Popular Science Monthly/Volume 37/June 1890/Glass-Making IV
THERE are few objects of manufacture which better than glass illustrate the immense preponderance in value of human labor over crude material. It is a substance which might serve economists as a parallel to their favorite illustration of the comparative values of a steel watch-spring and the bit of iron-bearing earth from which it is wrought.
In the case of glass, the crude materials are so plentifully distributed in nature as to be almost valueless. The basis of the compound, sand, is so very abundant that it has furnished the symbol, in more than one parable, for quantity without limit. Like the unnumbered sands of the sea was a vast promise to the children of men. Somewhat less abundant than the sand are the other chemicals which it is necessary to mix with it in order to produce that double silicate which goes under the general name of glass. They are, however, far from being either scarce or expensive. The alkaline ingredient, the carbonate of soda, is made from common salt, a mineral whose wide distribution in nature is at once apparent when one recalls the fact that the sea, thirty or forty times in bulk the total elevated mass of the earth, is one vast storehouse of the substance; that salt springs or brines abound at our very doors—in New York State, in Michigan, and in Virginia; and that vast deposits of the solid rock-salt are to be found in Louisiana and Prussia. The third ingredient, the lime, is simply calcined limestone, a rock which forms whole ranges of hills, and is found in every corner of the globe. For the production of the fine flint glass, or crystal, which forms the special subject of the glass-worker's skill, it is also necessary to add a fourth ingredient, red lead or minium. As this is the oxide of an easily reducible and useful metal, it is naturally considerably more expensive than the earthy ingredients, but its cost is still far within the limits of moderation. The Rocky Mountains and the Mississippi Valley furnish lead ores in such abundance that the compounds of the metal may fairly be classed among cheap products. The total cost of the "batch" can not be more than a few cents a pound. Compare this with the value of the finished products. The finer cut glass will sell for perhaps as many dollars a pound, while the finest cameo glass may bring almost as many hundred, It must not be supposed, however, that the difference, or even the
greater part of it, goes into the pocket of the manufacturer. A fair proportion reaches that destination, but by far the larger share goes for meat and bread and coal, houses and cloth, to sustain the life of the army of men, women, and children by whose labor these dull earths and oxides are transformed into the brilliant carafes and bowls which adorn our dinner-tables.
Much the greater part of this increased value is conferred upon the glass by the dexterous hand-work expended in the atelier, rather than by the coarser operations which attend the furnace process. This, however, is the basis of all that follows, and the beginnings of the finest cut-glass bowl or cameo vase are to be sought in the mixing-room, where the crude materials are put together. In different establishments the proportions vary, as in the manufacture of all other forms of glass products, and even in the same establishment uniformity is far from absolute. Although, glass is supposed to be a fairly definite chemical compound, each manufacturer has his own notions on the subject, and occasionally he changes his mind, or perhaps his supplies come from a different locality. The result, in either case, would be a slight change in the composition of the batch. A typical mixture would be for every hundred parts of fine white sand about forty parts of alkali (carbonate of soda), ten parts of burned lime, and forty parts of red lead.
It will be noticed that the batch is essentially different from that used in the manufacture of window and Of bottle glass. It differs both in the character and the quality of the materials employed. The ingredients common to the several mixtures must be much purer for use in the production of table and household glassware of the finer grades. Care is taken that the sand shall contain no iron; and, in order to free it from any admixture of loam or other disadvantageous earthy materials, it is subjected to a washing process before it is brought to the mixing-room. By this treatment the more finely divided matter, such as clay and the like, is carried off with the water, while the coarser sand settles to the bottom of the washing-troughs. Further, in the selection of the alkali, the cheaper sulphate of soda is never substituted for the carbonate, as is frequently done in the manufacture of bottles.
In the processes of the atelier the competition is a question of quality rather than of quantity. The element of human labor is so large that it would not be economical to expend it upon an inferior grade of glass. The workers, or rather the men who direct them, go on the principle of those wise domestic economists who reflect that the cost of labor in making up clothing is approximately constant, and who therefore do not feel that they can afford to buy shoddy.
