Another method is, to spread a thin plate of gold upon the steel, then heating them both, and burnishing the gold down, it will adhere, but so slightly as to have but little durability; and the heat must be so considerable, that it frequently injures the temper of the steel.
In the Philosophical Magazine, vol. ii. a new mode of gilding steel is described, as being the same by which the Sohlinger sabres are ornamented. A solution of gold in nitro-muriatic acid, (aqua regia,) being poured into about twice as much ether, the latter will float upon the surface of the acid ; but if shaken together, the gold will be taken up front the acid by the ether; which may then be separated, by pouring the mixture into a long glass funnel with the tube stopped, and when it is completely at rest, the tube being opened, will run off the acid ; and being again stop ped, will leave the ether, with gold in solution.
This solution of gold being spread upon the surface to be gilt, the ether evaporates and leaves the gold, which, however, does not adhere very strongly, but may be fixed, by heating the steel moderately, and burnishing the gilding down.
Leaf Gilding —It is so called, because the gold is lami nated, by the operation of gold beating, into very thin leaves, which are cemented upon the article to be gilded, by gum, size, white of an egg, or drying oil. Leaf gilding can be applied on metals as well as wood ; or, with an appro priate cement, it may be laid on any substance which pre sents a surface sufficiently even, and free from pores. It is distinguished into burnished gilding and oil gilding. In the former, the leaves being cemented upon the work by gum or size, admit of being burnished or polished. This is sometimes called water gilding, because the size or gum is mixed up with water; but as this term is also applied to the wash gilding by mercury, it should be avoided, as tending to confusion. Oil gilding, is that in which the leaves are stuck on by fat or drying oil. The advantage is, that it will bear the weather, but, on the other hand, it will not admit of being burnished.
Burnished Gilding.—When this is laid upon wood, the surface must be prepared for it by a thin coating of size whitening, to fill up the pores, and make a closer ground for the gold leaf. The size used to mix up the whitening, is made from cuttings of parchment, or of glovers' leather.
These must be gently boiled in water for several hours, till the water extracts sufficient size to form a jelly when it cools. This size is strained through a flannel to clear it from the cuttings, and fine powder of whiting is added, being stirred up with the size until it forms a coarse paint whilst hot, but will congeal into a very close solid sub stance when cold. With this composition, when heated, the surface of the wood is coated or printed over several times, spreading it evenly with a painter's brush, and care fully laying it into all the hollows or cavities of the work, where it is carved. Each coat should be suffered to dry perfectly before another is applied, and the last must be rendered as smooth and even as possible. For this pur pose, it is brushed over with water before it is quite dry, and any lumps removed, at the same time the whole sur face is rendered closer. When perfectly dry, the priming of whitening must be examined to fill up the cavities, and the carved parts must be cut or scraped sharp with a knife, and polished up in parts with a Dutch rush. After this, the parts where the gilding is intended to receive a burnish, must be rubbed gently with a rag wetted with water. This produces a surface, which has a polish when dry.
The gilding size which is to cement the gold leaf, is now applied hot with a brush over all the parts intended to be gilt. This is made of the same size as before men tioned; but instead of the whitening, a mixture of bole ammoniac and tallow is ground together upon a marble slab; and, in order to render the mixture more easy, a little soap suds is put upon the slab. The size of parchment before mentioned, being diluted by double its quantity of warm water, this composition is added till it becomes as thick as cream. Some artists add black lead to the bole, at the rate of one-sixteenth of black lead ; and instead of tallow, they use a mixture of equal parts of olive oil and bees-wax. Others add colouring matter, such as vermi lion and fine yellow ; but these are quite useless, if they intend to cover the work completely with gold. The gild ing size is laid on in a thin coat, which is repeated when the first is dry, and sometimes a third time, which pre pares the work for the application of the gold leaf.