,? RE IA he No. 419 B—o9 x 14. No, 411. Mi No.419B Mi No. 426. il No. 423. i No. 429.—5 x 8%. No. 432—944 x 144: No. 433-—94 x 144. No. 434-64 x 11. any No. 429. Hil No. 432. Zi No. 433. [i No. 434. Hii No. 435:—54 x 84. No. 437.9% x 144. No. 438.—914 x 14%. No. 439.—9144 x 144. Not suitable for use on negative No. 437. No. 438. ii No. 439. Fig. 151. Samples of Ben Day tints as they appear when laid on the plate and on the negative. MEE indicates film laid on negative. 143 No. 440.-9144 x 144%. No. 441.—9%4 X 14%. No. 444.—9% X 14%. . No. 440. [ii No. 443. ii No. 444. Hi No. 445—54 x8. No. 505.—13 X 13. No. 506.—13 x 13. No. 507.—13 X 13. No. 445. | No. 505. No. 506. ii No. 507, 2 No. 509.—914 x 144. No. 511.94 x14. No. 512.—7 X7. No.513.-7 (x7. No. 509. [i No. 511. il | No. ee = No.513. ill No. 523.—914 X 144. No. 527.944 x 144%. No. 530.—94 x 1444. No. 531.—634 x II. No. 530. Si No. 531. i No. 532-—914 x 144. Fig. 152. Samples of Ben Day tints as they appear when laid on the plate and on the negative. MRE indicates film laid on negatwwe. No. 532. Sil 144 No. 518.—634 x 7% No. 520.—Half-tone. 133 to inch—934 x 9%. No. 524.—Half-tone. 150 to inch—934 x 93/. No. 525 —Half-tone. No. 526.—91%4 x 144%. 175 to inch—744x7% No. 528. No. 520. 100 to inch—634 x II, 140 to inch—5%4 x 8. No. 533.—Half-tone. No. 534.—Half-tone. 85 to inch—934 x 9%. 100 to inch—9% x 934. No. 535.—Half-tone. 120 to inch—9%4 x 9%. No. 536.—Half-tone. No. 537.—Half-tone. 133 to inch—934 x 934. 150 to inch—934 x 93%. Fig. 153. Samples of Ben Day tints as they appear when laid on the plate. 145 146 ‘THE PROCESS" ANDY RBRACTICE OF PHOTO ENGR RVING called “laying a tint.”’ When this ink impression is dusted with topping powder and burned in, the pattern or design so printed becomes a resist, and after the plate is etched, it will print as a duplication of the film design which had been transferred to it. This process makes it possible to lay tints on different areas of plates which are not so tinted on the original copy. Ben Day tints may also be laid on the original copy or on paper which may in turn be used in the preparation of the copy. (See Chapter XXII.) An inspection of the illustrations on pages 138-145, which show samples of the textures obtainable in Ben Day films, will make it clear that any attempt to duplicate any of these textures by hand on an original copy would be a very laborious task. In considering this process and its possibilities, it must be remembered that these tints will show only on areas provided to receive them. They must be laid on the metal plate before it is etched or on the negative before it is printed. They may be laid on clean, unprinted metal or on open areas of a metal print where there is no other resist to obscure them. When they are laid on a negative they add opaque elements which will print reversed in tone values on the metal. Even though a Ben Day tint be laid over the entire surface of a negative, it will only print through the transparent areas and a black stipple dot on the transparent parts will produce a corresponding white dot on a black area when the plate is etched. The effect of laying Ben Day tints on negatives is quite similar to stripping halftone tint negatives on them except that the Ben Day tint is printed on the negative with ink and the style of tint may be varied according to the tinting film used. The result of tints from various films laid on the nega- . tive is shown with the illustrations of the films laid on the } metal print and a comparison of the results obtainable may | therefore be readily made. All films are not suitable for use on negatives and only those which are suitable have been so illustrated. Fig. 154. Photomicrograph of The films are of various sizes, and are identified under Ben Day film No. 1, showing the printing surfaces in relief. their respective illustrations by a number. They consist of EAYING TINTS 147 Fig. 155. A Ben Day machine with film in position for laying a tint on a zinc print. Note the transparency of the film reveal- ing the areas to be tinted. The proper screen angle is obtained by twisting the zinc print as shown. a transparent sheet of composition similar to thin celluloid and are mounted in light rectangular wooden frames. One side of the film is smooth, while the other side is the relief surface of the tint which is inked and printed. The mechanical equipment necessary to lay these tints comprises a board 30’’ x 40”’, similar to a drawing board. Along the upper edge a metal bar is fas- tened on which travel two adjustable devices which are used to hold and set the Ben Day film. A clamp is provided which fastens to the wooden frame of the film and this clamp in turn is set between the two adjusting devices on the metal bar already described. This equipment is known as a Ben Day machine. When the film is in position on the machine, it rests flat on the surface of the drawing board, but may be lifted up like a hinged box cover, as the metal clamp carrying the film is pivoted at each end. One of the most important features of the machine is the fine adjustment made possible by means of the two adjusting devices. They are equipped with microm- eter screws which permit moving the film, once it is set in the machine, and shifting it in any direction desired even to the slight extent of the fractional part of 148 THE PROCESS AND PRACTICE -OF PHOTO-ENGRAVING @ PHILIPPINE PACIFIC ISLANDS t {> sf <) PAS et PN gg Fig. 156. Reproduction of a line copy of a map to Fig. 157. Reproduction of a zine print gummed out so that the be tinted 1n the areas which represent land. Ben Day tint will adhere only to the desired areas. This reproduc- tion 1s a 200 screen halftone with a flat zinc colour plate to show the gum. one one-hundredth of an inch. The film and the clamp which holds it may be re- moved from the machine and replaced with such accuracy that the pattern of its printing surface will fall in the same position each time. There are so many different instances in which this tinting method is employed that, as in the description of some of the other processes, only a typical case is illustrated. . The reproduction in Fig. 156 illustrates an original copy, the plate from which is to show tint No. 434 over all the white areas indicating land. The line negative of the original copy is made, turned, the print made on metal, developed, topped LAYING TINTS up and burned in and the plate is given 149 a cleaning.bite in a weak acid bath. This cleanses the metal and frees it from scum, but before it is etched, it is sent to the Ben Day department to have the desired tint laid on it. The metal print is tacked to the board of the machine, in such a position that the film when clamped to the adjusters Fig. 158. Rolling up a Ben Day film with special ink. will rest on top of the print. As the tint is to be laid in only certain parts of the plate, all other areas must be protected or “stopped out.” Stopping out is done with a medium called “gamboge” and 99 66 the operation is called “gamboging,” “gumming out,” or “stopping out.” Gam- boge is a gelatinous substance soluble in water and is applied with a brush, com- pletely covering and protecting all areas which are not to be tinted. It is painted with most exacting care up to the outline of the area to be tinted. The tinting film is placed on an inking pad, with the relief surface upward, and is inked with a hard roller and the special ink. ‘This operation is quite similar to the inking of an etched plate except that the ink is greasy and somewhat stiffer than printing ink, the stiffness being necessary to prevent it from running down into the depressions of the relief film. The distribution of ink on its surface must be very correctly judged, as too much ink would produce a heavy imperfect tint, and too little ink might result in an imperfect resist. The inked film is then set in the machine and allowed to rest gently against the metal print. ‘The impression is then transferred to the print by rubbing the back or smooth side of the film with a burnisher, stylus, or a small roller. This rubbing or rolling must be even, uniform, and over the entire area of the parts of the print to be tinted. The film is then carefully lifted from the plate, leaving its inked impression Fig. 159. Printing the film on the zinc print by pressure with a roller. on the metal. Iso)6©6u THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING > DVANIAN AUlqdiIttH4 2aqanAtéi Fig. 160. Reproduction of the gummed-out zinc print after Fig. 161. Reproduction of the zinc print after the gum the tint has been laid. has been washed off. Note that the tint appears only in the areas which were not protected by the gum. 200 screen halftone used for both reproductions. A solid zinc colour plate has been printed on fig. 160 to represent the gummed area. The plate is then removed from the machine and washed in warm water, which dissolves and removes the gamboge. The original ink print, however, as well as that applied by the tinting film, are not affected by the water owing to their greasy nature. The result is that the tint remains only in the desired areas, excess tint being removed with the gamboge when it washes off. The print is dusted with topping powder, which adheres to the ink of the added tint, is burned in and the plate is etched. When the Ben Day process is to be employed, due consideration should be given LAYING TINTS Is to the characteristics of the copy. It must be remembered that tints are added by this “eT ke “PACIFIC process. They appear as added black ele- Sa ae ments when laid on the plate and as added white elements when laid on the negative. If it is desired to show a Ben Day tint on any area already black, one of two methods must be employed. Either the black area must be removed from the print in order to expose the metal on which to lay the tint, or else a tint which is the reverse of the one desired must be laid on the negative. Very few Ben Day films are made up in the two forms nec- essary for use on either negative or print. If no suitable tint is available, then resort must be had to removal of the obscuring black Meee wetnertnetal print, Additional labour: Fiz 162) The finished plate resulting from the opero- and expense are thus involved, which could PRIA PA aL Se ese SA ag a have been avoided had sufficient consideration been given the process when pre- paring the copy. Ben Day tints are usually laid on zinc. The majority of the tints are sufficiently open to permit their use on zinc, also the usual practice is to employ them in conjunction with line work, which is on zinc in the majority of instances. Fig. 163. Reproduction of azine print Fig.164. The zinc print washed off Fig. 165. The finished plate. gummed for certain areas to be held. of the exposed area preparatory to lay- ing the Ben Day tint. These operations are necessary because the tint used 1s one which will not produce the desired result when laid on the negative. iz. THE PROCESS AND RRACTICE, OF VPHOTO-ENGRAVING These tints are laid on copper when occasion requires and the general procedure is the same as that employed on zinc. If conditions require the removal of the top from any part of a print then the ink top of the zinc print is to be preferred as it may be more readily removed than the hard enamel of the baked glue top. When it is necessary to remove the ink top from part of a print, gamboge is employed to hold the areas which are not to be removed. ‘They are accurately painted in with the gamboge, leaving exposed all the areas which are to be removed, which are then washed off with benzole. As the gamboge is not soluble in benzole, it acts as a protecting film covering the remainder of the print. If the removal of this ink area is for the purpose of exposing metal for laying a tint, the gamboge will protect the remainder of the print when the tint is laid. When the gamboge is washed off, the operation is complete and the tint will occupy the area which was formerly solid, while the other. parts remain unaffected. This method of holding certain areas and removing others may prove to be a very costly one if the subject requires elaborate and accurate gumming out. It may in fact be so involved as to represent more labour than would be required to make a new copy, suitably planned to obviate this additional work. When very small areas of resist are to be removed, they can sometimes be scraped away with a sharp-pointed knife blade, and not infrequently, areas are stopped out on negatives. The latter method requires the use of a medium called “opaque ’’ which is soluble in water and is applied with a brush. Exceptionally clean stopping out can be done in this manner SSS LG pe at — pease SSS and accomplishes the same result as re- moval of part of a print from the metal. The treatment of metal prints be- fore they are etched is not limited to laying tints. Solids may be produced by “painting in” and protecting the desired areas with a resist. — SN LZ Rs = SS 3 SS SSS SSS55 EO NS Fig. 166. Illustrating the method which must be employed in PATCHING TINTS AND SHIFTING patching unsymmetrical films. The joint at the left is imper- fect. In order to make a good joint a space must be left between Ben Day films are made only in cer- the two film impressions which 1s later filled in by hand work on the xine print before it is etched. (Film No. 309.) tain stock sizes, which are given with the LAYING TINTS 153 numbered specimens of each, as illustrated. When the area to be tinted is larger than the size of the available film, the impression must be repeated until the entire area is covered. Accuracy in setting the film for “‘patching,” as this repeating is called, is accomplished by the use of the tinting machine. ‘The fine adjust- ment of the micrometer devices which hold the film permits accurate matching of the edges of the tints when they are repeated. AlJl the textures, however, do not match up when repeated because of the nature of their design, and some will always show a joint which must be worked out by hand on the print. The tone of the film texture is another factor which must be considered in this process. The sizes of the dots, lines, or other elements comprising the different tints is shown by the illustrated specimens. Lighter tones than those shown cannot be laid from these films. Darker tones can be produced by shifting and “‘ doubling up” the film impression. A film which prints with a fine highlight halftone dot may be shifted by means of the micrometer adjusting device on the tinting machine so that a second impression may be made which will slightly overlap the first im- pression. This increases the area of the ink deposited on the metal, thereby pro- ducing a darker tone. It is an operation requiring both judgment and skill on the part of the operator and one which is employed only with suitable textures. Creat- ing as it does a double impression, it not only changes the area of the printed dot, but also changes its shape and, under certain conditions, this may result in a tint of quite a different appearance from that produced by a single impression. ‘The deli- cacy of the operation may be appreciated when the amount of shift is considered. If a halftone film is to be printed with an increase of 25 per cent. in tone, it means a shift which will overlap each dot on the second impression only 25 per cent. of its original size. If the screen is 120 lines to the inch, this may mean a shift of only one one-thousandth of an inch. Whatever its difficulties, it is one of the extensively used features of the process, and without it it would not be possible Fig. 167. The left half of the illustration shows an impression of a film and the right half shows the effect of shifting and printing to produ ce some of the effects obtained. the film nine times to get the desired width of line. (Film No. 17.) 164 ‘THE. PROCESS AND ®PRACIICE OFF POLO NG hay ING Ft 2S = Lite pe Courtesy The Stanley Works. Fig. 168. Line plate reproducing a line copy. dot surrounding the various tools. This tinting operation was accomplished by gumming out the print and double-printing a halftone negative into the back- ground. A smoother tint has been obtained than would have been possible had a Ben Day film been used, as considerable shifting and doubling up would have been required to obtain this tone. Although Ben Day films are made in halftone textures, it is advisable to use halftone negatives in their place when possible. Halftone negatives can be made in larger sizes than the tinting films, thereby avoiding a joint, and the size of the dot can be more readily controlled. When the Ben Day halftone film is used to produce a tone darker than that of the film, the doubled-up impression gives an elongated dot and if the tint is to be very dark, it may require shifting the film and doubling the impression four or five times. Results obtained in this manner will never be as satisfactory and smooth as those obtainable from a halftone tint nega- tive of suitable tone. When a tint negative is used for this purpose, it is printed into the desired area by surprinting. The area in which it is to be printed may be defined by the usual gumming-out method. Tints are seldom laid on halftone areas, because of the resulting pattern caused by conflict between the halftone screen and the superimposed tint. An effect simi- lar to woodcut tooling can be obtained by laying certain tints on halftone negatives, but the result is mechanical in appearance. It lacks the grace and technique of the hand-engraved line and is not generally practised. Tints are nearly always laid before the metal plates are etched, and it is seldom that any tint can be successfully laid on an etched plate, owing to the difficulty of getting the ink to adhere properly at the extreme edges of the printing surfaces when it is transferred from the film. Ifa tint must be laid on an etched plate, it is usually LAYING TINTS Iss Fig. 170. Halftone reproduction of a photograph with a solid Fig. 171. Result of graining the background of the etched plate background. with a box grain. done by the “box grain” method. This is a tinting method capable of producing an extremely interesting texture, which is illustrated in figures 170 and 171. The first illustration in this figure shows an impression from an etched plate. The next one shows the same plate after having been tinted with box grain. The mechanical equipment for laying this grain consists of a box about six or seven feet high and four feet square. About three feet from the bottom of this box a shelf composed of slats is placed on which the plate is laid face up. Below the shelf is a paddle wheel operated by a crank on the outside. The lower part of the box contains a quantity of bitumen dust. This is an asphaltum powder like the topping powder or “dragon’s blood”? which becomes an acid resist when melted. The front of the box is tightly closed, the paddle wheel is turned, and a cloud of the bitumen dust circulates throughout the interior of the box, and settles on the plate in the form of the grain structure illustrated. Skill and judgment are required to lay a box grain properly, as the position of the plate, the amount of powder stirred up by the paddle wheel and the length of time during which it is allowed to settle on the plate, and the amount of burning in are all controlling factors in the resulting strength and character of the grain. After the grain has been deposited, the plate is heated to melt the bitumen which produces the required acid resist. The use of the box grain is not limited to the graining of etched plates, and it may be employed on metal prints in the same manner as other tints, the necessary gumming out being utilized to define the edges of the areas in the usual manner. 136 THE PROCESS AND PRACTICE OF PHOTO-ENGRAN ING u t lg er | Sugellavien-fonit neuf t fiir Roig Leter oinriicfen ! Courtesy The Century Co. Fig. 172. Line plate reproducing a poster from a crayon draw- Fig. 173. The same subject tinted with a box grain laid on a Ing. copper print before etching. Figs. 172 and 173 show a reproduction of a line copy as well as a plate therefrom which has been grained with this process. The box grain is not used on the negative because the heat required to burn it in will break the glass. Owing to the closeness of the grain texture, it is not possible to etch such plates to any great depth, and the use of this process is therefore not advisable unless the plate is to be printed on a good grade of smooth paper. The tone laid by the majority of Ben Day tints is uniform or flat, similar to that produced by a tint negative. Some films are graduated, as shown by the specimens, but it is often necessary to produce a certain amount of tone variation with the flat- tone films. This is accomplished by shifting, doubling up, and applying graduated pressure when laying the tint. This effect is called “modelling,” and its possibilities are limited because of the uniform tone of the film texture. When films are doubled up the pressure required to print them may be gradually decreased, until they finally blend with the dots of the remainder of the tint. Pressure cannot be decreased too much because the LAYING TINTS 157 impression will be insufficient to transfer the required amount of ink to the plate if the pressure becomes too light. If the film is also shifted, a still greater tone variation can be obtained. When modelled areas are confined in small spaces, it is usually nec- essary to resort to the gumming-out method to define properly the limits of such tints. Some elaborately modelled effects may be too complicated to warrant the use of the Ben Day Process, and it may be found advisable to resort to the halftone process from a suitably modelled copy. avarererazezeresesesess Fig. 174. The variations in tone obtainable by shift- ing and doubling up a Ben Day film. Ten different shifts and impressions were required to produce this result, the original tone of the film being shown at the extreme lower margin of the plate. (Film No. 527.) Fig. 175. Reproduction of a simple outline drawing. Courtesy Southern Cotton Oil Company. Pig. 176. The same subject tinted with a variety of Ben Day films. Not only have different films been used, but numerous shifts were re- quired to produce this varied result. EE CHa Bit Raexcy. COLOUR WORK HE use of colours in printed matter opens up a very extensive subject be- cause practically all the steps in the process thus far described are multiplied by the number or nature of the colours to be used. The question of cost enters into this subject, especially as related to the size of an edition to be printed. The number of impressions made from a printing form is called ‘‘the run’”’ and when colours are used the whole run of a form must be re- peated for each printing colour used. In order to reduce printing operations, colours are combined to produce additional colour effects whenever possible. Combina- tions of colours may be effected with solids or tints and the variety which may be so produced is practically unlimited because of the various kinds and degrees of tints and the colours of printing inks available for use. In order that the process of colour-plate making and colour printing may be more clearly understood, the different processes are described in the order of their relative simplicity, the first of which is the solid line plate for colour work. SOLID ZINC LINE PLATES FOR COLOUR WORK THE simplest colour plates in this class are the “dissected plates.” As the name implies, the process consists of separating the printing surfaces and producing a Oe® Fig. 177. Reproduction of Fig. 178. Illustrating all Fig. 179. Illustrating Fig. 180. The two colour re- aline drawing made for repro- areas routed away except those all areas routed away ex- sult. duction as a set of two-colour to print in blue. cept those to print in yel- dissected plates. low. 158 COLOUR WORK 159 printing plate for each colour. Combinations of colours are not employed in this method but each colour plate prints by itself. A typical example of a two-colour set produced by this method is illustrated in figures 177, 178, 179, and I8o. The first essential of such plates is that the colours will print in their proper areas. This is called “register.” In order to assure accurate register, all such colour plates of a set are made from the same negative. The colour set illustrated was produced by making the usual line negative and etching two identical plates therefrom. ‘The plates were then routed and in one plate only the parts to print in blue were retained. All parts shown by yellow in the reproduction were routed away from this plate. The second plate was routed in a corresponding manner except that only the parts to print in ye//ow were retained, the