ndow -Glass 1 the Making William L.Monro _ American Window Glass Company Pittsburgh, Pa. U.S.A. Window Glass In the Making Window Glass in the Making An Art, A Craft, A Business BY WILLIAM L. MONRO President and General Manager American Window Glass Company _ «lh. cy ug b, American Window Glass Company PITTSBURGH 1926 rn wage oy, is =e ForREWoRD Definition of Window Glass CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER CHAPTER Appendix—U. S. Govt. Master Specifications I TE III IV XV XVI CONTENTS Uses Quality Glass—Its Origin Composition Melting and Refining Ladling and Blowing Flattening Annealing Cutting and Sorting Boxes and Packing Labels, Quality Slips, and Branding Warehousing and Shipping Defects in Glass Window Glass Wave - Our Productions Comparison of Glass with Comments Index 107 } FOREWORD F the world were deprived of window & glass today, civilization would beturned ie @ back at least 500 years. Without it we % would be compelled to forego many of the conveniences, comforts, and luxuries of modern life and would revert to the inconveniences, the discomforts, and the hardships of medieval times. No matter where we go or what we do, we are confronted by the ever-increasing uses of window glass. In fact, it is in such general use that probably none of us, except those closely allied with the pro- duction of window glass, has any appreciation of its importance or realizes how essential it is, and has been, to the progress of mankind. It is the purpose of this book to tell enough about window glass to give architects, dealers, contrac- tors, home-builders, and all other users a better understanding of its nature and characteristics, in otder to render them more competent to judge the quality. With this knowledge they will demand “The Best Glass’’ obtainable and will refuse to ac- cept glass of inferior quality, especially when pay- ing for the better article. This knowledge is not only of interest but of great value to every user of window glass. 10 Window Glass in the Making Such information has not been available hereto- fore in books or other publications, for there is practically no literature on the subject of window glass. During years of study and experimental work in the development of a new process of manufacturing window glass, and by the expenditure of millions of doJlars in bringing that process to complete commercial success, we acquired a comprehensive understanding of it that could not be gained in any other manner. Yet we realize that there is much we do not know about it. In that respect we differ from what the renowned, and probably the most learned man of his time, Professor Jowett, of Baliol College, was reported to have said, ‘‘All that known is, I know it; what I know not is not knowledge.” ; To acquaint the reader with much of the knowl- edge that we have acquired, it is our intention to define window glass; to point out the variety of its uses in order to show how they are affected by the quality; and to explain what is meant by the term, ‘“quality.’’ This will be followed by an account of ~ the origin of glass for its bearing on the compo- sition. We shall then describe briefly our process of man- ufacturing window glass, by tracing the raw ma- terials of which it is made through the different Window Glass in the Making 11 steps of the process until they finally appear in the form of flat sheets of clear glass, ready for use. However, it is not the intention to go into a technical description of the process of manufacture, such as will interest only the trained chemist or the glass engineer, but to describe it in such a man- ner as will interest those who desire to add to their fund of useful information, and those who have not the time to give to a highly technical exposition of the subject. For the benefit of those who desire a more com- plete commercial knowledge of window glass, its various thicknesses and qualities, with the rules for grading, and the method of glazing, an Appendix is added, wherein is set forth an exact copy of the “U. S. Government Master Specification for Flat Glass for Glazing Purposes,”’ so far as it relates to window glass, with our notes and comments thereon. The Appendix also sets forth the fourteen reasons why our glass is ‘“The Best Glass.”’ American Window Glass Company DEFINITION OF WINDOW GLASS 2) PAGS Qsvarry we think of window glass as a a K hard, clear, brittle substance, and do not ( +7) ;) realize that, at a sufficiently high tem- Sy perature, it becomes a liquid.Whencold, it an great tensile strength and elasticity. Everyone who played marbles, when a child, had his favorite ‘‘glassie,’’ that could be used only because of that elasticity. | Glass is a poor conductor of heat. One end of ashort rod of glass can be held in the bare hand without discomfort while the other end is being melted in a furnace. The chemists say that it is an amorphous substance —that is, having no regular structure; and diaphan- ous—that is, translucent and transparent. They go further; and say that it is a salt. No matter how it is defined or described, to con- _ vert ordinary sand mixed with a few other in- gredients into a bright, clear substance of fine qual- ity, which we call window glass, and which affects so greatly our welfare and happiness, is an art that requires the science of the chemist, the genius of the engineer, and the technique of the artist. CHAPTER I USES ) a material that would let in the light M/@9 and keep out the elements, that would keep in the heat and shut out the cold. Its develop- ment has kept pace with the progress of civiliza- tion. From the skin tents of the Nomads to the solid doors and shutters in the cabins of the fron- tiersmen; from the rice paper and oiled parchment in the windows of the Orient to the dazzling bril- liance of the crystal palaces of the Occident, we trace its ever-increasing uses. Today it is in such general use that it has become known as “‘common window glass.’’ Recognizing this fact, Congress has used this designation in many of the tariff laws. Not always has it been such a commonplace arti- cle. Even as late as the fourteenth century Richard II issued a writ to scour the counties of Norfolk, Northampton, Leicester, and Lincoln, to find glass to repair the windows in the castle at Stamford, built in honor of his mother. In the sixteenth century, window glass was so The Skin Tent— The habitation of many nomadic tribes before glass gave permanence to civili- Ration. 14 Window Glass in the Making expensive in Germany that the law provided that on the death of the owner of a building, the glass belonged to his executors, but the windows went to theheirs, ‘‘for the houseis perfect without theglass.’’ As late as 1686, Sir R. Worsley, writing of his travels, said, “‘In all ye great towns of Italy, except Genoa, and in this city (Murano), they have paper in their sashes instead of glass.’’ For centuries it continued to be regarded as a lux- ury and was taxed accordingly, down torecent times. _ It is aquestion whether the ‘‘window tax”’ has been entirely abolished in all European countries to this day. We see so much window glass and can obtain it so easily and so cheaply that we fail to appreciate its value or the effect it has on our lives. We do not realize how it changes the lives of those who would otherwise be obliged to live in shadows and dark- ness. Isak, the hardy frontiersman in Knut Ham- sun’s ‘‘Growth of the Soil,’’ found it a bright and wonderful day when he was able to put glass in the windows of his hut. He was no longer obliged to depend upon the firelight to enable him to work at his bench. Some idea of the extent of its use here may be gained from the fact that the American Window Glass Company has six large factories in different parts of this country. These have the capacity to pro- A residence— Pasadena, California Window Glass in the Making 15 duce annually about three hundred million square feet, or six million fifty-foot boxes of window glass, which makes this Company “‘The World’s Largest Producer’’ of window glass. If all this glass were of single thickness, cut 24 inches square, and packed in fifty-foot boxes, and these boxes laid on the ground end to end, they would make a sort of boardwalk extending 2651 miles, or from the Atlantic to the Pacific Coast. Window glass has an almost endless variety of uses. An enormous quantity is consumed for other purposes than glazing; that is, putting it into win- dow frames. Of course, the largest amount is glazed in windows and doors of houses, schools, churches, colleges, hospitals, hotels, stores, greenhouses, fac- tories, in fact buildings of every kind. Considerable is used in street railway and railroad coaches, in car- riages, trucks, and automobiles. Much is used for other articles such as eyeglasses, photographic dry plates, lantern slides, microscopic slides, X-ray plates, vanity cases, toilet articles, pictures, mirrors, showcases, counters, shelving, tops for desks, tables, and for furniture of every description. WHY USE WINDOWS? Few people appreciate sufficiently the importance of windows in buildings. There should be as many as possible; but if limited in number, they should A residence— New York City Peres ga Ty eri a IEEE PMN ans ea eeR Tl it. t= nam 16 Window Glass in the Making be as large as possible. The old Gothic cathedrals were built with the windows as large as possible, and just enough stonework to support the building. In factories,workrooms, offices, hospitals, school buildings, and homes, the use of clear window glass to “Let in the Sunlight’’ is of compelling impor- tance, for with it you let in health and happiness. The sun’s rays are nature’s greatest purifier, which the medical profession has recognized by using “artificial sunlight’’ for disinfecting wounds, and . for therapeutic treatments. Careful and exhaustive tests have demonstrated that workers in a factory in which the windows are glazed with clear window glass do better work than those in factories in which obscure glass is used. When at the workbench, the opportunity of *‘catch- ing a glimpse’ of the outside world exerts a psycho- logical effect on the workers. It takes away the feel- ing of confinement and promotes cheerfulness and contentment. A contented workman always does the best work. For economical reasons there should be plenty of windows in a building. Window glass costs less per square foot of wall space than lumber, tile, or brick. At the present time, in a modest brick dwelling of avetage size, the window glass represents less than one-half of one per cent. of the total cost of the building. fat LER II QUALITY ity,’’ or how it may be determined. “Quality’’ in window glass covers not only the chemical composition and physical properties, but alsothe grade of the glass from the standpoint of de- fects. It may be of good quality so far as its composi- tion and properties are concerned, but of very poor quality as regards the defects. The differences in com- position and properties can only be discovered by analysis and test; but in grading, they can readily be detected by comparing different makes of glass. Grading is separating the lights, or panes, of glass into different grades or classes of quality, according to the character, size, number, and position of the defects, which affect not only the appearance of the glass itself but of the objects viewed through it. The casual observer notices these defects, but thinks they are inherent in the process of manufacture, and therefore unavoidable. He does not know that they are unnecessary, and that window glass which is 17 18 Window Glass in the Making practically free from them may readily be obtained. A beautiful house showing the care, thought, and artistic sense of the architect who planned it, is often disfigured by the poor quality of the glass he unwittingly permits to be placed in the windows. The enjoyment of one’s home is sometimes spoiled by defects in the glass that hinder the vision. Fre- quently the appearance of a fine picture is ruined by the execrable quality of the glass used in the frame. The pleasure of a ride through an interesting part of - the country in a railway coach, street car, or an auto- mobile often is taken away by the poor quality of the glass through which one is obliged to view the scenery. Glass of poor quality not only spoils the view, but offends the eye, and irritates the nerves of one compelled to view continually objects distorted in appearance by its defects. A very large amount of window glass produced is of such poor quality that it is not fit for commercial use and is really rubbish which should be remelted. Instead of disposing of it in this manner the inca- pable manufacturers who produce this glass putiton the market at low prices. Notwithstanding its poor quality, such glass is finally used for many purposes for which it is grossly unfit. This would not be pos- sible if more were known about it. Window Glass in the Making 19 ' THE BEST GLASS”’ The American Window Glass Company produces a very large quantity of a highly perfected product of beautiful lustre, graded to the highest possible standard and known as ‘‘The Best Glass.’’ It is suit- able for every purpose. Its production is possible only with a process conducted on scientific prin- ciples, by a Company that has built up, after years of effort, an organization of highly skilled employ- ees, who pride themselves on their workmanship as greatly as the Company prides itself on its product. Every user can obtain ““The Best Glass’’ if he in- sists upon having the American Window Glass Company’s brand and is competent to judge the quality of the glass furnished. The price of it is not substantially different from that of glass of inferior quality. CHAP Tite GLASS—ITS ORIGIN / RHE origin of glass is still in doubt. Many ee howe theories have been advanced by ancient fh) : qy } ou P “es fd BY WS § and modern writers to explain its dis- the Egyptians discovered glass; others claim it was a discovery of the Chinese. Probably the most accu- rate account of its origin, and certainly a very plaus- ible one is that related by C. Pliny the Second in his “History of the World,’’ Volume 36, Chapter 27. According to Pliny, there was in Phoenicia a short river, called Belus, that flowed from Lake Candeboea to the sea. Its waters were muddy and unwholesome, and nothing was to be found on its banks but sand. This had been cast up by the sea, and from frequent washings by the waves was pure and white and suit- able for making glass. One day some traders, who had been gathering a cargo of nitre, sought, along the banks of the river, stones on which to mount a tripod to cook their food. Not finding any, they were obliged to use blocks of nitre taken from their cargo. Under the heat of the fire, the sand coming into contact with Illustrating the discovery of glass as related by Pliny _ the Second Window Glass in the Making 21 the nitre, which acted as a flux, formed a vitreous substance— ‘glass. Though there is room to doubt that this is the true account of the origin of glass, there are certain basic features in it that make it appear not only plausible but easily possible. From our later know!l- edge, we know that sand alone may be fused intoa vitreous mass by applying a very high degree of heat; and that by mixing with it a quantity of soda, the temperature required to do this is greatly les- sened. By using nitre, which contains a large per- centage of soda, these ancient traders used an ingre- dient that materially lowered the melting point of the sand and made possible its reduction into glass. To demonstrate the possibility of the discovery of glass in some such manner, we recently caused a wood fire to be made in the open air. Small logs were laid on a bed of glass sand mixed with an equal quantity of carbonate of soda. In order to se- cure accurate information of the degree of heat that could be obtained from such a fire, a standard pyrom- eter couple was inserted into the bed, and frequent readings taken. The fire was kept burning about two hours. The highest reading, 2210 degrees Fahren- heit, was obtained when the fire had been reduced to a mass of burning charcoal. After the fire had completely burned itself out, the wood ashes were removed and a portion of the bed was found to be i Residence— Brookline, Mass. 22 Window Glass in the Making fused into a vitreous mass—the same kind of glass discovered by the Phoenicians. In a similar demon- stration, with a bed of glass sand mixed with an equal quantity of nitre, a like result was obtained; but when a bed of glass sand unmixed with any other ingredients was used and subjected to the same kind of a fire, there was not the slightest trace of any fusing of the sand. It seems quite plausible, therefore, that glass was first made somewhere along the shore of the Sea. Many centuries after Pliny, it was found that when seaweed was burned, its residuum, called ‘then = contained a large amount of carbonate of soda. Sub- sequently this was used in making glass, and there became known to the trade the term, “kelp glass.”’ It requires no great stretch of the imagination to think that at some time there had been kindled along a sandy shore a great bonfire of dry seaweed, with perhaps a lot of driftwood, which left amid its charred embers the vitreous mass we now call glass. Owing to the impurity of the raw materials and to the cruder methods of manufacture, the glass made by the ancients was not the bright, clear, transparent article in use today, but was much dark- er and contained many bubbles and foreign parti- cles, which made it more translucent than trans- parent. Saint Paul refers to this feature when he A Virginia Plantation House Window Glass in the Making 23 says, ‘For now we see through a glass, darkly’’— I Cor., xiii, 12. Centuries elapsed before this discovery by the Phoenicians was put to any practical use. In fact, we may say that glass really had to be rediscovered before glass articles of any kind could be produced. While it is not the intention to go into the history of glass making, the story of its origin is recounted for the bearing it has on the development of the various compositions subsequently used in making window glass. — | N . % XID p= WEB Other Ingredients 22 Total 100.00 It is interesting to know that the composition of French window glass that was being produced at the date of that analysis, about 1855, was almost identical with that of the Pompeiian glass. Such glass was of very poor quality from the standpoint of strength and resistance to discoloration or “‘fade.”’ Windows in Sussex i} = hel WRENS! | 3 28 Window Glass in the Making COMPOSITION OF GLASS MADE BY OTHER PROCESSES At the present time many factories using some of the other new processes of making window glass require molten glass that can be worked at com- paratively low temperatures without devitrifica- tion. Devitrification, as its name indicates, is the changing of the glass from a liquid condition into a white, opaque solid that does not have the charac- teristics of glass. It is usually caused by maintain- ing the molten glass at too low a temperature, which varies according to the composition of the glass. It begins with the formation of very small crystal-like particles resembling large grains of very white sand or small stones, which cause enormous breakage during the process of manufacture. These gradually become larger and more numerous, until they finally permeate the entire body of glass and change it into a hard white substance resembling porcelain. This is often called ““The Porcelain of Réaumur,”’ after the celebrated French physicist who first made a study of this change in the glass. It is interesting to know that if this devitrified mass is subjected to a sufficiently high heat, it will again become liquid glass. In our process of manufacture, the glass is worked at such a high temperature thatit doesnot devitrify. Window Glass in the Making 29 This enables us to use a composition that produces glass with the best physical and chemical properties. To obtain glass that will not readily devitrify at the low temperatures required for those other proc- esses, very important changes are made in the com- position, which produce a quality of glass inferior to ours from the chemical and physical standpoints. The changes are as follows: 1. The percentage of silica is lowered. Therefore less heat is required to melt the composition, but the resultant glass does not have the strength or durability of window glass containing a higher percentage of silica. 2. The percentage of soda is increased. This en- ables the composition to be melted at a lower temperature, but makes the glass less dense and more hygroscopic; that is, causes it to sweat more readily. 3. The percentage of lime is lowered. Reducing the amount of lime in the composition causes the glass to set, or harden, more slowly and thereby lowers the temperature at which it can be worked without devitrifying. This reduction, however, causes the glass to have less ductility and less body, and increases the tendency of the soda in the glass to attract the humidity of the air; or, in other words, renders it more deliquescent. 30 «© Window Glass in the Making As a result of these changes in the composition, the glass produced by those processes analyzes about-as follows: | Silica 72.00% Lime 10.75 Soda 15.50 Alumina 75 Other Ingredients 1.00 Total 100.00 Glass of the foregoing analysis does not have the same strength or durability as glass that contains the correct proportions of the different ingredients, and it is much more susceptible to attack by mois- ture. It will therefore lose its brilliance of surface more quickly by discoloring, z.e., fading, staining, or rusting. ’ ie Oe fot ER V MELTING AND REFINING @)\(@) fit the raw materials thoroughly mixed a (2y/) in suitable proportions, then comes the melting. Formerly this was done in J furnaces built to contain large clay pots in which the composition was melted. In mak- ing window glass this system has been entirely superseded in this country by the continuous melt- ing regenerative tank system, which uses either producer gas or natural gas for fuel. The American Window Glass Company has thir- teen continuous glass melting tanks, or furnaces, of the most modern construction, five of which are much larger than any other glass melting furnaces in the world. The largest ones are 30 feet wide, 140 feet long, and 5 feet deep. To visualize a tank of such size, picture an enormous swimming pool with a capacity of 172,627 gallons, filled with 1800 tons of molten glass, varying in temperature from 2200 to 2700 degrees Fahrenheit. If all the glass in one of these large furnaces were made into a light or pane of single strength thickness one foot wide, it would extend for a distance of six hundred miles, or from Pittsburgh to St. Louis. 31 CHARGING THE FURNACE Testing Laboratory constantly checking purity of materials Window Glass inthe Making 33 In the modern continuous melting tank system, the raw materials are placed in the furnace along with some broken glass called, ‘‘cullet,’’ which facil- itates the melting. Then they are exposed to the heat of the furnace in the melting zone until they ate entirely reduced to a viscous mass, full of bub- bles formed by the gases given off during the melt- ing, which have not yet been able to escape during that process. Additional raw materials are fed into the furnace at regular intervals as rapidly as the preceding charges are melted. The furnace is main- tained at the melting temperature continuously for months, and there is no cessation of the melting, the taw materials being fed in at one end, while the molten glass is taken out at the other end, except during the usual Sunday shutdown. This continues until the furnace has been burned out to such an ex- tent as to need repairs. The melted viscous mass of glass moves slowly down the furnace, passing through a hotter zone, which renders the mass still more liquid, and thus allows the pent-up gases to escape. This is the re- fining process. If the temperature of the refining zone is not high enough, or if the glass passes through it too quickly, the glass will not be prop- etly refined and will contain bubbles of various sizes, some quite large, and some as small as a pin point. POURING MOLTEN GLASS (The last ee preceding the drawing or blowing process) Bd Ladle Bosh which cools the ladle after the fe process Window Glass inthe Making 35 The refined glass continues on its way through the furnace to the working zone, gradually cooling as it gets farther away from the fire of the furnace. By the time it has reached that zone, it should be sufficiently cooled to permit the necessary handling by the workmen. Unless the furnace is properly con- structed, it is impossible to secure the even grada- tions of temperatures necessary to obtain glass of suitable working consistency. Our furnaces have demonstrated their efficiency in this respect by pro- ducing more glass of good quality than any other window glass furnaces of which we have any knowledge. linders into ing cy short lengths S S BLOWING AND DRAWING THE CYLINDERS GBA PTER VI ~LADLING AND BLOWING ] rmRODAY, window glass is either blown in Gy i wy the old-fashioned way by hand and lung ( ; iQ power, a method that is fast dying out, (54 KO) or is drawn in sheet form from a fore- hearth attached to a tank furnace, or is made by the American Window Glass Company’s method of drawing and blowing it mechanically in the form of large cylinders, a process invented by John Lubbers. In our process, by means of a ladle that holds enough glass to make one large cylinder, or as much as would fill a good-sized bass drum, the molten glass is ladled from the huge melting furnace into a comparatively small pot located in a fixed position beneath the drawing and blowing machine. This pot is reversible; that is, with a working cavity on each side, and is mounted in a small furnace, or heated drawing kiln. Each of our very large tanks has twelve of these drawing kilns, and each of the smaller ones has eight. As soon as the upper cavity of the pot is filled with molten glass, the operator lowers into the glass