Gilding. There are many processes of gilding, varying with the nature of the substance to be gilded, and the kind of effect required to be produced, but they may all be classified under three heads—viz. (1) mechanical gilding, (2) chemical gilding, (3) encaustic gilding.
The first is used chiefly for gilding wood, plaster of Paris, leather, paper, and other substances. If the object to be gilt is a picture or mirror frame, consisting of a plain wooden moulding, then, after getting a coat of oil-paint, from four to ten coats of fine whitening mixed with fine glue are put on, each in its turn being smoothed with pumice-stone and fine sand-paper. This done, a coat of gold-size is given to those parts which are not to be burnished; but those which are receive only a coating of clear animal size. Both of these prepared surfaces now receive the gold-leaf, which is laid on by means of a broad thin brush called a tip, and further pressed on with a thick soft-haired brush. Those parts which have been gold-sized are in this way oil-gilt, and will stand washing; while such portions as have been gilt on the size preparation in order to be burnished will not bear soap and water. If the picture-frame is much enriched with fine raised ornament, the surface to be gilt is previously prepared with oil-paint and gold-size alone, as the coating with whitening destroys the sharpness of the work. The result, however, is more tender and less durable.
Japanner's Gilding.—Where gilt ornaments are to be put on a japanned ground, they are, by one method, painted with gold-size, and gold-leaf afterwards applied. By another method, rather more than the space the ornament is to occupy is wholly covered with gold-leaf, adhering with isinglass. The ornament is then painted on with asphaltum, which protects the gold beneath it while the superfluous leaf is being washed away. A little turpentine will then remove the protecting asphaltum so as to display the gilt ornament. Japanners' gold-size is a mixture of linseed-oil, gum-animi, and vermilion.