GILD′ING

Syn. Dorure , Fr. The art or proce of covering the surfaces of bodies with a thin film of gold, for the purpose of increasing their durability or improving their appearance. For the sake of brevity we shall briefly notice the leading varieties of gilding, and their applications, in alphabetical order. Gilding, Burnished. This is distemper gilding to which a ‘face’ has been given with the ‘burnisher.’ It is chiefly employed for the polished portions of the frames of pictures and mirrors, the more prominent parts of statuettes, . Gilding, Chemical. Those varieties in which the film of gold is formed on the surface through the agency of chemical affinity, in opposition to mechanical gilding, in which the gold is made to adhere by the intervention of some glutinous substance. Gilding, Cold. The articles (copper or bra ) to be gilded, after being softened, annealed, and polished in the usual manner, are rubbed with a little gilding powder by means of a piece of cork moistened with a solution of salt in water; after which the work is burnished with a piece of hematite or polished steel. (See below .) Gilding, Distemper. This is applied to wood, plaster, marble, . It is commonly performed in this country by giving the wood, first, a coating of good size, and next, several succe ive coats of size thickened with finely powdered whiting, Spanish white, or plaster of Paris until a good face is produced; observing to let each coat become quite dry, and to rub it perfectly smooth with fine gla paper, before the application of the following one. When the proper ‘face’ is obtained, the surface is thinly and evenly gone over with gold size, and when this is nearly dry, the gold leaf is applied, and afterwards burnished with an agate or dog’s tooth. The proce , as adopted by the Paris i an artists, who greatly excel in this species of gilding, is very complicated, and is divided into at least 17 distinct operations, each of which they declare to be e ential to its excellence. Gilding, Electro-. See Electrotype . Gilding, Grecian. In this variety sal-ammoniac and corrosive sublimate, equal parts, are di olved in nitric acid, and a solution of gold made with this menstruum; after slight concentration the liquid is applied to the surface of silver, which immediately becomes black, but on being heated exhibits a rich gilded surface. Gilding, Japanner’s. The surface is covered with oil size thinned with spirits of turpentine, and gold, in powder, is gently dabbed on with a puff of wash leather. This gives the appearance of ‘frosted gold.’ A coating of varnish is next given, followed by exposure to a gentle heat in the ‘stove.’ Gilding, Leaf. This term is commonly applied to the gilding of paper, vellum, ., by applying leaf gold to the surface, previously prepared with a coating of gum water, size, or white of egg. It is usually burnished with an agate or dog’s tooth. Gilding, Mechanical. See Chemical gilding ( above ). Gilding, Mercurial. See Wash gilding ( below ). Gilding, Oil. This species of gilding may be divided into several operations. The following are the abridged instructions of a Paris i an artist on the subject:—1. The surface is prepared by a coating of white lead in drying oil.—2. Another coat is given, made with calcined white lead or ma icot, ground in linseed oil and turpentine. 3 or 4 coats of this mixture are often given, at intervals of at least 23 hours, observing to carefully smooth off each coat with pumice stone or shave gra before the application of the following ones.—3. The ‘Gold Colour,’ or paint, is next applied. It is usually very adhesive gold size, or the bottom of the pot or dish in which painters wash their brushes. For this purpose it is thoroughly ground and strained.—4. When the gold colour becomes partially dry and sufficiently tenacious, the gold leaf is applied, and pre ed on with a wad of cotton-wool or a soft brush. It is now left for several days to harden.—5. A coat of spirit varnish is next given, and the object is cautiously pa ed over a chafing-dish of charcoal, observing to avoid stopping the motion of the piece whilst doing so, as the work would then become discoloured and blistered.