a 37 COMPLETED CYLINDER (Cylinders in foreground being cut into short lengths) Carrying glass before splitting Window Glass inthe Making 39 hollow stem blow pipe, with a mushroom-shaped head. This blowpipe is hung on a cage that travels vertically between a pair of guides erected above the pot and is connected to a telescoping air sup- ply pipe. A motor driven fan supplies the air pres- sure. The blowpipe, having taken hold of the glass, is then slowly elevated by the machine, which, at the same time, introduces at the glass level a small quantity of air. As the blowpipe is elevated, the amount of air is gradually increased, and the plastic glass is uniformly and gradually distended in a swelling curve like the neck of a bottle, until it at- tains the diameter desired for the cylinder. The machine then continues to elevate the blowpipe and automatically furnishes the amount of air needed to keep the cylinder distended to a uniform diameter until it reaches the limit of the length of its draw. When the cylinder is completed, the lower end is severed from the glass in the pot; and by another mechanical device it is quickly lowered into a horizontal position and placed on a “‘horse,’’ a receptacle especially designed to receive it. As soon as one cylinder is completed, the potisreversed, and the other side of the pot is turned up into the drawing position, ready to receive a ladle of glass for the next cylinder. During the drawing of one Ay wv Window Glass inthe Making 41 ‘cylinder, the fire in the kiln melts out the cold glass remaining in the under side of the pot after the drawing of the preceding cylinder and prepares ‘it to receive the glass for another cylinder. This renders the operation practically continuous. Like mushrooms, these huge cylinders grow from the molten glass in the pots, rising slowly and silent- ly, impelled as if by an unseen power, to a great height, until their tops almost disappear in the shadows of the building structure. When finished they resemble enormous bottles. Some idea may be gained of their size when you consider that if one of them were filled with milk it would hold 6804 quarts, or about seven tons. They are made in various lengths, diameters, and thicknesses. The diameters are regulated by the air pressure introduced into the cylinder, and average about 30 inches in commercial operation, although we have made them 48 inches. The diameter of the pots from which they are drawn, of course, limits the diameter of the cylinders that can be made. Their length is limited by the height of the struc- ture on which the machines are placed, and by the amount of glass the pots will hold. The cylinders usually are about 48 feet in length from blowpipe to “‘hole end.’’ The thickness is regulated by the speed of draw, and varies from 1/39 to %A¢ of an inch in thickness. Windows along @ street in Wales 42 Window Glass in the Making ADVANTAGE OF OUR BLOWING PROCESS Our mechanical process of drawing and blowing the cylinders imparts to the glass a preliminary annealing, and so affects the physical structure of the glass as to render it stronger and tougher than window glass made by any other process. It in- sures a uniformity of thickness in the glass, far superior to that produced by the hand blowing method, and equal in every way to that made by any other process. CAPPING After the large cylinder has been laid on the horse, the upper part, or cap, and any uneven por- tion of the “‘hole-end,’’ are removed, and the re- mainder of the cylinder is cut up into sections of the desired length by means of electrically heated wires. This process is known as “‘Capping.”’ SPLITTING The sections of the large cylinders are prepared for the next stage of the process (the flattening) by cutting them lengthwise into segments of the re- quired sizes, either by means of an electrically heated iron, or wire, or by a diamond splitting tool. This is known as ‘‘Splitting,’’ or ‘“Cracking-open.”’ When the cylinders are made of small diameter, the sections usually are only split once lengthwise, and are not cut into segments. Llivia in the Pyrenees Pear rIER Viti FLATTENING RHE ‘‘cracked-open’’ sections of the long a me cylinders of small diameter, and the Ae () segments of the cylinders of large di- Og Lay) By ameter are now ready for the next steps in 1 the process—the flattening and the annealing. For this purpose, furnaces, or ovens, of special de- sign are required. In this country these ovens are all of the same general type, but in Europe quite a dif- ferent type of flattening oven is used. Although many improvements have been made from time to time in various other steps of the proc- ess of manufacturing, practically none had been made in the flattening process for more than one hundred years, until the American Window Glass Company recently worked out certain changes. These make it possible for this Company to secure better results than can be obtained by any other producer of cylinder drawn glass. The flattening ovens used in America consist of a horizontal revolving wheel built in four segments and mounted in a furnace, or oven, divided into four compartments. On each segment of this wheel is placed a perfectly flat and highly polished clay 43 aH U] i wit 2 Ut} | ! AMA THE FLATTENING PROCESS (A perfectly flat glass of high lustre is thus produced.) Annealing accomplished within the lebrs gives the glass strength and greater resistance to breakage Window Glass in the Making = 45 |stone, known as a ‘‘flattening stone.’’ The oven, of |course, is heated to the required temperature, and an linlet canal, or “‘stick hole,’’ is provided for intro- |ducing the glass into the highly heated portion of |the oven. | The glass is placed on a small carriage, which is shoved into the heat of the oven adjacent to the \flattening wheel. When the glass has been heated to the required temperature, it is then lifted from this catriage and placed on the flattening stone. It is now sufficiently plastic to permit it to be flattened. If the glass has been introduced into the oven in the form of a segment of the cylinder, the workman at once uses a water-soaked and charred block of wood, called a flattening block, or polisher, with which he rubs or “‘irons’’ the surface of the glass and flattens itintoa sheet, whichconformstothesmooth surface of the flattening stone. When properly done, the block imparts a beautiful lustre or polish to the surface of the glass. If the glass has been introduced into the oven in the form of sections of cylinders of small diameters jthat have been split open lengthwise, the workman is obliged to open up the cylinder withaspecial tool, by spreading it along the lengthwise split or “‘crack- open’’ to such an extent that the edges of the split fall away from one another toward the sides of the 46 Window Glass in the Making flattening stone. He then takes the charred bloc and irons, or polishes, the glass as before. | Much better results are secured by flattening seg ments of the cylinder than by flattening the entit| cylinder. The development by us of the forme method of flattening resulted in a great improve ment in the character of the work, in the freedo from defects, and in the appearance of the finishei sheet, over that secured by the old-fashioned method Pear teR VIII ANNEALING still at a high temperature and must be | WE ) \s) d) J NX slowly cooled to permit its being placed Hay) \ (og 5 in the annealing oven. This cooling ef- ject is accomplished by the subsequent passing of he glass, while still on theflattening stone, through ‘ooler sections of the oven, remote from the fire, until it comes into the section known as the “‘piling yven.’’ It is now sufficiently cooled to permit the workman to insert a large thin-pronged fork of \teel underneath the flattened sheet and to place it bn the rods that carry it through the annealing »ven, or lehr. The annealing of the glass consists simply in re- lucing the temperature of the heated sheet of glass slowly and gradually between two certain temper- atures, which constitute the critical range of tem- peratures for annealing, and then continuing the ‘eduction of the temperature until the glass is suf- ficiently cooled to permit it to be handled. If the iglass is passed too rapidly through this critical ‘range of temperatures, it will not be properly an- 47 48 Window Glass in the Making nealed, and it will be hard, brittle, difficult to cu; and it will not withstand ordinary handling : shipping without excessive breakage. In the orc: nary oven, these gradations of temperature are s} cured by advancing the sheet slowly on the rods the lehr from the piling oven to the discharge et) of the oven. In order to secure the best possible results in tl flattening and annealing, the American Windo Glass Company has recently made many changes i the old style flattening ovens and lehrs. The: changes make possible the production of windoy glass that is absolutely flat, so far as its use for con mercial purposes is concerned. It is as flat as gla: made by any of the flat sheet drawn processes. It is annealed so perfectly, as shown by Goverr ment tests, that it equals the annealing necessary i glass made for optical use, which requires the bes possible annealing. This results from the double ar nealing which the glass receives in this process. ] is annealed first during the drawing of the cylindet and again, in its passage through the annealing ove: or lehr. DIPPING AND WASHING When the sheets of glass are removed from th discharge end of the annealing oven, or lehr, the ate dipped and washed in a bath of muriatic aci a ee a Window Glass in the Making 49 diluted with hot water. This is a very important step in the process. The glass, as it emerges from the lehr, has a considerable amount of free alkalies, or other foreign particles on the surfaces, occasioned by the process of manufacture. These foreign par- ticles must be removed; or otherwise, if the glass becomes wet, or sweats, they set up the chemical action that attacks the surface of the glass and causes it to discolor, z.e., fade, stain, or rust. The acid bath thoroughly cleans the surface of the glass of all these foreign particles. TYPICAL CUT ¢ CExg D ert workmen here Truck ks are used to despatch shipment tatar LER IX CUTTING AND SORTING with a diamond ome in a cutting tool, but it can be cut just as well with a steel wheel. When the large sheets of glass are placed on the cutting table, the defects that have been made in all the different steps of the process become appar- ‘ent. The skilled cutter sees these at a glance and 'quickly cuts the sheet into the sizes and qualities desired, so far as the quality of the glass will per- ‘mit. The cutter then “‘sorts’’ or ‘‘grades”’ the glass into the different qualities, according to the stand- ards of the company. The skill and judgment of the cutter in know- ing what defects are properly permissible, in any certain quality, are the most important factors in establishing a reputation for high quality glass. All the different processes of manufacturing window glass produce some poor glass, and the reputation of a firm for high quality glass is affected by the ve 52 Window Glass in the Making amount of poor quality that is sent back to be re} melted, instead of being packed and sent out to the trade. SORTERS The various sizes, qualities, and thicknesses of the , cut glass are kept separate. All these are carefully examined again by skilled sorters, or inspectors who rectify any mistakes in grading by the cutters, and who are finally responsible for the finished product conforming to the Company’s standard of quality and thickness. In the grading of the glass, the quality is deter- mined by the defects—the glass of better quality naturally contains fewer and smaller defects than the glass of poorer quality. The rules for grading the glass will be found in the Appendix under the proper heading. After the glass has passed this inspection it is) sent to be packed. eee ER xX BOXES AND PACKING eS a tule, in this country, all window glass is packed in boxes containing the near- x ) est number of lights or panes that will iacked in boxes containing as nearly as possible 100 quate feet. Some of our specialties are packed in voxes containing 300 square feet. All our boxes have reinforcing cleats at the tops nd bottoms of the heads. They are made according 0 a definite, uniform rule for the various sizes and hicknesses. The Company’s name, the number of he factory, and the size of the glass to be packed n the box are all neatly branded by a branding ma- hine on one of the heads of the box. For packing the glass in the boxes, we use long, pecially threshed, rye straw, which must be kept ibsolutely free from all moisture, or else the damp- 1ess in it will attack the surface of the glass and sause the glass to fade or discolor. The glass, when finally packed, is thoroughly cushioned by the straw from contact with any part of the box. All glass is packed in long rye straws to insure safe transportation. CHAPTER XI LABELS, QUALITY SLIPS, AND BRANDING «(fy RANY dealers furnish a large amount < single thick glass toconsumers as doub. AX ) thick; and a great deal of glass of a lov h Kes grade of quality as being of a high¢ grade, because of the increased profit that can made by these substitutions. This would not kt possible if buyers had more knowledge of windoy glass and its process of manufacture. When deale1 resort to that practice, they must change according ly the branding placed on the boxes by the man ) ay ew WAS NS ufacturers. On each light of ““A” and “AA” quality gin pre duced by the American Window Glass Company is placed a label bearing a copy of the Company’ registered trade mark and certifying the qualit and strength of the glass. If the glass is not s labeled, it is of a lower grade than “‘A”’ quality. In each box of glass of a grade inferior to ““A’ quality, there is placed a slip of paper, known as : “Quality Slip,’’ on which is printed the Company’: Windows on a . Florentine Bridge — Gi fat I ite yi if (i WA te F Window Glass in the Making = 55 ume and a certificate of the quality and thickness ‘ the glass contained in the box. ‘These labels and quality slips are a protection zainst the substitution of a lower quality for a igher quality of glass or of single strength for ouble strength. They are an insurance or guarantee ) the buyer of the thickness and quality of the lass as packed by us. When a quality slip is not yund in a box of glass of the American Window lass Company’s manufacture, an explanation 10uld be obtained to account for its absence. On the printed head of each box of glass of reg- lar quality, the packer stamps with a steel die, the tters designating the different grades of quality. AA” indicates the best quality; ‘‘A’’ the next best; id “B” the next lower grade. On boxes of ‘‘off-quality’’ glass, is stamped the ord “Fourth,” or the letter “‘C.”’ The latter indi- ites the poorest grade of glass packed. The Com- any s name never appears on boxes containing ‘“C” uality. If the glass is double thick, the word ‘“‘Double’”’ is amped across the printed head. Boxes not so latked contain single thick, unless otherwise iarked. The names of the cutter, packer, as well as a num- *r are stenciled on the printed head of each box. rom these it is possible to learn the exact date the Venetian Palace 56 Window Glass in the Making glass was packed, and to trace it back through the different departments that handled it, to t machine on which it was made. In case of any co plaint or question regarding the glass, it is essent that the Company be informed of the marks the box. | Payee RX TI WAREHOUSING AND SHIPPING WBEYTER the glass is packed, it is taken to the ij Eo! Ns S) " ¥Y warehouse to be stored or is sent out t badly ventilated warehouses are certain to have uch trouble with the glass fading, even though 1e composition be of the very best. Everyone who as occasion to store glass for any length of time 10uld inquire carefully into its analysis and ascer- in whether it has been dipped in the muriatic ath, so as to make sure that it can be stored safe- r. In case it is not of the proper composition or has ot been properly treated, it is certain to discolor or ide in a very short time when exposed to moisture. When shipping the glass, the greatest care is xken in loading the cars. The boxes must be se- ately wedged and braced to avoid shifting in trans- ort. Much unnecessary breakage is caused through morance or carelessness of shippers in the proper yading of glass. When a car is properly loaded, the lass will carry with practically no breakage in ‘ansit, and is almost invariably received by the astomer in perfect condition. 1¥ 5 CHAPTER XIII DEFECTS IN GLASS MELTING DEFECTS =F the materials used in making the gla PR have not been of sufficient purity ar Vile 6 fineness, or are not well mixed in co MES E59 rect proportions, or if the furnace hz not been operated in a proper manner, the glass wi contain many defects that could have been avoidec Of the defects that may be found in any kind of glas: the following are the most important ones, occurrin in the melting and refining stages of the process: 1. STONES—These may be of silica or clay resulting either from particles in the compositio too large to be melted, or coming from the furnac structure itself. They may also be caused by wron proportions of the ingredients, by devitrification, c by the improper operation of the furnace. No mai ter what the cause or the nature of them, the never should be permitted in the finished product They not only disfigure the glass but cause grea breakage. , 2. SEEDS AND BLISTERS—Frequently, afte Windows in a Bavarian Town Hy Window Glass in the Making 59 1e glass has reached the working zone, we find bub- les of various sizes, formed by the gases given off y the chemical action that takes place in melting, r by atmospheric air enclosed in the composition, thich, from various causes, have not been able to scape. Similar bubbles are also formed in working wrough the carelessness or incompetence of the rotkmen in permitting small portions of air to be aveloped in the glass. In the subsequent stage of 1e process these bubbles are elongated to a greater r lesser extent, taking on an elliptical shape ac- ording to their size and the process of manufacture. he very small ones are called ‘‘seeds,’’ while the irger ones are called ‘‘blisters.’’ 3. WAVES OR REAM—These are wave-like steaks or bands visible in the finished glass when iewed at a sufficiently sharp angle or in a reflected ght. They appear to be of a slightly darker green- h tint, and are slightly thicker than the other por- ‘ons of the glass. They indicate a lack of homo- eneity in the glass, caused either by irregularity in ne heat of the furnace or by a change in the kind t proportions of the materials filled in the furnace. carcely any glass is entirely free from them. Some- mes they are heavier and more numerous than at ther times. When they are quite light they are very ifficult to detect and cause very slight distortion; Windows in a French Chateau = 60 Window Glass in the Making but when they are heavy, the distortion is consid) able. This defect is properly called, ‘“‘ream.”’ 4. CORDS AND LINES—“‘Cords”’ is the nay given to threadlike streaks often found in glaj, that appear to be of a different nature from the mip portion of it. They hinder the vision through ti glass. Sometimes they cover the entire piece, a} at other times only a portion of it. | They are caused either by a too sudden lowerip of the heat of the furnace or by the chilling of tk glass that is being ‘‘worked up’’ into the finishi product. ) In the hand-blowing process of manufacture thj usually extend around the cylinder in more or lis irregular fashion. In the mechanical process, thi extend in parallel lines in the direction in which t) glass is drawn and are sometimes known as “‘lines) 5. STRINGS—These are fine transparent threals of glass that are not made in the ordinary meltii but which come from the vitrifying of some porti| of the furnace structure. They are of an entirely d/ ferent nature from the body of the glass and a readily noticeable when they have been incorp rated into the finished product. | 6. KNOTS—Knots are small particles of gla that have not been as thoroughly melted as the re| of the glass. They are of the same color as the gla Windows— Mt. Athos, Greece Window Glass inthe Making 61 put noticeably of a different nature. Sometimes they are entirely clear, like very small glass beads; at other times they may have a grain of sand imbedded n them. It is a defect quite similar in character to stones, except that the stones are not vitrified like ‘he knots. They should never be allowed in the inished product because they disfigure the appear- ance of the glass and cause excessive breakage. FLATTENING DEFECTS Formerly many defects were introduced into the zlass in this step of the process, though our recent nventions demonstrate that none of them are in- 1erent or necessary; all result from either careless- 1ess or lack of skill by the workmen, or failure to ontrol the process scientifically. The following are the principal defects found in ome of the flattened glass: 1. BURN—This results from running the oven it too high a temperature or permitting the glass © remain too long on the flattening stone. This auses the glass to have a faintly pimpled or slightly is glass that has been marred by the rolls in some f the sheet drawn processes. 2. WRINKLES—These resemble corrugations anded appearance. \ When glass is burnt it has the same appearance \ \ ed Caneo—an old harbor is of Crete Or 2 ee ae we at wd ‘i y 4 aly alamo 62 Window Glass in the Making in the glass caused by the sheet not having been « tirely ‘‘ironed out’’ on the flattening stone. Glass containing wrinkles never should be pack« because they always cause breakage. 3. COCKLES—These are slightly raised plac on the surface of a sheet of glass, caused by the fa ure of the flattener to “‘rub out”’ properly the fl: tened sheet. When these are found in cylinder made glass, tl defect is identical in appearance with the humps a depressions found in glass made by some of the she drawn processes. OTHER DEFECTS SCRATCHES—The most common defect in : glass is scratches. They are found in every kind glass that is made, regardless of the process of ma ufacture. From the time the glass passes from t. plastic state to the solid, it is liable to be scratch at every stage of the process and with every ha dling. They are usually caused by the lack of care skill on the part of the workmen, but sometimes | the process of manufacture. They are on the surface of the glass. Some are ve large and heavy, while others are very fine, ligt and almost imperceptible except to the train eye. Few realize how easily glass can be scratch tia ie itil Window Glass in the Making 63 by drawing a hard, rough substance across its sur- face, or how the scratches disfigure it. More good glass is spoiled by scratches than by any other defect. _ FADED GLASS (Stain or Rust)—AIl window glass, regardless of its composition, is susceptible to attack by chemical action that begins with mois- ture, and will therefore discolor or fade, no matter ‘whether or not it has been previously dipped or washed in the dilute muriatic acid bath, unless the acid bath is sufficiently strong to cause the surface of the glass, when dried, to show an acid reaction. Glass not so treated will discolor or fade very much more quickly than the glass that has been so treat- ed. If the acid bath is too strong, it produces a _“hum,”’ or cloudy appearance on the surface of the glass, which renders it very difficult to detect the defects. Sometimes manufacturers use an excessive amount of the acid to hide the poor quality of their glass. When moisture occurs on the surface of the glass, either from sweating or from any other cause, and it comes in contact with ordinary dirt or carbon, it sets up a chemical action that attacks the surface of the glass and causes the discoloration that we call “‘fade.’’ This is sometimes called “‘stain’’ and sometimes called ‘‘rust.’’ It manifests itself at first 64 Window Glass in the Making by an iridescence on the surface of the glass, a though carbon oil had been placed on it, whic dulls its lustre. If the chemical action continue a sufficient time, the glass then takes on a froste: appearance, which will gradually increase,until th) glass finally becomes opaque. Glass containing toi much soda or too little lime will fade very quickly Careful housewives have spent many hours o wasted efforts trying to wash or rub off the oil-lik) stain, caused by ‘“‘fade,’’ on the glass in the win dows of their homes. In the early stages of fade, th! discoloration can be removed only by dipping thi glass in an acid bath; but if the glass has becom quite opaque, nothing can be done to restore it! former brilliant surface. | Sener ' ie lek XIV WINDOW GLASS WAVE ‘at a sharp “ae between the line of sight and the glass. It results from the fact that the outside surface of the cylinder is longer than the inside; and when flattened, it must be compressed, as it were, within the same space as the inside surface. It is not a defect. All window glass, no matter by what process it is made, presents an appearance practically identi- cal with that caused by the window glass wave, when it is viewed at the same angle. In some of the sheet drawn processes it is much more pronounced, and causes greater distortion. Prior to the invention of the sheet drawn proces- ses, it was believed that glass drawn in sheet form would have an entirely different appearance from cylinder made glass. Unfortunately, the expecta- tions of the inventors were never realized. All such glass still retains the characteristic appearance of cylinder made window glass. In the sheet drawn processes this results from slight temperature varia- 65 66 Window Glass in the Making tions in the bath of glass or lack of homogeneity F | When the plastic glass is subjected to the drawin| and stretching strains, these differences in the glas temperatures produce a more or less wavy appeat ance in the drawn sheet, similar to that of th window glass wave in cylinder made glass. CHAPTER XV OUR PRODUCTIONS RG Microscopic Slides Lantern Slide Glass Photo Dry Plate Glass Diagnostic X-Ray Glass 16-0z. Picture Glass Single Strength Glass Double Strength Glass 26-0z. Glass 29-0z. Glass 34-0z. (42 millimeter) Crystal Sheet 39-0z. (%.6”, or 5 millimeter) Crystal Sheet We also produce the following ‘‘Processed Glass’’: Ground Glass Chipped Glass, 1 Process Chipped Glass, 2 Processes - When glass is described as of a certain weight, it means the weight per square foot of that thickness. 