GILDING

The application of a superficial coat of gold on wood, metal, and other materials. The beauty and durability of gold render it the most valuable of all ornamental substances; but, on account of its weight and high price, its use in these respects would be exceedingly limited, were it not the most extensible and divisible form of matter, so that it may be made to cover a larger surface than an equal quantity of any other body. Metals are usually covered with gold by the proce of -water gilding. It consists in perfectly cleaning their surface, and then, in the case of silver, for instance, rubbing it over with a solution of gold in mercury, called amalgam of gold: the ve el is then heated over a clear charcoal fire, by which the mercury is driven off, and the gold left adhering to the silver surface, upon which it is afterwards burnished. The surface of copper or bra is usually prepared by cleaning and rubbing it over with a solution of nitrate of mercury, which amalgamates the surface, and enables the gold amalgam, when subsequently applied,to adhere; heating and burnishing are then resorted to as before. Bra and copper buttons are gilt in this way; and the requisite quantity of gold is so small that twelve dozen buttons of one inch diameter may be completely gilt upon both surfaces by five grains of gold. Other kinds of gilding are performed by gold leaf, which, if intended for out-door work, is laid on by the help of gold size, which is drying oil mixed with calcined red ochre; or, if for picture and looking-gla frames, they are prepared by a size made by boiling parchment clippings to a stiff jelly, and mixed with fine Paris-plaster or yellow ochre. The leaves of books are gilt upon the edges by brushing them over, while in the binder's pre , with a composition of four parts of Arm in i an bole and one of powdered sugar candy mixed up with white of egg; this coating, when nearly dry, is smoothed by the burnisher, then slightly moistened, and the gold leaf applied and burnished. To impre gilt figures on book covers, the leather is dusted over with finely-powdered mastic: the iron tool by which the figure is made is then moderately heated and pre ed upon a piece of leaf-gold, which slightly adheres to it; being then immediately ap- 510 [s. 530]