The use of stains and chemical baths for changing the colour of the wood employed by the intarsiatori was common from the time of Fra Giovanni da Verona, to whom Vasari ascribes the invention, but is most distinctive of the work of the later Dutch and French marqueteurs. Receipts for the purpose were handed down from master to pupil, and while sometimes held as traditional secrets to be jealously guarded, were sometimes committed to writing; and several of these manuscripts have come down to us. The following have been collected from French, German, and Italian sources, and though not all of equal value, show the way in which the ancient workers produced the effects, most of which we admire in the present day:—

To stain wood yellow (No. 1).—Put saffron in water, and when it is well steeped place the jar over hot coals. Then spread the stuff over boxwood with a brush. To make it brilliant let it dry, and put it with oil on the wood to be coloured. (No. 2.)—Take the plant turmeric (curcuma longa), grind it to powder; put an ounce into a pint of spirit (12 oz.), and leave it for a day. If the tone is required reddish, add some dragon's blood. (No. 3.)—A cheaper but duller colour is to be obtained from steeped French berries, then dried, with weak alum water brushed over it. Thin pieces are dipped in it. The solution of French berries may be made thus—Take 1 lb. of French berries, and a gallon of water with ½ oz. of alum; boil for an hour in a pewter vessel, and filter through paper. Evaporate till the colour appears strong enough. Another receipt says 4 oz. of French berries put to steep in a pint of water is to have added to it 1 oz. of hazel nuts and as much alum. Wood may also be stained yellow with aqua fortis, used warm, and then immediately placed near the fire. The aqua fortis must not be too strong, or the wood will go brown or black. This is apparently the same thing as Vasari calls "oil of sulphur," used in his time for colouring wood. A Nuremberg receipt book says that the plant Tournesol (croton tinctorium) may be steeped in water, and this solution mixed with yellow colour and glue may be spread over the wood warm, and finally polished with a burnisher. Holtzapffel gives the following:—A bright yellow stain may be obtained from 2 oz. of turmeric allowed to simmer for some hours in 1 quart of water in an earthen vessel, water being added from time to time to replace evaporation. Sparingly applied cold, it stains white woods the colour of satin wood. A canary yellow results from immersing the wood in the liquid, which can be rendered permanent without polishing by a strong solution of common salt. Washing the stained surface with nitro-muriate of tin for about a minute changes the colour to orange. The work should then be well rinsed in plain water to check the further action of the acid. Treating the canary yellow with 2 oz. of sulphate of iron dissolved in 3 quarts of water, after it has been allowed to dry, dyes a delicate olive brown. A tincture of ¼ oz. of turmeric to 3 oz. of spirits of wine, allowed to stand for some days and well shaken daily, gives a rather higher colour.

Red may be produced by (No. 1) taking a pound of Brazil wood, with some rain water, a handful of unslaked lime, and two handsful of ashes; soak all for half an hour in water, "cook" it, and pour it out into another pot, in which is a measure of gum arabic. The wood to be coloured must be cooked in alum water, and then brushed over with the warm colour; the result is a splendid scarlet red. If the wood was first grounded with saffron water and then had the Brazil decoction applied, the result was orange; a spoonful of lye made a browner colour, with a little alum. If whiter wood was taken the colour was correspondingly brighter. (No. 2.)—Orcanda or Akanna root powdered, with nut oil, gives a fine red. (No. 3.)—Put lime in rain water, strain it, scrape Brazil twigs in it, then proceed as in No. 1. You can also soak the Brazil in tartar. The same colour with Tournesol steeped in water gives a fine purple when spread on the wood. Lebrun gives the same receipt, adding that the beauty of the colour is increased by rubbing with oil, and that pear wood is the best to use. Another receipt says:—Make a strong infusion of Brazil wood in stale urine or water impregnated with pearl ash, 1 oz. to a gallon; to a gallon of either of which put 1 lb. of Brazil wood. Let it stand for two or three days, often stirring it. Strain the infusion, and brush over the wood boiling hot; then, while still wet, brush over with alum water, 2 oz. to a quart of water. A less bright red may be made with 1 oz. of dragon's blood in a pint of spirits of wine, brushed over the wood.

Holtzapffel gives for red stains the following:—Dragon's blood, an East Indian resin, gives a crimson with a purple tinge. Put a small quantity in an open vessel, and add sufficient linseed oil to rather more than cover it; it will be fit for use in a few days, when the oil may be poured off and more added. This dissolves more readily in oil than spirit. The colouring matter of Alkanet root, from which another red may be obtained, is contained in the rind, so that small pieces are the most useful. A deep red of a crimson character may be made with ½ oz. of raspings of Brazil wood macerated in 3 oz. of alcohol. A wash of logwood (see below) given with the brush, and when dry followed with a wash of Brazil, produces a deep, full colour, and when the two are applied in the reverse order a more brilliant colour of the same kind. A decoction of Brazil (4 oz.) allowed to simmer for some hours in 1 quart of water yields a rather brown-red stain. Treating light woods so stained with nitro-muriate of tin gives a brilliant crimson of a purple tinge.