blue areas being routed away, thus producing a set of two-colour plates, each one consisting only of the areas to be printed in the respective colours. Colour dissection by routing the printing areas of etched plates can be properly done only when clearly defined open spaces exist between them. The router must be afforded a definite guide to follow and allowance must be made for the shoulder left by the routing bit to be trimmed off later. When such colour areas are close together, they are usually dissected on the zinc prints before they are etched. Certain areas are held and others removed, by employing the gamboge protection while the exposed areas are washed off with benzole. Colour dissection may also be accomplished by scraping away parts of the ink print. If the areas are small, they are removed entirely, but if they are large, it is only necessary to scrape away the edges to establish a line of separation as a guide for the router. The more intricate forms of solid line plates for colour work are those which employ not only the dissective method, but which also deal with overlapping of colours and the production of solid areas which are not solid in the copy. There are two reasons for overlapping colours: one is to assure register and the other is to produce an additional colour by combination. It is not good manufacturing practice to make such plates with one colour printing only up to the edge of a neigh- bouring colour. The slightest inaccuracy in the printing operation may result in a white line showing between the colour areas and this must be provided against by allowing the colour areas to overlap slightly on the edges. This is called a “lap” and provides for slight variations in register without the appearance of objection- 160 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING Courtesy Louis H. Frohman Fig. 181. Reproduction of a line drawing to be re- Fig. 182. Reproduction of the stained xine after the print has produced in two colours, registering with a slight “lap.” been washed off. able defects. The subject illustrated in fig. 185 is typical and demonstrates the necessity for this lap. Without it, the slightest variation from absolute register would cause a white line to appear between colours on part of the subject. The production of these plates requires a change in manufacturing procedure from the method which has been described, as the lap which does not exist in the copy must be produced in the plates. The plate representing the principal colour or outline is called the “key plate” and in the illustration shown is a reproduction of the copy without change. The colour plate, however, represents an area which is white on the copy and, in addition, it slightly laps the key plate. All colour areas of this plate were painted in by hand before it was etched. When painting in is done for this purpose, it is necessary that an accurate guide appear on the metal. The guide afforded by the usual ink print will not suffice because it is a re- sist and covers areas which are to ap- pear in the colour plate. The guide is therefore made in the form of a “stain” on the metal, by immersing the zinc print in a weak solution of nitric acid, which discolours the exposed Fig. 183. The stain painted in for the colour plate. areas of the metal. The ink top is ioe BT ae A ce COLOUR WORK 161 Fig. 184. The blue plate. Fig. 185. The finished colour plates. washed off with benzole and the image appears as a discolouration on the metal which is bright in all other parts where it was protected by the ink print. Thusa light but distinct image is produced on the metal, but which is not a resist. ‘The desired areas are then painted in with asphaltum and are made enough larger than the guide afforded by the stain to provide for the required lap. The plate is etched and finished in the usual manner. The manufacturing principles by means of which a lap of different printing areas is obtained are utilized to lap colours for the production of additional colours. A key plate of blue and a colour plate of yellow will produce a green where they over- lap. The required overlap of the necessary areas is produced by painting in on Fig. 186. The blue plate of Fig. 187. The yellow Fig. 188. Three colours ob- a two-colour set. plate of a two-colour sel. tained with two printings. This illustrates another type of dissected colour plates, but shows overlapped areas used to produce the third colour. prints, or on stains, or by holding areas with gamboge. ‘This method is illustrated in figs. 186, 187, and 188. Typical examples only have been used to illustrate these methods as conditions change with every different copy, but the basic principles remain constant and are briefly summed up as follows: 162, THE PROCESS-AND) PRACTICE OF PHOTO-ENGRAVING When simple in outline and clearly separated, colour areas may be dissected by routing. When complicated or of a nature which prevents dissecting by routing, colour areas must be separated on the metal prints before they are etched. Areas which are to be changed from the form or shape of the ink print must be painted in on a stain. Overlapping areas must be painted in or held on stains or prints before they are etched. BEN DAY ZINC PLATES FOR COLOUR WORK CoLour work is not limited to the use of solid plates. Line plates representing the key of colour sets, as well as the colour plates themselves, may be tinted by Ben Day films or halftone tint negatives, or they may be of solid and tinted areas com- bined. The method for making such plates follows the same scheme of operation as is employed for laying tints on any plates. The method of separating or lapping colours follows the procedure which has been explained for solid plates. It is a combination of the separate methods and makes it possible to produce a great va- riety of tones and colour combinations. ‘The key plate is usually made from a regu- lar zinc print, with the addition of such tints as may be required. The colour plates, however, are generally made on stained prints as it is unusual that any areas of the key print are retained and duplicated in the colour plates. The strength of tone required is produced by the usual method of shifting and doubling up the impression from the Ben Day film, and as these tints are employed to reproduce single or combined colours, extraordinary skill and colour judgment must be exercised. Solid areas are painted in as on solid colour plates. Ben Day colour plates may be combined with each other or with solid plates, line plates, halftones, or “process” colour plates. (See Chapter XVI for description of process colour plates.) The nature of these Ben Day colour plates depends upon the colour effect to be produced. If the tints to be combined are from halftone films, they must be laid at an angle to each other, to avoid a screen pattern. This also applies when they are combined with halftone plates. The films of grains or other unsymmetrical arrangements of the elements need not be run at an angle as ~ they do not produce the repeating screen pattern. It has been found that the necessary angle to avoid screen patterns is 30 degrees. This means that the rows of dots in one screen must cross the rows of dots in another COLOUR WORK ® ® e ® ; @ ® = e *o tee So? *e PRONE ete 3 \y @ @°e,@ @°6.0@ 0° Se, haf a9 ce? ocr hs © ive eure a ¥ oe a 36. one o @® @@ ie q ee* > ee @ ar e®@ e eee f°? e re, © Ol . See “Ast ° °° : sores, ; @ 8 Fig. 189. Enlargement of two halftone Fig. t90. Enlargement of three halftone Fig. rot. Enlargement of four half- plates crossing at a 30° angle. plates, each crossing at a 30° angle. tone plates, three of which are at a 30° angle, but the yellow is between two others 15° from each. The single dots projecting beyond the circular screen pattern show the screen angles as well as the colours. The inner circular pat- terns show the effect produced by the overlapping dots. screen at an angle of 30 degrees, as has been illustrated in the description on screen effects. The formation of the halftone screen is such that its lines cross at an angle of 90 degrees, or at a right angle. If screens are to be superimposed at angles 30 degrees apart, it is apparent that only three can be so placed, the three 30-degree angles being all that can be placed within the 90-degree angle of the screen itself. This fact limits the number of superimposed colours to three; if they are all to be sepa- rated by a 30-degree angle, and if halftone screens are to be used. A light halftone tint can be run but 15 degrees from another colour, and although this does make a checkerboard pattern, it will be lost in four-colour printing by the superimposing of the other colours. Ben Day colour plates to be used with a halftone key plate are made on stained prints from the halftone negative. The removal of the ink print of the halftone negative and using the stain as a guide permit the changes in screen angles required. This whole process of colour-plate making by means of solids or tints printed alone or superimposed, may be compared with hand-colouring. Each plate is made by hand to print only in the desired area and in the strength of tone required. It is, therefore, necessary that a definite, accurate colour guide be supplied with the original to be reproduced. It is not advisable that the copy be in colours, because they will act on the line negative and become confused with the uncoloured image required for the key plate. It is always necessary to eliminate these colours either Fig. 192. The key plate of a three-colour halftone and Ben Fig. 193. The finished Ben Day yellow plate. Day set. This plate was made from one wash drawing and two line drawings and required inserting and sur-printing. Zinc stains from this negative were used for the colour plates. DURANT'S TN at Sta | o dar d | Oday in bE The Better Way in Automotive Sransportation : his Mat «17 91925 wud Courtesy Durant Motors, Inc. Fig. 104. The finished Ben Day blue plate. Fig. 195. The finished black, yellow, and blue plates printed in register. From drawings by J. A. Mitchell of the Arrow Press. 164 COLOUR WORK 165 by photographing the colour with special colour-sensitive plates or painting the colours out with white, because all colours will be replaced by the hand-made print- ing plates. (See Chapter XVI for description of colour-separation negatives.) Colour separation will not be necessary if the colours are not put in the copy. COLOUR PLATES FROM TRANSFERS ALTHOUGH it Is usual to make colour plates from prints of the same negative used for the key plate, occasions sometimes arise when this method is inadvisable or impracticable. In such instances an impression is made on metal by means of a ‘“‘transfer”’ from the finished key plate. This is done by proofing the key plate on a sheet of paper or celluloid, which in turn is laid on a polished piece of clean metal and the image is transferred thereto by printing pressure. The metal may be stained and the transferred image removed for subsequent gumming out or paint- ing in or such other operations as may be required for the making of the colour plate. Transfers are employed in making colour plates to fit vignetted or silhouette halftones. Silhouetting and vignetting, being done by hand, do not always follow the identical outlines of the original copy. When colour plates are to be made which must register with outlines of silhouetted or vignetted edges, better re- sults are obtained if they are made from transfers of the key plate after it has been finished. Lack of register is almost sure to result when a halftone is outlined, routed, and trimmed by hand by one group of operators and a colour plate also made by hand by another group of operators. HAND-CUT COLOUR PLATES Cotour plates are often made from either prints or transfers, by outlining the areas with a graver, routing the plates to remove the excess metal. This method 1s employed because of its economy when the outlines to be followed are not compli- cated. It is often much quicker to outline and rout a plate than it is to go through the necessary operations of gumming out or painting in and etching it. The method is used more often on solid plates than on those which are tinted, because of the difficulty of obtaining the necessary outline guide on the tinted plate. If a plate has been etched, the etched areas must be filled in level with the rest of the printing Ze l= / iy p a Fig. 196. Reproduction of a pen drawing to be used in mak- Pig. 197. The finished black plate; made on a zinc print. ing a set of four-colour Ben Day plates. Sito been to bo Cook, at he Queer. lad ! ul Fig. 198. The finished yellow plate. Made on a zinc stain. Fig. 199. The black and yellow plates printed 1n register. 166 “. The black, yellow, and red plates printed in register. Fig. 201. Fig. 200. The finished red plate. Made on a zinc statin. Courtesy Doubleday, Page & Co Fig. 203. The four colours printed in register. From drawings by Ruth Hambidge for Pinafore Palace Series. 167 Fig. 202. The finished blue plate. Made on a xine stain. 168 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING surface before a transfer can successfully be made uponit. The outline is never as distinct as when the transfer is made on flat, clean, unetched metal. COPPER PLATES FOR COLOUR WORK CopPeEr Is seldom used for solid colour plates as it offers no advantages over zinc and is more costly. It is used for key plates if the nature of the copy requires a copper etching, and Ben Day tints may be laid on copper prints as has been ex- plained in the description of black and white work. Its use for Ben Day colour plates is rare, because no satisfactory method has yet been found for producing a suitable copper stain to act as a guide when the top is removed. It is often used for making tinted colour plates employing a halftone tint negative instead of the Ben Day tint. This affords a clean uniform tint which may be cut to the required size and shape by employing a transfer from the key plate. Such tints cannot be modelled or graduated in the usual manner employed with the Ben Day films, but some variations can be produced by local re-etching. When the box grain is employed, it is advisable to use copper, especially if the grain used is a very fine one. Box grain colour plates are sometimes made on copper by using transfers and outlining a guide on the metal with a tool. ‘This takes the place of a stain and the plate may be gummed out and the box grain laid. Ben Day colour plates, combined with either line or halftone key plates, are not intended to reproduce all classes of colour work. The fact that the colour plates are made by hand must be considered. Unfamiliarity with the process has allowed ‘ the erroneous impression to exist that it is a “‘cure all’”’ and that Ben Day plates will print where other plates will fail. Halftone Ben Day plates will print no better than regular halftones of similar fineness of screen, for, as a matter of fact, the half- tone Ben Day films themselves are made from etched halftone plates of tint nega- tives. The Ben Day tints of other textures and which are more open than the halftone films will print no better than any line plate of corresponding fineness. The process is essentially one of convenience. By its use tints are added to plates which would otherwise have to be added to the copy, usually at considerable cost and inconvenience. CHAPTER XVI PROCESS COLOUR WORK HE method employed to reproduce coloured copies or objects, by means of halftone plates and with not more than four printing colours, is called “Process Colour Work.” Those who are familiar with the principles of colour, colour photography, photo- graphic colour separations, and colour printing will find no radical colour theories exploited in this chapter. On the other hand, a warning must be given the reader who is venturing into this subject for the first time. In order to understand the basic principles of the process, the whole subject of colour must be viewed from its scientific angle and we state frankly that it is a difficult matter to do so. Unless all of the features and principles explained are most carefully studied, the process will be less clear at the end of the description than it may have been at the beginning. Light is the medium by which we see objects, whether they be black and white or in colours. But what is light? Before one can grasp colour principles, it is es- sential that light and its properties be analyzed, at least superficially. Light is an elaborate series of vibrations or waves, as has been explained in the chapter on Lenses and Light. The peculiar characteristics of these waves are that they are not all of the same wave length, and each different wave length 1s a different colour. If the variation in wave length is slight, the variation in colour is corre- spondingly slight. It is possible to separate light into these component colour parts by what is called “dispersion.” It may be done with a spectroscope, which is a highly scientific instrument used for this purpose, or by means of a prism. The prismatic dispersion is what produces the effect of colours in the cut facets of dia- monds, cut glass, and the familiar prisms of glass chandeliers. It is most completely demonstrated in the rainbow, which is produced by dispersion of light in the rain- drops. The scientific explanation of dispersion is an extremely technical subject and one which would only tend to confuse the description of process work were it 169 170 THE PROCESS AND PRACHICE OF PHOTO-ENGRAYVING included in this chapter. The foregoing homely examples of dispersion are offered as evidence that light can be dispersed and then will appear in the form of its com- ponent colours. The fact that it zs composed of colours is the important feature, and the whole principle of the process hinges upon it. In order to have a standard of measurement or for purposes of comparison, the name “white”’’ has been given to light which contains all of the known colours. When white light is dispersed by a spectroscope, all of the rainbow colours appear clear and distinct and, as the spectroscope provides means for measuring the differ- ‘6 ent colour regions, scientific ‘‘white light’? can be measured, compared, and stan- dardized. The individual colours of white light are numbered in thousands, but for convenience are divided into seven groups. ‘These are the colours of the rain- bow: Violet, Indigo, Blue, Green, Yellow, Orange, and Red. These are called the colours of the spectrum and, as sunlight is the most standard light for purposes of comparison, its dispersion is called the “solar spectrum.” These colours of the spectrum are elementary and are not produced by combi- nations of colours. So far as science has been able to determine, they are elements just as much as gold and silver. Different substances reflect and absorb light in different ways. If they reflect all the colours of white light they appear white. The mixture producing this effect takes place in the human eye. In order to see certain colours, others must be eliminated. Elimination is caused by absorption. Thus when viewed in white light: A substance appearing black is absorbing all light, reflecting none. A substance appearing white is absorbing no light, reflecting all. A substance appearing neutral gray is absorbing half of the white light and reflecting half. A substance appearing green is absorbing all colours except green, which it reflects. It may be difficult to accept the fact that colours primarily exist in light rather ‘ than in “coloured” substances, but it can be readily demonstrated. The human eye looking through coloured glasses sees changes apparently wrought in the colours of the view. ‘The scenic effects on the stage produced by coloured lights offer another demonstration. Materials which appear bright blue in PROCESS COLOUR WORK 171 daylight appear green by gas light. In every instance the change is due to the light, not to the material itself. ‘The light contains the colour and the substance controls the amount absorbed or reflected. It is customary to call colour-reflecting substances by the name of the colour which they reflect, and it would be quite inconvenient always to refer to them as ’ “reflecting green,” and so on. Coloured substances may be either transparent or opaque. Those which are transparent allow light to pass through them. This is called “transmitting light.” The colours of transparent substances are caused by the amount and degree of ab- sorption. White glass appears white because it will transmit all colours. Red glass transmits red light and absorbs all others. Light does not pass through opaque substances, but is reflected by the substance itself. Red velvet reflects red light and absorbs all other colours. Substances may transmit or reflect more than one colour, and they take on the hues caused by the combinations so transmitted or reflected. Absorbed colours effectually disappear, so far as vision is concerned, and appar-. ently these rays are transformed into heat. This may account for the fact that black clothing is warmer than white. As the colours of light and their combinations are the means by which all colour effects are produced, it is not difficult to appreciate that a correct combination of printing ink of similar colours will reproduce a coloured object or copy. The two ’ words “‘correct combination” represent the basis of colour reproduction. Fortu- nately, colour-sensitive photographic plates, aided by coloured glasses or “filters,”’ enable photography. to separate the colours of copies into their component parts, thereby affording the means of obtaining the relative strength and tone of each printing colour to duplicate the original colours or their combinations. (Note. The following describes the three printing colours used for colour re- production. Four printings are often used in this process, but the fourth plate is usually for printing in black or gray. See description of the four-colour process.) It has been explained that not more than three halftone plates can be superim- posed at the usual 30-degree angle without producing an objectionable pattern. For this reason, three printing colours are employed in this process. The ideal method would be to use the seven rainbow colours, but this is impracticable for 172. ‘DHE PROCESS AND PRACTICE OF (PHOTO-ENGERAVING commercial reasons and therefore the seven have been rearranged into three. This has been done on a scientific basis, extending over years and through exhaustive research and experimentation. The correctness of their hue is of the utmost importance and they have been practically standardized by the various ink makers of the world. These three colours are called yellow, red, and blue. They are not primary Fig. 204. The inner circle represents the seven rainbow colours: violet, indigo, blue, green, yellow, orange, and red. The outer circle represents the three printing colours and shows the approximate regions of the original seven which each printing colour should represent. The reproduction 15 a set of three-cclour process plates made from a hand-coloured drawing. The outer circle shows the three printing colours actually used. PROCESS COLOUR WORK 173 colours in the scientific sense as they represent certain combinations of the original seven. The colour chart illustrated shows the original seven colours, and surround- ing it, the three printing colours. These latter are arranged so as to show the by “region”’ of the original seven which each represents. This rearrangement of the spectrum colours is a compromise, but it is apparently a fair one because it has made possible the beautiful colour work characteristic of our most successful publications. Colour reproduction with these three colours is called the ‘“Three-Colour Process”’ and requires three halftones, made from photographic colour separations. One will be printed in yellow and it must represent all the values and strength of yellow in any part of the copy. ‘This not only means yellow values as they appear to the eye, but all yellow which may be a component part of any other colour or combination. The second halftone will be printed in red; the third one in blue. Both the red and the blue are made on the same principle as the yellow and they represent the respective values and strength of red and blue of the copy or any of their colour combinations. If all values of yellow are to be separated and isolated by themselves, all other colours must be excluded. Using the colour diagram as a guide, it will be found that the colours to be excluded are the blue and red. If the copy is photographed through a violet-coloured glass or filter which will transmit only blue and red, these will be the only colours to affect the photographic plate and they will be the /ightest parts of the halftone plate. A second photograph must be made which will repre- sent all of the red of the copy. This requires elimination of all yellow and blue, which is accomplished by use of a green filter. The third photograph, to represent all blue areas, requires exclusion of all yellow and red, for which an orange filter is used. Thus by means of the three filters, violet, green, and orange, three photographic records are obtained showing the amount of the printing colours yellow, red, and blue which will be required to reconstruct the colours of the original. The colours of the filters must be as scientifically accurate as to hue and density as those of the printing inks in order that they will transmit their respective colour regions prop- erly, absorbing all others. Two facts should be explained in connection with this process. The photo- graphic colour separations are not themselves in colour. ‘They are black and white COLORS OF COPY REFLECTED TO FILTERS GREEN FILTER YELLOW RED : ABSORBED ABSORBED YELLOW TRANSPARENT ON NEGATIVE RED TRANSPARENT ON NEGATIVE BLUE TRANSPARENT ON NEGATIVE RED AND BLUE OPAQUE ON NEGATIVE YELLOW AND BLUE OPAQUE ON NEGATIVE YELLOW AND RED OPAQUE ON NEGATIVE YELLOW SOLID ON PLATE RED SOLID ON PLATE ‘BLUE SOLID ON PLATE RED AND BLUE ELIMINATED YELLOW AND BLUE ELIMINATED YELLOW AND RED ELIMINATED YELLOW AND RED PRINTED IN REGISTER YELLOW, RED AND BLUE PRINTED IN REGISTER Fig. 205. Diagram illustrating absorption and transmission of coloured light by the three colour filters. The three printing colours used are the same as those employed in fig. 204, and have been superimposed in the centre of the overlapping circles at the top and bottom of the illustration, producing the effect of black. This reproduction 1s from solid zinc line plates. A fourth printing of black has been used for the type and that portion of the diagram representing the negatives. 