The earthy materials—sand, alkali, and lime—give substance and transparency. Fused together, they form ordinary glass. The additional ingredient, the red lead, has a special function to perform It has for its immediate object an increase in the weight of the glass; and since in general an increase in weight means an increase in refracting power, its ultimate object is an additional brilliancy in the product. Every one has noticed the heaviness of cut glass; or, if he has not, and enters a shop to buy a piece of it, the shop-keeper is very apt to call his attention to the fact—particularly if the price be correspondingly heavy—assuming that weight is an undeniable guarantee of quality and brilliancy. If you object to the price, he puts the piece into your hands and says confidingly, "Just feel the weight of it!" The argument is a pertinent one, but not altogether conclusive, for there are many other elements besides weight upon which the merit of the product depends. It is quite possible to have the glass too heavy for beauty, since the dense lead compounds have a tendency to separate from the lighter silicates, and, consequently, if present in too large amounts, they make the glass streaky and mottled. In general, lead glass for domestic uses has a specific gravity of from three to four—that is, it is from three to four times as heavy as an equal bulk of water. The brilliancy given to the glass by its increased density has attached the name crystal to this particular product.
It is essential that the several ingredients should be thoroughly mixed, and to this end the operation is carried out mechanically.Fig. 2.—The Process of Engraving on Glass. The materials are fed into the upper end of a slowly revolving hopper, whose axis is slightly inclined to the horizontal, and are thoroughly mixed by the time they reach the discharging end. A dainty pink powder falls into the receiving bins. Its subsequent baptism by fire transforms the opaque into the transparent. The furnaces employed for this purpose are of the type common to other glass-melting processes—simply a circular and intensely heated chamber, surmounted by a stack, and provided with radial openings to permit the blowers to dip their blow-pipes into the molten contents of the fire-clay crucible-pots.
The scene around this industrial caldron is quite as busy as that which has its center in the bottle furnace, and is even more varied. The workers are fashioning objects of the most diverse shape and for the most unlike purposes. Some are blowing lamp-chimneys, others gaslight globes, or decanters or dishes. In the center of the apartment a large press, with engraved steel dies, is squeezing the plastic " metal "—for so the glass-blower designates his still fluid glass—into decorative panels for car-windows and transoms. As one passes from one end of the large room to the other, he will see almost every conceivable shape in glass, suited for table or other domestic usage, taking form in the hands of the adroit workers. It is the scene of an intense and a highly ingenious activity. The bottles and dishes and globes intended for sub-sequent treatment in the atelier are all blown, the manipulations being varied in accordance with the special form it is desired to produce. As a rule, it may be said that it is cheaper to produce the pressed glass than the blown, since less time is required in Fig. 3.—The Operation of making Ground Glass Globes. fashioning the articles; but for the finer work the blown is always preferred, as glass worked exclusively in the air has a much more brilliant surface than that which has been formed in contact with the faces of the iron mold. The plain articles thus shaped are known in the trade as " blanks." The largest manufacturers of cut and engraved glass also make their own blanks, but there are a number of establishments which confine themselves exclusively to the processes of ornamentation. The articles intended for such decoration go from the blower to the annealing leer, where they are permitted to pass through a chamber of brick-work some sixty to eighty feet long, subjected to a gradually decreasing temperature for a period of twenty-four hours or less, according to the circumstances of the work. The articles to be annealed are placed in wrought-iron cars, and are slowly moved through the leer, coming out perfectly cold.
It is in this way that the blanks are prepared for the atelier proper. Here one finds a number of very interesting operations going on side by side. The untechnical visitor will perhaps be most attracted by the cutting process, since the results are so brilliant, and the articles possess so staple a value. He will get a good insight into the general principles by following the process of cutting a carafe.
