GOLD.—Chemical Gilding.

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different sizes, and a little instrument, termed atip, for laying the leaf on the moulding. This lastinstrument consists of two pieces of card gluedtogether, with the ends of a row of camel’s hairsfastened between them, and projecting from 1 to1A inch. The gilder having moistened with watera few inches of the moulding about to be gilded,and having cut a leaf into stripes suited to the widthof the part on which it is to lie laid, touches one ofthese stripes with the tip, to the hairs of which itslightly adheres, and transfers it to the moistened partof the moulding When the whole of the mouldinghas been thus covered, it is set aside to dry.

The burnishing is performed by rubbing brisklyover the gold a piece of flint or agate. This greatlyincreases its brilliancy, and does not injure the gold-leaf on account of the foundation of gold-size andwhiting which yields under the hand. The partswhich are to be in dead gold or matt are left un-burnished, but over these a very thin clear sizeis passed, and when dry the gold is carefully wipedwith soft cotton wool. The work is completed bywetting the matt parts with a pencil dipped in clearfinishing size. The moulding is then passed into thehands of the frame-maker, who cuts it up and formsit into a frame of the required size.

When the frame or other article to be gilt is some-what richly ornamented, oil-gilding is resorted to. Inthis case the moulding is first whitened as before, butis then at once made up to the required shape anddecorated with composition ornaments before theapplication of any further primings. In this statethe gilder receives the frame, and his first operationis to wash it, in order to free it from oil or otherimpurities. He then gives it two or three coatingsof thin-white, mixed with a little soft clay, andseveral additional coatings are given to the partsintended to be burnished. Two or three coats ofa moderately strong size called clear-cole are nowspread over the whole, after which the oil gold-size,consisting of a mixture of boiled linseed-oil andochre, is laid on smoothly with a brush. After sixor eight hours, when the oil-size has been partiallydried, the gold-leaf is applied as before, except thatin this case no water is used, the oil serving thesame purpose. For deep ornaments the gold ispressed in with cotton-wool, and in this case thegilding has to be repeated to remove the irregularfractures known by the gilders as spiders' legs. Thework, which has still a ragged appearance, is nowcarefully gone over and smoothed with a brush—superfluous gold being removed from some partsand worked into others. This operation is termedslewing. The parts to be burnished are then treatedas before, and finally the frame, after being dusted,is sized with clear size and yellowed on the outside.

Another application of gold-leaf is to book-gilding.When the book is bound in leather, the back andsides to be gilt are first covered with a coating ofisinglass, or white of egg, dissolved in a large pro-portion of water, and termed eglaire. This isallowed to dry, and when the gold-leaf is aboutto be laid on, a woollen rag, slightly moistened

with hog’s lard or sweet oil, but so as to feel almostdry to the touch, is rubbed over the leather. Thiscauses the adherence of the gold-leaf, which is laidon over the whole space intended to be covered bythe figure; and is then imprinted with a hot brassblock, cut to the required design or letters. Forthis purpose a blocking-press is employed, and inthe upper bed is a cavity containing a row of gasjets for keeping the block at the proper tempera-ture ; the superfluous gold is readily brushedoff the parts which have not received the im-pression. Books bound in cloth are treated in thesame manner, except that they do not receive thepreliminary coating of glaire, as this is replacedby a portion of the glue under the cloth beingraised by the heated block. .The edges of theleaves of books are gilded in the bookbinder’s pressby applying a solution of isinglass or white of egg,moistened with oil, and then laying on the gold-leaf, which is firmly pressed down and burnishedwith agate, bloodstone, or polished steel. Insteadof isinglass or albumen, the serum of bullock’sblood is often employed.

Chemical Gilding. — Metallic surfaces may begilded either by applying the gold in the state ofan amalgam, an operation which is termed water orwash-gilding, or by introducing the articles into asuitable solution containing gold, when this metalis deposited, owing to the chemical action whichtakes place. This latter is called gilding by im-mersion.

Water or IFcrs^ gilding consists in applying evenlyan amalgam of gold to the metallic surface to begilt, and then dissipating the mercury by heat so asto leave on the surface a film of pure gold. Ordinarybrass answers very well for gilding on, but the alloywhich is now generally preferred is a mixture ofcopper, nickel, and zinc, which may be so pro-portioned as nearly to resemble gold in colour. Toform the amalgam, a small quantity of gold, reducedto grains or thin plates, is heated in a crucible tillit becomes faintly red, and then thrown into mer-cury, also previously heated till it begins to emitvisible vapour. The proportion of mercury to goldis generally as six or eight to one. The mercury isthen stirred with an iron rod till all the gold is dis-solved. The crucible containing the two metals isnow removed from the fire, and the amalgam throwninto water, where it separates itself from the excessof mercury as a pasty mass; the whole is thensqueezed in a bag of chamois leather in order toremove this superfluous mercury, which howevercontains gold, and is therefore employed in subse-quent operations. The amalgam left behind is ofthe consistency of butter, and contains about 67 percent, of gold and 83 of mercury.

Before the application of amalgam to the surfacesof articles to be gilded, they must undergo severaloperations in order to remove grease, &c., whichwould prevent contact between the metal and theamalgam : these are annealing, pickling, and cleansing.

The first of these is performed in a brick ovenin which is placed an iron grate containing in-