Page:The American Cyclopædia (1879) Volume VII.djvu/824

 808 GILDING mand to overlay boards and bars with gold. That the early Egyptians understood it well is evident from the gilding of the coffins of The- ban mummies, in which the gold leaves resem- ble those now prepared. Homer makes men- tion of it, and the later Greeks thus decorated the exterior sculpture of their temples and statues. The Romans after the destruction of Carthage applied the process to ornamenting the ceilings of their public buildings, and at last of their private houses also. The thick- ness of the leaf is spoken of by Martial as like a vapor, and by Lucretius the substance is compared to a spider's web. According to Pliny, an ounce of gold was made into 750 leaves, each four fingers square. This is about three times the thickness of the leaf now in common use ; but some qualities are so thin that 290,000 sheets make a pile only one inch in height ; and specimens have been made only sipfyj^o of an inch thick, which is 1,200 times thinner than ordinary printing paper. In modern times the use of gilding in archi- tecture has been earried to the greatest extent by the nations of Further India. It is practised by them with great skill and in the most pro- fuse manner. Besides the method of gilding by covering objects with gold leaf, there are processes of modern invention, distinguished as chemical gilding, in which the gold is incor- porated with the substance of the article it covers, and the same quantity is thus made not merely to spread over a much larger sur- face, but to be permanently attached to me- tallic bodies, so as to withstand the action of heat and of atmospheric agents without injury ; an art incompatible with the attainments of the ancients in chemistry. Gilding with gold leaf is distinguished as the mechanical branch of the art ; and of this there are two distinct processes, one of which is called burnish gild- ing or gilding in distemper, and the other oil gilding. In the former the article to be orna- mented, as the moulding of a picture frame, is received from the joiner before it is made up. A priming of hot size and whiting is first applied, and when dry all irregularities in the moulding are corrected with the same com- position, made of the consistency of putty, which then receives four or five coats of the priming. This, which is now ^ to -fa of an inch thick, is carefully trimmed around the edges and smoothed with pumice stone and glass paper. This is the foundation for the so- called gold size (the bed upon which the gold leaf is to be laid), a composition of clay, red chalk, plumbago, suet, and bullock's blood ; or, as used by the French, of a pound of Arme- nian bole to two ounces of red hematite and as much galena, each ground by itself in water, then mixed and ground with a spoonful of olive oil, and at last tempered with a clear white glue carefully prepared from sheep skins. When used, it is first melted with thin size, and while warm is laid on with a brush. The leaf is then laid on by means of a brush called a tip, an operation which requires con- siderable dexterity. When the whole is cover- ed and dried, the work, or any portion of it, is burnished with smooth agates or flints set in handles for this use. Oil gilding is practised by several different methods. For large objects, especially those exposed to the weather and of metallic composition, the priming used in Paris is white lead mixed with linseed oil and a little oil of turpentine. For equipages and in- door work a varnish polish is much used over the gold. For elaborately designed frames oil gilding and burnish gilding are often employed upon the same piece, care being taken that the applications for the former do not touch the spots intended to be burnished, which are treated in the manner already described. The frames intended for this process are furnished to the gilder made up. They are then thor- oughly washed, and afterward receive two or three coatings of thin white, and more upon the parts to be burnished. A strong size called clear cole is then laid in several coats over those parts only intended for oil gilding, and upon this the oil gold size, a mixture of boiled linseed oil and ochre. By standing over night this becomes ready for the gilding, which is effected without using water. The gold leaf is pressed with cotton wool into all the depressed portions, and when all is laid the work is smooth- ed over with a brush, by which its irregulari- ties are removed, and the gold is uniformly distributed. Book covers are ornamented with gilt letters and figures in the following manner. If of cloth, the leaf is laid on over the parts to be ornamented, and the cover is then placed in a press, in which a heated metallic block, having the intended designs cut upon its face, is powerfully pressed against the cover as in printing. The heat of the block causes the glue on the back side of the cloth to melt and come through, and thus fasten the figure to the fabric. Leather covers receive an application of gelatine or of the white of egg dissolved in water, upon which when dry an almost imper- ceptible application of oil is made with a rag, and the gold leaf is then laid to be pressed as in the case of the cloth. The edges of the leaves are gilded in the bookbinder's press, the same gelatine solution and oil being applied, upon which the gold leaf is laid and afterward bur- nished. Chemical gilding is particularly ap- plicable to metallic surfaces, but other surfaces, as of wood, leather, or paper, may be coated with some preparation by which they are ren- dered fit for it. Wash or water gilding is the branch of this art in which the gold is applied by means of an amalgam of gold and mercury. In other processes it is deposited from its solu- tion. Copper, or an alloy of copper with a lit- tle zinc, or zinc and nickel, or brass, is well suited for the amalgamation process ; the nearer the color is to that of gold the better. The surface to be gilded must first be thoroughly cleaned and brightened and freed from oil; and it is then advisable to wash it over with a