The blank itself is perfectly plain—a simple, heavy bottle with smooth surface. Its proportions are good. The decoration is to consist of a twenty-four-pointed star on the bottom, a series of more or less complicated diagonal cuttings on the bulging sides, and six or eight broad facets around the neck. To these may be added a number of features of less prominence, such as a series of oval facets around the base of the carafe, and some smaller cuttings at the top. It is the glass-worker's custom to begin with the star on the bottom. This is cut entirely by the eye, no design being traced on the glass. The first process is known technically as "roughing" it, and consists in cutting the design in the glass with coarse tools, which leave rough facets, but remove most of the glass to be cut away. The roughing-wheel is made of iron, and is about two feet in diameter. It is mounted on a axis. The face of the wheel is about seven eighths of an inch broad, and is kept supplied with a mixture of coarse sand and water allowed to constantly drip upon it from a hopper above. The wheel makes about a thousand revolutions a minute, the speed varying with the character of the work to be done. It is slower for the deeper cuttings. The workman seizes the carafe with both hands, and presses the bottom firmly against the edge of the rotating wheel, making a cut across the center, and as far each way as it is desired to have the star extend. Then he turns the carafe around one sixth of a revolution, and makes a similar cut through the center, judging of the distance entirely by his eye. A second turn of one sixth of a revolution, and a third cut along a diameter is made. This gives a six-pointed star. The intervening spaces are then divided by similar cuts, and the spaces thus formed again divided, giving a twenty-four-pointed star.
A tyro in the art would make a very poor figure of it, but the regular cutters become exceedingly expert, and are able to make comparatively perfect designs in this seemingly off-hand fashion. A trained eye will, of course, have no difficulty in detecting inaccuracies, but the designs are symmetrical enough for all purposes of decoration,
The cutting does not yet possess much beauty, for its faces are as rough as ground glass. Already, however, it begins to show the promise of what it is to be. In treating the bulging sides of the carafe, greater difficulties present themselves in disposing the pattern symmetrically. It is, therefore, the custom to paint a number of guiding lines on the surface of the glass. A few circular lines surrounding the carafe, and a few up-and-down lines afford a series of intersections which are sufficient to enable the cutter to develop a uniform pattern. In the same way the facets surrounding the neck are determined by a couple of limiting circles, and similarly with the secondary part of the decoration. This completes the rough work.
The second process is that of "smoothing" and is carried out by means of wheels made of a natural stone found in Scotland, known as the Craig Leigh stone. A large part of modern Edinburgh is built out of this material. It is a compact silicious stone, wearing very uniformly, and almost free from that tendency to crumble which characterizes the majority of our native sandstones. The stone wheels are about the same size as the iron wheels used in the roughing process; but their cutting edges, instead of being smooth, are beveled, thus giving a sharp edge in the center of the face. Fig. 4.—The Sand-Blast in Operation. This is occasionally sharpened by regrinding, or by holding pieces of flint against the beveled faces of the revolving wheel. A tiny stream of water falls constantly against the face of the stone. Each cut made on the iron wheel is gone over on the stone, and, by the finer friction, the surface of the facets becomes smooth and transparent. The carafe is slowly becoming an object of beauty.
Next in the order of the processes comes the polishing, which is effected by wooden wheels mounted as before and supplied with pumice or rotten-stone. Red willow is considered the best material for the polishing-wheel, though poplar is also frequently used. The hard woods are found to be less suitable for the purpose. The wooding—for so this third process is called in the atelier—gives a fine finish to the smoothed facets and adds greatly to their brilliancy. It is a process, however, which is only practicable in cases where the cutting is rather deep. Where it amounts to little more than a tracing, the wooden wheel would be of slight use.
Still a fourth process is required before the carafe is ready to be washed and placed on sale. It is that of brushing. The brush is made of spun glass, and is applied in the form of a wheel as a burnisher. Those who have seen gilt used in china-painting will recall the pencils of spun glass with which the gilding is burnished after being fired. The rapidly revolving brush of glass cleans out the cuttings more perfectly than could be done in any other way, and adds the final luster to the facets. The carafe is now completed. Other articles are cut in much the same way, slight modifications being made to suit different shapes and patterns.
At the present time very good copies of cut-glass articles are made in pressed goods, and at about one twentieth of the cost; but the difference between the two products can readily be detected. Not only are the pressed goods less brilliant, but the edges of their facets are visibly rounded from the fusion, and fail to give the sharp, clear faces of the genuine cut glass. One can tell the fine article at once by simply rubbing his finger over the cutting. The sharp edges of the genuine article are unmistakable. Another attempt to combine beauty and economy is made by cutting some prominent feature of a pressed-glass article, and letting the brilliancy thus obtained make amends for the duller facets of the less exposed portions. In this way pressed-glass decanters are made quite presentable by being supplied with well cut stoppers, and covered dishes pass muster through the merit of their brilliant knobs. Still another device is that of grinding off the faces of pressed-glass goods, and thus securing, as the result of a much cheaper process, the sharp edges and well-polished faces of the real cut glass. The process, however, is not a very successful one. It sounds better than it works out in practice. Wares treated in this way have the serious defect of lacking brilliancy when compared to the air-blown glass and entire cutting. They are now made in but small quantity, for they can not compete in public estimation with the ordinary pressed goods, since they cost about five times as much, and are far from being five times as effective.
