The proper japan grounds are either such as are formed by the varnish and colour, where the whole is to remain of one simple colour, or by the varnish with or without colour, on which some painting or other decoration is afterwards to be laid. This ground is best formed of shell-lac varnish, and the colour desired; except in the case of white, which requires a peculiar treatment, as we shall presently explain, or when great brightness is required, in which ca3e also other means must be pursued. The following is the composition and manner of perparing the shell-lac varnish:- "Take of the best shell-lac, five ounces; break it into a very coarse powder, and put it into a bottle that will hold about three pints or two quarts; add to it one quart of rectified spirits of wine, and place the bottle in a gentle heat, where it must continue two or three days, but should be frequently well shaken. The gum will then be dissolved, and the solution should be filtered through a flannel beg, ana when what will pass through freely is come off, it should be put into a proper sized bottle, and kept carefully stopped up for use.
The bag may also then be pressed with the hand till the remainder of the fluid be forced out; which, if it be tolerably clear, may be employed for coarser purposes, or kept to be added to the next quantity that shall be made," Any pigments whatever may be used with the shell-lac varnish, which will give the tint of the ground desired, and they may be mixed together to form any compound colours; but, with respect to such as require peculiar methods for producing them of the first degree of brightness, we shall particularize them below. They should all be ground very smooth in spirits of turpentine, and then mixed with the varnish. It should be spread over the work very carefully and even with a camel-hair brush. As metals never require the priming of size and whiting, the japan ground may be applied immediately to them, without any other preparation than cleaning, except in the instances referred to below.
The forming a ground perfectly white, and of the first degree of hardness, has not yet been attained in the art of japanning, as there are no substances which can be dissolved, so as to form a very hard varnish, but what have too much colour not to deprave the whiteness. The nearest approach, however, to a perfect white varnish already known, is made by the following composition:- "Take flake white, or white-lead, washed and ground up with the sixth of its weight of starch, and then dried; temper it properly for spreading with the mastic varnish prepared in the following manner: - take five ounces of mastic in powder, and put it into a proper bottle, with a pound of spirit of turpentine; let them boil in a gentle heat till the mastic be dissolved, and if there appear to be any foulness, strain off the solution through flannel." Lay these on the body to be japanned, prepared either with or without the priming, in the manner as above directed, and then varnish over it with five or six coats of the following varnish: - "Provide any quantity of the best seed-lac, and pick out of it all the clearest and whitest grains; take of this seed-lac two ounces, and of gum animi three ounces, and dissolve them, being previously reduced to a coarse powder, in about a quart of spirit of wine, and strain off the clear varnish." The seed-lac will give a slight tinge to this composition; but it cannot be omitted where the varnish is wanted to be hard, though where a softer will answer the end, the proportion may be diminished, and a little crude turpentine added to the gum animi, to take off' the brittle-ness. A very good varnish entirely free from brittleness may be formed by dissolving gum animi in old nut or poppy oil, which must be made to boil gently when the gum is put into it.
The ground of white may be laid on in this varnish, and then a coat or two of it may be put over the ground, but it must be well diluted with oil of turpentine before it is used. This, however, is a long time in drying, and is more liable to injury than the other, from its tenderness.
Blue Japan Grounds may be formed of bright Prussian blue, or verditer glazed over with Prussian blue, or of smalt. The colour may be mixed with the shell-lac varnish, as before directed, hut as the shell-lac will somewhat injure the colour by giving it a yellow tinge, where a bright blue is required, the method before directed in the case of white grounds must be pursued.
For a Scarlet Japan Ground, vermilion may be used; but its effect is much improved by glazing it over with carmine or fine lake. If, however, the highest degree of brightness be required, the white varnish must be used.
For Bright Yellow Grounds, king's yellow may be used, and the effect will be heightened by dissolving powdered turmeric root in the spirit of wine, of which the upper or polishing coat is made, which spirit of wine must be strained from off the dregs before the seed-lac be added to it to form the varnish. The seed-lac varnish is not equally injurious here, as in the case of some other colours, because, being tinged with a reddish yellow, it is little more than an addition to the force of the colours.
Green Grounds may be produced by mixing the Prussian blue, or distilled verdigris, with king's yellow, and the effect will be rendered extremely brilliant, by laying them on a ground of leaf-gold. They may any of them be used successfully with good seed-lac varnish, for the reasons before given.
