Page:The American Cyclopædia (1879) Volume VIII.djvu/34

 20 GLASS PAINTING stitutod by Mr. C. Winston of England, who during his life made the subject of painted tfla^ in its antiquarian aspects a special study, jiinl tlio earliest specimens were carefully ana- lyzed. The results reached made it eay to re- produce both the quality and the color of the an- cient glass. Glass painting, which is more prop- erly a process of staining, differs from all other styles of pictorial art, except the painting of por- celain. The colors are different, being wholly of mineral composition, and are not merely laid on the outside, but fixed by being fused into the material, undergoing in the operation chemical changes that develop the brilliancy and transparency of which the compounds are susceptible. The colors are mixed with a flux of much easier fusion than the glass, and with some vehicle, as boiled oil or spirits of turpen- tine. The mixture is usually laid on with a brush as in ordinary painting ; and the glass being then exposed to heat, the flux melts and sinks into the body. None of the clear bright colors are perceived until the work is com- Sleted, and the artist consequently labors un- er great disadvantage in applying the mate- rials that are to produce them. He is guided either by lines drawn on the back side, which show through, or by a cartoon or drawing on paper placed there. In the early use of glass for windows, especially those of churches, bril- liant colors were highly esteemed, and great success was attained in the methods of color- ing. A bright red color was imparted by the ancients with the protoxide of copper. In later times it was found impracticable to suc- ceed with this on account of the tendency of the copper to pass to a peroxide and produce a green tinge ; but the practice has been again introduced with success by the Tyne company in England, at Ohoisy in Franco, and in other places. The discovery of the preparation of gold and tin, called purple of Cassius, also af- forded another means of producing a brilliant red. In the history of the art two leadidg processes have been prominent. From the earliest period until about the middle of the 16th century the method described by Tho- ophilus and known as the mosaic system pre- vailed. In this process the glass was colored in the manufacture, and blocks of different colors having been brought together, the. outlines and shading of the design were produced by the ap- plication of an enamel color. About the time incut ioiu-il it was discovered that all colors be- sides yellow, brown, and light red, which had previously been imparted by this method, could be given to glass by moans of the enamel pro- cess; but the works produced by this method were greatly inferior to those by the mosaic sys- tem. There has been a spirited controversy between the advocates of the German method of glass painting, in which enamel is used, and the English glass painters, who avoid the use of enamel as far as possible, as it sometimes scales off. It seems to be conceded that the beauty of the cathedral glass of the 18th and 14th centuries was in the brilliancy of the glass and the skilful arrangement of designs and colors, and not in any enamel work. The ordinary method of glass painting, as prac- tised in England, is to use for the colored parts of the design pieces o^ glass differently colored in the process of manufacture, and to employ only one enamel color, brown, for tracing the outlines and painting the shadows of the pic- ture upon the glass. The enamel brown, like any other enamel color, consists of coloring matter mixed with pulverized glass, called flux or enamel. When this is laid on the surface of the glass and heated in an oven or furnace, it melts, in consequence of being more fusible, while the glass is merely at a red heat; on be- ing cooled it hardens and produces a perma- nent color on the surface of the glass. The general colors of the design, 'therefore, are not produced by the painter, but by the glass ma- ker; the former, as has been stated, using pieces of glass already colored. The only ex- ception to this is in the case of yellow, which is produced on the glass by applying a " stain," the principal ingredient of which is oxide or chloride of silver. On being exposed to the action of a red heat, the yellow stain penetrates the glass and imparts to it its tint, the prepa- ration of silver being afterward brushed off. This process was discovered in the early part of the 14th century, and has been used to im- part a yellow tint to uncolored and most kinds of colored glass. The various tints of yellow are the only ones that can be produced on glass without altering its surface. By putting on a second or third coating of the silver oxide and burning in, orange and red stained glasses are produced. The process of producing a paint- ed glass window is an interesting one. The artist first makes an outline on a small scale of the stone work of the window, within which ho sketches the design, indicating the colors to be used and the general treatment of the subject. A full-sized drawing or cartoon is next made, from which a "cutting drawing" is traced, showing the lines where the strips of lead are to go, and omitting all other de- tails. On this latter drawing, on which the colors of the design are indicated by outlines, the pieces of different colored glass are laid and cut with a diamond, each piece being cut out of that particular color or tint required. The artist now arranges the pieces of different colors in their proper places on the cartoon, and traces the outline of the design upon them. On being heated in an oven, the opaque lines vitrify and are formed indelibly on the surface of the glass. After the outlines have been thus "burnt" on, the glass is taken again to the painter, who covers the cartoon with a sheet of colorless glass, or if large a portion of it at a time. Thus having the cartoon for a guide, he arranges in their proper places on the sheet of colorless glass the pieces on which the outlines have been traced, and secures them firmly with drops of melted resin and