67 i, Fi e oy Ea a igi ne 68 Window Glass in the Making | A square foot of window glass one inch thic weighs, on the average, thirteen pounds. All of the foregoing productions are of the sa composition and are made by the same process They differ from one another only in the thickness flatness, and selection of quality, according to th special purpose for which the glass is to be used. | MICROSCOPIC SLIDES, LANTERN SLIDE GLASS, PHOTO DRY PLATE GLASS, AND DIAGNOSTIC X-RAY GLASS The above named productions are all of the sam general class. They are much thinner than othe glass, and they require absolute flatness and thi very best quality. We are the only manufacture in this country who can produce such glass. Year: ago attempts were made to produce it here by thi hand blowing method, but without success. Ir 1913, after some years of experimenting and ar enormous expenditure of money, we began its pro: duction on a commercial scale, and succeeded in pro- ducing a quality superior to that of imported glass. Shortly after the close of the war, the Europear manufacturers resumed the production of this glass and sold it in this country at prices with which we could not compete, notwithstanding our superior quality. As a result, we were obliged to curtail very greatly our production of this kind of glass. Windows on a by-street of Constantinople Mf . ie a, Window Glass inthe Making 69 When our country went into the war, we were the only manufacturer here that could make the kind of zlass required for eye pieces for gas masks. These were made of very thin glass, cut into circles about 2% inches in diameter. They were subsequently slaced together in pairs with a thin coating of iquid celluloid between them and were then sub- ected to very great pressure. If the glass was not serfectly flat, or was not cut with a perfectly smooth sdge, the celluloid would not bind the two circles jogether sufficiently to permit them to be used. This process had the effect of rendering the glass “non-scatterable’’; that is, pieces would not break off and fly, when it was struck a very heavy blow. Jnder the concussion the glass would crack, but ull the particles would remain firmly held together oy the celluloid binder. Through the patriotic assistance of men, women, ind children of a Red Cross Unit during the war, in olunteering to learn to cut this glass when other abor was not to be had, we were able to furnish 17,000,000 of these circles for the use of our army und the armies of our Allies. 16-OZ. PICTURE GLASS We are the only manufacturer making 16-oz. Picture Glass in this country. Prior to our making 2 gms - Ae f EZ “ ; en jngam ea saat i eh am a0 koro \ty 0 Jl ganna amo Windows at Bastia, @ port of Corsica Wake 5 —_ ——— a Taare “at San : re 54 70 Window Glass in the Making it, all such glass was imported from Europe, b our glass proved to be of such superior quality thi very little is now imported. It is thinner than sing strength window glass, ranging in thickness fre 1214 to 14 lights to the inch, but is graded to much higher standard of quality. It is sold in th grades, under the trade designations of ‘‘Superfine which is the best quality; ‘‘Selected,” which is very fine quality but not quite equal to the be and “‘Commercial,” which is a somewhat poor grade but superior to ““B” quality window glass. In producing it great care must be taken at eve: stage of the process, and only the most skilled m¢ handle it. As a result, it has the even thicknes flatness, smoothness of surface, lustre, and freedo from defects so necessary in glass used in framir high grade pictures. It is purposely made thinner than ordinary wit dow glass in order to transmit more light than tk thicker glass. Its exceptional quality makes it als especially adaptable for usein mirrors, French door and for any other purposes that require glass of vet attractive appearance rather than of great strengtl In order to protect the buyer of this glass again: substitutions, a special label is placed either on eac light or on the paper that is placed between tk lights in all boxes of ‘‘Superfine”’ and “Selected quality. Pagoda of the - Sung Dynasty Window Glass in the Making 71 SINGLE AND DOUBLE STRENGTH WINDOW GLASS More than 90% of all the window glass used an- ually in this country is in these two thicknesses. he single strength, as its name would imply, is yuch thinner and consequently lighter in weight aan the double. That is really the only difference dfar as the glass itself is concerned. Greater care s always taken with the double strength glass and he most skilled men are used in making it, on ac- ount of the increased difficulty in handling it. Vhile the rules for grading are the same for both hicknesses, yet the double strength is apt to appear lightly better than single strength. The greatest ossible care is used with both of these thicknesses, nd there should be no material difference in the tading. The thinner glass should be used in places vhere the strength or thickness is not an important actor; but where the windows are exposed to very avy winds, it is safer to use the double strength lass. There is considerable difference in the prices of he two thicknesses—the single strength naturally osting less. The buyers should be able to distin- ish between the thicknesses. After the glass has een glazed in the sash, it is very difficult to detect he difference. By tapping the glass with some hard A Government Building in Rio de Janeiro 72 Window Glass in the Making substance the thinner glass resounds more faintly than the double thick. Complete details as to the thickness, flatness, and the rules for grading the above named production: will be found in the Appendix under the prope headings. F Those who use our glass for whatever purposes window glass is required, can be assured of having “The Best Glass’’ made. In the evenness of its thickness, in the flatness of its surface, in the bril: liance of its polish, in its durability and physica strength—it is not equalled by window glass mad¢ by any other process. 26-OZ. AND 29-OZ. GLASS These two kinds of glass differ from the regular} double thick glass in their thickness, special flat- ness, and higher standard of quality. Those tre- quiring glass slightly heavier than double thick and of a specially fine quality, will find that this glass will meet their every requirement. ~ CRYSTAL SHEET 2k 34-OZ. AND 39-OZ. OR 346” GLASS We introduced our 34-0z. and 39-oz. or %e glass to the trade as ‘‘Crystal Sheet,” a really beau- tiful glass. Its quality is so exceptional, its flatness so wonderful, and its uniformity of thickness so uy £3 “iff 4 ) a ia as (Sas SNS ac Tee are en ae ey re RA, ALL ry ( . " oo a x finn 2 if 3 a \ ) ay NS Ne 7 India—the Balconies of Lahore aa ford se Window Glass inthe Making 73 wfect that it is adaptable for many purposes for hich plate glass has ordinarily been used. In the aaller sizes 1t presents such a fine appearance that ly an expert can distinguish it from plate glass. It is suitable for glazing office buildings, hotels, spitals, public buildings of all kinds, and dwell- gs, in which not only the appearance of the glass very important, but the thickness and strength as ell. Large quantities of it are used in automobiles, 1 windshields, bodies, and accessories. It is also sed for typewriter keys, clock faces, showcases, yunters, shelving, car windows, small mirrors, * and table tops, and other furniture. All this glass is handled with special care. It is acked with paper between the lights, and every ght is labeled to identify the quality and thick- ess for which it is sold. Being thinner and consequently lighter in weight ian plate glass it does not require window sash of yecial construction, nor the use of extra heavy ish weights, which are necessary when using plate lass. It is also much cheaper than plate glass which sts about one-third more than our Crystal Sheet. Recently, large amounts of thick window glass ave been imported from Europe, in competition Syn ith our Crystal Sheet glass. Some of it is sold as emul | a= meu ; WN eeaat 44 millimeter glass, corresponding to 34-oz. glass; é WEE ; ad some is sold as 5 millimeter glass, which corre- Miesisae\" f= Ln a | Windows in ; Wen Guanajuato, Mexico Wi aw B eee, — ae 74 Window Glass in the Making sponds to 39-oz. or %6” glass. This foreign glass i made by a sheet drawn process that requires a dif of good window glass. Analyses show it to be high in soda, low in lime, and low in silica, and it there fore lacks the strength, density, and resistance t fade or stain of our glass, and it will not warehous as well. PROCESSED GLASS This is either in the form of ground glass o chipped glass. Ground glass is made by sandblast ing one surface of clear window glass, which give it a slightly frosted appearance that renders it sui able for obscuring purposes. This glass is often subsequently coated on thé ground side with glue, and placed in heated drying kilns. In drying, the glue “‘cracks off,”’ taking wit it thin particles of the surface of the glass, produc ing a chipped effect. When the glass has been suk jected to this process only once, it is known a ‘‘chipped one process,’’ but when the process is re peated, it is known as “‘chipped two processes.”’ | The chipping gives the glass a very attractive an unique appearance. The surface appears to hay leaves of all sizes, kinds and shapes, cut into th glass with all the beautiful veinings seen in fores leaves. The chipping, of course, hinders the trans Window Glass in the Making =_75 nission of light. Very beautiful effects can be pro- luced with this glass, either by itself or in com- ination with ground glass. It is very suitable and \ost attractive when used in door lights, transoms, abinets, screens, partitions, and windows. CHAP TERA ve COMPARISON OF GLASS \ BY glass is subject, we wish to call thé ¥4/@.4 reader’s attention to the fact that all} Those described under the heading, “‘Melting De fects,’’ are common to all kinds of glass, without any exception. In addition, each kind is subject top certain other defects that are incidental or character- istic of the process of manufacture. | OTHER WINDOW GLASS Comparing window glass made by different proc- esses, one will find the same kind of defects in each, though they may result from different causes. One process will accentuate certain kinds of de- fects, while other processes accentuate others. The process is never an argument as to the quality of the product. That, as we have seen, depends largely upon the methods of manufacturing. | Some processes of manufacturing window glass 76 Window Glass inthe Making 77 ave certain advantages over others. For the most art these are confined to an economy of labor, fuel, r both. Our process not only effects these econo- lies, but with our manufacturing methods it en- bles us to produce a larger percentage of glass of ae higher grades of quality than any other process 1 use throughout the world today. On account of the composition we use, our ethods of drawing and blowing, and the double nealing which the glass receives, our glass is less tittle and has a better nature than any other win- ow glass. In the Appendix we have inserted tables showing e tensile strength and modulus of rupture of our lass. A comparison of these tests with similar sts of any other window glass, plate glass, or olled glass, proves that our glass is stronger per nit of thickness than any other glass. In conclusion, the superiority of the American Vindow Glass Company’s glass over any other vindow glass may be summed up in the following losing sentences: It is the most durable glass. It is the strongest glass. It is “The Best Glass.” APPENDIX U.S. Government Master Specifications with our comment (U.S. Government Specifications are printed in Italics) APPENDIX Cj WING TO THE FACT that single strength ® window glass costs much less than the > double strength glass, and glass of a Zy lower grade of quality costs much less han glass of a higher grade, some dealers taking dvantage of the fact that few buyers of window lass are familiar with the rules for grading glass, esort to the practice of substituting the thinner lass for the thicker glass, and the lower grades of uality for the higher grades. This practice has teatly increased during the past few years on ac- ount of the severe competition in the business, nd innocent purchasers suffer as a result of it. Buyers heretofore have been unable to protect hemselves against these substitutions, by reason of ot having any positive and authoritative infor- ration regarding the thicknesses of window glass nd the rules for grading it. This information is now urnished by the United States Master Specifica- ion, prepared by the Bureau of Standards, after ery exhaustive study and research. It is known as orth ; in this eee 81 82 Window Glass in the Making This Specification was officially adopted by t Federal Specifications Board on April 1, 1924, f the use of the Departments and Independent Esta lishments of the Government in the purchase flat glass for glazing purposes. It is a valuable gui for manufacturers, architects, jobbers, dealers, g] ziers, users, and buyers generally, regarding the siz thicknesses, qualities, and rules for grading winde glass. A careful study of it will qualify one to jud window glass, and to know whether the glass ft nished is of the thickness and quality for which was bought. Since this ‘‘Master Specification’’ was publishe number of changes have taken place in the charact of the window glass produced in this country, ai in the designation of some of the qualities. Atte tion is called to these changes under the appropria headings. We have also added such explanato notes and comments on the ‘‘Master Specification as will give the reader a clearer understanding the subject. Those who wish to buy window glass of t highest quality, that conforms in every way tot “Government Specification,’’ should specify t American Window Glass Company’s brand—‘‘T. Best Glass.’’ It is the best glass for the for teen reasons we have outlined at the end of tl pamphlet. . ‘ * Window Glass in the Making 83 Architects who desire ‘The Best Glass’’ for the uildings they design should specify it as follows: “All window glass to be used in this building shall be the American Window Glass Com- _pany’s make or equal thereto, and shall be (here specify the thickness and quality of glass desired), All “A” quality glass furnished must have the manufacturer’s label on each light.” ‘the American Window Glass Company’s glass is pecified, the company will follow up the job when- ver requested, without any expense to the party equesting it, and report whether the glass furnished xc kind, quality, and thickness specified. Definition of Clear Window Glass” “Crear Winpow Guass’’—Transparent, relatively bin flat glass having glossy, fire finished, apparently plane nd smooth surfaces, but having a characteristic waviness f surface which is visible when viewed at an acute angle r in reflected light. “Crear Winpow Guass’’ és made at present by hand lowing, or by machine blowing and drawing into cylinders nd flattening, or by drawing directly into a sheet, the sur- ace finish being that obtained during the drawing process.”’ The ‘‘characteristic waviness” referred to in the oregoing definition should be distinguished from he heavy waves frequently noticed in glass of poor uality. These have the appearance of wide bands ® rc 84 Window Glass in the Making or streaks extending across the sheet, of a slight! darker tint than the main body of the glass. It is defect called “ream” and causes considerable di tortion. “General Principles Involved in Grading Glass” “All flat glass contains some imperfections and t, principle employed in grading is to exclude all defects th, would be objectionable in a given grade. This is difficu to do since there are no sharp lines of demarcation betwe grades, and experienced inspectors will differ in judgme as the quality of the glass approaches the limits of t grades. Small lights must be quite free from imperfectios as compared with larger ones, and the center of any she should be clear whereas the edges may contain more pt nounced defects.”’ “Central Area of the Sheet” “In window glass the central area of the sheet is co sidered as being a circle having a diameter equal to ha the width of the sheet or an ellipse having one diamei equal to half the length of the sheet and the other diamei equal to half the width of the sheet.”’ ; Terms “The following terms shall be used in specifications. applying to clear window glass: seeds, blisters, ‘? burns, scratches, strings, cords, stones.’ | To these should be added ‘‘ream’’ and “cockles pa be 3 Window Glass inthe Making 8; Fr: Ja ap Definitions, causes, and brief descriptions of these arious imperfections are all set forth in the chap- of ‘Defects in Glass.”’ Yefects Prohibited in All Grades Stones, knots, very heavy lines or cords, long or uised blisters, wrinkles, heavy burn, foreign par- icles adhering to the surface of the glass, deep sratches, fade or stain, and in general every defect dat might cause excessive breakage is prohibited 1 all grades of window glass. Method of Examination” “The method of examination is described in these speci- cations im order to make the results more uniform and efines the condition under which glass should be exam- ued because the distance from the glass, the angle between 0¢ glass and the line of sight, and the intensity of light I) affect the visibility of imperfections. “These specifications should be interpreted by examining be glass in the following manner, with reference to the efinitions of defects listed in the glossary (U. S. Speci- cations): “The glass should be examined when placed in a position imilar to that of a glazed light with the observer's eye on Tevel with the center of the sheet, and looking through the lass from a distance of about 36 inches into the light from clear sky without any sun or any close background. “The visibility of waves, lines or cords depends chiefly pon the angle of observation, and the intensity of these 86 Window Glass in the Making 3 defects can be classified on this basis. The values given fi angles are the angles the line of sight makes with the she of glass when in a vertical position. Slight tovernem the head horizontally through an angle of two or thr degrees will make waves or lines more perceptible.” i “Acceptance or Rejection” j “Acceptance or rejection of a shipment or delivery sha be based on an examination of the following quantities: ‘* For orders of 100 lights or less, all shall be examine for orders of 101 to 500 Lights at least 50% shall be amined; fororders of 501 or more lights at least 25% sha be examined. Boxes shall be selected from the shipme at random. q “Tf not more than 10 per cent of the lights examined a 4 below quality, the shipment shall be accepted provided ti lights below the specified grade are not distinctly below ti none, limit of the next lower grade. “Tf, however, an entire shipment of 500 lights or ma examined, not more than 5% may be below quality.” The foregoing specification was drawn to cov the delivery of glass ‘‘to the job” in small lots. } carload shipments it is customary to judge the gla: by the quality found in 25 or 50 boxes of the s i ment, selected at random. | “Specifications for Clear Window Glass for Glazing” “Clear window glass for glazing is made in several ¢ es Rong a 4 Window Glass in the Making 87 ferent qualities and in the varying thicknesses shown in Table 1, page 95. “Single strength and double strength window glass is regularly supplied in two standard qualities, known as A quality and B quality. A limited amount of this glass, known as AA quality, which is especzally free from defects, is sometimes selected for special purposes and may be spec- ified if desired. It must be borne in mind, however, that the total amount of AA glass produced by the manufacturers does not exceed 3% of the total amount of window glass produced. “There is also a limited amount of single strength and double strength glass produced in a quality inferior to B quality, and is known as Fourth quality. The amount of glass produced in this quality also represents a very small percentage of the total window glass produced. “A quality of single strength glass inferior to Fourth Quality is also produced in very limited quantities, and is known as C quality. This is the lowest grade of glass that 15 packed and marketed in this country. “Window glass is also produced in thicknesses heavier than double strength, and according to its thickness it is classified as (1) 26-02. glass; (2) 29-02. glass; (3) 34- 0x. glass; (A) 39-0z. or 3A” glass. _'26-0z. and 29-02. glass are produced only in A and B Be slisies. _ "34-02. and 39-0z. or 346" glass are produced in glazing and factory run quality.” 88 Window Glass in the Making RULES FOR GRADING “AA” Quality : This quality requires the best grade of glass ob tainable, but it does not require perfect glass or sub- stantially perfect glass. As a matter of fact, it is | impossible to produce flawless glass of any kind, in| large sizes or quantities. The finest glass made only) approximates flawless glass; and the larger the di-| mensions, the more flaws it will contain. | Defects of various kinds are permissible in this) quality, but they should be very slight or not dis- coverable except on close inspection. In general, the center of each light must be prac-| _ tically free from defects. Each light must be viewed) as a whole, and not judged by single defects in ‘7 ferent parts of the light. | On account of our very high standard of grading, | it is impossible for us to produce this quality in| sufficient quantities to enable us to fill orders for it| quickly. Buyers who insist upon having it must ex- pect greater delay in the shipment of their orders than when ordering the other qualities. | The price of this quality is considerably hight than that of ‘‘A” quality. This is made necessary by the large amount of waste occasioned in manufac- turing this quality and by the additional lab cost involved in producing it. Window Glass in the Making 89 “A” Quality “The defects permitted in this quality are faint strings or lines, slight burn, small seeds, small blisters, and light scratches. “No light shall contain all of these defects, and those present may not be grouped when in the central area of the sheet. “Strings, lines, or burn specks shall not be of such inten- sity that they are visible when observing the sheet at an angle greater than 30 degrees between the line of sight and the glass. “Waves shall not be visible at an angle greater than 20 degrees with the glass. “Blisters shall not exceed 14 inch in length unless they occur near the edge of the sheet. “In general, the central area of the light shall be practt- cally free from defects, and the appearance of the light as a whole shall be such that there is no perceptible interference with the vision as long as one 15 not looking through the glass at an acute angle.’’ It is exceedingly difficult to judge defects by view- ing the glass at a specified angie, for the reason that the slightest motion of the head or the eye will change that angle. Moreover, the eye takes in such a large portion of the surface, that one part of the sheet will be viewed at one angle and another part will be seen at a very different angle. rl 90 ~=©6- Window Glass in the Making The limit of the angle at which waves are visible is too low. There is no good reason why waves or ream may not be visible at as large an angle as strings and lines without unduly affecting the quality. _ “A” quality should be used in windows of all buildings the appearance of which is an important used even in the finest buildings is either “’B” quality oreven a lower grade, becauseit is cheaper, although doubtless a very large percentage of it is specified in ‘A’ quality. A building glazed with the poorer | grades of glass does not present the appearance of one glazed with “A” quality. : No specific rule can be laid down as to the size of any defect permitted. A defect too large for a small light might be permitted in a much larger light. The location of the defects also determines the nu m- ber and size permitted. Seeds and small blisters that would not be permissible in the center of the light would be allowable if remote from the center. To protect the architects and buyers who desire to use the best quality of window glass, we adopted the practice of putting a label on each light of “A” and “AA” quality. For their further protection the architects and buyers should be able to distinguish the inferior see of glass when they see them. Window Glass in the Making gt RB” Quality “This quality admits of the same kind of defects as A quality, but they may be larger, heavier and more nu- merous. “Occasional scattered blisters not more than V4 inchlong may occur over the central area of the sheet. Larger blisters up to 1 inch in length may occur about the bordering areas. “Waves should not be of such intensity that they are vis- ible when observing the sheet at an angle greater than 45 degrees with the glass, unless on the border. “Burn spots may be visible when looking directly through the glass, but they must not cause any appreciable de- pression and the speckled appearance must not be so great as to interfere with vision when examining the glass in the Specified position.’ In general, the defects permitted in this glass are SO prominent as to attract the attention of the casual inspector at once; but they should not be so nu- merous as to prevent a considerable portion of each . from being reasonably free from them. In buildings where the cost of construction is the most important factor, ‘“B’’ quality glass should be used. However, great care should be taken to obtain the highest standard of ‘‘B’’ quality. There are many factories turning out glass branded ‘‘B’”’ quality 92 Window Glass in the Making which is really only “Fourth,” and even “‘C”’ qual- ity. Such brands are always sold at lower prices than our “‘B” quality, but the difference in prices does not compensate for the great deficiency in quality of the cheaper glass. Buyers should insist upon having the q American Window Glass Company's quality slip in each box of “‘B” quality. “Fourth” Quality Since the Master Specification was published, the amount of single strength and double strength glass produced in this quality has increased very greatly. Glass of this grade is known to the trade as ° off quality”’ glass, and is not subject to rejection on ac | count of defects. No very definite rules can be laid down for the grading of this quality. Glass that is too poor for ““B’’qualityis usually classed as “Fourth” | quality, unless the defects are so many and so glar- ing that they leave practically no portion of the’ light free from them, in which case it is classed as| “C” quality. It may contain many prominent defects that will hinder the view or distort the appearance | of objects viewed through it. These include blisters, heavy lines or cords, ream, cockles, and heavy burn. | On account of the disfiguring and distorting de- fects found in glass of this quality, it should never be permitted to be used in dwellings, schools, or other buildings where the appearance of the build- Window Glass in the Making 93 ing or the vision of the occupants is a factor. It sells at very much lower prices than “‘B’”’ quality, and much of it is substituted for ‘‘B” quality in window sashes that are sold in markets where ‘‘price is the only consideration.’’ “C” Quality This is another type of ‘‘off-quality’’ glass, of a lower grade than “Fourth” quality. It is really rub- bish that should be remelted instead of being sent out to the trade. Such glass is usually not fit for use for any purpose except hotbed sash, and it is gen- stally produced only in single strength, in a limited aumber of small sizes, none of them larger than 12x 18. It is sold at very much lower prices than‘‘Fourth” quality, and is frequently substituted for ‘“‘Fourth’’ quality, or even ‘‘B’” quality in markets where the buyers do not have sufficient knowledge of window glass grading to enable them to detect the differ- once. It may contain any and all the defects found in window glass, except such as will cause excessive breakage. — “C” glass is not subject to rejection or claims on account of defective quality. It always shows a much higher breakage in shipment than glass of the better qualities. 94 Window Glass in the Making All 26-0z., 29-0Z.;3 4-0z., and 39-02. or 346” glass Pe by us : known to the trade and sold a “Crystal Sheet.’ ig The 26-oz. and 29-0z. glass is produced i in “A” ot **B”’ quality only. RULES FOR GRADING HEAVY SHEET WINDOW GLASS OR “CRYSTAL SHEET”: “Heavy Sheet Window Glass Glazing Quality’ ; “The same specifications for selecting provided for A quality single strength and double strength glass shall apply.” 7 “Factory Run Quality” 7| “This quality is the run of glass as produced by the factory. It may contain glass of very good quality a 1d some glass of very ordinary quality. However, the glass that contains heavy cords, lines or strings over the entire surface, raised blisters, cap strings, stones or batch par- ticles causing a rough surface, or depression, or having its surface covered with heavy burns, wrinkles, deep scratches or stone, shall not be included in this quality.” | The terms used by us to designate the qualities of next best quality. The latter embraces glass of all qualities as produced, without selection, except that glass containing very large or very many disfiguring Window Glass in the Making 95 if XG : = Bcts, such as those described under the heading, ‘Factory Run Quality,’’ is culled out as ‘‘off- yuality”’ glass and sold as ‘‘OB” quality. Stock sheets are sold as ‘‘Selected Quality Stock Sheets.’ This includes the sheets of glass of all qualities just as produced, except those containing 30 many or such large defects, as would render it im- possible to cut up the sheets to advantage. These poor quality sheets are set aside and sold as ‘“OB” quality stock sheets, at materially lower prices than = ‘Selected Quality Stock Sheets.” “Table 1—Tolerances in Thickness and Average Weight of Clear Window Glass.”’ be Thickness Number of Average es in lights per weight 2 inches inch in a e Min. Max. Min. Max. eS. Single Strength ...... .080 .100 10.5 12.0 18.5 Double Strength ..... 111 .125 8.0 9.0 24.5 26-0z. Glass......... His 2135" 7.5 8.0-26.0 29-0z. Glass......... 135 .148 6.5 7.0 29.0 34-02. Heavy Glass... .150 .175 6.0 6.5 34.0 39-0z. Heavy Glass.. .176 .205 5.0 5.5 39.0 Microscopic Slides... 038 .045 22 to26 9 Lantern Slides ea .050 .055 18 #020 11 Photo Dry Plates.... .062 .071 14 #016 14 X-Ray Plates ees .071 .080 12% to 14 16 16-0z. Picture ....... .071 .080 12144014 16 96 Window Glass in the Making Glass that is slightly thicker than the maximum) specified for that strength is always accepted ; r within the specification, unless it is so much thicket that it is not suitable for the purpose for which it is to be used. A purchaser, however, is not obliged to accept glass that is appreciably thinner than the minimum allowed for that strength. q| As arule, the thickness is judged by the thickness of all the glass in the box, and should not be re a) bee =F oe (@) eS © Wa O < ia’) O ay om @) nee 2 ct a m a rst) =} ie fe) oO e) By ct 2 mt o 2) +a =) ig) ” n and should not be demanded. “Tolerances in Thickness in Individual Sheets” ‘Thickness of individual sheets shall not vary mote thickness may be equal to the tolerance allowed for that class.’ “Sizes Obtainable” (U.S. Govt. Specifications) “The maximum dimensions recommended are: Width in Length in inches inches For Single Strength ............ 40 50 4 : For Double Strength ........... 60 80 For Heavy Sheet ...........0.04- (66. 9G ee oe. Soa aati 3.) , Window Glass in the Making 97 Single strength glass is made up to 54 inches in agth, but we do not take orders for sizes in this ickness larger than 84 united inches. Nor do we ke orders for heavy sheet glass in sizes larger than be “Glass must be cut to dimensions ordered with an al- wable tolerance of ¥32" per 1%" of thickness.” Flatness” “All clear window glass shall be relatively flat. Slight weature, provided it is regular, will be allowed, but the naximum deformation or bow shall not make an arc sigher than 0.5% of the length of the sheet. Reverse curve r crooked glass is not allowable.” Since the above was published we have developed |new process of flattening, which enables us to pro- luce window glass that is absolutely flat from any sommercial or practical standpoint. We guarantee his new-process-flattened glass to be as flat as any window glass made by any other process. This new process also anneals the glass better han the old process, which makes it softer to cut and less liable to break in handling than the glass lattened and annealed by the old methods. : “GLAZING” “Window os should ALWAYS be glazed with the convex side out.’ 98 Window Glass in the Making The above Specification was drawn when practi: cally all window glass was bowed, but now the greater portion of all window glass produced is flat The glazing is one of the most important factor in the appearance of the glass. All window glass. whether bowed or flat, and irrespective of the proc. ess by which it is made, has one side that presents a better appearance when glazed to the outside. In the case of bowed glass, it is the convex side. When! so glazed, such glass not only looks better, but it will withstand greater wind pressure and concus- sion shocks than if glazed with the concave side out From the standpoint of putting the glass into th sash, flat glass can be glazed with either side out; but from the standpoint of the appearance of th glass in the sash, it is just as important to gla ze it with the proper side out as it is when glazing bowed glass. In glazing flat glass, the side on which the glass was cut should be glazed to the outside, as all glass is usually cut on the best surface. To distinguish on which side the glass is cut, ii is necessary to examine carefully the edges of tht glass. The edge of the surface on which the glass| was cut will have a slightly nicked or roughened appearance, made by the cutting tool, while under part of the edge will show a slightly wavy appearance caused by breaking the glass apart. Sr eal grin Se Cap eh. em bien Window Glass in the Making 99 _ If the windows of a house glazed with window glass are viewed from the outside, and present a smooth, lustrous appearance, and show clear, well defined images of objects reflected in them, one may be sure they have been glazed with the proper side out. But if they present a rough, battered ap- pearance, and distort the images of objects reflected in them, they have been glazed with the wrong side out. Of course, glass that contains humps and de- pressions on its surface will not reflect properly, no matter which side is glazed to the outside. _ Inthe framing of pictures it is also very important that the better side of the glass should be framed to the outside. Otherwise it will interfere with a proper view of the picture, and portions of it will appear distorted. All window glass, no matter by what process it is made, has a ‘‘grain’’ that extends in the direction the glass was drawn. Ordinarily, in glazing, this “grain” should be vertical in the sash or frame, as the glass presents a much better appearance when viewed in a reflected light if so glazed. But when glazing sash to be used in automobiles, railroad coaches, or other vehicles, the “‘grain’’ should be horizontal in the sash. When so glazed the view from the vehicle is clearer and freer from distortion than when the “‘grain’’ is vertical in the sash. When i Pe tea 100 }6© Window _ Glass in the Making ordering glass for vehicles, the dimension that is to | extend horizontally in the sash should be specified first, and the vertical dimension last, in order tha t | the glass may be cut accordingly. | STRENGTH OF “THE BEST GLASS” In order to produce a grade of window glass that | would be justly entitled to be called ‘The Best Glass,’’ judged from every standpoint, the Ameri= can Window Glass Company used the results : a very large number of scientific and practical tests of numerous kinds of glass. Those tests include th 1c following: ; Tensile strength; elasticity by bending and tor sion; strength of glass in frames to show its resis- tance to impact, to slow loading at the center, and to uniform loading over the entire area; annealing; extent of expansion by heat; determination of the modulus of rupture by bending, impact, loading. and torsion; chemical composition; and others. — Many of these tests were made by the Unite States Bureau of Standards which tested approx imately 5000 samples of glazing glass of various types and makes for strength with transverse loam and impact to determine the modulus of ruptur Several thousand samples were also tested for var- ious properties in the laboratories of the University of Pittsburgh and other testing laboratories. Window Glass in the Making ror MODULUS OF RUPTURE Of all the tests made, that of the modulus of rup- ture is the most important to the glass user. The technical term ‘‘modulus of rupture’’ is ‘‘the meas- ure of the force which must be applied in order to produce rupture,’’ z.e., to break the glass, when subjected to tests for bending, impact, loading, or torsion. Its value is expressed in pounds per square inch and signifies the average load required to pro- duce the rupture under any of the four tests above mentioned. RESULTS Those tests demonstrated the superiority of the American Window Glass Company’s brand ‘‘The Best Glass” in the matter of tensile strength and modulus of rupture over any other window glass, plate glass, or rolled glass. _ Furthermore its higher modulus of rupture proves that ‘“The Best Glass’ will withstand greater wind pressure than any other glass. For the benefit of those who desire precise infor- mation as to the modulus of rupture of our glass, we submit a copy of a diagram (Fig. 1) prepared by the *United States Bureau of Standards, Department of Commerce, showing the modulus of rupture of *Presented by A. E. Williams, of the Bureau of Standards, be- fore the Glass Division, American Ceramic Society, Pittsburgh Meeting, February, 1923. By permission of the Director of the Bureau of Standards, Department of Commerce. eur, '* 102 Window Glass in the Making 7 various thicknesses of clear window glass and \% inch polished plate. This diagram shows the ove t whelming superiority of the clear window glass in \ the matter of modulus of rupture. . 