The tones of the stained woods may be rather largely modified, by the colour of the polish used upon them. The lightest colours therefore, are polished with the lightest coloured lackers, or varnished with a white varnish, the ordinary hardwood lacker being used upon the darker. All the softwoods being also very absorbent, they usually receive a coat of size, mixed in the proportion of one part of ordinary size to from two to three parts of water; this is applied tepid and allowed to thoroughly dry, prior to their being polished or varnished, to fill the pores of the surface, both to economize time and lacker, and to render the polish more permanent. The fluids in many cases will also raise the grain of the wood, so as to slightly roughen the smooth turned surfaces. No attention is paid to this until the work has received a moderate coating of the polish or varnish employed; the surfaces are then gently rubbed down with fine glass paper, carefully avoiding the extreme edges turned on the work, from which the colour may be more readily removed, after which it is re-polished.
A very serviceable deep red stain of a crimson character, employed either to imitate mahogany, or to tinge and vary the colour of the actual wood, is obtained from half an ounce of the raspings of Brazil wood macerated in three ounces of alcohol. The colour this gives to mahogany may be varied by also coating the work with the logwood stain mentioned below; a wash of this last given with the brush, and when dry followed by a wash of brazil, produces a deep full colour, and when the two are applied in the reverse order, a similar but more brilliant colour. A decoction of four ounces of brazil wood, allowed to simmer for some hours in one quart of water, yields a rather brown red stain. White woods stained with this, and when dry treated with a solution of half to one ounce of pearlash in one quart of water, vary in colour, according to the original depth of tone given to them by the brazil stain, from browns suitable for cocoawood, to deeper purplish browns, adapted for kingwood. The iron solution already mentioned, produces a rich purple brown, an excellent imitation of full coloured rosewood or peruvian wood. White wood stained with the brazil, and then subjected to the action of alum, four ounces dissolved in one quart of water, acquires a light pink, which, helped by the grain of the wood answers fairly for tulip wood. Treating the lighter coloured woods stained by brazil with nitro-muriate of tin, gives a very beautiful, brilliant crimson of a purple tinge; this is of no great service in imitating other woods but is largely used upon toys. ' A brown red stain is made from a decoction of two ounces of logwood dust in one quart of water, or from half an ounce of the logwood in three ounces of alcohol. This is employed to darken mahogany and other coloured woods, used either alone or with separate applications of the brazil as above. Nitro-muriate of tin applied on the logwood stain, gives a deep dusky crimson purple, very suitable for full coloured kingwood and for imitating many other hardwoods, darkened by long exposure. The logwood, subsequently treated with the alum solution, yields a medium purple, both darker and of a bluer tone than that obtained from brazil wood. Treated with the pearlash, it affords a brown, darker than that obtained by this alkali from the brazil wood, and in like manner used for cocoa wood.
A jet black may be given to all the woods, by using the logwood stain, followed by a solution of iron, in the proportion of an ounce of sulphate of iron to one quart of water; and a less intense black, by the same mixtures about three times diluted. Further dilution will afford various degrees from black to gray; the light silver gray given to the white woods turned at Spa, may be produced by immersing the work in a decoction of four ounces of Sumach in one quart of water, and afterwards in a very dilute solution of sulphate of iron; the works so stained are then sized and varnished with hard white, or with sandarac varnish.
A dilute solution of bi-chromate of potash is frequently employed to darken oak, mahogany and the coloured woods, to which it imparts a brown shade, useful to give the appearance of age; this stain requires using with some care, as its effects are continuous, and are not altogether stayed by thoroughly washing the work with water when the required depth of tone has been reached. It may also occasionally be necessary to follow the opposite course, that is to reduce the depth of the natural colour of the material: most of the woods may be more or less bleached by immersion in a strong solution of oxalic acid applied with heat.
Ivory when turned to its finished form, has its surfaces dyed by immersion in many of the before mentioned water stains, and in some others. The process presents no difficulties, but being both rapid and cumulative, it requires close attention that it may be arrested the moment the required tone is attained; only two or three pieces of ivory can therefore usually be dyed to precisely the same colour at one operation. The pieces are always first polished with whiting and water, and when washed quite clean from the whiting, are then prepared for the stain by a short immersion of from three to five minutes in acidulated cold water, in the proportion of one part of muriatic acid, the ordinary acid of commerce, to forty or fifty of water; or, in an equally weak solution of nitric acid. This cleansing fluid extracts the gelatine from the surface of the ivory, and is essential to the attainment of a perfectly uniform colour; extreme cleanliness, and the absence of any grease or accidental soiling are as necessary, with which view the work in process of staining is at no time touched by the fingers, but is removed from one vessel to another by flat pieces of wood, attached to each other at one end by a curved metal spring, after the form of a pair of sugar tongs, separate pairs being kept for the different colours. Subsequently to its treatment with the acid, the ivory is invariably again placed for some minutes in clean cold water, that has been boiled, before it is transferred to the stain.