174 PROCESS COLOUR WORK 175 until the halftones from them are printed with the coloured printing ink. Each respectively represents the correct values of one of the three colours. Secondly, the colours absorbed by filters should not be confused with those which are elimi- nated from the printing values in the halftones. Since it is very easy to become confused in this subject, a chart is given (fig. 205) which shows the colours of light transmitted as well as those absorbed, and it also shows the printing colours. Process colour work is divided into three groups, indicated by the number of printing plates employed. They are the Duograph, employing two printing col- ours; the Three-Colour Process, and the Four-Colour Process. -Duographs are used to reproduce copies which have been made in two colours or in black and a colour. ‘They are not unlike the plates produced by the halftone key and Ben Day colour-plate process, except that the colour plate of a Duograph set is photographic instead of being made by hand. It has been explained that when two-colour copy is to be reproduced by the halftone and Ben Day method, a photograph must first be made, eliminating the second colour in order to enable the production of a key plate. The values of the second, or colour plate, are then supplied by Ben Day films and are hand made. Elaborate copy will be more accurately reproduced if the second plate is photographic, and that is the purpose of the Duograph process. The key plate is made with all colour eliminated as far as possible and the second plate is photographically made to be used for the colour only. From a technical standpoint the process may be considered more of a method of producing two-colour effects rather than reproducing them. It is used for re- productions from black and white copy also. (See description of Colour Plates from Black and White Copy.) The Three-Colour Process lends itself essentially to full colour reproduction. It employs the principles of colour separation and the use of the special printing colours which have been described. In theory it will reproduce any class of colour copy, but in practice it is sometimes modified by the addition of the fourth printing plate for black or gray, when it is called the “ Four-Colour Process.” This modification becomes necessary because the manufacture of printing colours or other materials and appliances employed in the graphic arts has not yet been brought to perfection. Theoretically, solid yellow, red, and blue when prop- 176 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING erly superimposed on a sheet of white paper will, in the aggregate, absorb all colours and produce the effect of black. In practice they produce a remarkably black effect, but every condition under which the plates are made and printed even to the exact strength, hue, and intensity of the ink, must be scientifically correct. These conditions are never met commercially, and a black so produced may look bluish or deep brown. Neutral shades of gray, or colour tones which are soft and of a subdued grayish hue, are sometimes disappointing in a three-colour reproduc- tion unless all conditions are correct. For these and many similar reasons it has been found expedient to use the fourth printing plate on richly toned subjects of deep colour values, as well as for the production of true blacks and grays. It is especially valuable commercially, when type matter forms a part of the copy. The superimposing of yellow, red, and blue type matter to produce black letters is an undertaking to tax the skill of any printer, therefore the fourth or black plate becomes of distinct commercial value in such instances. (Four-colour process plates can also be made from black and white copy. See description of Colour Plates from Black and White Copy.) In four-colour process sets the screen angles in the heavy colours—red, blue, and black—are 30 degrees apart as in three-colour sets. ‘The yellow plate is made at a 15-degree angle from the red. While this produces a pattern it is obscured by the other colours. (Refer to fig. 191.) MAKING PROCESS COLOUR PLATES BrieFLy outlined, the method of producing process plates is as follows: The colour copy is photographed through the colour-separation filters on specially pre- pared colour-sensitive photographic plates, thereby obtaining a photographic rec- ord of each colour to be used. From each of these colour separations halftone plates are printed, etched, and finished by re-etching, burnishing, outlining, routing, tooling, trimming, in much the same manner as though they were to be black and white plates. Special care is taken to preserve the required values for each colour. The plate for each colour is made with the halftone screen at a suitable angle to avoid a pattern and are printed on a printing press in their respective colours, in perfect register on top of one another. The various tone effects obtained by PROCESS COLOUR WORK Toy, means of the colour separations and the subsequent work by the finisher, and the different colours of printing ink used, eventually reproduce the colour effect of the copy. This is an outline of the process which will afford a guide in the detailed ex- planation of the process, which may otherwise seem complicated and involved. MAKING COLOUR SEPARATIONS PHotoGraPuic plates having colour-sensitive emulsions must be used for making colour separations. The usual wet plate employed in black and white halftone photography is highly sensitive to white, violet, and blue, but is extremely insensi- tive to other colours. It has been explained that when a photographic plate is in- sensitive to a colour, that colour does not act on the emulsion and will appear as the darkest part of the print. The necessity for separation of all colours requires an emulsion which is sensitive to all. Such plates or emulsions are called “ panchro- matic.” As colour separations are usually made through a halftone screen, the photographic properties of the plates or emulsions must be such that suitable half- tone negatives may be made withthem. Dry plates which fulfil these requirements are called “ Panchromatic Process Dry Plates.” ‘This is to distinguish them from dry plates which, though sensitive to all colours, are unsuited to use with the half- tone screen. A wet plate emulsion also used for process work is called “Collodion Emulsion.” It is similar to the ordinary wet plate emulsion except that the silver is combined with it and its chemical ingredients cause it to be sensitive to all colours. The method of making colour-separation halftone negatives is called the “Direct Method.” The older and now little-used method is called the “Indirect pe Ao od Fig. 206. The silver grain Fig. 207. The silver grain Fig. 208. The silver grain Fig. 209. The silver grain structure of a wet plate half- structure of an emulsion half- structure of a process dry structure of an ordinary dry tone negative. tone negative. plate halftone negative. plate halftone negative. These reproductions are from photomicrographs of the same areas of four different halftone negatives. Each halftone negative 1s from the same original copy and each has been intensified, cut and finished. The magnification is about 50 diameters. 178. THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING a ne ot Sea Fig. 210. A typical process camera equipment for colour work, showing the position of the camera and turn table and a prism on the lens employed to reverse the image. Method,” in which colour-separation negatives are made without the halftone screen, producing a “continuous tone negative”’ from which positives are made and, again from these, the halftone negatives. This requires three times the number of operations necessary for the direct method and it is only employed in unusual cir- cumstances, which have been described in the description of ““Halftones Direct from Objects” or when the copy is very large. When conditions are such as to make it impracticable to make a halftone negative direct from an object or other copy for black and white reproduction, the difficulties are multiplied when process colour work is involved. Excessively large copy must first be photographed by the con- tinuous tone separation negatives and then reduced to the required size when the halftone negatives are made. There are many other instances where the direct method is impracticable, but under all except unusual conditions it is universally employed. For the direct method the process camera is mounted on the usual stand but PROCESS COLOUR WORK 179 equipped with a turn table. As process negatives are not turned in the usual man- ner to preyent reversal of the image, they must be suitably reversed when they are made. Negative turning would almost surely produce variations of the image, due to stretching or shrinkage causing lack of register. Reversal of the image is accom- plished by using a prism or reflecting mirror on the lens and turning the camera to a position parallel to the copy. The image is reversed by reflection in the mirror and then passes through the lens to the photographic plate which produces the same result as though the negative had been coated, stripped, and turned. Prisms are optical instruments made to work with accuracy and precision in conjunction with the lens. The position of the cam- era, prism, and lens as used for direct process work is shown in fig. 210. If } a colour subject is to be reproduced | reversed in position, the prism 1s omit- ted and the camera turned on the stand | to the normal position used for black and white negatives. The halftone screen used for process work is the same as that used for black | . and white, except that it is mounted in : : ss Courtesy Repro-Art Machinery Co. _ the screen holder in a circular frame so Fig. 212. The circular halftone screen and screen holder employed it may be rotated to give the different eC screen angles required. If means are not provided for rotating the screen, the copy must be rotated on the copy board in order that each colour may be photographed at its proper screen angle. Copy boards are sometimes made on the turn-table principle to afford suitable means for rotating the copy. In addition to the usual means provided for the different diaphragms required for halftone negatives, provision is also made for the use of the colour filters through which the copy must be photographed. There are many methods employed for this purpose and various kinds of filters are used. They may be of coloured glass, celluloid, gelatine, or a glass cell containing a liquid dye, the essential being that the colour be correct and of the proper density. Their position in relation to the lens 1 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING varies with different styles of equipment. ‘They may be attached to the front or in back of the lens or can be inserted in a slot in the lens barrel. Filters have been used which were the full size of the camera and placed directly in front of the half- tone screen or in front of the photographic plate. They have even been placed in front of the illuminating arc lamps. When placed in the diaphragm slot in the lens barrel they are usually of the thin gelatine type and are combined with the halftone stops. ‘Their position is unimportant as compared with the fact that they must completely encompass the light passing to the photographic plate. The making of colour separation halftone negatives involves the action of light through the halftone screen, and the same optical principles of producing dots as in the black and white process, The three-stop or the single-stop method may be Fig. 212. A flat etched black plate of a duograph set. A Fig. 213. The finished black plate. line negative of the lettering has been combined with the halftone negative by double-printing. PROCESS COLOUR WORK I ) ‘oc COPY aD ‘nce, COPY CO _ Fig. 214. The flat plate from the red separation negative. Fig. 215. The finished red plate. The lettering has been combined with this plate by double- printing in proper position to register with the black. employed, but the length of exposure is greatly increased by the use of the colour filters. Length of exposure depends upon the density and colour of the filters, the sensitiveness of the emulsion used on the photographic plate, nature of the copy, illumination, and sizes of diaphragms. In some instances it may be necessary to increase exposure to eight or ten times the amount which would be required were no colour filter used. If duographs are to be made, two negatives are required. The filters used must be such as to give the required colour separation, and this will depend upon the colours in the copy. Usually two of the regular separation filters will afford suitable separation, but special filter colours may be used if the subject re- quires. Three negatives are made for the three-colour process and four for the 182 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING aS Yi: ri! Courtesy Collier’s Weekly. Fig. 216. The flat red and black plates printed in register. Fig. 217. The finished red and black plates printed in register. It will be interesting to inspect the impressions from the flat black and red plates shown in figs. 212 and 214 and compare them with the finished result in fig. 217 and note the degree of colour separation obtained. Also note the result of hand finishing by com- paring the flat and finished plates of each colour. four-colour process. Identical filters are used for the three colours of each of these processes, but the fourth plate is made through a yellow filter or combination of filters, which gives the approximate balance of all colours. Register marks are placed on copies before the separations are made. These are reproduced on all negatives in identical relative position and afford a guide in registration of the plates when they are proofed. Since the plate for the fourth printing is usually black or gray and represents a compromise colour, the effect of this separation must be manipulated to obtain whatever result may be required to combine with the other colours and reproduce the copy. Sometimes all of the colours must be filtered out of this fourth separation, by making multiple exposures PROCESS COLOUR WORK 183 with all three colour filters, leaving only a photographic record of the actual black or gray in the copy. After the halftone separation negatives are finished, whether they be for the duograph, three-, or four-colour process, they are printed on the metal in the usual manner and burned in. Each halftone print contains the tones, modelling, and values of the respective colour, but at this stage they are not at all suited to be etched and proofed in colours. It is a characteristic of the halftone process that solids of the copy have fine shadow dots all through them and that the lightest areas have fine highlight dots over them. This applies to colour halftone negatives as well and the importance of adjustment of these tones is multiplied by the number of colours. A white area of a monochromatic copy, even though it has screen all over, may appear sufficiently light when contrasted with surrounding darker tones, but similar white areas of colour copy would be impossible when reproduced with correspond- ing highlight dots of all the colours. Deep tones appearing sufficiently dark in a one-colour plate, though showing shadow dots, will not carry enough colour in process plates to combine properly with other colours for correct reproduction of the copy. Such dark areas are therefore painted in solid on colour plates by the colour etcher or finisher, whose judgment determines the amount of painting in or stop- ping out, and then the plate is etched. Etching is also done by the finisher, as the dot size for every colour tone must be carefully watched. Sometimes a number of short bites are required, painting in being required before each bite until finally the various tone values are deemed correct. Areas in which no tone of a colour is to appear are outlined and routed, or painted in and etched out as in black and white halftones. On complicated subjects like rugs, carpets, or other materials of involved design, the painting in or cutting out represents a tremendous amount of labour and patience. An important requirement for the success of this fine detail finishing is that the shapes of all areas to be painted in or cut away be distinct so that the fin- isher will have a guide to work by. Sometimes, absolutely correct colour separation will cause such shapes to lose their distinction, affording no guide for finishing, as, for example, a light yellow design on a light blue background. ‘The separation nega- tive for the blue plate will eliminate yellow but the result will be as though it had been changed to white and a light halftone screen will appear over all such areas in Fas ae Fig. 218. The yellow plate of a three-colour process set. Fig. 219. The yellow plate finished. Flat etched. 1LUCRORD A Pav eene 4 LI- STORY § ALL STORY FEKLY§ WEEKLY 10¢e% OCTOBER 6 %w34°° Ml 10¢z OCTOBER 6 Fig. 220. The red plate flat etched. Fig. 221. The red plate finished. 184. Ale STORY Rade LY 10S OCTOBER 6 ae Fig. 222. The blue plate flat etched. Fig. 223. The blue plate finished. BARGOSY BALL: STORY WEEKLY Cite of fQueen of the Night” iO¢es “OCTOBER G SEee” Courtesy Frank A. Munsey Co. ‘ p ¥ ai Sok gee & - , pas . : ie) Aa 5 : BY THE S j t ay z # CORY YDt : YEAR See 4 nae Fig. 224. The three-colour set of flat etched plates printed in register. No finishing has been done on these plates. Fig. 225. The three-colour result from the finished plates. From painting by Modest Stein. 185 Fig. 226. The finished yellow plate of a four-colour set. Fig. 227. The finished red plate of a four-colour set. Fig. 228. The finished yellow and red plates printed in Fig. 229. The finished black plate. register. 186 ister. ERRATUM The painting by Norman Rockwell, used for the color plates shown on pages 186 and 187 was loaned by the Edison Lamp Works, Harrison, N. J. Unfortunately, credit for their courtesy was incorrecily printed on page 187. Courtesy Wevisheus ras Co. Fig. 232. The finished four-colour set. From painting by Norman Rockwell. 187 Fig. 230. The yellow, red, and black plates printed in reg- Fig. 231. The finished blue plate. The same comparison obtains between the flat plates and the fin- ished plates of a four-colour set as it does in the two and three colour. Hand-finishing of the finest type is absolutely essential. Fig. 226. The finished yellow plate of a four-colour set. Fig. 227. The finished red plate of a four-colowr set. Fig. 229. The finished black plate. Fig. 228. The finished yellow and red plates printed im register. 186 Fig. 230. The yellow, red, and black plates printed in reg- ister. Courtesy We Fig. 232. The finished four-colour set. From painting by Norman Rockwell. 187 stinghouse Lamp Co. Fig. 231. The finished blue plate. The same comparison obtains between the flat plates and the fin- ished plates of a four-colour set as it does in the two and three colour. Hand-finishing of the finest type is absolutely essential. 188 THE PROCESS AND: PRACTICE OF PHOTO-ENGEAY ING the blue plate. This must be removed to prevent combining with the yellow plate and producing a green, but a definite indication of the outlines must appear on the etched plate so that the finisher can cut away all the areas which must be elimi- nated from the plate. Such a condition forces the photographer to produce a sepa- ration negative in which the detail will show, even though it be incorrect in colour values. The finisher must then restore the values to correct relation with the other colours, by burnishing, re-etching, and tooling. Process colour work is by no means an automatic process, because of the diff- culties of practice as compared with theory. The separation negatives usually afford a sound basis on which the colour plates may be worked up by the finisher, but they demand not only the usual manual skill but also a knowledge of and eye for colour. The plates illustrating the two- and three-colour process are shown flat etched without any work by the colour finisher as well as finished. They demon- strate the effectiveness of the finishing operations. After completion of each plate, it is proofed in its respective colour. Exact register is essential so that each colour will print in its proper position on top of the underlying colours. PROCESS PLATES FROM BLACK AND WHITE COPY Wui_e the three- and four-colour processes are usually employed to reproduce full-colour copy, black and white copy can also be reproduced in colour by these plates. Subjects are sometimes too large or unsuitably situated both as to location and illumination, to permit making colour separations of them. Flower gardens, land- scapes, fashions posed on living models, or similar subjects cannot be depended upon to remain motionless during the long multiple exposures. Paintings and other works of art, often too large or too valuable to be removed to a studio, sometimes lack proper illumination for this process and conditions may prevent the use of suit- able artificial light. Under such conditions it may become necessary to make a black and white negative and photographic print of the original and then make the colour process plates from the black and white print. Two, three, or four halftone negatives are made, using the proper screen angles, but each negative must be of such tonal quality as to permit the plate being manip- PROCESS COLOUR WORK 189 ulated to produce the required relative colour values. Since the copy is devoid of colour, the negatives lack the definite variations in colour values produced by colour separations. The plates are therefore painted in, re-etched, burnished, tooled, and routed to produce, by hand work on the plates, the proper colour values of each printing plate of the set, which are lacking in the negatives. The process is sometimes called the “Fake Process,” but in reality the results are quite the opposite and splendid colour results are often obtained by it. In order to give the colour-finisher a suitable foundation on which to work, the angle negatives are made rather flat and lacking in contrast. Being neither too dark nor too light, the plates from them may be re-etched and burnished to simulate quite faithfully the true colour separation values required for the final colour re- production. The process 1s at its best only a substitute for that employing colour separations and is used only when the other is impracticable. Plates made by the artificial or “Fake” method must necessarily be extensively manipulated to force the values to the required degree of light or dark tones, and therefore are seldom as truly photo- graphic in appearance as those made from separations. Sometimes middle tones must be burnished to a very dark tone which takes from their etched depths and slightly lowers the printing surface. Likewise, middle tones of connected dots are required to be lightened to such a degree that the dots will print as highlights. If they are too well connected to break apart properly by re-etching, they must be cut a9 apart with a “shooter.” ‘This is a multiple graver with which the colour-finisher actually cuts grooves between dots to separate them. It produces a clean tint and separates the dots evenly, but has a tendency to make the tone appear flat and lacking in detail, and the plate must be burnished to restore detail so lost. Not- withstanding its shortcomings, it is a method often employed. PROCESS AND BEN DAY PLATES COMBINED Ben Day plates are sometimes combined with process plates to reproduce black and white copy in colour. Instead of making four halftone angle negatives only three or sometimes two are made. These are used to make the plates for the dominant colours or those in which great detail or modelling must appear. The plates for the less dominant colours may then be made by the Ben Day process. 