—6. The work is ‘finished off’ with pale oil varnish. For out-door gilding and common work the varnishing proce is generally omitted. This species of gilding is applied to woodwork, plaster, metal, . Gilding, Varnish. This is a mere variety of oil gilding, applied to equipages, furniture, mirror and picture frames, ., the surface being highly varnished and polished before it receives the size or gold colour; and after the gilding has become quite dry, a coat of spirit varnish, fumed with the chafing dish as above, is applied, followed by 2, 3, or more coats of the best copal varnish, at intervals of 3 or 4 days each. The whole is, lastly, carefully polished with tripoli and water. Gilding, Wash , Amalgam g. , Mercurial g. , Water g. This consists in the application of a thin coating of amalgam of gold to the metallic surface (bra , bronze, or copper) to be gilded, and the subsequent volatilisation of the mercury by heat. It is the usual method of gilding articles of copper and its alloys, and po e es great beauty and durability when skilfully executed. The occupation is, however, an unhealthy one, owing to the continual exposure of the workman to the fumes of mercury. The furnace invented by M. D’Arcet obviates this evil, as the whole of the volatilised mercury is carried off, and again condensed for further use. It should, therefore, be adopted by every water-gilder who studies economy and the health of those in his employ. The proce of water gilding consists in several distinct operations, and can only be succe fully performed by those who have been schooled in the art by an apprenticeship to the trade. It would, therefore, be waste of space to enter into details here. Formulæ for several of the articles employed for the purpose will be found in the alphabetical places in this work. Gilding, Water. See above . Among the applications of the proce of gilding that deserve a separate notice are the following:— The gold letters and figures on the covers of BOOKS are thus formed:—Gum mastic, in fine powder, is dusted over the surface to be gilded; an iron or bra tool bearing the design upon its face is then heated to a proper temperature, and gently pre ed upon a piece of leaf gold, which slightly adheres to it; the two are then transferred to the cover, and the tool is gently pre ed on it, by which means the mastic softens and retains the gold. The loose gold and powdered mastic are then dusted off with a brush. Gold leaf will adhere to leather without the use of mastic, but not so firmly as when it is employed. The edges of the leaves of books and paper are first cut perfectly smooth, and then washed over with a solution of isingla in weak spirit, or with a varnish made of Armenian bole, 4 parts, and powdered sugar-candy, 1 part, mixed up to a proper consistence with strained white of egg. The coating is allowed to dry, and is then smoothed with a wet rag, after which the gold leaf is applied and polished with the burnisher. Bra buttons , formerly so much in demand, are covered by a rough species of wash gilding. The buttons are polished in the lathe and thrown into a pan with a little amalgam of gold, and as much aquafortis diluted with water as will wet them all over. Here they are well stirred up, until they a ume a silvery appearance, when they are washed with clean water. They are then submitted to a sufficient heat in a suitable apparatus, until the mercury is volatilised. The buttons are next cooled, and well to ed and rubbed about with a painter’s brush; and are, lastly, burnished by washing them well with beer or ale grounds. Twelve dozen (1 gro ) of buttons, of 1 inch in diameter, may be perfectly gilded on both sides with only 5 gr. of gold. By an Act of Parliament, which is still unrepealed, this is the smallest quantity of gold permitted to be used for a gro of buttons of the above size. Gla , PORCELAIN , and EARTHENWARE , are gilded by blending powdered gold with gum-water and a little borax, and applying the mixture by means of a camel-hair pencil; the article is then heated in an oven or furnace, by which means the gum is burnt, and the borax, vitrifying, cements the gold to the surface. It is afterwards polished with a burnisher. Names, dates, or any fancy device, may thus be permanently and easily fixed on gla , china, earthenware, . Japanned work is gilded by the method explained as ‘Japanner’s gilding’ ( above ). Leather is gilded in the same way as the covers of books. (See above .) For common work, silver leaf, or even tin foil, is applied to the surface, previously covered with size or white of egg, and after being burnished down and dried, is washed over with gold-coloured lacquer. The LETTERS of sign-boards and the ornamental gilding for out-door work are done by first covering the design with yellow paint, then with oil gold-size, and when this is nearly dry applying the leaf gold, observing to shield it properly from the wind, lest it be blown away or become