Purple Grounds may be produced by the mixture of lake or vermilion with Prussian blue. They may be treated as the rest with respect to the varnish.
Black Grounds may be formed by either ivory-black or lamp-black; but the former is preferable. These may be always laid on with the shell-lac varnish, and have their upper or polishing coats of common seed-lac varnish.
Common Black Japan Grounds on Metal, by means of heat, are thus performed: The piece of work to be japanned must be painted over with drying oil, and when it is moderately dry, must be put into a stove of such heat as will change the oil black without burning it. The stove should not be too hot when the work is put into it, nor the heat increased too fast, either of which errors would make it blister; but the slower the heat is augmented, and the longer it is continued, provided it be restrained within a due degree, the harder will be the coat of japan. This kind of japan requires no polish, having received, when properly managed, a sufficient one from the heat.
The Tortoise-shell Ground, produced by heat, is not less valuable for its great hardness, and bearing to be made hotter than boiling water without damage, than for its beautiful appearance. It is to be made by means of a varnish prepared in the following manner:- Take one gallon of good linseed oil, and half a pound of amber; boil them together till the oil becomes very brown and thick; strain it then through a coarse cloth, and set it again to boil, in which state it must be continued till it acquire a consistence resembling that of pitch; it will then be fit for use. Having thus prepared the varnish, clean well the substance which is to be japanned; then lay vermilion, tempered with shell-lac varnish, or with drying oil very thinly diluted with oil of turpentine, on the places intended to imitate the more transparent parts of the tortoise-shell. When the vermilion is dry, brush the whole over with black varnish, tempered to a due consistence with the oil of turpentine. When set and firm, put the work into a stove where it may undergo a very strong heat, which must be continued a considerable time: if even three weeks or a month it will be better.
This ground may be decorated with painting and gilding in the same manner as any other varnished surface, which had best be done after the ground has been hardened; but it is well to give a second annealing with a more gentle heat after it is finished. A very good black japan may be made by mixing a little japan gold size with ivory or lamp-black; this will bear a good gloss without requiring to be varnished afterwards.
Of Painting Japan Work. Japan work should he painted with colours in varnish; and in that case, all pigments or solid colours whatever may be used, and the peculiar disadvantages which attend several kinds, with respect to oil or water, cease with regard to this sort of vehicle, for they are secured by it, when properly managed, from the least hazard of changing or flying. The preparation of colours for this use consists, therefore, in bringing them to a due state of fineness, by grinding on a stone in oil of turpentine. The best varnish for binding and preserving the colours, is shell-lac; this, when judiciously managed, gives such a firmness and hardness to the work, that, if it be afterwards further secured with a moderately thick coat of seed-lac varnish, it will be almost as hard and durable as glass. The method of painting in varnish is, however, more tedious than in oil or water. It is therefore now very usual in the japan work, for the sake of dispatch, and in some cases for the freer use of the pencil, to lay the colours on with oil well diluted with spirits of turpentine.
This oil or japan gold size, as it is called, may be made in the following manner: - Take one pound of linseed oil, and four ounces of gum animi; set the oil to boil to a proper vessel, and then add the gum animi gradually in powder, stirring it well, until the whole be commixed with the oil. Let the mixture continue to boil till it appears of a thick consistence, and then strain the whole through a coarse cloth, and keep it for use. The colours are also sometimes laid on in gum water, but the work done in this manner is not near so durable as that done in varnish or oil. However, those who practise japanning for their amusement only, and consequently may not find it worth their while to encumber themselves with the preparations necessary for the other methods, may paint with water colours. If the colours are tempered with strong isinglass size and honey, instead of gum water, the work will not be much inferior to that done by the other method. Water colours are sometimes laid on grounds of gold, in the manner of other paintings, and look best without any varnish over them; and they are sometimes so managed as to have the effect of embossed work. The colours in this way of painting are prepared by means of isinglass size corrected with honey or sugar candy.
The body with which the embossed work is raised, is best formed of strong gum water, thickened to a proper consistence with bole armenian and whiting in equal parts; which, being laid on in the proper figures, and repaired when dry, may be then painted with the intended colours tempered in the isinglass size, or in the general manner with shell-lac varnish.