« PreviousContinue »
It is a great improvement in all kinds of japanned work, to harden the varnish by means of heat; which in every degree that it can be applied, short of what would burn or calcine the matter, tends to give it a more firm and strong texture.
Where metal forms the body, a very hot stove may be used; and the pieces of work may be continued in it a considerable time, especially if the heat be gradually increased; but where wood is in question, heat must be sparingly used, as it would otherwise warp or shrink the body, so as to injure the general figure.
LACQUERING. Lacquering is the laying either coloured or transparent varnishes on metals, in order to
produce the appearance of a different colour in the metal, or to preserve it from rust, or the injuries of the weather.
Lacquering is used where brass is to be made to have the appearance of being gilt ; where tin is wanted to have the resemblance of yellow metals; and where brass locks or nails, or other such matters, are to be defended from the corrosion of the air or moisture.
The principal substance used for the composition of lacquers, is seed-lac ; but for coarser purposes, resin or turpentine is added, in order to make the lacquer cheaper.
for Brass, to imitate Gilding.
Take of turmeric one ounce, and of saffron and Spanish annotto, each two drachms. Put them
into a proper bottle, with a pint of highly rectified spirits of wine, and place them in a moderate heat, often shaking them for several days. strong yellow tincture will then be obtained, which must be strained off from the dregs through a coarse linen cloth; and then, being put back into the bottle, three ounces of good seed-lac, powdered grossly, must be added, and the mixture placed again in a moderate heat and shaken till the seed-lac be dissolved, or at least such a part of it as may. The lacquer must then be strained, and must be put into a bottle well corked.
Where it is desired to have the lacquer warmer or redder than this composition, the proportion of the annotto must be increased ; and where it is wanted cooler, or nearer to a true yellow, it must be diminished.
The above, properly managed, is an extremely good lacquer, and of moderate price; but the following, which is cheaper, and may be made where the Spanish annotto cannot be procured good, is not greatly inferior to it.
Take of turmeric root, ground, one ounce, of the best dragon's blood half a drachm. Put them to a pint of spirits of wine, and proceed as above. By diminishing the proportion of dragon's blood, the varnish may be rendered of a redder or truer yellow cast.
Saffron is sometimes used to form the body of colour in this kind of lacquer, instead of the turmeric; but though it makes a warmer yellow, yet the dearness of it, and the advantage which turmeric has in forming a much stronger tinge in spirits of wine, gives it the preference. Though being a true yellow, and consequently not suffi.ciently warm to overcome the greenish cast of
brass, it requires the addition of some orange coloured tinge to make it a perfect lacquer.
Aloes and gamboge are also sometimes used in lacquers for brass ; but the aloes is not necessary. where turmeric or saffron is used; and the gam.' boge, though a very strong milky juice in water, affords but a very weak tinge in spirit of wine.
A Lacquer for Tin, to imitate a Yellow Metal.
Take of turmeric root one ounce, of dragon's blood two drachms, and of spirits of wine one pint; add a sufficient quantity of seed-lac.
A Lacquer for Locks, fc.
Seed-lac varnish alone, or with a little dragon's blood : or a compound varnish of equal parts of seed-lac and resin, with or without the dragon's blood.
A Gold-coloured Lacquer for gilding Leather.
What is called gilt leather, and used for screens, borders for rooms, &c. is only leather covered with silver leaf, and lacquered with the following composition.
Take of fine white resin four pounds and a half, of common resin the same quantity, of gum sandarach two pounds and a half, and of aloes two pounds; mix them together, after having þruised those which are in great pieces, and put them into an earthen pot, over a good fire made of charcoal, or over any fire where there is no flame. Melt all
the ingredients in this manner, stirring them well with a spatula, that they may be thoroughly mixed together, and be prevented also from sticking to the bottom of the pot. When they are perfectly melted and mixed, and gradually to them seven pints of linseed oil, and stir the whole well together with the spatula. Make the whole boil, stirring it all the time to prevent a kind of sediment that will form, from sticking to the bottom of the vessel. When the varnish is almost sufficiently boiled, add gradually half an ounce of litharge, or half an ounce of red-lead, and when they are dissolved, pass the varnish through a linen cloth, or flannel bag.
The time of boiling this varnish should be about seven or eight hours. This, however, varies, according to circumstances. The way of knowing when it is sufficiently boiled, is by taking a little on some instrument, and if it draws out and is ropy, and sticks to the fingers, drying on them, it is done; but if not, it must be boiled till it acquires these qualities.
Gilding is the application of gold to the surfaces of bodies: it is of two principal kinds, according to the method of applying the gold.
Wood, leather, paper, and similar substances, are gilt by fastening on leaves of gold by means of some cement. But metals are gilt by a chemical application of the gold to the surface. This last is called water gilding.
The gilding of wood, and similar substances, is of three kinds; oil gilding, burnished gilding, and japanners' gilding, which we shall severally describe,
after noticing the materials and tools necessary for going to work.
There are three kinds of gold-leaf in common
Pure gold-leaf, which is made by hammering gold between the leaves of a book made of skins, till they are sufficiently thin.
Pale leaf-gold, which has a greenish colour, and is made of gold alloyed with silver. . - Dutch gold, which is brought from Holland, and is in fact only copper-leaf coloured by the fumes of zinc. It is much cheaper than true leaf-gold, and is very useful where large quantities of gilding are wanted, which can be defended from the weather, and where great nicety is not required; but it changes its colour entirely when exposed to moisture; and, indeed, in all cases, its beauty is soon impaired, unless well secured by varnish. It is therefore only a cheap substitute for true gold-leaf, which may be useful where durability is not an object.
Of the Instruments necessary for. Gilding.
The first instrument is the cushion, for receiving the leaves of gold from the books in which they are bought. It is made by covering a board of about eight inches square, with a double thickness of flannel, and over that, a piece of buff leather, and fastening it tight round the edges.
The knife for cutting the leaves into the requisite sizes should be made like a pallet knife, and should not have its edge too sharp.