crumpled before being properly attached. The work is, lastly, varnished. Polished metals may be gilded by one or other of the methods already noticed. Articles in silver, copper, bra , and bronze, are usually coated by the proce of wash or water gilding; or, directly, by the application of gold leaf, as follows:—The piece or article is heated to a bluish tint, and gold leaf pre ed gently and carefully on it with the burnisher; heat is again applied, and the proce repeated with fresh leaves of gold until the gilding has acquired the proper thickne and tone. The surface is lastly polished with the burnisher, or is coloured in the usual manner at the stove. This succeeds with iron, steel, silver, copper and its alloys, . Another method for polished articles in iron and steel, which, however, is le durable than the preceding, is to apply an ethereal solution of gold to the surface with a camel-hair pencil. The ether flies off and leaves the surface coated with gold, which is then polished as before. In this way, any fancy device or writing may be executed on steel or iron with extreme facility. Silks , SATINS , WOOLLENS , IVORY , BONE , ., may be readily gilded by immersing them in a solution of neutral terchloride of gold (1 of the salt, and 3 to 6 of water), and then exposing them to the action of hydrogen gas. The latter part of the proce may readily be performed by pouring some dilute sulphuric acid on zinc or iron filings, in a wide-mouthed bottle, and placing it under a jar or similar ve el, inverted, at the top of which the articles to be gilded are suspended. the surface with a camel-hair pencil dipped in the solution. The design, after a few minutes’ exposure to the hydrogen, shines with all the splendour of the purest gold, and will not tarnish on exposure to the air, or in washing. Gilded thread or GOLD THREAD is merely a thread of yellow silk covered with a very thin flatted wire of gold, by means of a revolving wheel. Wire (copper, silver, or bra ) is occasionally gilded, in coils, by a similar proce to that adopted for BUTTONS ; but more frequently as follows:—Rods (usually of silver) are covered with gold foil of a thickne proportionate to the quality of the intended wire, and the compound bar is then drawn into wire, in the usual way. 100 gr. of gold was formerly the lowest legal quantity that could be employed for 1 lb. of silver. Patents. Among the varieties of chemical gilding may be mentioned 1. (Elkington’s patent— German gilding , Bonnet’s GILDING PROCESS .) The articles to be gilded, after being perfectly cleaned from scale or grease, and receiving a proper ‘face,’ are suspended, by means of wires, in the gilding liquid (boiling hot), and moved about therein for a period varying from a few seconds to a minute, or longer; the precise time required depending on the newne and strength of the liquid. When sufficiently gilded, the articles are withdrawn from the ‘solution of gold,’ washed in clean water, and dried; after which they undergo the usual operation of the articles of a weak solution of nitrate of mercury previously to the immersion in the gilding liquor; or the deadening may be given by applying a solution of the nitrate to the newly gilded surface, and then expelling the mercury by heat. The gilding liquor.—Take of fine gold, 5 oz. (troy); nitro-muriatic acid, 52 oz. (avoirdupois); di olve by heat, and continue the heat until red or yellow vapours cease to be evolved; decant the clear liquid into a suitable ve el; add of distilled water, 4 galls.; pure bicarbonate of pota a, 20 lbs.; and boil for 2 hours. The nitro-muriatic acid is made with pure nitric acid (sp. gr. 1·45), 21 oz.; pure muriatic acid (sp. gr. 1·15), 17 oz.; and distilled water, 14 oz. This proce , though patented by Mr Elkington in England, was in reality discovered and first practised by M. Bonnet, a foreigner. Articles thus gilded do not bear friction and the operations of being put in colour ( mise en couleur ) so well as those gilded by the mercurial proce , or by the methods of cold or leaf gilding as applied to polished metals. 2. (Talbot’s patent.) By this proce polished metallic articles are gilded by simple immersion in a solution of gallic acid in water, ether, or alcohol, to which a solution of gold has been previously added. Silvering and PLATINISING may be effected in the same manner, by using a solution of either of these metals instead of one of gold. ⁂ These and other chemical proce es have been almost completely superseded by the certain and economical proce of ELECTRO-GILDING . See Electrotype .