[ 6z ]

spread upon the piece, one after another is dry, so asto cover the grain of the wood, and the imperfectionsleft by the tool, and form a perfectly smooth surfacefor applying the gold upon : over this is commonly spreadsome of the same size mixed with yellow ochre. Thesecompositions do not well admit of the gold being bur-nished i and therefore, where burnished gilding is re-quired, another mixture, called gold-size, is either laidabove these, or applied on the wood at first. The gold-size is composed of tobacco-pipe clay, or bolar earths,ground with a smaller proportion of ruddle and blacklead, and tempered with a little tallow and oil olive. Inthese points there is little uniformity among the work-men, the same end being obtainable by different means,among which we cannot perhaps distinguish any superio-rity in the effect of one to that of another, and of whichfancy or prejudice have often chosen the more com-pounded in preference to the more simple. The principalcaution, in regard to the gold-size, seems to be, to useno more of the unctuous materials than is necessary forprocuring the due consistence ; and to make a trial ofthe preparation previous to its being employed in anywork of consequence.

For some purposes, the gold is used in powder, which,from its being kept in shells, is called shell gold. Thisis prepared by grinding gold leaves, or gold-beaters frag-ments, with a little honey ; and afterwards separating thehoney from the powdered gold by means of water. Goldmay be reduced also, by dissolving it in mercuiy, andevaporating the mercury in the fire, or by dissolving it inaqua regis, and precipitating with certain additions, ofwhich hereafter, into a powder, more subtile than caneasily be obtained by mechanical comminution.

Gilt