As a term in ornamentation diaper is applied to a surface covered with a flowered pattern sculptured in low relief, or to a similar pattern in painting or gilding covering a panel or flat surface. Research Diaper
Gilding is the art of applying gold-leaf or gold in a finely-divided state to surfaces of wood, stone, or metals. It is a very ancient art, being practised among the Egyptians, Greeks, Romans, and Ancient Persians. The processes employed through more modern times have been very varied. Metals are gilded either by what is called chemical gilding, mercurial gilding, by electro-gilding (electro-plating), or by the application of gold-leaf. Copper and brass, for instance, may be gilded by the process called wash or water gilding, with an amalgam of gold and mercury. The surface of the copper, freed from oxide, is covered with the amalgam, and afterwards exposed to heat until the mercury is driven off, leaving a thin coat of gold.
Gilding is also performed by dipping a linen rag in a saturated solution of gold, and burning it to tinder, the black powder thus obtained being rubbed on the metal to be gilded, with a cork dipped in salt water, until the gilding appears. Iron or steel is often gilded by applying gold-leaf, after the surface has been well cleaned, and heated until it has acquired the blue colour which at a certain temperature it assumes. Several leaves of gold are thus applied in succession, and the last is burnished down cold.
One process of chemical gilding was by dipping the article into a solution of gold, what is termed Elkington's solution being composed as follows: 5 oz. (troy) of fine gold; nitro-muriatic acid, 52 oz. (avoirdupois); dissolve by heat, and continue the heat until the cessation of red or yellow vapours; decant the clear liquid; add 4 gallons of distilled water, 20 lbs of pure bicarbonate of potassa and boiling for two hours.
Gilding on wood, plaster, leather, parchment, or paper, is performed by different processes of mechanical gilding. The first of these is oil-gilding, in which gold-leaf is cemented to the work by means of oil-size. In the case of paper or vellum the parts to be gilt receive a coat of gum-water or fine size, and the gold-leaf is applied before the parts are dry. They are afterwards burnished with agate. Lettering and other gilding on bound books are applied without size. The gold-leaf is laid on the leather and imprinted with hot brass types. Brass rollers with thin edges are employed in the same way for lines, and similar tools for other ornaments. When the edges of the leaves of books are to be gilt they are first cut smooth in the press, after which a solution of isinglass in spirits is laid on, and the gold-leaf is applied when the edges are in a proper state of dryness.
Japanner's gilding is another kind of mechanical gilding, which is performed in the same way as oil-gilding, except that instead of gold-leaf a gold dust or powder is employed. Frames of pictures and mirrors, mouldings, etc, are gilt by the application of gold-leaf, or by the cheaper process of 'German gilding,' that is, by tin-foil or silver-leaf, with a yellow varnish above.
Porcelain and other kinds of earthenware, as well as glass, may be gilt by fixing a layer of gold in a powdered state by the action of fire. The gold-dust or powder required in this operation may be obtained by precipitating it from a solution in aqua regia, either by means of iron sulphate or proto-nitrate of mercury. In order that the gold powder may be applied to the surface of the article to be gilt it must be well mixed with some viscous vehicle, such as strongly-gummed water. It is then laid on with a fine camel's-hair brush. Research Gilding
Gold-beating is the art or process of producing the extremely thin leaves of gold used in gilding, etc. Traditionally, the gold is cast into ingots weighing about tow ounces each, and measuring about 0.75 inches broad. These ingots are passed between steel rollers until they form long ribbons of such thinness that a square inch will weigh 6.5 grains. Each one of these is now cut into 150 pieces, each of which is beaten on an anvil until it is about an inch square. These 150 plates are interlaid with pieces of fine vellum about four inches square, and beaten until the gold is extended nearly to the size of the vellum leaves. Each leaf is then divided into four, interlaid with goldbeater's skin, and beaten out to the dimensions of the skin. Another similar division and beating finishes the operation, after which the leaves are placed in paper books ready for use. Research Gold-Beating
Oil gold size is an adhesive used in gilding carved or modelled work, gilding large letters in wood or metal and for large areas where a solid gold background is required. Formerly oil gold size was prepared from linseed oil exposed to the air until it became fatty and then tinted with ochre, driers added and thinned down with polled oil or varnish. Research Oil Gold Size
Dutch metal is an alloy of about eleven parts of copper to two of zinc, the proportions varying according to the colour, which may be from copper to pale gold. The alloy is made into leaves like gold-leaf and is used for imitation gilding, either in leaf form or as powder. Research Dutch Metal
Egg glair is a substance consisting of fresh egg white mixed with lukewarm water, and used in gilding to prevent gold leaf from sticking to varnished or enamelled work. Research Egg Glair
A mordant is an adhesivecompound capable of uniting with dye-stuffs to form insoluble pigments, and thus, if the reaction is made to take place in the fibres of a fabric, fix the colour in it. Mordants are mostly used in cotton and wool dyeing, and also in gilding to attach gold leaf and in paints intended for non-ferrous metal surfaces so as to etch the surface and provide better adhesion for the pigment. Research Mordant
In gilding, a mop is a soft camel-hair brush used in the gilding of carved, moulded or modelled work, for the purpose of pressing the gold leaf into the crevices and intricate parts of the work. Research Mop
In architecture the term reredos refers to a number of things: a screen or partition wall behind an altar (altarpiece); the back of a fireplace; the open hearth, upon which fires were lighted, immediately under the louvre, in the centre of ancient halls. For more than 1000 years the episcopal seats and choir stalls were in line with the altar wall; but about the close of the 11th century they were brought forward, and the reredos, or screen, erected between them and the congregation. In the course of time the reredos came to be richly decorated, either with carved niches or with paintings or tapestries. In Spanish churches the reredos is the most decorative feature, often as wide as the nave and reaching to the vaulting of the roof. The materials employed are wood, stone, and alabaster. At Toledo and Seville painting and gilding are added. In Christchurch, Hampshire, is a reredos somewhat resembling the Spanish style. Other richly-decorated and carved examples may be seen in the cathedrals at St Albans, Manchester and Durham. The most famous, however, is that in the church of St Etienne du Mont in Paris, which contains a fabulous carved double stair and balustrading. Research Reredos
The Probert Encyclopaedia was designed, edited and programed by
Matt and Leela Probert
Abbreviations
Research Diaper