In the most artistic circles there is at present a slight reaction against cut glass in favor of the light and graceful articles made in blown glass. But meanwhile the sale of cut glass grows larger each year, for the improvements in the method of production bring it within reach of an increasingly wide circle of buyers. It promises to remain a standard article of manufacture, for its brilliancy will always attract admirers, and any disappearance will be but temporary. The old-fashioned chandeliers and candelabra, made with pendants of cut glass, are pushed out of the market by newer metallic goods, only to periodically reappear from their obscurity.
Alongside of the cutter's wheel one sees a corner of the atelier devoted to a species of cutting in miniature, which goes under the name of engraving. The cutting instrument is a small copper disk, sometimes as tiny as a dentist's tool, and sometimes several inches in diameter. It is mounted with its axis horizontal, and is made to rotate very rapidly. The cutting is lone underhand,
instead of overhand, as in the former operation, which means, in the language of the outside world, that the article to he engraved is brought into contact with the rotating disk from beneath, instead of being pressed against its upper surface. The disk is supplied with a mixture of emery and oil. This is the real cutting agent; the disk simply applies it. In almost all cases the work is done solely by the eye, without any guiding lines whatever. Frequently the engraver originates his pattern as he goes along—a species of improvising which is quite full of interest to an on-looker. In time the men become very skillful in this sort of work, and are quite ready in thinking out new designs. It is entirely a matter of experience, the work depending largely on a nice sense of touch, since the glass is for the most part obscured by the spattered emery and oil. In this way geometric designs of considerable complication, wreaths and flowers, birds, fishes, and dragons, are traced on goblets and other table-ware, as well as on globes and similar articles. It is also the process by which initials and monograms are cut on glass, and its frequent application for this purpose is familiar to every one who is not nearsighted.
The tracery is accomplished sooner than one would fancy. As a rule, it is used in connection with some other form of ornamentation. Frequently in the case of globes there is a light tracery around the central portion, and plain bands at the top and bottom. These are put on very expeditiously, and, consequently, at little cost. The process is known technically as "obscuring." The globes are mounted on a lathe over a sand-box, being fastened between plates of cork in order that they shall not be fractured by the jar. The workman presses a bundle of soft, annealed iron wire against the surface of the quickly rotating globe, and, almost in less time than it takes one to tell about it, the band is completed. The band at the other end of the globe is put on in the same way. If two parallel bands are to be put on near together, the bundle of wire is in two parts, and both bands are made at the same time. The wires simply determine where the obscuring shall be. The real grinding is done by the sand and water with which the surface of the globe is kept constantly supplied. By using a larger bundle of wire, and passing it over the entire surface of the globe, the obscuring is made complete, and we have the so-called ground-glass globe.
The obscuring process is used in connection with both cutting and engraving, a design frequently being brought out much more beautifully by reason of the obscured or translucent background. In this case, however, the cut pattern must not be subjected to the final brushing process, for the glass brush would smooth the obscured surface and give it the almost transparent character displayed by ground glass when moistened with oil or water. The effect would be to make the portion of the glass around the cutting look constantly wet—an undesirable form of decoration. Some of the most pleasing designs are thus produced by a combination of two or more processes. However fully and artistically a plain glass globe may be decorated, there is apt to be an unpleasant effect of thinness of design from the unrestricted passage of the light through the transparent portions. But by obscuring the entire surface of * the globe, and then cutting even a very modest design upon the background so prepared, the result is much more effective. The transmitted light, from its subdued character, is also more agreeable. The cutting is done in the so-called "mud-box"—a designation which has arisen from the fact that the spent sand or mud from the cutting of heavier articles is here utilized.