190 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING COLOUR SCHEMES AND GUIDES In any colour process utilizing black and white copy, a suitable colour scheme or colour guide must be provided. This may be in the form of a colour sketch, which should be accurate if a faithful colour reproduction is expected. A hand-coloured photograph is suitable, or a proof from one of the plates of the set may be coloured. Such a proof is usually made from the black plate of a four-colour set or the blue plate of a three-colour set after the plate has been flat-etched. It is called a “flat proof for colouring’? and may be coloured with water colour. The most accurate and photographically faithful colour guide is the Lumiére Autochrome. (See page 196.) ‘This is a colour transparency, made photographic- ally, reproducing all the colours of the original. They are not difficult to make but require suitable photographic conditions for their proper exposure. They are de- scribed more fully in the chapter on Photography of Colours. COMBINING SUBJECTS FOR PROCESS PLATES ALTHOUGH most users of process colour work realize the difficulties presented by separate colour copies to be combined into one set of colour plates such combinations are sometimes necessary. ‘The difficulties presented are much greater than in black and white work because of the multiple colours and the necessity for retaining absolute register of all colour plates. ‘There are three methods which may be employed and their choice depends upon the manufacturing facilities at hand, the nature of the work, and last but not least the skill of the operators. The order in which they are described is not to be assumed to be the order of their adaptability. When direct separation halftone negatives are made on collodion emulsion, they may be stripped and set up by the procedure employed for black and white nega- tives. Combining the negatives for the first colour does not present any difficulty, but when the negatives of the next colour are combined, the set up must register exactly with that of the first colour. Register must be so exact that not only will the image itself be in proper position but the screen angle must be accurately main- tained. The practice is usually to lay the glass, on which the second negatives are to be set up, on top of that carrying the first, which have been combined. View- ing the work by transmitted light and taking care that the angle of view is directly PROCESS COLOUR WORK Ig] above the work and not from one side, reasonably accurate register of the negatives may be effected. ‘This operation must be repeated for each colour of the set, and no means afford a check on the accuracy of the work except the results of the colour proofing. Another method is that employed in double printing. ‘This is very laborious, especially if more than two subjects are to be combined. One colour of one subject is printed on the metal and the corresponding colour of the second subject is double- printed on the metal in proper position. Overlapping parts are scraped away be- fore burning in, and the combination is accomplished for one colour in the same manner as that sometimes used on black and white work. Combining the remain- ing colours in accurate register presents a very great difficulty. Elaborate and accurate register marks must be placed on the metal, to which corresponding marks on each succeeding colour must be registered. This may require first finish- ing one colour and pulling a transfer from it on to the metal in order that such regis- ter marks may be made. ‘The registration of the colours in each double print is then made by placing the negatives in register with these register marks and scrap- ing away any overlapping parts as in the first plate. This method is so complicated and so apt to produce inaccurate results that it is seldom employed if it can be avoided. The third method may truly be called a “fake” method, as it resorts to a subter- fuge. The colour copies to be combined are first photographed and paper prints made from them. ‘These photographic prints are combined to make a one-piece black and white copy, taking the place of the separate colour copies. The plates are then made by the “fake”? method which has been described, thus eliminating elaborate negative inserting or double printing. CHAP i WResxevit PHOTOGRAPHY OF COLOURS HE photographic principle applied to colour separations is used also for reproducing colour copies in black and white. Its purpose is to produce in one colour the correct relative values of the various colours of the original. Photographic negatives so made are called ““Orthochromatic”’ or “ Ilsochromatic.”’ They translate the values of colours into relative values of black and white. The ‘ trade calls them “orthos.”’ The method utilizes colour-sensitive photographic plates and the principles of colour absorption by means of colour filters, but the success attained depends largely upon the manner in which the exposure is made, the colour of the filter used, and particularly the operator’s judgment of colour values. The ordinary wet plate used for halftone photography is quite insensitive to brown, red, orange, yellow, and yellow-green. A photographic emulsion which is insensitive to a colour is not affected by that colour during exposure and the result is the same as though it were black. Consequently copies composed of the colours to which the emulsion is insensitive reproduce dark and lacking in detail. Practically all photographic emulsions are highly sensitive to violet, blue-purple, and blue, and these colours reproduce as a light tone. In order to reproduce all such colours in their correct black and white or “monochromatic”’ (single colour) tone values photographic plates must be used which are sensitive to all colours. Colour filters are also used to absorb or restrain the ‘‘actinic”’ colours, as the violet, blue-purple, and blue colours are called. Partial absorption causes these actinic colours to act less rapidly on the photographic emulsion and tends to even up and balance the whole tone effect of the colours photographed. The method is by no means automatic, as an even, balanced, monochromatic reproduction of a colour copy will not necessarily produce a satisfactory result, even though it be scientifically correct. The effect to be obtained is the essential feature, and this must be varied by skilful manipulation of filters and photographic plates. 192 PHOTOGRAPHY OF COLOURS 193 Fig. 233. Halftone reproduc- Fig. 234. Halftone reproduc- tion made with ordinary wet plate tion of the same colour chart but from part of the colour chart shown made from an orthochromatic nega- in fig. 205. tive. Filters of various colours are used in this process, depending upon the results to be obtained. They range from pale to deep yellow and may even be modifica- tions of the process colour filters. The process filters of orange, green, and violet are also often used. The effect of the yellow filters is partially to absorb the actinic colours. Pale IN Wetland PW GekOkh 7 ALL- STORY § ALL- STORY WEEK Die W.bE NEY Y Perkins eh Austho “of Queen of the Night: |O¢es OCTOBER 6 wews42° [ME 10¢e8 OCTOBER S2F409 Fig. 235. Halftone reproduction made with ordinary wet Fig. 236. Halftone reproduction from the same painting but plate from the painting reproduced in fig. 224. made from an orthochromatic negative. By comparing these reproductions with the colour plates of the same subjects, the necessity for the use of orthochromatic negatives will be apparent. 194 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING blue will reproduce slightly darker through a yellow filter than when no filter is used. Pale yellow is not affected by this filter but is transmitted in full intensity. This restraining action will be recognized by photographers who have used a “‘ray filter” to photograph clouds in a blue sky. Blue sky, being practically as actinic as white clouds, does not show the same distinction on a photographic negative as it does to the eye. When restrained by a yellow filter, however, it reproduces slightly darker than the clouds and produces the necessary contrast. ‘The deeper the yellow colour of the filter, the darker the blue sky will appear. Orthochromatic negatives made without the halftone screen are called “con- tinuous tone”’ negatives. Photographic prints are made from them for reproduc- tion. When the halftone screen is used in conjunction with the colour-sensitive photo- graphic emulsions and the colour filter, the negatives are called “direct orthochro- matics” or “direct orthos.’’ Process emulsion or process photographic plate or films must be used when the halftone screen is employed, as for colour-separation work. Photographic procedure is the same as for any halftone or continuous tone nega- tive, except as related to the filters. Some copies require the use of more than one filter in order to translate their colour values satisfactorily. A copy consisting of tones of blue, green, and red presents a difficult problem. A yellow filter restrains the blue but at the same time transmits some green and red, and the effect is to bring all three colours to a flat monochromatic value, lacking the necessary con- trast. A partial exposure with the yellow filter, followed by an additional exposure with a green filter, will restrain the blue and red but will transmit the green, making it lighter, thereby producing a contrast of values. There is no rule which may be followed for this work, and the operator must judge the means necessary to obtain the effect required in order to translate intelligently the colour values and intensity of the original copy. COLOUR SEPARATIONS FOR BLACK AND WHITE WORK A COLOUR-SEPARATION negative differs from an orthochromatic in that it entirely eliminates a colour or combination of colours, while the ortho reproduces all relative values in monochrome. Faded or very weak colours may be reproduced in greatly PHOTOGRAPHY OF COLOURS 195 strengthened tones by means of colour separations. An indistinct blue typewritten letter or a washed-out signature will reproduce almost sharp black and white if photographed through an orange filter. A faded yellow photograph will appear practically in its full original strength of tone if photographed through a blue filter, and if a wet plate is used, which is insensitive to yellow, no filter need be used. This may raise a question in the mind of the reader as to how a faded yellow copy may be photographed on a wet plate which is insensitive to that colour. It is the whites of such copy which photograph. ‘The faded yellow does not act on the wet plate, therefore appears dark, producing the necessary contrast with the white areas. Orthos or colour separations are used in the preparation of the halftone key plate of Ben Day colour plates when the original is in colour. As the colours are to be printed from the hand-made colour plates, it is essential that they be eliminated from the key plate. This is accomplished by a colour separation with one or more filters, which eliminates all colour values. If this is not done, the black and white key plate will carry relative values of all the colours of the copy which will de- teriorate and possibly destroy the colour effect of the actual colours printed from the colour plates. COLOUR SEPARATIONS FOR LINE WORK ORTHOCHROMATICS are not used for line work because they comprise tones and the line process does not reproduce any values except solids. If a copy is of such an actinic colour that it will not yield a necessary solid which may be etched into relief, a separation negative is required to produce the required solid. As the reds and browns naturally reproduce dark, it is only the colours like blue which need be so photographed. These may usually be reproduced sufficiently dark with a yellow or orange filter to permit their use for line reproduction, unless the colour is extremely weak, in which case the copy may have to be remade, or intensified by drawing over it with black ink. Colour separation is used to eliminate colours from copies for line work, especially in line colour plates. A line copy on a yellow or red background must be so photo- graphed as to eliminate these colours else it will all reproduce as a solid black with- out distinction between the black and the colour. If any colour to be eliminated is not defined in shape and form by the key colour of the copy, its shape and place in 196 ° THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING the copy will be lost in the colour separation. It then becomes necessary to define first its outline by drawing around it a fine black outline called a “guide line.” This outline serves as a guide for making the colour plate and is removed from the key plate before it is proofed. THE LUMIERE AUTOCHROME ALTHOUGH not a part of the photo-engraving process, the Lumiére autochrome is a helpful accessory, especially for making photographic colour guides. It is a process of colour photography which reproduces colours on a glass plate with a single exposure and is used extensively to supply a colour scheme for colour plates when the original object or copy is not available for the usual colour-separation method. The sensitized plates are of glass, to which a layer of dyed starch grains has been applied. These starch grains represent very nearly equal proportions of orange, green, and violet, and are protected by a waterproof varnish. Over this the film of colour-sensitive photographic emulsion is added and the plates are supplied in this form, ready for exposure. The starch grains are microscopically small and do not overlap. Intervening spaces are filled in with an opaque substance so that no light can pass through the plate except through the dyed grains. Exposure 1s made through the plate by placing it in the plate-holder with the glass side toward the lens. The image thus passes through the dyed grains before reaching the photographic emulsion. This causes a series of colour separations, each dyed starch grain acting as either the orange, green, or violet filter. When developed the plate is not fixed in the usual manner with hypo or cyanide but is immersed in a solution of potassium permanganate, or potassium bichromate and sulphuric acid. ‘This dissolves the silver which has been affected by light and de- velopment, the action being the opposite of hypo or cyanide. At this stage the plate is a positive instead of a negative due to the reversing action of the fixing solution. The unreduced silver remaining in the emulsion is now exposed to daylight or strong artificial light and redeveloped in the regular developer which gives the full strength of light and shade to the image. It is not only a positive in values, but is in full colour as well, due to the colours of the starch grains which show through the transparent areas of the positive. Any PHOTOGRAPHY OF COLOURS 197 areas of orange which have passed through the colour grains have been transmitted by orange grains only. If developed as a negative, the emulsion affected by this transmitted orange light would be opaque, but having been re-developed into a posi- tive these areas are transparent and are directly in line with the orange grains. When viewed by transmitted light, orange grains are seen through these transparent areas, thereby reproducing the colour which has passed through them. Similar action takes place through the green and violet grains and the result is a photo- graphic diapositive in full colour. A special yellow filter is used with these plates to restrain the highly actinic colours and render a better colour balance. While it is possible to make three- or four-colour reproductions of Autochromes, the starch grains and the opaque filling between them present a serious difficulty. The reproductions are usually very “grainy” in appearance and no satisfactory means has as yet been found to eliminate this trouble. | By extremely skilful manip- ulation in making the colour separations and in the subsequent finishing operations, interesting results are often obtainable. They have the distinct advantage of being direct colour reproductions and are consequently more accurately photographic, both as to image and colour, than hand-made originals or hand-coloured prints. CHAP Rh Ray rly PROOFING AND PRESSES ROOFS from photo-engravings are made by inking the surface of the plates and printing them on paper by pressure. To print in their true values, plates must be correctly inked and the printing pressure must be such that the ink will be transferred from the printing surfaces to the paper, duplicating the shape and size of each element of the printing area’ “Too much ink or pressure will create a spreading effect, causing the proof to appear too dark. Insufficient ink or pressure will produce a light proof of imperfect or incorrect values. Proofing methods in general use employ the “hand” proof press and inking roller. The press is called the “Washington Hand Press”’’ and although modern in construction and design, does not represent a radical departure from the fourteenth- century printing press. The presses of the early days of printing applied pressure by means of a screw-bearing operated by a hand lever, forcing the platen downward on the form. ‘The Washington hand press employs a similar hand lever, actuating a toggle joint which forces the platen downward by a wedging action of the parts and is designed to afford ample, even pressure, which is essential for proper printing. The platen is pulled upward to its normal position by coil springs. These presses consist of a heavy frame supporting the platen, toggle joint, and hand lever. To this frame a track is attached, carrying roller bearings, which support the press bed. ‘This bed is rolled into position under the platen for printing and rolled out again to remove the printed sheet and to re-ink the plate. ‘The bed is moved to and from the printing position by a crank. When a plate is to be proofed it is inked with a composition hand roller and placed face up in the centre of the bed, which is centre-marked for this purpose. A sheet of paper is placed on top of it and sheets of packing are laid on the paper to prevent direct contact with the steel face of the platen. The bed, with the plate, paper, and packing, is rolled into printing position and the lever is pulled over. This operates the toggle-joint mechanism and, by a wedging action, forces the platen down on the paper, creating 198 PROOFING AND PRESSES 199 the impression necessary to transfer the ink from the plate to the paper. The lever is released to its original position, the bed is rolled, the packing removed, and the printed sheet carefully removed from the plate. This is the principle employed for proofing, but the practice is not so simple, because of the variations in the nature of the printing areas and the different kinds of paper and ink used. In spite of the uni- form thickness of the metal used, the nu- merous plate-making operations tend to make it slightly uneven. The tones of the subject which may range from light to dark and which are produced by printing ATI PRT SHETR: Tot etree alma areas of varying sizes, also represent a fac- ROT INE AIMS SES SOBER DAA LEG Se tor to be considered. ‘The printing pressure must be equalized over all areas, and this is the purpose of the operation known as “making ready.” “Overlays” or ““underlays”’ of varying thickness are used over or under parts of the plate to in- crease or relieve printing pressure as required by the nature of the printing surfaces. Hand-press proofing is generally and preferably done before plates are blocked. Additional finishing or corrections are usually required after the first trial proof has been pulled and such work should be done on plates before they are blocked. A steel slab on the bed of the press, of the same thickness as blocking wood, provides the necessary solidity under the plates and brings the printing surface up to “type high.” This slab must be removed to proof a blocked plate. Ink distribution is a most important feature of proofing, or in fact of any printing operation. Printing presses are equipped with ink fountains, distributing rollers, and form rollers, but the hand press depends upon hand distribution and inking. Hand-press rollers are of composition, about three inches in diameter and from twelve to twenty inches long. The ink is stiff and is distributed evenly on the roller by spreading it out on an ink slab (usually a lithographic stone). The plate 200 —THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING is placed on another slab, alongside the ink slab, and between two metal strips the same thickness as the plate. ‘The plate is evenly rolled up with ink, the metal strips acting as ““bearers,”’ preventing the edges of the plate from sinking too deeply into the roller, which is soft, and also preventing the roller from touching the slab. PROOFING A LINE PLATE AFTER the line plate has been inked, an impression is taken to determine if any inequalities of impression exist. Usually a “flat’’ impression is sufficient on line plates, owing to their comparatively open Fig. 238. Inking a line plate. character, and underlays are seldom nec- essary. If bearers have been left on, they also will be inked and must be covered over unless they are to be allowed to print. A paper mask called a “‘frisket’’ is used to cover bearers or other dead metal to be masked out, and these are made by pulling a flat proof on news or manila paper and cutting out all the areas to appear in the finished proof. The remaining paper is then laid on the inked plate, leaving only the printing areas exposed. Friskets must be removed before each inking, and if they are to cover isolated areas, they may have to be in numerous pieces and carefully placed in position before each impression. The thickness of the frisket paper will create additional pressure on the areas Fig. 239. The inked plate in position on an underlay show- Fig. 240. Illustrating the frisket placed over the bearers. ing the bearers. PROOFING AND PRESSES 201 Fig. 241. Relling the bed into position for the impres- Fig. 242. “Pulling the press over” to make the impres- sion. The plate has been covered with the necessary packing sion. to create the right amount of impression. which it covers and although no ink will be transferred to the proof paper by these covered areas, the printing areas will be subjected to decreased pressure by reason of the frisket paper which surrounds them. ‘This must be compensated for by increasing the pressure on the printing areas with corresponding thickness of paper under them. This is the purpose of an underlay. When a frisket is placed on the dead metal around a plate and a sheet of similar thickness is placed under the print- ing areas, the metal is pushed up in the printing impression. This deflection of the metal, while slight, is sufficient to raise the printing areas enough to make a suitable impression and at the same time the additional pressure from the frisket paper is counteracted by the fact that there is no underlay under these areas of the plate. Line plates usually require no more make-ready than a simple flat underlay. Overlays are seldom required for them, but, when used, are prepared in the same manner as those for halftones, which are fully described in the follow- ing pages. PROOFING A HALFTONE ConsIsTING, as they do, of thou- Fig. 243. Removing the proof from the plate. sands of fine dots, halftones require 202 THE PROCESS AND PRACTICE’ OF PHOTO-ENGRAVING greater and more careful preparation for proofing than line plates. ‘The ideal print- ing condition is one that causes every dot to touch the paper with just enough pressure