3 ep eee ee ee MODULUS OF RUPTURE { 15000 OF CLEAR SHEET AND POLISHED PLATE GLAS om RY vf Ni Lo ” YU vnunet ama = 13000 £S Se RY ee E: sf go Si. g - gh B ss? 3 S 8 Ss tas | 11000 SK —_8_*_f§__* HG 38 & yy : Sos... + Sys 3 Ww Ss e a Ss BS = 3 * ‘ faa] 9000 aus : : eo Soa NON ee 5 7000 as) 3 WEIGHT FIG. I The figures given in the diagram for the modulus - of rupture of clear window glass are identical with the figures furnished to the American Window Glass Company by the Bureau of Standards, showing the results of numerous tests conducted by the Bureau of Standards on samples of the American Window Glass Company’s glass submitted to the Bureau for Window Glass in the Making 103 purposes of tests. The results of the tests by the reau of Standards on the American Window Glass ompany’s glass for modulus of rupture were con- firmed by similar tests made by other testing lab- a \ The Tensile strength tests of the American Win- ow Glass Company’s brand, ‘“The Best Glass,” show a tensile strength of 5100 pounds per square inch. Similar tests conducted on other kinds of glass demonstrated that none of them approeched the tensile strength of ‘The Best Glass.” Fourteen Reasons - FOR YOUR SPECIFICATION OF “The BEST Glass” 1 Our melting furnaces are the largest iat the world and produce perfectly melted 7 glass. ia 2 Our improved mechanical process of drawing and blowing gives our glass greater tensile strength and higher mod- ulus of rupture than any other window glass, plate glass, or rolled glass; con- sequently, it offers greater resistance to wind pressure. ‘ 3 Our latest improvements in our blow- ing machines enable us to provide ab- solutely perfect cylinders, which make it possible to secure the best flattening re ever obtained. | 4 Our new method of flattening gives ou glass a perfectly smooth surface, andl brilliant polish, unequalled byany orhes window glass. 104 oe : oh Rs Ete ee o a Ay) r fh NPT aay Ne at pola nas - ee eae wee 5 6 Window Glass in the Making 105 Our glass has less wave than any other glass, and consequently, shows less distortion. Our glass is flat; it contains no reverse curves. 7 Our glass is uniform in thickness. 8 9 Our glass is perfectly annealed and, therefore, does not break as easily as poorly annealed glass. Our glass is washed and thoroughly cleaned in an acid bath, which prevents discoloration and permits ready detec- tion of defects. Our glass cuts perfectly on both sides. Our glass is graded to the highest standard of quality. Our grading is the recognized standard for the United States, and is higher than the foreign standards. Our glass does not break in shipment on account of the uniformity of flat- ness, well made boxes, great care in packing and skillful loading. 14 Our entire process is conducted on scientific principles. “AA” Quality 55, 87, 88 _ Acceptance or rejection of _ shipments 86 Acid Bath 48, 49, 51, 57, 63- 64, 105 ; “Air supply for blowing 39, 41 “Analyses of glass 17-74 Annealing 42, 44, 47-49, 77, 97, 100, 105 | Bionealin g lehrs 48, 49 ae Quality 54, 55, 87, 88— 91, 94 PAcchitects specifications 18, 83 _ Arsenic 26 _ Ash, soda 26 # Automobiles, glass for 15, 18, 73, 99 a particles in glass 94 e Beginnings of window © glass 1 eyes) Bending test 100-103 - Blisters 59, 84, 85, 89, 90, 92, 94 - Blowin g cylinders, air 5 supply 39 5. Blowing window glass 39, 83, : > 104 _ Blow pipe 39 ‘Bosh, ladle 34 _ Bow in glass 97, 98 Boxes, Packing 53, 54, 105 —“B” Quality 55, 70, 87, 90, : 91-92, 93, 94 _ Branding of boxes 53, 54 _ Breakage caused by knots 61 Caused by wrinkles 61-62, 85 Caused in loading 57 During manufacture 28 INDEX Due to defects 58, 85, 93 Due to poor annealing 48, 105 In handling 97 In shipment 93, 97, 105 Brick cost compared with glass 16 Brilliance of polish 50, 72 Brittleness, of glass 26, 48, 77 Bubbles 22, 33, 59 Bureau of standards 81, 100, 102, 103 Burn 61, 84, 85, 89, 91, 92, 94 “C” Quality 55, 87, 92, 93 Capping of cylinders 42 Carbon 26, 63 Carbonate of soda Pe. Carload shipments 86 Cars, loading 57 Central area of sheet ~ 84, 88, 89, 90, 91 Charcoal, ground 26 Charging the furnace Be! Cheerfulness, promoted by clear window glass 16,18 Chemical composition affects quality ¥7. Chilling, causes cords, lines 60 Chinese discovered glass 20 Chipped glass 67, 74-75, 101 Clay 58 Clay pots for melting 31 Cleaning of glass 105 “Clear sheet glass’’ 101, 102 “Clear window glass” 16, 83 Cleating of boxes 53 Coal, crushed 26 Cockles 62, 84, 92 Coke 26 Color of glass 26 “Commercial” Quality 70, 94 “Common window glass’’ 13 Comparison of glass 76-77 Complaints 56, 93 Composition of glass 25-30 Concave side of glass 98 Concussion shocks 98 Convex side of glass 97, 98 Cords and Lines 60, 84, 85, 89, 92 Corrugations in window glass 61 Cost of window glass 16, 19, 71, 81, 88, 90, 91,:93,.95 “Cracking open” 42, 43, 45 Critical range of annealing temperature 47, 48 Crystal sheet glass 67, 72-74, 87, 94, 95, 101 Cullet, used in melting 33 Curves in glass 97 Cut sizes 94 Cutting and Sorting 51-52 Cutting qualities 48, 97, 105 Cylinders 36, 37, 39, 40, 41, 42, 43, 65-66, 104 53 57, 63 Decolorizers 26 Defects 17, 18, 22, 46, 49, 52, 53, 58-64, 61-62, 65, 70, 76, 84, 85, 88, 89, 90, 91, 92, 94, 95, 97, 104-105 Defects, location of 90, 91 Defects, number permitted 91, 92, 94, 95 Defects, sizes permitted 90, 91, 92, 94, 95 Dampness causes fade (et a Definition of clear window > glass Deliquescent glass 29 Deformation ; 97 Density of glass 26, 29, 74 Devitrification 28-29, 58 Dimensions of window glass 97, 99, 100 Dipping and washing 48- Discoloration 27, 30, 49, 53, 57, 63-64, 74, 105 Discovery of glass 20 Dirt and moisture cause chemical action . Distortion of window glass . 18, 59-60, 92, 93, 99, 105 Double strength glass 54-56, 67, 71-72, 81, 87, 92, 94, 95, 96, 97; i Drawing cylinders 36, 37, 7 Drawing window glass 36, a % 38, 66, 77, 83, 104 Drawn process, flat sheet 48 Durability of window Z glass 29, 30, 72; 7m Dwellings, glass for 73, $ 92 Elasticity of glass 12, 10 0 Elements, glass keeps out 13 Evenness of thickness 72, 105 Examination, method of _ 85 Expansion by heat test 100 “Factory Run” Quality 87, 94, , Faded glass 27, 30, 49, 53, 5% 63-64, 74, 85 Federal Specification Boards «82 Fire finished | Flat sheet drawn process 48, 61, 62, 65, 74, 83 a. 63 ni . Flattening 43-46, 83, 97, 104-105 Flattening defects 46, 61-62, 97, 104-105 Flattened sheets 45, 46, 62, 65, 97, 104-105 “Flattening stone’’ 45, 62 Flattening temperature 45, 61 Flaws in glass 88, 89, 90, 92, 94, 95, 105 Flux, nitre as a 20-22 Foreign grading standards 105 _ Foreign particles 49, 85, 94 “Fourth Quality” 55, 87, 92, 93 Frosted appearance of glass 64, 74 Furnace operation 32, 33, 58, 59, 60 Furnaces for flattening 43 Furnaces for melting 31, 33, 35, 104 Fuel for melting 31 Gas, for melting 31 Glazing 97, 98 **Glazing’’ Quality 87, 94 Glossy surface of glass 83 Glue coating 74 Government Specifica- tions i gor Government tests 48 Grade measured by defects 17-19, 84, 85, 88, 89, 90, 91,92, 94, 95, 105 Grades, substitution of 54-56, 81, 82, 93 Grading, rules for 81-103 Grading glass 51, 52, 81-103, 105 ' Grain in glass 99 Greenhouses, glass for 15 Ground glass 67, 74-75, 101 Hand blown window glass 37, 42, 68, 83 Handling of glass 48,62, 71,97 Health, glass aid to 16, 18 Heat, Conductor (glass) 12 Heat test 100 Heavy sheet window glass 94, 96, 97 “Horse”’ for receiving cylinders 39, 42 Hot bed sash 93 “Hum” 63 Humidity affects glass 29 Humps in window glass 62, 99 Hygroscopic glass 29 Impact tests 100-103 Imported glass 68, 70, 73 Ingredients, proportion of 58 Inspection 52 Iridescence on the surface of glass 64 Iron causes greenish tints 26 Iron, heated for splitting 42 Kelp glass 22 Kiln, heat drawing 37, 41 Kiln, heat drying 74 Knots 60-61 Labeling quality and thick- ness 54-56, 70, 73, 90, 92 Ladling and blowing 37-42 Lantern slides 15, 67, 68-69, 95 Laws, tariff 13 Lehrs, annealing 44, 48 Light, glass lets in 13, 14, 16 Lights, paper between 70, 73 Lights per inch 95 Lights, sizes of 93 Light transmitted through glass 70, 75 26, 27, 29, 30, 64, 74 Lime, burnt 26 Limestone 26 Lines 60, 84, 85, 89, 90, 92, 94 Loading 57, 100-103, 105 Lubbers, John, inventor 37 Lumber, cost compared with glass Lustre of glass Lime 16 19, 44, 45, 64, 70, 104 Machine blowing 83, 104 Machine, drawing and blowing Manganese - Master Specifications 79-97 Materials used 58, 59 Mechanically drawn and blown cylinders 36 Melting and refining 31-35, 104 Melting defects 58-60, 76 Sipe 26 Microscopic slides 15, 67, 68-69, 95 Mirrors 15, 70, 73 Mixing of materials 58, 59 Modulus of rupture 27, 77, 100-103, 104 Moisture, action of 27, 30 Moisture causes fade 53, 57, 63 Muriatic acid 48, 51, 57, 63 Natural gas for melting 31 Nitre, used in making glass 20-235:22 ‘“‘Non-scatterable” glass 69 “OB” Quality 94 “Off-Quality” glass 55, 92, 93, 94 Opaque glass 64 Optical glass 48 Origin of glass 13, 20-23 Oven, annealing 47, 48 Ovens, flattening 43, 45, 48, ou 335 105, 70, Ba Packing Paper between lights Partitions, glass for 75, Photo dry plate glass 15, 67, 68-69, 95 Physical properties affect quality i Physical strength 72 Physical structure of glass 42 Picture glass 15, 18, 67, 69-70, 90 Pipe, blow | 15 15. Plates, photographic X-ray > Plate glass 73, 76, 77, 101, 102, 104 Polish, brilliance of 72, 104 Polisher for flattening 45 Polished plate glass 101, 102, ; 04 Polish produced in flatten- “a a ing 44, 45, 104 Pompeii, glass found in 27 : Porcelain of Réaumur 28 Pots, clay, for melting 318 Pot, reversible 37, 395 4. Pressure, wind 71, 98, 102,104 Price of window glass 16, 71, 4 81, 88, 90, 91, 93, 95 Processed glass 67,74-75, 101 : Producer gas, used for melting Production of American 7am dow GlassCo. 15, 104, 105 Pyrometer couple po “oy Quality labels RB : yt aan Quality of materials 58, 59 Quality slips 54, 55, 70, 92 Quality of window glass 17- 19, 26, 55, 81-103,105 Raw materials melted 33 Ream 59-60, 83, 84, 90, 92 Refining process 33 Regenerative tank system 31 Rejection of shipments 86, 93 Resistance to impact 100-103 Reverse curves a. Rippled appearance 65 Rolled glass 76, 77, 102, 104 Rules for grading 81-103 Rupture, modulus of 27, 77, 100-103, 104 Rust 63-64 Rye straw for packing 53 Salt cake 25 Salt, glass is a 12 Sandblasting 74 Sand, imbedded in knots 61 Sand, used in making glass 12, 20-22, 25 Shipments 48, 57, 86, 93, 97, 105 Shocks, concussion 98 Silica, used in glass making 25, 27, 29, 30, 58, 74 Single strength glass 54-56, 67, 71-72, 81, 86, 87, 92, 93, 94, 95, 96, 97, 101 16-o0z. picture glass 67, 69-70 Size of cylinders 41 Size of defects permitted 90, 91, 92, 94, 95 Sizes, cut 94 Sizes obtainable 96 Sizes of lights 93 Sizes of sheets 51,52 Slides, lantern 15, 67, 68-69, 95 Slides, microscopic 15, Gi, 68-69, 95 Smooth surface of glass 70, 83, 104 Soda ash 26 Soda used in making glass 21, 22, 25, 26, 27, 29, 30, 64, 74 Sorting 52 Specifications, Government Scratches 62-63, 84, 85, 89,94| Complete 79-97 Screens, glass for 75| Clear window glass 86-87 Seaweed, furnishes kelp 22 | Stain . 30, 63-64, 74, 85 Seeds and blisters 58-59, 84,| Standards, Bureau of 81, 100, | 85, 89, 90, 91 102, 103 Segments of cylinders 42, a Standards for grading 105 5 : S , flattenin 45, 62 ““Selected’’ Quality 70 Pee metas 58, 84, 85, 94 Selected stock sheets 95 seapet . ee gee Sheet drawn window glass 37, Bree eats mV etChonncs 31, 48, 61, 62, 65, 74, 83; ee bi Gicer celected stock g5 | Storing raw materials in Dh, bins 24 Sheets, sizes 51, 32 f ki Shipment, breakage in 93, 97, pO Dees. = 105 | Streaks 59, 83 Strength, single and double 54-56, 67, 71-72, 81, 86, 87, 92, 93, 94, 95, 96, 97, 101 Strength of window glass 12, 27,29, 303-42, TL, 73; 7 4e0 Ws 100-103, 104 Stretching strains 66 Strings 60, 84, 89, 90, 94 Substitution of grades and qualities 54-56, 81, 82, 93 Sulphate of soda 25, 26 Sunlight, glass letsin 13, 14, 16 Superfine “Quality” 70 Surface, brilliance ' Sweating of glass 30, 72 29, 49, 63 Tanks for melting 31 Tariff laws, window glass in 13 Temperature changes 65-66 Temperature, flattening 45, 61 Temperature, melting 33, 35 Temperature, annealing 47, 48 Tensile strength of glass 12, 42, Fis 73; 74, 4 iy 100-103 Terms of clear window glass 84 Testing glass 17, 38, 48, 100- 103 ‘The BEST Glass” 19, 72, 77, 82, 100, 102, 103 Thickness of picture glass 70 Thickness of window glass 55, 67, 73, 81-97, 101, 102, 105 34-oz. crystal sheet 67, 71-T4e : 87, 94, 95, 101 4 39-oz. crystal sheet 67, 72-7an 87, 94, 95, 101 Tile, cost compared with ae glass 16 . Tolerances in thickness 95,96 Torsion test 100-103 Toughness of window a glass 6, 42 Transmission of light ee through glass 70, Toa 26-oz. glass 67, 72, 87, 94, 95, _ 101 y 29-oz. glass 67, 72, 87, 94, oa ap eS 4 at 42, 103 xs United States Bureau of oS Standards 81, 100, 102, 103 S Bris United States Government Master Specifications 79-97 ci United States grading a . standards a = Te Uniformity of thickness Warehousing and shipping ay) Washing of glass 105 , Wave in window glass 59-60, — 65-66, 83, 85, 89, 90, 91, 105 — Weights of window glass 67, 95 Wind resistance 71, 98, 102, a 104 73,99 35, 599 61-62, 85, 94 Windshield glass Working zone Wrinkles X-ray glass 4s, 67, 68-69, 2