These processes are all purely mechanical. They depend upon the direct friction between the glass and the abrading powder, or between the glass and the cutting stone, as in the case of the smoothing process. It is possible, however, to bring about this grinding action by less direct pressure. One of these indirect methods—the sand-blast—deserves particular mention, both because of its commercial importance and because of its ingenuity. Some years ago there was published a book which pointed out, with more or less cunning, a prototype in nature for nearly all our mechanical devices. The author did not, I believe, mention the sand-blast, but he might well have done so, for it is a direct imitation, though perhaps an unconscious one, of a process which Nature has been using very effectively ever since the first blast of wind carried the earliest sand-grains against the Eozoic rocks. This natural sand-blast has done not a little in altering the appearance of the face of the earth. In the Rocky Mountains there are many curiously sculptured rocks in the comparatively rainless districts, which owe their carving almost entirely to this agency. Still more striking, perhaps, has been the effect of blowing sand upon the monuments of antiquity. Those who have seen the Obelisk, in Central Park, New York, or have read descriptions of it, will probably recall the fact that on those sides which were originally exposed to the desert wind the hieroglyphics have been entirely worn off by the grinding action of centuries of blowing sand. The action is precisely the same in the atelier, except as to the matter of time. A strong blast of air, charged with particles of sharp, clean sand, will obscure a plain glass surface in the course of a few seconds. It is applied very ingeniously. The design to be traced on the glass is cut out of soft rubber, and the stencil thus formed is held firmly against the surface. The blast of sand-carrying air is secured by means of an exhaust, and is so Fig. 7.—The Process of Etching. arranged that it may be made to enter a sheet-iron box placed so that its upper surface shall be at about the level of an ordinary table. There is a round opening in the top of the box, somewhat larger than the pattern to be ground, but not so large as the sheet of rubber in which it is cut. Glass and rubber are then pressed against the opening, and, by means of a pedal, the blast is turned on. In a very short time, scarcely more than five or ten seconds, the blast is turned off, and the stenciled pattern is found ground on the glass. So quickly does the blast do its work that the capacity of the machine may be said to be limited only by the speed with which the operator can adjust things.
The action of the blast is rather interesting. The soft-rubber stencils will endure many exposures, while the hard flint glass is perceptibly worn away in a few seconds. The reason of this is that the little particle of moving sand can not be brought to rest immediately. However quickly its flight is arrested, there is an appreciable interval of time during which its motion must be parted with. Striking against the soft and flexible rubber, the sand is brought to rest gradually, for the rubber is sufficiently depressed by the Lilliputian blow to dispose of the motion stored up in the particle. When, however, the sand strikes against the hard and rigid glass, there is no giving way possible. The grains must either stop instantly or else they must penetrate between the molecules of the glass. In the latter case they would naturally detach little fragments in sufficient number to roughen the surface of the glass and make it translucent. Experience shows that this is precisely what happens. If the naked hand be held over the blast, a pricking sensation is felt, but the skin is not broken; it is too pliable. Thin sheet-iron stencils are sometimes substituted for those of rubber; their elasticity makes them fairly durable.
The sand-blast was invented by an American, but, as the original patent has expired, any one is at liberty to use the machine. The inventor has since made a number of modifications and improvements, which are protected by subsequent patents. The newer form is used, I believe, more in England than in this country—not so much from a failure on our part to appreciate its merits, as from a dislike of the peculiar royalty arrangements. The machines are sold, and a certain royalty charged each week, whether the works are running or not. As such an arrangement makes the expense a constant quantity, while the income is a variable, it is not acceptable to the majority of American glass workers.
Other agents besides mechanical find employment in the atelier. One of the properties of glass which makes it most highly esteemed, in both the household and the laboratory, is its almost total indifference at ordinary temperatures to acids and other corrosive chemicals. It is slightly acted upon by the strongest sulphuric acid and by steam under great pressure, but only after the lapse of considerable time. There are few substances, however, which are not, Achilles-like, vulnerable in some one particular. In the case of glass, the effective solvent is the comparatively rare compound, hydrofluoric acid. It is not strange, therefore, that in the numerous manipulations to which glass is subjected this fact should be utilized. It forms the basis of the one chemical process of the atelier, that of etching. It is a process readily and cheaply carried out, and from its effectiveness it is one of increasing importance. The piece of glassware to be treated is protected, in those parts which it is desired shall not be acted upon by the acid, by some substance indifferent to it, such as wax, paraffin, or a specially prepared ink. The parts not coated are thus the only ones exposed when the piece is plunged into the bath of hydrofluoric acid. They are soon bitten by the acid, and in this way the design is traced upon the glass. As globes for lamps and gas are the subjects most frequently chosen for this treatment, the process can, perhaps, best be understood by following such an article through the several stages of its decorative development. The designs are adapted from a variety of sources. The draughtsman is supplied with drawing-books containing examples of conventionalized flowers. From this unit he works out a design of proper size and shape—that is, something which when wrapped around the globe shall cover just one half of it, and so, by repetition, the whole. He traces his designs on a panel of heavy plate
Fig. 8.—Four Stages: To the right, the plain ground globe; then the globe wrapped in printed paper; next, the printed globe, with the paper removed; and finally, to the left, the finished product.