A brown red is made from a decoction of 2 oz. of logwood dust in 1 quart of water, or ½ oz. of logwood in 3 oz. of alcohol. Nitro-muriate of tin used on it gives a deep, dusky crimson purple. The same treated with alum solution yields a medium purple, darker and bluer than that from Brazil.

White wood stained with Brazil and then treated with alum (4 oz. dissolved in a quart of water) acquires a light pink tinge. Another receipt for pink or rose red says:—1 gallon of infusion of Brazil wood, with 2 oz. additional of pearl ash; but it is necessary to brush the wood often with alum water. By increasing the proportion of pearl ash the red may be made still paler, in which case make the alum water stronger.

For purple one brushes the wood over several times with a strong decoction of logwood and Brazil, 1 lb. of logwood and ¼ lb. of Brazil to a gallon of water boiled for an hour or more. When the wood is dark enough let it dry, and then lightly pass over with a solution of 1 drachm of pearl ash to a quart of water. Use this carefully, as the colour changes quickly from brown red to dark purple.

Jet black may be made by using the logwood stain, followed by a solution of iron, 1 oz. sulphate of iron to 1 quart of water, and a less intense black by the same mixture about three times diluted. The Italian receipt books are well provided with receipts for producing black, which suggests that most of the ebony used in inlay was factitious. A 15th century MS. says:—"Take boxwood, and lay in oil with sulphur for a night, then let it stew for an hour, and it will become as black as coal." Evidently this means what Vasari calls oil of sulphur, aqua fortis. Others are founded upon the application of a solution of logwood, followed by one of iron. "Stew logwood till the liquid is reduced to one-third of its bulk, mix with stone alum, and leave for three days. Mix iron filings with very strong wine, and let it stand for twenty-four hours. On the quantity of iron filings the depth of the tone depends. Lastly, ox-gall is dissolved in this mixture, and the whole is three times worked over." An English receipt says:—"Brush the wood over several times with a hot decoction of logwood; take ¼ lb. of powdered galls, and set in the sun or other gentle heat in 2 quarts of water for three or four days; brush the wood over with it three or four times, and, while wet, with a solution of green vitriol in water, 2 oz. to a quart; or use a solution of copper in aqua fortis, then the solution of logwood, and repeat until black enough." A German receipt says:—"Take half a measure of iron filings and a pennyweight of sal ammoniac, and put into a pot of vinegar; let it stand for twelve days at least. In another pot put blue Brazil and 3 measures of bruised gall apples in strong lime lye, and let it stand for the same time. The wood must be first washed over with lye, and then with hot vinegar, and finally polished with wax." "Pear wood may be grounded with Brazil steeped in alum water, then coloured with the black which the leather-stainers use, twenty times." Another says:—"Take a pennyweight of fine silver, with a pound of aqua fortis; add a measure of water, and soak the wood with it." The best wood for imitating ebony is holly; also, box cooked in olive oil is good for it, or well-planed pear soaked with aqua fortis, and then coloured with ink several times; or stew the wood in lamp-black, and soak with oil.

Blue may be obtained by the use of a solution of copper brushed hot over the wood several times; then brush hot a solution of pearl ash, 2 oz. to a pint of water, until the wood becomes perfectly blue. The copper solution is prepared in this way:—"Take of the refiner's solution of copper made in the precipitation of silver from the spirit of nitre; or dissolve copper in spirit of nitre, or aqua fortis, by throwing in filings or putting in strips of copper gradually till all effervescence ceases. Add to it starch finely powdered, one-fifth or one-sixth of the weight of copper dissolved. Make a solution of pearl ash and filter it; put gradually to the solution of copper as much as will precipitate the whole of the copper. The fluid becomes colourless. Wash the powder, and when so well drained of water by means of a filter as to be of the proper consistence, grind well together, and lay out to dry. This makes dark verditer." Indigo may also be used, prepared with soap lees as when used by dyers; brush it over the wood boiling hot. With a solution of cream of tartar, 3 oz. to a quart of water, and boiled, brush over the wood copiously before the moisture is quite dried out. A German receipt says:—Put 4 oz. of Tournesol in three parts of lime water to cook for an hour and spread it on the wood. "Wood coloured green with verdigris can be made blue by using pearl ash." This is the process described first.

For green verdigris dissolved in vinegar may be used; or crystals of verdigris in water, brushed hot over the wood. A 15th century MS. gives a traditional mode thus:—"Wood, bone, small leaves, and knife handles can be made green by strong, red vinegar and brass filings mixed together with a little Roman vitriol and stone alum in a glass vessel. When it has stood for a day the object is dipped in it, and steeps itself in the liquid. The colour will be very permanent." A German receipt says:—"Take walnut shells from the green fruit, and put in very strong lye with some copper vitriol and alum to stew for two or three hours. The wood must be put in strong wine vinegar for several days, then it is put in the above-mentioned mixture, to which ground verdigris mixed with vinegar is added. Or you can mix this ground verdigris with vinegar with some winestone, let it clarify, and spread the wood with the filtered stuff. The addition of saffron makes a grass green."