to transfer its ink to the paper and produce the printed impression. This requires not only an even flat printing surface of the plate, but a correspondingly even surface of paper. To meet this condition, “coated”? paper was introduced some twenty-five or thirty years ago. The pulp base of the paper is coated with a clay surface which fills in the inequalities of the pulp and when ironed out in the paper-making machine presents a very smooth, even printing surface. On this coated paper a normal squared halftone without its bearers would seldom require either underlay or overlay. Strips of metal, laid along the edges of the plate, serve as bearers and prevent the paper from bending on the edge of the plate and creating a heavy or dirty edge on the proof. This is called a “hard edge.” If the usual bearers are on a squared plate, a flat underlay is sufficient unless the subject is large or of more than the ordinary range of tone contrasts. An underlay is prepared by placing the plate, face up, on a sheet of paper a little larger than the outside dimensions of the plate and marking its position with a pencil. Three thin pieces of cardboard or metal may be used as guides in place of the pencil marks and are pasted to the underlying sheet so that they will touch one side and an ad- joining end of the plate. In this position, a proof of the plate is made, care being taken that the proof paper aligns with one edge and an adjoining side of the under- lay sheet. This alignment of the proof paper permits it to be registered in position later so it will coincide with the position of the plate. A knife cut is made in this proof, cutting between the edge of the printed area and the impression of the bearers. This incision is completely around the printed area except for a small piece at each corner to keep the inside piece from falling out. The inside piece, representing the printing area of the plate, is pasted to the back of the underlay sheet and its registra- tion with the plate is assured by first aligning the outer edges of this sheet with those of the underlay sheet. When in position, the corner pieces are cut through and the excess paper removed, leaving a double thickness at a point which will be directly under the printing area of the plate when it is placed in proper position with rela- tion to the guides or pencil marks. The excess paper may be used as a frisket. Large plates, or those of extreme contrast, may require additional thicknesses of paper pasted to the underlay, to PROOFING AND PRESSES 203 create additional pressure locally. This automatically relieves pressure from those areas not so built up. Registration of these additional thicknesses is made possible by the image showing on the proof used as the underlay. Silhouetted and vignetted plates require more elaborate underlays than squared plates due to the variations in size and shape of the printing areas. Underlays are only used to obtain uniform pressure on the printing surface. Lack of uniformity in pressure may be due to a number of factors. The frisket, slight variations in thickness of metal, and size are the principal ones, especially on plates which are so large as to require great printing pressure. A heavy impression will tend to squeeze the paper into the open areas between the printing surface and the bearers. ‘To relieve this condition, which occurs mainly on the outer edges of the printing surface, an underlay is made which is smaller than the printing area. This relieves pressure on the edges and equalizes the printing impression over the entire surface. Usually a sheet of thin tissue will suffice for such underlays. THE OVERLAY THE purpose of an overlay is to reduce printing impression locally, on areas which cannot be suitably relieved by an underlay. When the fine coated paper is used with squared plates, overlays are seldom required, because the size and shape of each halftone dot is controlled during the manufacturing process, and if each dot prints with just the right impression, no local variations of pressure will be needed. Vignettes must be relieved on the edges so that the pressure will decrease as the actual edge of the metal is reached, otherwise the plate will print with a hard edge. Overlays are used on such plates for this purpose. To prepare an overlay for a halftone, a proof of the plate is pulled after the underlay has been placed in position. Any areas requiring increased pressure will be apparent because they will print light on this proof. Areas to be relieved, such as extreme highlights or vignettes, will appear too heavy. The proof is laid face up on a piece of tracing paper and all areas to be made ready are indicated by out- lining them with a pencil. Additional thicknesses of paper are then pasted to the areas which are too light. These may be pasted to the face or the back of the proof, as all areas have been outlined on the back by the tracing paper. When the im- pression is made with the overlay in position additional pressure will be created by 204. THE PROCESS AND PRACTICE (OF PHOTO ENGRAVING these extra thicknesses of paper and will also cause a slight decrease in pressure on all areas which are not built up. Pressure may be still further relieved by cutting away areas of the overlay if required. To be properly effective an overlay must exert its varying pressure in exact regis- ter with the corresponding areas of the plate. ‘This is accomplished by making the sheet carrying the underlay double the size of the plate, allowing one half of it to remain under the plate and the other half protruding so that it can be folded over the plate when the impression is to be made. The overlay is attached to this upper fold, in exact register with the plate. When the plate is replaced in correct position after inking, the overlay will register with all impressions as they are made. The method of inking, covering the plate with sufficient packing, friskets, and pulling the impression is the same for a halftone as for a line plate—the overlay sheet usually being folded on top of the last packing sheet with a piece of press board laid over it. Overlays are never placed directly on top of the proof sheet, because the edges of the built up parts would cause too abrupt or sudden changes of pressure. The various thicknesses of packing between the proof paper and the overlay create a more gradual variation of pressure. Fig. 244. A detail view of a halftone overlay. The various thicknesses have been separated to show their character. = “ae a Fig. 245. A vigneited halftone, 150 screen, with 205 no make ready. 206 THE PROCESS, AND PRACTICE OF PHOTO-ENGRAVING Fig. 248. The overlay folded into po- sition on top of the packing directly above and in register with the tlates, ready for the impression to be pulled. Fig. 247. A make-ready sheet show- ing two halftones in position. The un- derlay is in position on the under side of the sheet in register with the plates. The overlay 1s shown 1n position on the other half of the sheet. The character of a halftone overlay and the amount of packing used is varied with the character of the plate and the nature of the proof paper. Flat subjects require less make-ready than those of strong contrasts. Elaborate vignetted sub- jects of strong contrasts and great detail require very extensive make-ready. The amount of packing is used not only to distribute the overlay pressure, but also to vary the amount of squeeze. Larger plates require a greater squeeze than small ones, as one pound of printing impression on a plate one inch square becomes a hundred and forty-four pounds on a plate a foot square. “The whole problem re- solves itself into making all areas press the paper just enough and no more than necessary to transfer the ink to the paper without change in shape from that of each part of the printing surface. As in all other departments, the result will indicate the judgment and skill of the craftsman. The type of make-ready and the amount of ink and pressure must be determined by the proofer. PAPER CoaTED paper was at one time as standard a material in the photo-engraving industry as zinc or copper. The demand for the use of dull-finish, uncoated, or PROOFING AND PRESSES 207 antique papers has gradually driven coated paper from its place of honour as the only suitable stock on which to print halftones. When halftones are to be printed on dull-coated, super-calendered, English or machine finish, antique or news paper, _ they should be proofed on the grade of stock selected. This offers the printer definite evidence or “proof” of what he may reasonably expect from such plates on the special grade of stock to be used. Coated paper, being smooth, takes a printed impression on its surface of each halftone dot. The uncoated or antique papers are of uneven surfaces with high and low spots. A halftone printed on the surface of such paper will print on only the high spots unless it is squeezed into it. Sufficient squeeze to force halftone dots down to the bottom of any low areas punches others quite deeply into the high areas. As a certain amount of ink rests on the sides of all dots as well as on their tops, the sides print where the dots are punched in and appear darker than normally. If the paper cannot be changed, the plate to be printed on these grades of paper must be changed, so all highlight dots are re-etched to a much lighter tone than when made for use on coated paper. Middle tones and shadow dots are also opened up and when the plate is squeezed into the paper, it does not print too dark, since allowance has been made for the gain in colour. Some of the antique-finish papers are soft and lend themselves to this squeezing of the plate into their inequalities, while others, which are hard, repel the plate and cause some dots to skip and fail to print. The impression will look broken or mealy and a more open, coarse screen must be used. News paper also requires a coarse screen because the paper, though soft, is so crude in texture that, under printing pressure, it will push up between the dots and produce a heavy, mottled im- pression as though the plate were filled up with ink. Coarse screens produce larger open spaces between the dots which, when deeply etched, prevent the appearance of being filled up. The printing surfaces of the highlight dots are larger than those of finer screen plates and do not punch into the paper so readily. The fact that such highlight dots are large does not increase the intensity of the highlight tones, because of the correspondingly larger areas of white surrounding them. The illus- trations which are shown in connection with this problem of paper are explained by their titles. Fig. 249. Photomicrograph showing the Fig. 250. Photomicrograph showing the Fig. 251. Photomicrograph showing the edge of a piece of newspaper. edge of a piece of super paper. edge of a piece of heavy coated paper. These are all cross-sections and clearly show not only the nature of the paper pulp itself, but also the contours of the surface on which the plates are to print. Cross-sections of coarse and fine screen halftones are represented by white outlines, in the same scale tion as the photographs were made—about 50 diameters. of magnifica ESS sq Fig. 252. Diagram showing the impression of a 120 screen halftone on a piece of coated paper. the surface of the dots only. Fig..253. Diagram showing a 120 screen halftone being printed on rough paper. The impression ts just sufficient to take the ink from the surface of the dots. Consequently some dots do not print as they do not come in contact with the low areas of the rough surface. Fig. 254. Diagram showing a 120 screen halftone being sufficiently squeezed into rough paper to make all dots touch. This creates excessive pressure from the high spots in the paper, causing the ink to spread and also taking ink from the sides of some dots. This will produce a heavy, muddy result. Fig. 255. Diagram showing a 65 screen halftone printed on rough paper. Although the printing area of each dot is larger than shown in the foregoing diagram, the increased space between dots will produce the desired tones of light and shade and will obviate the heavy, muddy result produced by the finer screen plate. Magnification in all four diagrams about 4o times. 208 PROOFING AND PRESSES 209 COLOUR PROOFING Proorinc colour plates on hand presses follows the same general procedure as for black and white plates, except in minor, though important, details. The make- ready is completed in the usual manner but provision must be made to register addi- tional printing plates with the impressions that have preceded them. ‘The register marks placed on the negative or copy appear in identical relative position on all plates. A very fine punch mark is made in the centre of each register mark on every plate before it is proofed. After the first colour is proofed, needle holes are punched in the proofs, exactly in the centre of the punch hole in the register mark. When the plate for the following colour is inked and in position on the press, the first colour proofs are registered to it by using these punched register holes. Needles are run through them and fitted into the corresponding punch marks in the second plate. The paper is gently pushed off the needles on to the plate, keeping the need- les in position until the paper is at rest, when they are removed. ‘This brings the register marks of the proof into register with those on the plate and assures register of all other areas. This operation must be repeated for each proof and each colour proofed, and may be employed for any kind of colour proofing on hand presses. Register of proofs is also obtained by using guides instead of register marks and needles. The guides are thin pieces of metal or card pasted at the side and one end of the sheet of paper on which Fig. 256. “Pinning a proof.” The wmpression from one colour the plate must be placed The proof plate having been made, the needles are punched through the centre ; of the register marks on the proof and fitted into corresponding paper is then placed against these guides register marks on the plate for the next colour, assuring register in the proofing. for each impression made. Although this may appear a more simple operation than the needle method, it is not used as often, because the plate, removed for inking for every impression, must be re- placed accurately in relation to the guides and each succeeding colour plate must be correspondingly registered. 210 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING INKS Tue colours of ink used for proofing colour plates depend upon the nature of the plates, the paper used, and the results to be obtained. Solid or Ben Day colour plates, as well as duographs, are usually proofed in such special colours as are required. Three- and four-colour process plates are proofed in “process” inks of practically standardized colours, of yellow, red, black, and blue. It is customary to print in this rotation, but if suitable inks are used, the printing order may be changed. ‘The yellow, or the first colour run, is usually an opaque ink. All succeeding colours should be translucent. The nature of the process is one employing certain colours which must produce additional colours. This colour ’ “production” is caused by the translucent nature of the inks which act like colour filters. Light passes through the printed impression to the paper, is reflected back to the eye, and creats a colour sensation. Opaque colours suffice for single-colour impressions but not for multiple use as they would prevent the light from passing through to the wnderlying colours with which they combine to produce additional colours. All process colour-printing employs the use of superimposed colours, and all types of colour plates, which print certain colours on top of others, to produce additional colour effects, should be printed with translucent inks. The process is called “subtractive” because it subtracts, by colour absorption, certain colour rays and transmits those which be- come visible by reflection from the paper. Green is not actually produced by over- lapping a film of yellow ink on a film of blue. Green is an elementary colour in white light and is simply the only colour which is not absorbed by the combined ab- sorbing qualities of yellow and blue. When white paper is not used for process colour work, the plates and inks must be modified to compensate, as much as possi- ble, for the colour of the paper. Opaque ink is used on paper of a colour which it is desired should not show through the printed impression. Cover papers, particularly, come within this class as their colours are often so strong as to neutralize the effect of a printing colour unless it 1s opaque. In order that the printer may be able to duplicate the results evidenced by colour proofs, “progressive” colour proofs should be made. In process work especially, PROOFING AND PRESSES 211 the complete colour effect depends on the amount, strength, and printed value of each colour used. A complete full-colour proof will not show the values of each colour, therefore single proofs and combinations of colours in the order of their print- ing rotation are made. A set of progressives of a four-colour plate set consists of a yellow proof; a red proof; yellow and red combined; a black proof; yellow, red, and black combined; a blue proof; and finally all four together. Progressives should be made of all colour plates, not only to show the printing values of each colour, but also to show the detail of each printing plate. OTHER PRESSES Tue ideal method of proofing any plate 1s the one that will simulate the eventual method of the print shop as closely as possible. Photo-engravings are made for more than the making of an exquisite proof. They must be printed on power presses, possibly from electrotypes or stereotypes, and with long runs. The proof Fig. 257. The Victoria press. One of the many types of heavy power presses used for colour proofing. 212 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING Ess; — a 4 Fig. 258. A Hacker press. A modern type of proofing press employing a cylinder instead of a flat platen for the impression. should be what its name implies, namely a demonstration of the printing qualities of the plate. Modern proofing methods and equipment are therefore being rapidly developed to simulate actual printing conditions, both as to paper, pressure, and ink distribution. Small printing presses of the platen type make a flat impression of the whole printing area at one time. Ink fountains and distributing rollers provide a uniform flow of ink to the form rollers, and such presses are usually employed for proofing process work. It is essential, especially on process work, that ink distribution be as nearly uniform as possible, and if a plate requires a reduction or increase in colour, it must be re-etched or burnished—not reduced by using /ess ink or increased by using more. Such procedure would cause a printer great inconvenience when attempting to print the plate in a form with others that had been made for normal inking. These presses are not generally used for proofing black and white work because of the usual presence of bearers on such plates, the additional make-ready required PROOFING AND PRESSES 213 on account of the thinner ink necessary for use in the ink fountains, and their smaller capacity as to size of plates. Rapid developments are being made, however, in the production of proofing presses operating on mechanical principles similar to those of the printing industry. These are of the “cylinder”’ press type, so called because the impression is taken with a cylinder instead of the flat platen. The paper is held to the cylinder by grippers and the flat bed carrying the plates or printing form travels in precise unison with the rotating cylinder. The advantage of the cylinder press is that only a small area of the paper on the cylinder is in contact with the printing form at one time and what would ag- gregate as a great printing pressure on a platen press is reduced to a minimum on a cylinder press. ‘This permits of greater actual printing pressure, which is often nec- essary. he proofing presses constructed on this cylinder-press basis are so simple and accurate in operation as to make them suitable for the pulling of the few proofs required by the photo-engraver. They are equipped with form rollers, ink slab, distributing rollers, and ink fountain, and produce proofs which are in every way comparable to the results obtained on the larger-power cylinder presses. CHAR DE Rwexlx BLOCKING RINTING presses for relief printing are designed to take forms or plates which are type high (.918 inch thick) and therefore all photo-engravings must be mounted to meet these requirements. Wood or metal may be used for the base on which the plate is mounted and the latter is preferable, as it affords a firmer and a more solid printing base. Wood, however, is more often used owing to its smaller cost, and the comparative ease with which it may be cut, planed, or trimmed. It is specially prepared for this purpose and is known as “blocking wood.” Maple, cherry, and mahogany are usually employed and must be kiln-dried to minimize the possibility of warping. In addition, the blocks are made up by glue- ing narrow strips together, running the grain of each strip at a different angle from that of the adjoining strip. For large plates, blocking wood is sometimes laminated; a number of thin layers being glued together with strips of muslin between them. The best kiln-dried or laminated blocking wood is supposed to be free from mois- ture, but even these blocks will warp on occasion and no method of permanently preventing this difficulty has been found. A method, seldom used, 1s that of soaking the wood in oil. It may take weeks for the oil to permeate the fibre of the wood sufficiently, but if no moisture exists in the wood when it is oil-soaked, it is not so likely to warp, because moisture cannot enter it after oiling. Blocking wood is obtainable in suitable thicknesses for use with metal of dif- ferent gauge, to insure the blocked plate being type high. It may also be used slightly thicker than required and planed on the back after the plates are blocked. Plates are fastened to the wood blocks by nails. Line plates and silhouetted and vignetted halftones usually have a sufficient margin of routed, low metal, through which the blocking nails are driven, but squared line plates or halftones must have the bevel or blocking edge extending beyond the printing surface. Nail- ing may be done by hand or a nailing machine. The hand method is slow and a 214 BLOCKING nail hole must first be drilled in the blocking margin of the plate to pre- vent the metal from being bent when the nail is driven. Motor-driven nailing machines are extensively used. They drill the hole and seat the nail by pressure, which may be regulated to prevent bending the metal. When blocking nails are seated too deeply, they draw the ad- jacent metal of the plate into the wood and lower the printing surface at that point. The usual blocking practice is to nail the plate to a slightly larger block, squaring it with one side of the block when placing it in position. 215 Fig. 259. Detail view of nailing machine. All four sides of the block are then cut with a table saw or “‘ buzz saw”’ close to the printing surface, accurately squared and aligned with the printing area, so that the plate will be in correct vertical or horizontal position on the block. Gauges and guides on the table saw provide means for accurate squaring, and specially designed 9d 6¢ “saw trimmers, blocks to extremely accurate dimensions. Fig. 260. A block line plate. Fig. 261. micro edgers,” and similar devices are manufactured to trim Many of these special trimming and A block halftone, showing the blocking bevel all around. 