glass. The surface is coated with a special ink made of lamp-black, rosin, and wax, and the design then picked out by means of a sharp tool. The plate, thus prepared, is subjected to the action of a strongly acid bath of hydrofluoric acid for a period of from fifteen to twenty minutes. The uncovered parts of the plate are deeply eaten away. The ink is then washed off, and the plate is ready to print from. Frequently designs are etched on both sides of the panel, both for economy of material and of storage.
The printing is done on a simple engraver's press, the impressions being taken upon smooth, white paper, somewhat heavier than tissue. As the ink used for the purpose has a decided tendency to become stiff and unmanageable in the cold, a gas-flame is kept constantly burning under the engraving plate. The sheets of paper as they come from the press are covered with a thick layer of ink in those portions which correspond to the parts of the globe not to be etched. While still fresh, the printed sheets are passed to a girl sitting at a neighboring table. She cuts off the superfluous paper surrounding the design, and wraps the print around the globe to be treated. A second print serves to cover the globe completely. The paper is pressed tightly against the glass, and the wrapped-up globe then warmed over a gas-stove for a few moments. The paper is left on for a day or so, and when it is finally removed the design is found transferred to the glass. It will be seen that the process is not unlike that by which in former years decalcomania were attached to china and marble, to their supposed ornamentation.
The globe is now a study in black and white, and is ready for the etching proper.
The acid-room—for such is the name applied to the apartment where the etching process is carried out—is a truly villainous place. The atmosphere is so charged with hydrofluoric acid that it has a sharp smell and a most irritating effect upon the bodily economy generally. The instantaneous photograph of the bath had to be taken with more than customary expedition, lest the ninety-dollar lens in use should be fouled by the fumes. The man in charge of the process wears rubber gloves, and has his face partially protected from the fumes by a thick, bluish-white ointment. His appearance, in consequence, is far from prepossessing. The protection, however, is of a very superficial character. It leaves the eyes and the breathing apparatus entirely exposed. The operators soon show the ravages of the unwholesome atmosphere. Poor, pale ghosts of men, with red and blinking eyes, one wonders that, in a world so full of wholesome activities, they should be willing to sacrifice the best part of themselves in such an unnecessary cause. It is one of the saddest features of modern industrial life that things become so vastly more important than men, that both employers and employed—the responsibility is a joint one—come to look upon the ledger account as the first consideration and manhood the second. Dainty as are the products of this industrialism, I find myself taking less pleasure in them as I go more among the workers, and see what a price of dull routine and unwholesome labor is paid for the wares. If beautiful things are necessarily the product of unbeautiful lives, I am quite willing to forego the things. Under the present industrial régime, one feels almost an accessory to the degradation of human life if he purchase articles made on a large scale under the factory system. Morally, there is complicity, however unwilling we may be to admit it. It is a question worth considering whether political freedom and industrial slavery represent an ideal with which any people may worthily remain content. An industrialism is conceivable, with hours so reasonable and conditions so wholesome that the lives of the workers shall be as beautiful as the wares they produce. Whether this will result from the present competitive system carried to its extreme, or from a substituted co-operative system, remains to be seen. In the atelier, the main process in operation is the transformation of moving, human energy into the stored-up
energy represented by a highly wrought product. One may be pardoned, then, if his thought turns occasionally upon the source of the energy, the man. It is not an agreeable reflection to present to the reader that the majority of our brothers in large cities are living bitter, hateful lives, but I believe that it is a true one. It is perhaps well to entertain the thought for a moment, since our people, presumably sympathetic and compassionate, not only do not deplore this sacrifice of the best elements in human life, but on the contrary hold up as an ideal for whose protection and extension the national policy should chiefly exert itself, that very industrialism under which this sacrifice takes place. Food, clothing, shelter, and the household goods and gods have value only as they minister to human life. But, by a curious inversion, these things are now held to be of greater importance than the life which they were originally intended to conserve. The savagery of modern times wears a different garb from that of the past, but it is none the less of the essence.