A silver grey may be given to white wood by immersion in a decoction of 4 oz. of sumach in 1 quart of water, and afterwards in a very dilute solution of sulphate of iron. A dilute solution of bichromate of potash is frequently employed to darken oak, mahogany, and coloured woods. This should be used carefully, since its effects are not altogether stopped by thoroughly washing the wood with water when dark enough. To bleach woods, immerse them in a strong, hot solution of oxalic acid.

Since ivory is often used in inlaying and is sometimes stained, a few receipts for its staining will not be out of place. These come from Holtzapffel's book:—A pale yellow will be given by immersing the ivory for one minute in the tepid stain given by 60 grains of saffron boiled for some hours in half-a-pint of water. Immersion for from five to fifteen minutes produces a canary yellow brighter or deeper according to the time given, but all somewhat fugitive. A stain from 4 oz. of fustic dust and chips boiled in 1 quart of water produces similar but somewhat darker and more permanent results. Ivory subjected to either of these stains for fifteen minutes, and then placed for one to three minutes in Brazil water stain acquires an orange colour. If then treated with nitro-muriate of tin, an orange of a brighter, redder tone is produced; transfer to a clean water bath directly the required colour appears, as the nitro-muriate of tin acts very rapidly upon the ivory.

Fine scarlet cloth is used for dyeing various tones of red. A piece about a foot square may be cut into shreds and boiled, with the addition of 10 grains of pearl ash, in half-a-pint of water from 5 to 6 hours. Immersion in the liquid for from three to ten minutes gives tones of pink; for one hour and subsequently for half-an-hour in an alum mordant gives a pink of a bright crimson character. When the ivory is from two to three hours in the tepid stain a crimson red results, and the addition of 1 part of sulphuric acid to 60 of stain gives billiard ball colour. Pinks of a different and duller full tone may be obtained by immersion for three minutes in Brazil water stain, followed by treatment with nitro-muriate of tin; when the Brazil is used for six minutes a deeper colour results. Fifteen minutes in Brazil, then treatment with nitro-muriate of tin and immediate washing gives a duller and deeper red than the first red-cloth stain. The depth of colour may be increased by longer immersion or a higher temperature. A dull scarlet or brick red is made by the Brazil bath, followed by thirty to sixty minutes in an alum mordant.

The cloth stain for one hour, followed by pearl ash for half-an-hour, gives a bright purple; if iron is used instead of pearl ash a sombre purple results; if you add alkalies to the stain instead of sulphuric acid you obtain purple reds. Fifteen minutes in Brazil, and then three or four in pearl ash gives full red purples deepening to maroon. Five minutes in logwood water stain gives a good warm brown; half-an-hour, a chocolate brown. Ten minutes in logwood stain, washing, and one or two seconds in pearl ash, and instantly washing again gives a deep red brown, and if one minute in alum instead of pearl ash a deep purple brown.

Blue stains may be made from sulphate of indigo, ½ drachm to 1 pint of previously boiled water, with 10 grains of carbonate of potash added. One to two minutes' immersion and immediate washing yields a delicate turquoise, five minutes a bright full blue; and ten to fifteen a considerable depth of colour. Blues are rather fugitive. Staining with saffron or fustic for five minutes, and then with indigo for the same time, produces a clear pea green; with indigo for ten minutes, a deep grass green. The greens from fustic are more permanent and yellower. The sequence of the stains also affects the green, the last used having most effect. Blue stain first for fifteen minutes, followed by fustic for thirty, stains ivory the green used for table knife handles—a colour which may also be obtained by immersion for some weeks in a clear solution of verdigris in dilute vinegar and water.

Before applying these stains the ivory must be prepared by first polishing with whiting and water and washing quite clean. Next immerse it for three to five minutes in acid cold water (1 part muriatic acid to 40 or 50 of water, or the same proportion of nitric). This extracts the gelatine from the surface of the ivory. Extreme cleanliness and absence of grease or soiling is most important; the ivory is not to be touched by the fingers, but removed from one vessel to another by wooden tongs, one pair to each colour. After treating with the acid, place the ivory in clean, cold, boiled water for some minutes. Water stains are used, but strained or filtered and warm or only tepid, for fear of injuring the surface of the ivory. Increasing the temperature also sometimes deepens or changes the colour. The best temperature is 100 deg. Fahr. When sufficiently stained the ivory is well rinsed in water, and if there are two colours on top of each other always well rinsed before going into the second bath. After thoroughly drying, repolish by friction, first with a few drops of oil on a soft clean rag; continue with a dry clean rag till the oil disappears.

An old Italian receipt for polishing wood blackened to imitate ebony runs thus:—"Is the wood to be polished with burnt pumice stone? Rub the work carefully with canvas and this powder, then wash the piece with Dutch lime water so that it may be more beautifully polished. Then it is to be cleaned with another cloth. Then the rind of a pomegranate must be steeped, and the wood smeared over with it and set to dry, but in the shade."