216 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING squaring machines are equipped with pica gauges to permit blocks to be trimmed to point measurements. This method provides blocks which are readily locked up in forms with other matter such as type or printers’ “furniture,” all of which are made up on point measurement. FLUSH BLOCKING Any plate blocked with the printing surface flush with the edges of the block is said to be “blocked flush.” It Fig. 262. Trimming a blocked plate on the table saw. is usually designated as “flush all around,” “flush bottom” or such other indication of the edge to be flush as will serve to indicate the style of blocking desired. The purpose is to eliminate the blocking bevel in order that the printing surface may be brought closer to type or other matter in a printing form. Line plates, vignettes, and silhouettes, or any plate which requires no blocking bevel, may be flushed by trimming the blocks as required. Straight bevelled edges must first be trimmed flush and then fastened to the block by other means than the blocking nails. This is done by “anchoring” or “slugging.” Slugs or anchors are usually brass ; screws, the heads of which are soldered to the back R@ - of the plate and anchored to the block with lead or \ solder. The number of slugs required depends upon . the size of the plate and the amount of flushing. They are usually spaced about three or four inches a apart and one half to one inch from the flush edge. Fig. 263. A small halftone blocked flush The block is drilled with a hole for each slug re- 7 quired, the aperture being slightly larger than the screw to be used. Each screw is soldered to the back of the plate with a blow torch; the drilled holes in the block are chamfered and the openings made larger on the surface than on the inside and the block is placed on the back of the plate with the screws extending into the drilled holes. Molten lead or solder is poured into the holes and anchors the screws in position. BLOCKING The screws are not quite long enough to project beyond the back of the block and the shape of the hole prevents the metal from pulling through. Although anchoring is extensively used, it is not always satisfactory. The anchors are firmly held in place in the block, Fig. 264. Diagram show- ing the method of “anchor- but they sometimes break away from the plate where they ing” o¢“stugging” a plate to are soldered. If this happens while the press is running, the 4%?” plate may jump off the block into another part of the form and cause considerable damage. Slugs are also liable to affect the printing qualities of a plate owing to the fact that the parts so anchored are held firmly in contact with the wood block, while other areas, even though they may appear to be in close contact with the wood, are liable to spring slightly. ‘This will cause a variation in the printing pres- sure and the spots where the slugs are soldered to the plate may show in the printed impression. This will be more evident on a smooth, light tint than on a heavy varied one. COMBINING PLATES ON BLOCKS SEPARATE plates are often blocked together on a single block, but the practice presents difficulties, therefore its possibilities and limitations should be thoroughly understood. Combining should be done, preferably, when the negatives are turned, and in many instances proper combining cannot be obtained in any other manner. Allowing sufficient space between for nailing margin, plates which are.to be blocked together are laid on the block in the required position which is marked on the wood. They are then fastened with a single nail and their position verified with a gauge or square, after which the nailing is completed. When they are to be joined close together, it may be necessary to cut parts of the nailing margin away, and if one plate must be fitted into another, the operation may present quite a problem. When accurate alignment and position are essential, such separate plates are usually set up by the proofer. ‘Their position is indicated on an underlay sheet and they are pasted down and held in position for a moment in the proof press. A proof is then pulled to verify correctness of position, and they are then blocked. ‘The paper to which they have been pasted remains under them but is cut away from exposed areas. If this additional thickness of paper makes the blocked plates more than type high, they must be planed down to proper thickness. 218 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING MORTISING AND NOTCHING Ir 1s often necessary to provide for the insertion of type matter on blocked plates, and an opening must be made through the block for this purpose. When such an opening is in the form of a hole, zmside any area of the block, it is called a “‘mortise.”’ When it is on an edge it is called a “‘notch.”” Plates are mortised after blocking and the wood must be cut away clean and accurately. ‘The area to be mortised is marked, and a small hole drilled in the wood to permit the insertion of the blade of a jigsaw, by means of which the wood is cut away as required. Mor- tises may be of any desired shape, but a shoulder should always be left to permit nailing the plate firmly on the edge of the mortise. Careful consideration should be given the nature of a plate and its subsequent use when it is to be mortised. Under ordinary conditions enough wood usually surrounds the mortised area to afford means for carrying the plate, but thin borders, blocked close on the outside and mortised close on the inside, are often insufficiently supported. The grain of the wood block will run with two sides and across two ends and such blocks will surely warp. To avoid this, special blocks are made of thin strips like a picture frame, the wood grain running with the plate all around. Another method 1s to allow a greater margin of wood outside the plate so as to afford a sufficiently strong base, but this can be done only when the nature of the printing Fig. 265. A jigsaw used for notching and mortising wood blocks. Fig. 266. Mortising a blocked line plate. BLOCKING 219 Fig. 268. A blocked line plate notched. 1 form in which the plate is to be used permits the extra out- side margin. Notches are made with either the table saw or jigsaw. Fig. 267. A blocked line plate Lhe area to be notched is indicated on the block and the saw aoe cut is made into the block in the required shape and size. When a plate is to be removed from a wood block, the nails should first be pulled out or their heads routed off. It is not advisable to pry a plate off a block as the wood is tough and the nail heads will be drawn through the plate, bending the metal. The nails may be started from the wood by slapping the block on a metal or stone slab, holding the face of the plate upward. This will start the nails sufficiently to permit their being pulled out. On small plates it is better to split the block with a chisel at a point where the nails enter and reblock it on a new block as required. ROUTING DOWN THE WOOD LarGE routed areas of plates should be correspondingly routed from the wood blocks, to prevent the bottom of the routed area from printing. This is as essential on large areas as is deep etching on some types of plates. For this purpose a router bit of large diameter is used and the wood is routed down about one quarter of an inch. This is not advisable on colour plates with widely separated areas as the wood may shrink and destroy register. METAL BASES THE most satisfactory base for a photo-engraving is solid metal, and modern practice in the printing industry is to use special steel blocks for making up the base of a form to a required size. These steel bases are of a thickness which requires the use of metal 11 points thick. The plates are bevelled and held in position on the 220 THE PROCESS AND PRACTICE OF =PHOTO-ENGRAVING steel bases by means of hooks. Metal for both zinc and copper plates may be obtained 11 points y thick in use on patent blocks. Plates made on thinner metal are backed up with lead and planed to this thickness. This operation is called “ back- ing up for patent bases.”’ The molten metal may be poured on to the back of the plate, which is laid face down on a Fig. 260. A frame block made idee grain run- Steel table, or it may be first planed to the proper Cee eee aa aa ae Nels and then soldered to the plate. In cases where patent bases are not to be used and where a metal base is required for the plate, it may be soldered or nailed to solid lead bases which are the full thick- ness of a wood block. The backing up of plates to make them 11 points thick or mounting them on full metal bases is usually done by the electrotyper, as few photo-engraving estab- lishments are equipped with the necessary apparatus for this work. The method of procedure is described in the chapter on Electrotyping. Eleven-point (“heavy metal’’) plates to be used on patent blocks are not usually mortised, as the steel bases on which they are mounted do not provide means for the insertion of other matter in these spaces. When material is to be inserted in any area of an eleven-point plate, it is soldered in, making a complete plate of the combined material. GHAPTER XX PELCTROTY PING LTHOUGH electrotyping is not a department of the photo-engraving in- dustry, it is so closely allied to it that a brief explanation of the process seems appropriate. An electrotype is a duplicate of the original, whether it be a photo-engraving, woodcut, or a form of type matter and plates. A mould is made from the original in either wax or lead, in a moulding press, which is designed to operate with a great amount of pressure. A wax mould is a layer of hard wax spread evenly on a metal backing to a thickness of about three sixteenths of an inch. The wax face is placed on top of the plate or form to be moulded and then squeezed by the moulding press under a pressure ranging from two hundred to four hundred tons, causing the wax to fill completely all the low areas of the original. Lead moulds are made in a similar manner except that a thin sheet of soft lead is used in place of the wax and the pressure employed runs up to about two thousand tons. The pressure is so great on either the wax and the lead moulds that they will spread in any of the low areas of the plate or around the edges of it unless means are provided to prevent it. It is for this purpose that bearers or strips of dead metal are allowed to remain on plates which are to be electrotyped, as they confine the wax or the lead during the moulding process. The mould is removed from the form, placed in an electro-plating bath, and a “shell”? of nickel, copper, or both is deposited over its entire surface. It fills in all the contours of the mould, and when it is about eight or ten one-thousandths of an inch thick, the shell is removed from the mould and backed up with metal, pro- ducing a duplicate of the original. Backing up is accomplished by laying the shell face down on a solid steel tray. Tinfoil solder is then laid on the back and molten lead is poured on, metal strips being placed along the outside edges of the shell to confine the molten lead. The 221 222 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING solder melts and when the molten metal is high enough, the plate is allowed to cool and is then shaved down to the required thickness. This method is also employed for backing up original plates but it should not be used on plates which have been patched or repaired with solder, as the heat of the molten backing metal will melt the solder and spoil the patching or repaired parts of the plate. STEREOTYPES ’ STEREOTYPES, or “Stereos” are not unlike electrotypes, in that they are made from moulds. The mould is made in a paper, wood, or composition “mat’’ material and a casting of type metal from this yields the printing plate. ‘ The moulds made in the composition are called matrices or “mats” and being of light weight and flexible are often used in large advertising campaigns for distri- bution by mail to publications. Stereos are then made from them. The castings from the mats are the stereotypes and can be moulded either flat or curved, owing to the flexibility of the mat. Mats are not of such fine texture as moulding wax or lead used in electrotyping, hence are not used except on very coarse screen halftones, line plates, and type. CARE Re Xx REPAIRS AND CORRECTIONS REAT skill has been acquired by some operators in repairing or patching photo-engraved plates. In fact, such remarkable results have been accomplished under the stress of emergencies that advantage is some- times taken of the ability of these repairmen or “doctors.” The most common repair job is fixing scratches. During the necessary wash-up of inked forms in the printing industry, plates are often scratched by pins or other hard substances in the cleaning rags. Some scratches so produced are too deep and too wide to warrant repair and it is more economical to replace such plates with new ones. Superficial scratches, or those which are not excessively large, can usually Fig. 270. Photomicrograph showing the dots destroyed Fig. 271. The metal raised up in the scratch and new dots by a small scratch as shown in fig. 271. partly formed. be repaired satisfactorily, but the operation is an extremely delicate one. Scratches destroy the printing dots of a halftone and these dots must be replaced. An en- larged illustration is shown which demonstrates the amount of damage done by asmall scratch. The repair is accomplished by raising up a tiny burr of metal with a fine pointed tool, in the exact position previously occupied by the dot which was 223 224 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING Fig. 272. Electrotype of a scratched Fig. 273. The original ‘scratched halftone. plate repaired. destroyed. ‘Then the raised metal is shaved off so that the surface will be flush and level with the printing surface of the plate, and it is shaped up with a tool so that the refashioned dots correspond in shape and size to the dots which have been destroyed. This may seem to be a simple operation, but it will be apparent that it is, to say the least, a tedious one, if the scratch is extensive. A scratch an inch long and thin enough to destroy only one row of dots will require the rebuilding of 120 dots on a halftone of 120 screen. If the scratch is wider and destroys two rows of dots, 240 must be reconstructed. The method of raising these dots, shaving them off, and shaping them is illus- trated, and the results obtained are shown by an impression from the completely repaired plate. The impression which accompanies it and shows the scratch is from an electrotype of the scratched plate before it was repaired. Damage to plates is often more extensive than a mere scratch and sometimes larger areas are dented or lowered by the presence of foreign substances on the form during an impression. These dents can be repaired if they have not too seriously destroyed the structure of the plate, and are accomplished by hammering the metal from the back until it is raised to the level of the printing surface. The necessary dots must then be replaced or re-shaped in the manner explained. | Repairs on line work are not so difficult as those on halftones, because of the coarser nature of the subject. The metal can be raised with a tool and shaped as required or a drop of solder may be used to supply the necessary metallic founda- tion which is then cut and shaped as necessary. REPAIRS AND CORRECTIONS 225 PATCHING THE proper procedure for making a photo-engraving is to make it in one piece. Any necessary combining should be done by means of negative inserting. It is often necessary, however, to remake a part of a plate or to combine two or more separate plates, and this is usually difficult of accomplishment. When comparatively large areas exist between the plates to be joined, they need only be blocked together, but if one plate is to fit tight into another, each must be cut with a degree of care and accuracy which may be likened to that employed by a jeweller. Cutting and fitting are not so difficult as are the actual joining of the plates and holding them in position on a block for subsequent printing. ‘Tight joints seldom afford means for holding the plates by means of blocking nails. ‘Therefore, they must be soldered together. A soldered joint is never as strong as the zinc or copper used, and when a soldered plate is printed, there is always a possibility of the solder breaking away under printing pressure. This method should be considered only as one of emergency and should never be practised as regular manufacturing procedure. CHA Re xe PREPARATION OF COPY OPY for the photo-engraving process should be prepared with a full knowl- edge of the part this copy is to play in the production of a successful print- ing plate. Too much is taken for granted by many users of the process, and unsatisfactory plates which are often attributed to lack of ability on the part of the engraver are due primarily to the copy. In the preceding chapters the process has been described in detailed operations and the reasons for the following suggestions regarding copy will be readily appreciated. Certain fundamentals should be borne in mind regarding copy for black and white reproduction. Copy should be clean and flat, black and white, and in proper proportion. This applies equally to copy for line plates and halftones, and any deviation will involve additional work and expense. COPY FOR LINE PLATES “CLEAN” copy means not only that it should be free from dirt, but also free from conflicting elements such as unnecessary pencil lines, ragged or imperfectly applied patches, and similar defects. Pencil outlines are usually made to lay out subjects for line drawings, and these should be removed after the work is inked in. They are sometimes so dark or heavy that they become confused with the ink lines of the subject and reproduce with them, destroying the values of lines or other elements by making them heavy or dirty. Ifa blue pencil is used for the preparatory layout it will cause less diffi- culty than black, because blue photographs almost as light as white and it will auto- matically photograph out when the line negative is made. The fact that so many imperfections due to faulty copy can be eliminated from plates by routing or tooling creates an erroneous impression as to what will and what will not reproduce. Line copies which have been altered by the addition of pasted 226 PREPARATION OF COPY 227 paper or cardboard form a large majority of the trouble makers. When pasted additions are thin and cleanly applied they present little or no difficulty. It should be borne in mind, however, that these additional thicknesses will cast shadows when illuminated by the electric arc lamps and such shadows reproduce as though they were drawn lines. When patches are close to actual lines, these shadows produce “paste lines” which often conflict with the genuine lines ‘and impair them. They must be tooled away, which, to say the least, does not improve the appearance of the drawn line. All copy should be flat, free from wrinkles and waves. Unfortunately many thin cardboard copies are rolled for convenience in transportation and are difficult to flatten out. The rolling often breaks the fibre of the card and when such copies are mounted on the copy board, preparatory to making the line negative, lines in- tended to appear straight appear wavy. It then becomes necessary to pin the copy at every uneven spot in order to flatten it out. Flaps or covers pasted to thin copies often cause wavy lines because the copy buckles where the flap is pasted. Rubber cement is suggested for affixing covers to thin copies as it does not buckle them. Black and white line copy is to be preferred, although dark brown or red may be used because their effect on the wet plate emulsion is the same as black. Every ele- ment comprising a line copy should be a solid colour and not a shade or tone pro- duced by thinning or diluting the ink or paint. If the colour of the copy is not black or of similar “ non-actinic’”’ colours, separation negatives will have to be made. The actinic colours such as blue and violet photograph in almost the same intensity as white paper and become lost unless restrained with colour filters and colour-sensitive plates. Elements which are not solid must be reproduced by the halftone process. The line process falsifies the reproduction of tones by pro- ducing only solids where dark tones exist in the copy, or else produces only whites where light tones exist. Pen drawings made with diluted ink and in which the lines taper off to a thin shaded point are typical of this type of “diluted” medium. Line plates can be made from such copies but they will not yield accurate reproductions. While the effect of the copy is delicate and pleasing because of the soft, graduated effect of the lines, the line plate will reproduce them as absolute solids and the effect will 228 THE PROCESS AND PRACTICE OF PHOJO-ENGRAVING consequently seem heavy and thickened. Line copies with tones of a wash between solid lines should be reproduced by the halftone process. Line plates can be made from such copies if the tone of the wash is light enough to disappear from the plate, otherwise it may reproduce as a solid and destroy the lines by obliterating them. The fact that red will reproduce like black has led some artists to use a carmine for line copy. There is so much blue in this colour that it photographs too rapidly to be successfully used. When red is used it should be dark or of a strong yellow Cast. The blue or purple used for typewritten letters as well as the blue tone of some signatures requires a separation negative to make them available for use. In some instances the use of these negatives can be avoided by rewriting the body of the letter, using a black typewriter ribbon or black carbon paper. The signature can be inked over with black ink, or a tracing made of it on tracing paper. The headings of letters often contain red or other black-producing colours. These can be separated by photography or may be painted out with white if they are not to be shown. Yellow paper or backgrounds of similarly non-actinic colours can be painted over with white to avoid the use of separation negatives. In the case of a design or lettering which has been made on sucha _ background, it is not necessary to paint out the background entirely. It is sufficient that a white line be painted alongside such areas to produce the necessary separation and the remainder can be routed away in the plate. The white water colour or Chinese white used to paint out colours is used by many artists to clean up edges of lines or other forms and causes great difficulty when improperly applied. It has a tendency to turn yellow with age and repro- duces like black, and when applied too thick or in lumps, it will cast a shadow like a paste line. When used on black backgrounds to produce thin white lines or stipples, it is liable to be of a tone or “‘shaded” on the edges. This fault is op- posite to, although in the same class as, the diluted black line. The effect on the copy of these tone areas is not reproduced on the plate because the tones will re- produce as pure white and the white areas gain in size. This produces a lighter, more open effect than that of the copy. White so applied to copies should be intense enough to produce a uniform white line or dot. The result in the plate will then appear of similar tone. PREPARATION OF COPY 229 Photographic prints used as line copies should be clean, sharp, and of strong black and white contrast. Conditions which are not always suitable for proper photographic procedure often result in photographic prints which are not sharp or distinct. Copies of book pages, old prints, and similar subjects must be absolutely sharp and distinct if good results are expected from the plates. Soft edges on lines or gray tones between them tend to impair the reproductive quality. Steel and copper etchings represent a difficult type of line copy. Their lines usually have a stain of yellow on their edges, which reproduces dark and thickens the lines, some- times running them together in a solid mass. Line reproductions from blue prints require separation negatives, and even then the results will be faulty unless the blue prints are sharp and clean in the white. The size of line copy has considerable effect on the reproduction and has been explained in detail in Chapter II. Closely spaced lines on large copies, reduced to small-sized line plates, become so close that the white spaces between the line “fill up” and if an attempt is made to force the etching of these whites, the fine lines will be undercut and eventually etch away, producing a “‘chewed”’ plate. Proportions remain unchanged in photographic reduction or enlargement. A copy which is ten inches wide and eight inches high will remain in this relative pro- portion through all changes of reduction or enlargement. Means for determining relative proportions are available in the form of mechanical devices, computing scales, and formulas. The simplest and most used means is the diagonal line. If the extreme areas of a line copy are in- dicated by border lines, a diagonal is Fig. 274. A diagonal drawn across any copy will indicate the sizes im reduction. drawn by means of a straight edge or a string, from a lower corner to the opposite upper corner. The size to which the copy is to be reduced is measured off on the base line, starting at the point where it is joined by the diagonal. The depth in this scale of reduction will be found by measuring the vertical distance from the base line to the diagonal at the end of the 230 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING new line of measurement. The diagram illustrates this method. A transparent celluloid sheet is on the market which is used for this form of proportional measure- ment. It is ruled in quarter-inch squares and has a swinging diagonal celluloid strip pivoted to the lower left-hand corner. Placed over a copy it enables the re- duced or enlarged size to be easily read. Copies which have no straight edges but which consist of irregular outlines should first have corner marks indicated in order that the diagonal may be accurately placed. Arithmetical proportion may also be used. When a copy ten inches wide and eight inches high is to be reduced to five inchés wide, the height may be determined as follows: 10:5 = 8: x. The product of the two inside num- ’ bers or “means” equals the product ce of the two outside numbers or ‘‘ex- tremes, hls Sex 58— "40, mer ica 1ox# = 40./ If 10 «= 40, then % = 455 on eae adjustable Baoan the size to be determined. copies. Proportion can be rapidly computed with a slide rule, which will become a valuable asset to one who will persevere in mastering its principles. A scaling device patented by George C. Benedict, operated on the principle of the slide rule but subdivided into inches and fractions, makes proportional computation extremely simple. ‘This device and a slide rule are illustrated and shown set to compute the arithmetical problem given above. Proportions may be changed during the process of negative turning by cut- ting the negatives and setting them up in different proportion as explained in “Negative Turning and Inserting.”’ It is advisable that a scheme or guide be made when this method is to be employed. This will indicate how the subject will work out in the changed proportions and will also serve as a guide for the nega- tive turner. When separate copies are to be combined to make one plate, their proportions should be carefully computed and a guide furnished for the set-up. Carelessness or indifference to specifications for set-up result in delays due to lack of definite in- structions or because negatives will not fit in the manner indicated. PREPARA LIONSOF: CORY 221 TINTS ON LINE COPIES Ben Day tints are sometimes laid on paper, cut out, and pasted into line copies, to avoid laying the tint on the plate. This practice is feasible if the tint is of the correct mesh or coarseness for the amount of reduction. Ifthe tint is to be equiva- lent to a 60-screen halftone on the plate and the copy is prepared for reduction to one half size, the tint on the copy must be equivalent to a 30-screen mesh. Should A A se" yi NORE aaa ne 3 3 ils sl an yl iil ie i fi et suelo Fig. 276. A slide rule, set for the proportion of 10 reduced to 8. oom the same copy later be reduced to one ke Zann quarter size, the tint would be equiv- , yo EG alent to 120-line screen on the plate. It aa Agate opens NK is, therefore, advisable to lay tints on EXPLANATION: — Whatever position the inner circle is in all numbers, up to 99, in exact Jine on inner and outer scales bave the same ratio. EXAMPLE: — Copy is 15x 8% inches to be reduced to 9 inches sm long. What is the width? Place 15 (length) on inner scale exactly in plates rather than on copies, unless but =" \\ one scale of reduction is to be used and line with §% (width) on the outer scale, In line with 9 _ {reduced length) on inner scale find 5¢ (reduced width) oo ° . on outer scale. Reduced size O is 9 x S$ inches. ! a sult ab l € t In C Gc mploye d A SUMMARY:— When length and width of any rectangle 4. \@ arein line on the two scales then reduced or enlarged lengths and widths can be found in line on the eorresponding scales. Lengths an one seale and widths an the other COPIES FOR SPECIAL COARSE-SCREEN HALFTONES ALTHOUGH the 55-, 65-, and some- times the 85-line screens usually print FE esc iciie, aise sci for jhe proportion of, 10 satisfactorily in newspapers, much reduced to 8. coarser screens have been used with greater success. The process of stereotyping is liable to cause loss of definition in halftones for newspapers unless they are very open and deeply etched. Plates are often made for this purpose, of 40, 30, and even 25 lines to the inch. Halftone screens are not made coarser than 50 lines, so a special method is employed to obtain the coarser mesh. For a 4o-screen plate, a halftone negative of 120 screen is made, one third the size of the final plate. A photographic print is made from this negative, enlarged four or five times. Considerable work may be done on such an enlarged “screen print” by painting areas pure white, drawing in black lines or larger solid 232 ‘THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING areas, and then making a line plate of the required size. This reproduces all dots of the enlarged halftone screen print, as well as the blacks which have been drawn in, and all areas which have been painted white etch away as though the plate had been silhouetted or tooled by hand. ‘ ALLOWANCES FOR “BLEED” PLATES are often made which must print beyond the trimmed niargin of the sheet. Cover designs on magazines often employ this effect, the printing extending cleanly to the edges. This result is obtained by making the plates about one eighth of an inch larger than the trimmed size and trimming off the excess edge. Trimming the printed sheet and cut- ting off part of the printed edge is called a “bleed.”’ Copies for this pur- pose should have the required added margins only on the sides which are to bleed. LINE COPY FOR COLOUR WORK SINcE colour effects are applied by hand on colour plates: by painting in or the Ben Day process, they should be ab- sent in the copy. The copy should be in the form of a key drawing, supplying all pi. 258 4 “Certone.” Note the very coarse screen combined with line work throughout. line work and outlines. When colour areas are to appear, they should be indicated by thin black guide lines, which are re- moved during the process of plate-making. ‘‘Colour sketches” should be furnished separately from the copy. A separate sketch or a colour indication on tracing paper may be laid over the copy or a flat proof of the key plate may be coloured up as a guide. Colour areas are sometimes indicated on the copy by the use of a light blue wash. Since this reproduces like white it will not appear in the line negative. Yellow, red, and similar colours painted in on copies cause delay and additional expense when improperly used. When their use is advisable in order to denote the shape of colour areas, they should be separated from the black areas by means of fine whzte PREPARATION OF COPY 233 lines. ‘This affords a guide for separating the areas on the plate, but without this guide both areas will run together as they both photograph so as to produce solids. This white guide line is removed from the plate by painting it in before etching. Painting in is always necessary when colours are to be fitted close together, because in the mechanical operation of printing it is not always possible to strike one colour in exact register with another. A slight overlap must be provided to allow for varia- tion of register in printing and this is provided for by painting in on the plates. Separation negatives do not suffice unless such colours are completely surrounded by other areas of black or fine black guide lines, as their shape would be lost when the colour is eliminated by photography. PREPARATION OF COPY FOR HALFTONES PRACTICALLY all of the suggestions relating to line copy apply to that for half- tones as well. Cleanliness is more necessary on halftone copy because routing and tooling are not always practicable on halftones and no means exist for removal of spots or imperfections, except to reshape the dots in a manner similar to that employed for fixing scratches. This nearly always shows when imperfections are prominent and, therefore, halftone copy should be free from imperfections. Colours on copy for halftone reproduction have been explained and the means for reproducing their relative values have been covered in Chapter XVII. Pasting on halftone copies should be done so that edges will blend with the re- mainder of the surface, otherwise shadows will reproduce in the plate. Blending is accomplished by shaving the edges of the paster at the point of joining, so that it will be thin and will not cast ashadow. Even the joint should then be retouched and obliterated as much as possible. This is a procedure which is difficult and seldom accomplishes the desired result. Pasting the parts together and then rephotographing the joined prints is the best way to make the joints invisible. This furnishes a new print all in one piece on which joints can successfully be retouched. Combining by means of negative inserting has been explained in Chapter LX, but the same principles of proportions must be considered as on line copies. Pro- portions of copies for halftones cannot be so readily changed by setting up nega- tives because of the difficulty of making suitable joints in the screen negatives. 234. THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING Changes in proportion can be effected by “cropping” but this being the same as the actual cutting down of the copy may eliminate important parts of the subject. Retouching photographs by brush or air brush should be done with a colour which corresponds exactly with that of the photograph. If a photograph is of a warm black and retouching is done in a cold gray, the latter will reproduce lighter than the warm tones of the original and appear'as a different tone. This is espe- 6 cially true in “spotting,’’ where small white specks on the copy are touched in with black or gray. Unless the colour of the medium corresponds with the colour of original print, the retouched spots will show almost as clearly as though they had never been retouched. White areas of halftone copy do not reproduce pure white unless the screen is cut away during the finishing operations. When such white areas are to be re- tained, they should be clean. All marks or dirt on them will show in the reproduc- tion. This also applies to white areas at extreme edges, which are often marked with dimension lines used to indicate sizes for plates and other instructions. Dimensions should always be indicated in areas which are well outside of the areas to be included in the reproduction. Pencil lines indicating crop marks, rectangular lines indicating squaring up, or other marks indicating sizes or cropping should be outside the actual work limits. It is a wrong practice to draw pencil lines on copies to indicate the area to be included, since such lines will reproduce. They are seldom accurately drawn, and the plate must either be cropped inside of them to eliminate them or they must be ‘“‘run out” of the plate by tooling or other methods. INDICATING SIZES DIMENSION marks indicating sizes need be on one dimension only, unless plates are to be cropped or set up. In such instances it is advisable to mark such copies in the following manner: “Reduce to six inches wide and crop to eight inches high.” This indicates to the engraver that the subject may be cropped to yield the size de- sired, but it is advisable that the position for the crop also be determined and marked, else some essential feature of the copy may be cut off by arbitrary cropping BRE bARATION OF CORY 235 to get the required size. When negatives are to be combined, both dimensions of the finished plate should be given, for example: | “Reduce each to four inches wide and set up to six inches high.” A sketch or guide should be supplied showing the manner in which such negatives are to be combined. It is always advisable to indicate the size of the longest dimension. Copies which are long and narrow, like a border for a plate 24” x 12’, should be marked for reduction to 12 inches, not to a width of 2§ inches, as a slight error in measuring on the short dimension would make a great difference in the size of the long one. One- sixteenth-inch variation on the 2§’’ width would amount to nearly one third of an inch on the twelve-inch height. Dimensions for ellipses should be given both for width and depth, unless the copies are drawn in the shape of the ellipses desired. It is customary to consider the dimension first given to mean the width desired. Thus a size marked 10” x 8’’ would be taken to mean ten inches wide and eight inches high. Width is the name given to the measurement from left to right or horizontally. Height or depth is the name given for the measurement from top to bottom or vertically. Plates to be made in very small sizes such as, for example, one quarter of an inch and, in fact, any sizes up to about one inch, should be indicated on the copy in an enlarged scale. When copies are focussed for reduction on the ground glass of the camera, the image appears on the front of the glass nearest the lens. “The measurements are made on the back of the glass, and its thickness makes absolute accuracy almost an impossibility. A plate one quarter of an inch wide from a copy one inch wide is one fourth actual size. If dimension lines four inches apart are reduced to one inch, the scale of reduction will be the same, but accurate measurements will be more readily made. Such copies should be marked: “‘Reduce to one inch between marks.” Indications of sizes specified, for example, as “one quarter reduction”, are con- fusing and the question immediately arises whether the plate is wanted one quarter size or one quarter off. It is better that actual sizes be given or at least clearly indicate “‘reduce to one quarter size.”’ 236 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING MULTIPLE COPIES FOR COLOUR PLATES WirH a view of saving the expense of separating colour areas on line or Ben Day colour plates, separate copies are sometimes drawn for each colour to be used, but this practice often results in a greater final cost than if the copy were prepared in one piece. The practice of making colour plates from one-piece copy is to make multiple prints from the same negative to assure perfect register. If copies for each colour are separate, register may be impaired due to stretching of the negatives when they are turned. ‘This can be avoided by coating them with two or three films of rubber and collodion before turning. The safe way is the use of the prism to reverse the image and make negative turning unnecessary. If the copies are for both line and halftone on one set of plates, difficulty will be encountered. The size of the image photographed through the halftone screen will not be the same as when the screen is removed for line work and refocussing must be done. If an error in focussing occurs, register is lost and the work must be done over again. Separate copies may be used for different colours, when properly prepared, and for subjects which lend themselves to this method, but experience in this practice and familiarity with all manufacturing details are essential to its success. It is used sometimes for a special method employed in process work, known as the “blue- print”’ process. MULTIPLE COPIES FOR PROCESS COLOUR WORK Txis method is employed when the original is not in colour and the plates pro- duced by it are a modification of the “fake”? method. A continuous tone negative is made from the monochromatic copy and four blue prints are made therefrom. These should be made with the fibre of the paper running in the same direction on all prints and should be washed and dried at the same time. This is necessary be- cause the paper stretches or shrinks when drying and if conditions are identical for all prints, changes will be uniform in all. These blue prints are mounted on card stock with rubber cement which will not change their size, and each is then retouched to represent the colour values for each colour plate. It is a fake method whereby the values are supplied by hand PREPARATION OF COPY 237 in the retouching operation. Artists who are experienced in this work can produce very acceptable imitations of colour-separation values. Four-angle halftone negatives are then made from these separate copies as in the usual method for fake plates, and comparatively little work will be required on the plates as compared with the amount necessary, if all negatives were made from one copy. CHAP RE Roi SPECIAL METHODSAND OTHERSP ROG Resta. HERE are many “tricks of the trade”’ in photo-engraving which are some- times dressed up in fancy names and exploited as “discoveries.”” Notable among these is the process of making very coarse screen plates by enlarging from small halftones or prints from small halftone negatives. The method of pre- ibe, paring copies for this process has been described in the preceding chapter, and the resultant plates have been called by all sorts of special names— usually prefixing the name of the en- graver to the word “tones’’—giving ““Smithtones,” “Jonestones,’” and so on. They have also been called “Quar- tertones”’ though they are halftones just as much as any other screen plate. In addition to being made from enlargements of halftone negatives, they are also made by enlarging small halftone proofs. They may be made in any manner which suggests itself so | long as the result is a plate of the desired coarseness of screen and with detail added or taken away as required by the copy. Technically, all such plates are line plates, “asethemactual Fig. 279. A mezzograph plate. plate-making employs no screen. ‘The screen itself enters into the manufacture of the copy, not the plate. 238 SPECIAL METHODS AND OTHER PROCESSES 239 | THE MEZZOGRAPH Q Turis type of plate is unfortunately not entirely practicable for commercial use. It is a halftone but made with a screen which has a grain structure instead of cross lines. ‘The result is an interesting texture not unlike the box grain in appearance, but in etching and re-etching, the extremely fine grains in the highlights etch away, leaving open spaces which give a coarse grainy appearance to the highlights. It is also liable to undercut in etching, which makes it a bad plate for electrotyping, and the nature of the grain structure makes it unsuited to reproduce all types of copy. It is sometimes used to make colour plates to be run as extra colours with four-colour process plates as it has no screen angle and does not make a pattern. Mezzograph screens are made in various degrees of grain fineness from the ce equivalent of a 1oo-line screen up to 175. The making of the screens is a comparatively simple mat- ter as the grain is a natural one. The screen glass is coated with a resist, which is treated so it will ‘ ‘reticulate,’ forming the smooth, even, grainy struc- ture. In this condition the glass is etched with tec J hydrofluoric acid. No opaque filling is required be- a tween the grains as their form is such that light is refracted in passing through them and forms corre- sponding grain structures of highlights and shadows on the negative. SPECIAL SCREENS Ir ONE cares to experiment, many varieties of effects may be produced by using special screens. These screens Fig. 280. A halftone may be made photographically by first making drawings of the made with a_ special Screen. desired line effect and then making line negatives from them. ‘The 240 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING line negatives can then be used as screens. ‘The illustration in fig. 280 was made from a special screen produced in this manner. PLATES FROM TRANSPARENT PROOFS Many occasions arise where plates must be made to fit existing plates, embossing dies, type matter, and similar printing mediums. ‘They may be made by using proofs on thin translucent paper as negatives. The key plate supplied is carefully proofed on French folio stock and then bronzed with bronze powder or any other suitable substance to make the impression thoroughly opaque. Used as a negative, the translucency of the paper allows the light to pass, but the opaque impres- sion absorbs it and the metal print is then etched in the usual manner. The result is a plate which will print in all of the open areas of the key plate. It produces a “hair register’ job, however, as it does not provide for any lap. This method is es- pecially useful in making printing plates to fit embossing dies. PLATES FROM HALFTONE POSITIVES Tuts method is seldom used, but at times it may prove a simple means of meet- ing a difficult problem. A typical instance would be a halftone key plate requir- ing a colour plate for certain highlights but which is not to run under any shadow tones. Considerable hand work would be required to produce such a plate, but if made from a halftone positive it would automatically adjust itself to print only where desired as it would be negative to the key plate. The reason for making such a plate would be where printing requirements demanded running two colours wet as in the Saturday Evening Post. A heavy colour cannot be successfully printed on another heavy colour which has just been run, hence the demand by many publications that the total of both colours printed together must not exceed a whole tone. A three-quarter tone can be run on an underlying one-quarter tone and vice versa, so the plate made from a halftone positive regulates this to a nicety in some instances. ‘The screen angles must be arranged as for duographs else a pattern will result. MAKING NEGATIVE PRINTS FROM NEGATIVES REVERSAL of values in metal printing, yielding negative prints from negatives is often done during development of the print. The result is as though the print DEL Cla VIE REODS AND OTHER PROCESSES 241 had been made from a positive of the original negative. There are many methods, but the one most used is the hydrochloric acid developer. A print is made on zinc in the usual manner with bichromated albumen and an ink top. After development it is completely rolled up again with etching ink. It is then redeveloped with a weak hydrochloric acid solution which dissolves the albumen of the original print but does not affect the ink which has been applied in the second rolling up. The result is the reversal of the original print and it is then topped up and etched. This method is sometimes used to produce colour plates, but it gives hair register with absolutely no overlap. In fact, even though the print may register to a hair the etched plate may not fit, due to slight etching away of the edges. INTAGLIO PLATES InTaGLio plates have the image etched or engraved into the metal. They are inked all over and wiped or scraped on the surface before the impression is pulled. This leaves the ink 77 the plate and a heavy impression on soft or damp paper pulls the ink out of the depressed inked areas. Photo-engraved intaglio plates may be made for either line or halftone, but the metal prints must be made from positives or positive prints. Etching is not nearly so deep as for relief plates; only just enough to hold the ink. If there are large sunken areas, a grain is usually dropped in them and etched to give the bottom a slight “tooth” so that the ink will not wipe out when the plate is surface-wiped. ROTOGRAVURE RoToGRAVURE is an intaglio process but differing in one essential from an in- taglio halftone. The rotogravure tone values are produced by dots which are all uniform in size but which vary in intensity. In the intaglio halftone, as in the regular halftone, they are all of the same intensity but vary in s7ze. Rotogravure is printed from cylinders of copper. The original copy is first photographed on a continuous tone negative and a diapositive (transparency) made therefrom. The rotogravure screen is the opposite of a halftone screen, being com- posed of transparent lines with opaque intervening spaces. The width of the transparent lines is much less, proportionately, than on a halftone screen. A piece of carbon tissue (bichromated gelatine on a paper base) is then printed through the 242 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING screen. [he screen has no cover glass and is laid in absolute contact with the car- bon tissue. The result of this operation is to make a series of crossing insoluble lines on the tissue. Next, the diapositive is printed on the tissue, on top of the insoluble image of the screen. The various tones of the positive render the gelatine insoluble in varying degrees according to the tones of the positive. This double- printed carbon tissue is then moistened and wrapped around the copper cylinder and squeegeed into tight contact. Development in water will permit the removal of the paper backing leaving the gelatine around the cylinder to act as a resist. Instead of washing away the soluble gelatine, the whole cylinder is subjected to various baths of water and iron perchloride. This tends to wash away the soluble areas, but at the