But to return to the acid-worker, for his besmeared face and irritated eyes are still before us. The three windows of the little room in which he works are kept open winter and summer, in the hope of diluting the poisonous fumes—a clumsy arrangement at the best. It would be quite possible to have the atmosphere, if not entirely wholesome, at least comparatively so, by placing the acid bath directly under a good flue or exhaust, so that the escaping fumes should be drawn off artificially. Every chemist's laboratory contains such an evaporating closet.
The hydrofluoric acid employed for etching is a chemical unfamiliar to the majority of people. Its corrosive character, and the fact that it has few common uses, preclude such an acquaintance. The source of the acid, however, the mineral fluor-spar, is quite abundant in nature. It is so beautiful a mineral, occurring in nearly all the colors of the rainbow and in well-defined cubes and octahedra, that it is given a prominent place in all mineralogical cabinets. It is, therefore, probably better known than the acid derived from it. The mineral itself is a fluoride of lime, and, when treated with oil of vitriol, gives off fumes of hydrofluoric acid. These are exceedingly soluble in water, forming the ordinary hydrofluoric acid of commerce. The bath used in etching the globes contains in addition a certain amount of oil of vitriol. Glass plunged into such a bath will have its surface eaten away, but will remain transparent. The wooden trough containing the bath is from three to four feet long, and less than a square foot in cross-section. Half a dozen globes are treated at a time. They are mounted on a steel axle, separated from each other by washers cut out of thick rubber. These serve the double purpose of protecting the glass from injury and of keeping the liquid out of the interior. When the axle is put in place in the trough, the globes are about half submerged in the bath. The axle is given a slow rotary motion, and, at the end of about fifteen minutes, the etching is completed. The globes are removed from the bath, and another axle carrying six fresh globes put in its place. The chemical action consists in the formation of gaseous fluoride of silicon, the bath affording the fluorine and the glass the silicon. It is rendered more complete and more uniform by the rotary movement of the axle. The globes have now only to be washed, and nothing further remains but to sell them. The etching process is completed.
The solution of hydrofluoric acid leaves the etched portions of the glass transparent; but if some alkaline salt, such as ammonium or potassium sulphate, be present in the bath, the etched portions are rendered opaque. This reaction is utilized to obscure globes, in place of the grinding process already described. The globes have only to be dipped into such a bath for a moment or so, to be thoroughly obscured. As both sides of the glass are acted upon, the process of chemical obscuring is only used where the globe is not to be further decorated. In this same department the operation of "bisquing" is being carried on. If opalescent glass or colored translucent glass be dipped into such an alkaline bath for a brief, time, it will take the dull finish characteristic of bisque. Thousands of the so-called fairy lamps, in red and pink and blue opalescent glass, are treated in this manner. Glass surfaces which are subsequently to be painted on are also bisqued in order to facilitate the process. A very brief immersion makes the surface sufficiently rough to write on with an ordinary lead-pencil without the least difficulty. The large white plaques exposed for sale in the art-stores are prepared in this manner. The bath is contained in large wooden tanks, and the articles are simply dipped in by hand.
The products of all these processes—of cutting, engraving, grinding, and etching—are all more or less beautiful. The highest excellence is attained, however, when the several processes are combined in the production of the once greatly admired cameo glass. The best of this is now manufactured in England, but it has also been made, though with less success, in America.
