Buttons and articles of a similar description are often gilt only on their tops, or on some other portion of their surfaces, while the re mainder is left uncovered with gold, and of the native colour of the metal of which they are manufactured. This is accomplished by brushing them over the part to be gilt with a hard brush wetted with 'quick-water,' or by rubbing it with a piece of chamois leather similarly moistened. They are afterwards briskly rubbed with a dry brush. They are then put into the gilding-cap,' which is a white felt hat of a peculiar sort and shape. The amalgam is put into the gilding-cap along with them. The whole is then well shaken together for a few minutes, when the amalgam will be perceived clinging to the amalgamated parts of the goods, but leaving the remainder in their original state. They are then put into the cage, the mercury is evaporated, and they are afterwards heightened in the manner already described.
For larger goods, and where considerable portions of hidden surface are not required to be gilt, there are two modes of preventing the amalgam from adhering to those parts. One is to lacquer those parts, and, after the spirit of wine is thoroughly evaporated, to immerse them in the quick-water, and afterwards apply the amalgam. The other mode of applying the gold is to distribute the quick-water over the parts requiring it by a small brush or camel's hair pencil, and these then have the amalgam applied as before. If, as is some times the case, the goods are to be entirely covered, they are immersed at once in the quick-water. If the articles are of a kind which would be injured by revolving in the cage, the heating is effected by other means. Gilt articles are afterwards coloured to a deeper orange tint by the application of several che mical mixtures aided by heat.
Most gilt articles are burnished by a stone burnisher, formed of a polished piece of black hematite. This is fixed into a proper handle., Small articles, as buttons, &c., are placed in a lathe, and the stone applied to them as they revolve ; and those that do not admit of this are burnished by hand on a table or bench.
Steel and iron are gilt by being immersed in a mixture of the nitro-muriate of gold with sulphuric ether or alcohol. By combining these liquids together, an alcoholic solution of gold is formed, from which the metal is pre cipitated by the iron or steel.
Ivory may be gilt by immersing it first in a solution of sulphate of iron, and afterwards in one of nitro-muriate of gold.
The edges of the leaves of books are gilt by applying to them, when squeezed in a press, a composition of four parts Armenian bole and one part sugar-candy, ground together with the white of eggs. Gold leaf is then laid on, and is afterwards burnished by rubbing with a polished piece of agate.
The gilding of porcelain is accomplished by the application of gold-leaf during the process of its manufacture,.which is fixed by that in tense heat which confers on this substance its enamel or glaze, and is afterwards burnished by a stone as above described.
Carved wood or wood-mouldings are gilt by laying on a foundation of whiting and size, and a further series of layers of gold-size, to which leaf-gold is made to adhere by wetting the surface underneath it : this is ' burnish gilding.' In the gold is made to adhere by using oil-gold-size, instead of burnish-gold-size wetted with water. The former kind of gilding admits of being bur nished with a smooth piece of agate, but not the latter.
Glass may be gilt by applying leaf-gold to the glass when wetted with a solution of isinglass.
For the process of Electro-Plating, which is now much employed as a substitute for metal gilding, see ELECTRO-METALLURGY.
GIN, or GYN, a machine employed instead of a crane, chiefly by artillerymen, for the purpose of raising gums, howitzers, &c. on their carriages. It consists of three round poles, placed up in a pyramidal form, within which a windlass and tackle afford the means of raising weights. A similar contrivance is often used in the coarser kinds of Engineering.
Gin is also the name of a machine em ployed in the United States for cleaning cotton; in which a number of revolving spikes disentangle the cotton fibres.