same time penetrates the gelatine and begins to etch the surface of the cylinder. The degree of penetration is regulated by the strength of the solu- tion and the degree of solubility of the gelatine. The effect is that the highlights of the positive, transmitting the most light, have created the greatest degree of in- solubility. In these areas the acid penetrates less and does not etch so much. Correspondingly, the shadows of the positive, transmitting less light, leave the gelatine more soluble, and the greater penetration of the acid etches more than in the highlights. The insoluble crossed lines do not etch at all and produce walls of metal surrounding the dots, which are etched like cups into the plate. These oper- ations produce highlight dots which are shallow and will hold but little ink, while the shadow dots are deep and hold more. The printing from the cylinder is done with a very fluid ink, in which the cylinder rotates. A steel, razor-edged blade, called a “doctor,” scrapes the ink from the surface, leaving it in the cups. The ink is semi-transparent, resulting in tone dots which vary in intensity, according to the depth of the etched cup. They are all of the uniform size, established by the walls surrounding them which were made with the screen. FORMULAS Formulas are given only to demonstrate the chemical reactions in the different operations. They are often modified and greatly changed by different operators. I. Glass Cleaning Solutions (a) To remove gelatine films from negatives: Water 9 oz. Nitric acid 1 oz. (b) ‘To remove collodion films from negatives: Water 6 oz. Nitric acid I oz. (c) To clean new glass: Water 2 oz. Hydrochloric acid 1 oz. II. Substratum (albumen) Water 32 oz. White of one egg. III. Collodion (a) Line negatives: Ether 35 oz. Ammonium iodide 150 grains Alcohol 35 oz. Calcium chloride 40 grains Gun cotton I oz. (b) Halftone negatives: Ether 24 oz. Ammonium iodide 80 grs. Alcohol 24 oz. Cadmium iodide 120 grs. Gun cotton 240 grs. Calcium chloride 25 grs. Strontium chloride 20 grs. IV. Silver Bath (a) New bath: To a sufficient quantity of distilled water add enough silver nitrate crystals to test 40°. Add a few drops of nitric acid until the solution is just acid to litmus paper. (b) Old bath: Pour the bath into an evaporating dish and let it boil until the alcohol is driven off. Cool and add silver nitrate crystals and water to again test 40°. Filter and use. V. Developers (a) Line negatives: Iron sulphate 2 oz. Alcohol $ fluid oz. Acetic acid, glacial 1 fluid oz. | Water 20 fluid oz. (b) Halftone Negatives: é Iron sulphate 480 gr. Acetic acid, glacial 240 minims Copper sulphate 60 gr. Water to test 22° with hydrometer 243 244 FORMULAS VI. Fixing Solution Potassium cyanide I oz. Water 20 oz. VII. Intensifiers (a) Line negatives: (1) Lead nitrate 250 grs. Acetic acid, glacizl 200 minims Potassium ferricyanide 260 grs. Water 20 oz. Rinse in nitric acid 4 oz. and water 20 oz. (2) Mercury bichloride 1 oz. © Ammonium chloride 1 02. Water 20 oz. (3) Copper sulphate 500 grs. A Water to oz. B_ Potassium bromide 125 grs. Water Io oz. Mix A and B when dissolved. Wash well and apply Silver nitrate I oz. Water 20 oz. (b) Halftone Negatives: Use formula (3) above. VIII. Bleaching Solution Potassium iodide 40 grs. Iodine resublimed 20 gts. Water 20 oz. IX. Cutting Solution Potassium cyanide I oz. Water 20 oz. X. Blackening Solution Sodium sulphide 1 oz. Water 20 oz. XI. To Remove Stains Nitric’acid(C. Pieroz: Water 50 oz. AIT. Stripping Collodion Ether 32 oz. Gun cotton I oz. Alcohol 32 oz. Castor oil 1 oz. AIII. Rubber Solution Rubber cement 3 oz. dissolved in benzol 25 oz. XIV. Soaking Solution for Removing Negatives from Glass Weak solution of acetic acid XV. Sensitizing Solution for Line Work on Zinc White of one egg Ammonium bichromate 16 gts. Water 16 oz. Ammonia 6 to 8 drops XVI. Inking-Up Line Prints on Zinc Special ink used AVI. AVI: XTX. XX. AXXTI. XXII. Aa lly. IGN PG XA XXXVI. Aas, LOD ABEE FORMULAS Developing Line Prints Water and cotton Enamel Printing Solutions Le Page’s clarified glue 7 oz. Ammonium bichromate 6 drams Albumen of 8 eggs Dye Solution for Fish Glue Prints Methyl violet dye 1 oz. Dry Enamel Process Bichromate of ammonium 125 grs. White sugar powdered 270 ers. Chromic acid 80 grs. Etching Baths for Zinc (1) First bite Nitric acid, I oz. (2) Deep Etching Nitric acid, 2 oz. (3) Fine Etching Nitric acid, 13 0z. . Copper Etching Solution Iron perchloride Process Developer for Dry Plates Water 80 oz. Hydrochinon 2 oz. Potassium carbonate 6 oz. Fixing Solution Hypo 13 lbs. Acid Fixing Bath Hypo 9 oz. Water 60 oz. Reducer 10% Sol. Hypo 1 part Intensifier Mercury bichloride 4 oz. Blackener Ammonia I part Water 16 fluid oz. Ammonia 8 drops Water 20 oz. Albumen (2 eggs) Ammonia 20 minims Water 10 fluid oz. Water 99 oz. Water 80 oz. Water 80 oz. Water to test 42° Baumé Potassium bromide 14 oz. Sodium sulphite 4 oz. Water 60 oz. Potassium metabisulfite 6 drms. Chrome alum 3 drms. 10% Sol. Potassium ferricyanide 1 part Water 60 oz. Water Io parts 246 FORMULAS XXIX. Developer for Orthochromatic Negatives Water 80 oz. Sodium sulphite 4 oz. Metol 60 grs. Sodium carbonate 6 oz. Hydrochinon 240 grs. Potassium bromide 30 grs. XXX. Developer for Chloride Prints Water 40 oz. Hydrochinon 60 grs. Metol 14 grs. Sodium carbonate 4 oz. Sodium sulphite 3 oz. Pot. bromide, sat. sol. 40 drops XXXI. Bleach for Blue Prints Saturated solution sodium bicarbonate and water XXXII. Bleach for Silver Prints Saturated solution bichloride of mercury and water Sufficient alcohol to flow freely XXXIII. Bleach for Bromide Prints Saturated solution potassium cyanide I oz. Water 16 oz. Iodine 4 dram Add cyanide to iodine until solution is clear XXXIV. Table of Etching Depth in ypoy of an inch BOER EN 55 85 100 100 120 133 150 175 i ZINC ZINC ZINC COPPER | COPPER | COPPER | COPPER | COPPER Highlights 8.0 4.6 a2 2.6 es 2.3 2e0 1.8 Middle Tones| 5.0 ant 2.2 1.8 1-7 ie: 1.4 1.0 Shadows ce) oa 1.4 1.0 0.9 0.9 0.9 0.6 BIBLIOGRAPHY Abney, W. de W. A. “Treatise on Photography.” Chap. on Photo-Litho Transfers; Photoengrav. and Relief Processes; Half Tone; Photo Collotype. Tenth edition. N.Y. (1916) Abney, W. de W. A. The Photography of Colour (Journal Soc. Chem. Ind. 1gor) Abney, Wilkinson et al. “Bichromate Salts in Photography.” 28 pp. pap. London Ames, J. S. “Elementary Discussion of the Action of a Prism on White Light”’ (1905) Amstutz, N. S. “Photo-Engraving.” Revision of Jenkins—rewritten. Third edit. Chicago. 440 pp. illust. Anderson, Paul Lewis “Fine Art of Photography”’ (1880) Anderson, Paul Lewis “Photo-Mechanical Processes and Guide to Colour Work.” N. Y. Illust. Andrews, eC. “Colour and Its Application to Printing”’ (1911) Ault & Wiborg Co. “Zincology”’ (1910) Austin, Arthur C. “Practical Halftone and Tri-Colour Engraving”’ (1898) Bastelaer, Rene Van La Rivalité de la gravure et de la Photographie et ses conséquences; Etude du role de la Gravure en taille—douce dans l’avenir (Photography and Engraving) (1901) Bayley, R. Child: Editor “Photography Annual” (1891-1899 only) London. Contains a yearly review of pro- cess in photo-mechanical processes by Thomas Bolas Brothers, A. “Photography: Its History, Processes, Apparatus, and Materials.’’ Includes val- uable summaries of principal processes—Meisenback, Photo-Litho, Swelled Gelatine, Collotype, Gravure, etc. 367 pp. Several examples of processes as plates. Second edit. Revised. (1899). London Blaney, H. W. “Photogravure.” 43 pp. (1895). N. Y. 247 248 BIBLIOGRAPHY Boch, Joseph “Zincography.” Translated by E. Menken. Gives working detail of methods. (1886). London Bolas, Thomas “Application of Photography to the Production of Printing Surfaces” (1878); “Re- cent Improvements in Photo-Mechanical Printing Methods” (1884). Papers read before Society of Arts and pub. in the Society’s Journal Vols. XXVI and XXXII Bolas, T. . “Handbook of Photography in Colours” (London, 1900) Broun, Edward Lumsden “On Direct Colour Photography” (1908) Burton, W. K. “Practical Guide to Photographic and Photo-Mechanical Printing Processes.” Chapters 2 and 35 to 52 summarized, with working details and formulas all the known processes from 1842 to date of publication. 415 pp. canvas. Second ed. revised and enlarged. (1892). London Burton, W. K. and Pringle, A. “The Process of Pure Photography” (1889) Cole, R. S. “A Treatise on Photographic Optics” (1899) Cox, Arthur “Half Tone Printing.” London: Penrose Cronenberg, W. “Half Tone on the American Basis.’ 160 pp. illust. (1896). London Cundall, Joseph “Brief History of Wood Engraving” (1895) Denison, Herbert “A Treatise on Photogravure” (by the Talbot-Klic Process). 140 pp. illust. London before 1897 Dodge, Ozias “Experiments in Producing Printing Surfaces” (1908) Douthitt Diaphragm Corp. “Process Negative Making” (1921); “Directions for Douthitt Diaphragm System” ““Stunts’ in Photo Engraving” Detroit. (1922) Drifheld, Vero C. The Hurter and Driffield System: Photo Chemical Investigations and Method of Determination (Photo Miniature, 1903) Duchochois, Peter C. Industrial Photography (Photoceramics) (1893) Eastman Kodak Co. “Photography of Coloured Objects” (1920) BIBLIOGRAPHY 249 Eaton, Everett R. “Handbook for Process Photographers.’”’ Line and Half Tone negatives by the Wet Collodion Process. 51 pp. 6 x 33”. (1921) Elson, Alfred Walter “Reproductive Processes of the Graphic Arts”’ (1920) Fabre, C. Traite Encyclopédique de Photographie (1889) Farquhar, H. D. “The Grammar of Photo-Engraving”’ (1893) Fayette, Wilfred Photographic Chemicals (World’s Work, London, 1920) Fithian, A. W. Practical Collotype.” 88 pp. (igor). N. Y. Fitz, Geo. “Photo-Lithography.”” Translated from Vienna edition. 88 pp. illust. (1896). London Fitzsimons, R. J. “Colour Photography with Autochrome Plates” (1916) Flint, William R. Chemistry for Photographers (1920) Gamble, William “Wet Collodion Photography.” tor pp. illust. (1895). London Gamble, William “The History of the Half Tone Dot.” A paper read before the Royal Photographic Society of G. B. London. Jan. 19, 1897. See The Photographic Journal of that year Gamble, William “Line Photo-Engraving”’ (1900) Gamble, William “Photography and Its Applications”’ (1920) Gardner, H. A. “The Light-Reflecting Values of White and Coloured Paints” (1916) Geddes, J. D. Photography as Applied to Illustration and Printing (Journal Soc. of Arts, London). (1902) Geymet, I. “Traité Pratique de Gravure en demi-teinte par |’Intervention exclusive due Cliche Photographique”’ (1888) Goodman, Joseph “Practical Modern Metalithography.”’ London: Penrose. (19—) Gottlieb, Siegmund “Praktische Anleitung zur Ausubung der Helio Gravure”’ (1905) Grolier Club of New York “Wood Engraving—Three Essays” (1916) 250 | BIBLIOGRAPHY Tidasal. c, “Original—Gravuer—Linien-Raster”’ (1906) Hackleman, C. W. “Commercial Engraving and Printing” (1921) Hamerton, P. G. “Drawing and Engraving”’ (1892) Harland, John W. “The Printing Arts: Engraving, Lithography, and Printing” (1892) Harrap, Chas. “Metallography.” (Printing from Metals). London: Penrose. (19—). Pamphlet Hatt, Joseph A. H. “The Colourist”’ (1913) Horgan, Stephen H. “Horgan’s Halftone and Photo-Mechanical Processes” (1913) Horgan, Stephen H. “Photo-Engraving Primer’”’ (1920) Huebl, Arthur von “Die Photographischen Lichtfilter” (1910) Huebl, Arthur von “Three-Colour Photography with Special Reference to Three-Colour Printing” (1915) Huson, Thomas “Photo-Aquatint and Photogravure.”’ Klic Process and Machine Photogravure. 116 pp. illust. (1897). London International Congress of Applied Chemistry Photo Chemistry (1912) Ives, Herbert E. “Some Photographic Phenomena” (1910) Jenkins, Harry “ Amstutz’s Handbook of Photo-Engraving”’ (1907) Jenkins, Harry “Manual of Photo-Engraving.” (1896) first edit. 169 pp. illust. (1903). Chicago Killen, C. 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London : 3 5 , ‘ 1 i ‘i 5 ; < ‘ f ‘i AF | — + a7 ; : ee INDEX Aberration, 32 Blue Prints, 52 Absorption of light, 30, 171 Box Grain, 155 Acid, nitric, 24 Brushing up, 105 Acid resist, 6, 10, 24, 92 Burning in, 24, 25, 94, 95, 105 Actinic colours, 192 Burnishing, 117 Action of light on silver salts, 28 Albumen, insoluble, 24, 91 Camenrae27,.375150,:176 Albumenizing glass, 45 Camera Obscura, 6 Albumen, soluble, 24, 91 Camera stand, 37 Allowing for “bleed,” 232 Chalk, 109 Anchoring, 216 Changes in proportion, 85 Angle, screen, 70, 162 Charcoal, 117 Asphaltum resist, 99, 107 Chemical development, 7 Autochrome, Lumiere, 196 Chinese white, 228 Automatic Focus Camera, 43 Chloride Prints, 54 Circles and ellipses, 123 Backing up for patent bases, 220 Coarse screen plates, special, 231 Basic principles of photo-engraving, 10 Coated paper, 202 Bath, silver, 46 Cold top, 95 Bearers, 113, 120 Collodion Emulsion, 177 Ben Day Process, 137 Collodion, negative, 45, 57 Ben Day Film, 146 Collodion, stripping, 73 Ben Day Machine, 147 Colour filters, 171, 179 Ben Day Plates for colour work, 162 Colour guide or scheme, 163, 190 Ben Day and Process Plates combined, 189 Colour plates, Ben Day, 162 Ben Day tints on copies, 231 Colour plates, dissected, 158 Benedict proportional scale, 230 Colour plates from transfers, 165 Beveler, 120 Colour plates, hand cut, 165 Bevel for blocking, 214 Colour plates, overlapped, 161 Beveling, 120 Colour plates, solid, 158 Bichromated gelatin, 7 Colour progressive proofs, 210 Bichromated glue, 25, 94 Colour proofing, 209 Bichromate resist, origin of, 7 Colour sensitive photographic plates, 177 Bite, 24, 104 Colour sensitive wet plates, 177 Bitumen dust, 155 Colour separation, 173, 177 Black and white copy for process plates, 188 Colours of light, 169 Bleach Prints, 53 Colour work, 158 “Bleed,” 232 Colour work, process, 169 Blocking, 214 Combination plates, 130 Blocking plates together, 217 Combination plates, etching, 109 Blocks, wooden, 3 Combining line and halftone negatives for “Blow outs,” 132 special borders, 126 “Blueprint” process, 237 Combining plates on blocks, 217 255 256 Connected dot, 117, 130 Continuous tone negatives, 178 Copper Etching, 108 Copper plates for colour work, 168 Copper print, 25, 87, 94 “Copy,” 15 Copy board, 37, 40 Copy for line colour work, 233 Copy, for line work, 48 Copy illumination of, 42, 66 Copy, preparation of, 226 Copy, separate for colour work, 190 Cropping, 234 Cut film, 52 Cutting, 47, 63 Cutting negative for finishing line, 79 Daguerre, Louis J., 6 Daguerreotype, 7 Dead metal, 113, 120 Deep etching, 105 Depth of etching, 15 Detail stop, 60 Developing metal print, 23, 92 Developing papers, 54 Development, chemical, 7, 28 Development of wet plate, line, 47 Development of wet plate, halftone, 57, 62 Diaphragm, 32, 58 Diapositives, 49, 65 Dimension marks, 234 Dipping in Silver Bath, 46 Direct halftones, 65 Direct orthochromatics, 194 Direct process work, 177 Dissected plates for colour work, 158 Dots, halftone, 13, 58 Double printing, 96 Drag, 120 Dragon’s blood, 24, 105 Drop out halftones, 132 Drying line negative, 49 Dry plate halftone negatives, 67 Dry plates, process, 51 Duographs, 175 Duplicating with extra negatives, 84 Dye, violet, 95 Early history, some, 2 E. C. and R. Camera, 50 INDEX Electrolytic etching, 102 Electrotyping, 221 Eleven point metal, 220 Ellipses and circles, 123 Emulsion, collodion, 177 Enamel top, 25, 95 Etching 4s 10.024,.25.5102 Etching depth, 15 Etching ink, 23, 92 Etching machines, 102 Extra negatives, duplicating with, 84 Facsimile halftones, 132 Fake process work, 189 Bilroecutaes Filters, colour, 171, 179 Finishing, black and white, 109, 114 Finishing, colour, 183 Finishing line, black and white, 122 _ Finishing line, black, no white, 121 Finishing line, circles and ellipses, 123 Finishing line, no, 119 Finishing lines, cutting negative for, 79 Finishing line, special, 123 First bite, 105 First photo-engraving, 5 Fixing, 28, 47 Flashing, 60 Flat-plate, 25,109 Flat proof for colouring, 190 Flats, negative, 75 Flowing negative collodion, 45 Flowing stripping collodion, 73 Flowing zinc sensitizer, 88 Flush blocking, 216 Focal length, 35 Focus, automatic, 43 Focus, plane of, 28, 33 Focussing, 39 Fog, 48 Four colour process, 175 Fourth bite, 107 Four way brushing, 107 French folio proofs, 240 Frisket, 200 Gamboge, 149 Gelatin, bichromated, 7 ““Gertones,”’ 232 INDEX Glass, albumenizing, 45 Glass, flowing with negative collodion, 45 Glass for negatives, 45 Glass washing, 45 Glue, bichromated, 25, 94 Glue top, 25, 95 Grain, box, 155 Grains, pigment, II Grains, silver, 12 Graver, 124, 131 “Ground,” 4 Ground glass frame, 40 Guide for colour work, 163 Guide line, 196 Gumming out, 149 Gumming to hold, 151 Gutenberg, 3 Hacker press, 212 Hair line, 121 Halation, 61 Halftone, 13 Halftone, circles and ellipses, 123 Halftone copy, 15 Halftone Dots, 13, 58 Halftone, enlarged, 15 Halftone finishing, 114 Halftone from photograph, 14 Halftone, highlight, 132 Halftone, making a, 25 Halftone negative, making a, 55 Halftone negatives for colour work, 177 Halftone negatives from objects, 65 Halftone negatives on dry plates, 67 Halftone positives, 65, 240 Idalifone screen, 13, 55, 57 Halftone screen adjusting device, 41 Halftone screen for process work, 179 Halftone screen holder, 41 Halftone, silhouette, 126 Halftones of special coarse screens, 231 Halftones on zinc, etching, 108 Halftone, squared black and white line, 122 Halftone squared, no finishing line, 119 Halftone squared with black finishing line, 121 Halftone tint negatives, 65, 81, 154 Halftone, vignettes, 128 Hand cut colour plates, 165 Hand proof press, Washington, 198 bo Sat NW Heavy metal, 87, 220 Highlight halftones, 132 Highlight stop, 59 History, some early, 2 Horgan, S. H., 9 Illumination of copy, 42, 66 Indirect process work, 177 Ink, etching, 23, 92 Inks, printing, 210 Ink top, 24, 92 Inserting and turning negatives, 73 Insoluble albumen, 24, 91 Insoluble glue, 95 Intaglio engravings and etchings, 4 Intaglio plates, 65, 241 Intensification, halftone negative, 63 Intensification, line negative, 47 Introduction, I, 2 lodized silver, 6 Iris diaphragm, 35 Isochromatic negatives, 192 Ives, Frederic E., 8 Key plate, 160 Kinds of photo-engravings, Io Laying tints, Ben Day, 137 Lead mould, 221 Leather roller, 92, 136 Lens, 27 Lens barrel, 35 Lenses and light, 30 Lens, pin hole, 34, 62 Levy, Louis Edward, 8 Levy; Max, 9,°55 Levy screens, 55 Light, 27, 30 Light, absorption, 171 Light, action on silver salts, 28 Light, its colours, 169 Light, reflection, 171 Light, velocity of, 30 Line copy, I5 Line etching, 104 Line negative, appearance of, 48 Line negative, copy for, 48 Line negative, cutting, 47 Line negative, development, 47 258 Line negative, drying, 48 Line negative, fixing, 47 Line negative, intensification, 47 Line negative, making a, 23, 44 Line plate, 13 Line plate, enlarged, 15 Line plate, from shaded line drawing, 14 Line plate, from simple line drawing, 14 Line plate, making a, 23 Line plate, reverse, 51 Line plate, reversed, 51 Line plates, solid for colour work, 158 Line positive, making a, 49 Lining beveler, 120 Lumiere autochrome, 196 Magnesia, 109 Make ready, 199 Making a halftone negative, 55 Making a line negative, 44 Making a photo-engraving, 23 Making a zinc print, 88 Mats, 222 Meissenbach, Georg, 8 Metal bases, 219 Metal plates, development of, 4 Metal print, 23, 87 Metal print, developing, 23, 92 Mezzograph plates, 239 Moiré, 69 Monochromatic values of colours, 192 Mortising, 218 Moss, John, 9 Movable types, 3 Multiple copies for colour work, 236 Nailing machine, 215 Negative, appearance of, 28, 48 Negative collodion, flowing, 45 Negative collodion for halftone, 57 Negative collodion for line work, 45 Negative, duplicate, 84 Negative, extra, duplicating with, 84 Negative flats, 75 Negative for colour work, 177 Negative glass, 45 Negative glass, albumenizing, 45 Negative glass flowing, 45 Negative glass washing, 45 INDEX Negative, halftone, 55 Negative, halftone, from objects, 65 Negative intensification, 47 Negative, line, 23, 44 Negative line plates, 49, 51 Negative on dry plates, 67 Negative prints from negatives, 240 Negative, tint, 65, 81 Negative turning, 23 Negative turning and inserting, 73 Niepce, Joseph Nicéphore, 5 Nitric acid, 24, 102 Notching, 218 Objects, halftone negatives from, 65 Odd shaped dots, 62 One-stop method, 62 One-way screen, 62 Opaque, 134, 152 Origin of bichromate resist, 7 Origin of the screen, 8 Orthochromatic negatives, 192 Other processes, 238 Overlapping colours, 159 Overlay, 199 Padding, 60 Painting in for colour plates, 160 Painting in for re-etching, 116 Painting in solids, 99, 152 Panchromatic photographic plates, 177 Paper, 206 Papering, 60 Paper stop, 60 Paste lines, 227 Pasters on copies, 227 Patching plates, 225 Patent bases, 87, 200 Patterns, screen, 69, 162 Perchloride of iron, 25, 102, 108 Petit, Charles G., 8 Photographic plates for colour work, 177 Photographic printing on metal, 8, 23, 87 Photographic prints, 52 Photographic prints for line copy, 229 Photography of colours, 192 Photography, principles of, 27 Photogravure, 8 Photo-lithography, 8 INDEX 2 Pigment grains, II Retouching, 66, 234 Pin-hole lens, 34, 62 Retouching copies, 234, Plane of focus, 28 Reverse line plates, 51 Plate Holder, 40 Reversed line plates, 51 Point system, 87, 122 Reversing metal prints in development, 241 Ponton, Mongo, 7 Rolling up, 92, 134 Positive line plates, 51 Rotogravure, 241 Positives, 28, 49, 65, 82, 178, 240 Rouletting, 132 Potassium bichromate, 7 Routing, 24, III Preparation of copy, 226 Routing down wood, 219 Principles of photography, 27 Routing for colour, 159 Printing frame, vacuum, 90 Rubber solution, 73 Printing lamp, 92 Printing on copper, 94 Salt prints, 53 Printing on metal, photographic, 87 Saw tooth edge, 71 Printing on zinc, 88 Saw trimmer, 215 Printing out papers, 54 Scaling copies for reduction, 229 Prints, 28, 52 Scotch stone, 117 Prism, 42, 179 Scraping away, 99 Process and Ben Day Plates, 189 Scratches, repairing, 223 Process camera, 178 Screen adjusting mechanism, 41 Process colour work, 169 Screen angle, 70 Process dry plates, 51, 177 Screen angles for colour work, 162 Process lenses, 35 Screen distance, 57 Process plates from black and white copy, 188 Screen effects, 68 Process work, fake, 189 Screen holder, 41 Progressive colour proofs, 210 Screening, 81 Projected image, 27 Screen, origin of, 8 Proofing and presses, 198 Screen patterns, 69 Proofing in colour, 209 Second bite, 107 Proofs, 24 Sensitizing negative glass, 45 Proportion, changes in, 85 Separate copies for colour work, 190 Proportions of copies, 229 Separation of colours, 173 Pryor scale, 230 Shadow stop, 60 Sharpness of focus, 34 “Quarter tones,” 238 Shellac, 99 Silhouettes, 126 Ray filter, 194 Silver bath, 46 Re-etching, 109, 114 Silver, iodized, 6 Reflection of light, 30, 171 Silver prints, 53 Refraction of light, 30 Silver salts, action of light on, 28 Register in colour work, 159, 209 Silver, unreduced, 28, 47 Register marks, 182, 209 Size of image, 36, 39, 44 Relief plate, 10 Sizes, indicating, 234 Removing plates from blocks, 219 Slide rule, 230 Repairs and corrections, 223 Slugging, 216 Repeating patterns in design, 84 Solar spectrum, 170 hesist,/acid, 6, 10, 24;.92 Soldering plates together, 225 Resist, bichromate, origin of, 7 Solid line plates for colour work, 158 260 INDEX Solids, description of, 10 Transparent proofs used as negatives, 240 Solids, painting in, 99 Trimming, 121 Soluble albumen, 24, 91 Turning and inserting, negative, 73 Soluble glue, 95 Turn table, 42, 179 Special methods, 238 Type high, 214 Special screens, 239 Types, movable, 3 Squared halftones, black and white finishing line, 122 Undercutting, 24, 105 Squared halftones, black finishing line, 121 Underlay, 199 Squared halftones, no finishing line, 119 Unreduced silver, 28, 47 Stain on zinc for colour work, 160 Unusual finishing lines, 123 Stereotypes, 222 Use of tint negatives, 81, 154 StOPSe sees ‘ Stopping out, 107, 116 Vacuum printing frame, 90 Stripping collodion, 73 Velox prints, 54 Subtractive colour process, 210 Vibration, to counteract, 37 Surprinting, 84, 96, 154 Victoria press, 211 Vignettes, 128 Table saw, 215 Violet dye solution, 95 Talbot. Hox. 7 Third bite, 107 Washing negative glass, 45 Three colour process, 172 Washington hand press, 198 Three printing colours, 172 Waves, light, 30 Tinting, 81 Wax mould, 221 Tinting films, 137 Wet Plate, 46 Tinting with box grain, 155 Wet Plate Development, 47, 57 Tint negatives, 65, 81, 154 Whirling, 88 Tints, laying Ben Day, 137 Wood cut tooling, 131 Tints on copies, 231 Wooden blocks, 3 Tint tools, 132 Wood engraving, 3 Tone values, description of, 11 Tooling, 131 Zinc etchings, 8, 104 Top, ink, 24 Zinc halftones, etching, 107 Topping powder, 24, 94 Zinc halftones, finishing, 134 Topping up, 134 Zinc print, 24, 87, 92 Transfers for colour plates, 165 Zinc stain, 160 GETTY RESEARCH | mV 6 NSTITUTE IN AN 56 ee