The prototype of this variety of glass is the celebrated Portland vase, with whose history and mishaps most people are familiar. It was found about the sixteenth century in a sarcophagus in the neighborhood of Rome, and for more than two centuries adorned the salon of the Barberini family. When their collection was sold, the vase was purchased by the Duchess of Portland, for eighteen hundred and seventy-two pounds, and was loaned to the British Museum. Even in such safe keeping it came very near complete destruction at the hands of a madman named Lloyd, who gave it a heavy blow with a stick. It has since been repaired with such ingenuity that one can scarcely distinguish the numerous fractures. The vase is supposed to date from the time of the Antonines, and is one of the finest examples of ancient glass-making extant. The body is of a deep-blue color and the raised figures are of opaque white. For many years archaeologists believed that the vase was made of onyx, and described it as a most interesting cameo. It is now known to be made of glass composed of two layers.
The Portland vase was a hint to the glass-makers, and one that they made good use of. In the most elaborate examples of the modern product three colors are employed, and the effect, if the material has been judiciously managed, is exceedingly beautiful.
A vase is the best type of the cameo glass, since the function of the ware is almost wholly decorative. From beginning to end the process is one of great ingenuity. The basis of the vase is commonly of opalescent glass—that is, glass made opaque by the presence of some finely ground but insoluble oxide, or some such mineral as cryolite or fluor-spar. A lump of this glass is gathered on the end of the blowpipe and formed into a symmetrical shape by rolling on the marvering-table. It is then dipped at short intervals into two baths of molten glass of the colors desired. The composite lump is fashioned into shape by means of those various manipulations which the glass-blowers perform so adroitly. This gives a vase made up of three distinct layers of different colors. Its subsequent treatment is both chemical and mechanical. The design is painted on the glass by hand, or else transferred with special care from freshly printed paper, as in the case of the etched globes. The vase is then dipped into the bath of hydrofluoric acid and allowed to remain until both of the outer colors on the exposed portions are eaten off. It is now taken out, the ink washed off, and its subsequent treatment intrusted to the engraver. At this stage of the process only two out of the three colors are plainly visible, the intermediate one being seen simply as a colored line between the other two surfaces. By means of the engraving-wheel the outline of the design is made more clear cut, and enough of the outer layer removed to show the intermediate color as a delicate shading. An immense amount of work can thus be put upon a comparatively small article, and the cost meanwhile grows in proportion. Single pieces have been manufactured in England valued as high as two thousand dollars.
In spite of its great beauty and ingenuity, however, it is an undeniable fact that the cameo glass is losing rather than gaining in favor with the buying public. Some of the establishments which formerly produced it have ceased to do so. Several causes have been assigned for this lessened appreciation. Manufacturers say that the cost has been so far reduced that the rich will not buy it, and, in consequence, the middle classes no longer care for it. But such is not the general course of events in industrial matters, and the statement is to be taken with a grain of salt. The probable trouble is, that some of the cameo-ware has been produced in distressing colors and in unfortunate combinations. Injudiciously managed, it is easily possible to produce meager and inartistic effects. The average buyer has, therefore, been disposed to reckon with himself that, dollar for dollar, he could get more beauty elsewhere, and has accordingly gone there. The intrinsic merit of the ware is such, however, that an early revival of interest in it may be expected.
The processes of the atelier are much more varied than those described. These special ones have been selected as being among the most characteristic, particularly of American establishments. Moreover, they are types, and have an independent interest as ingenious adaptations of means to ends.
Before closing the door upon the atelier, the factor of its personnel deserves a moment's attention. I refer now to the workers—not in their social or human capacity, but merely as merchandise-producers. Their labor is expended almost exclusively in the creation of supposed beauty. It is true that the work is lavished for the most part upon objects of utility; but still it would all fall under the head of ornamentation, since the utilitarian quality in the products has been conferred elsewhere than in the atelier. It is curious, then, in view of this end, to find the workers of the most inartistic cult. In other departments of glass-making, and notably in the production of picture-windows, the possibilities of the material have attracted artists of the highest rank, and the results have been quite worthy of their effort. No such artistic invasion has taken place in this department. Considering the lives and training of the workers, the surprise is that they have realized as much beauty as they have. There is nothing in the atmosphere they breathe to cultivate such a sentiment. It is related of a celebrated Japanese cloissonné-maker that, having acquired a considerable sum of money from the sale of some of his choice wares at one of the Paris expositions, he expended the entire amount in the creation of a beautiful garden around his work-rooms, believing that such an environment would inspire his people to produce even more beautiful wares. I presume that a spirit such as this is possible only where one works for excellence rather than for money.