Black, on the other hand, although the name and rank of a color is denied it by the doctrines of theory is, for the dyer, most essentially a color requiring for its production the contribution of all colors, as can be shown by a simple experiment. If, for instance, within a circle, three equal circles, whose diameters are greater than half the diameter of the surrounding circle, are printed, one blue, one red and one yellow, so that the points of contact with the periphery of the outer circle are equidistant from one another, or form a regular triangle, their segments overlapping one another form four spherical triangles, one violet where red and blue cover one another, one orange where red and yellow come together, one green where yellow and blue are mixed, but the fourth is the centre, where parts of the three differently colored segments cover one another, is black, but toned by the color of the greatest intensity. In fact, black requires for its production more color, and is more difficult to dye than any color of the spectrum. It is not strange, therefore, that many more methods have been proposed and have been tried and adopted to dye black than for the production of any other color. Yet all these blacks are more or less tinted and are nothing more than the deepest shade, which can be produced with the aid of metallic salts, of blue, brown, gray, violet, green and even red. The only black upon ostrich feathers which may be justly called an absolute black is that produced after the method of Mr. Paul, as described in the front part of this book (page 53-56). It presents, besides, the advantage, that it can be completely done in eighteen minutes, while there are older methods which require not less than three days. Such, of course, will find no room here, but only the most reliable and expeditious, and safest of the older methods will be selected with due regard both to beauty of color and preservation of the precious material.
WHITE.
Naturally white ostrich feathers and bleached grays, like all material taken from the animal realm, retains even after scouring and bleaching a more or less noticeable yellowish tint, which becomes visible after some time even upon such as appear snow-white immediately after scouring. The cause is, probably, that the fat which is contained in feathers, as well as in wool and hair, and a part of which remains after the cleaning process, is oxydized by the action of the air. To perfectly and completely extract this remaining small amount of fat which does not hinder the subsequent dyeing operations, is not advisable; for, it has been observed that in that case, the feathers become brittle, and for this reason, scouring with soap is preferable to scouring with soda. It has been observed that colored matter taken from the animal body in the course of time loses its brilliancy of color and becomes dull; white feathers turn yellowish, even if perfectly protected against dust. To prevent this alteration, the bleached feathers are "dyed white," or rather blued or tinted; that is, the brilliancy of the white is heightened and the faint yellowish tinge neutralized by the application of a very light, scarcely perceptible tint of a complementary color.
For this purpose, for instance, indigo carmine (greenish white), indigo carmine with a very small addition of ammoniacal cochineal (reddish white), induline or extract of indigo (bluish white), or methyl violet 6 B. (direct white), are employed, and a few drops of acid added to the bath, either sulphuric, acetic or oxalic acid. The acid, however, can be dispensed with, as it scarcely has anything to act upon, and as only a diminutive amount of it is employed, the blued feathers are not rinsed but immediately dried from the blue-bath. The additions of dyestuff to baths must be made so small that they do not affect a coloring of the feathers but only a faint tinting. Rather too little dyestuff may be added, which defect can at all times be corrected by adding a few drops more of the coloring solution, than too much. In the latter case it would become necessary to bleach the feathers again and go over the whole process of preparing the raw material for dyeing.
BLACK.
I. Chrome Black.—Black being the most difficult color to produce, as above remarked, the feathers require a specially careful preparatory treatment in order to remove everything that might interfere with the purity, uniformity and brilliancy of the color, or cause less dyed, dull spots and streaks. Naturally gray feathers, however, need not to be bleached or decolorized but only careful treatment and attention. The feathers are for twenty-four hours laid down in a solution of twice their weight of calcined soda, ammonia soda being preferable for this purpose to Lablanc soda (old process soda), then taken up and carefully rinsed clean from the alkaline in warm water, or better, in two warm waters. In the case of particularly valuable feathers it is recommendable, before laying them down in the soda solution, to rub the stains of the feathers off with a piece of carbonate of ammonia or with a large soda crystal. After rinsing, the feathers are entered for one hour, at 170° F., in a bath containing forty per cent., of the weight of feathers, chromate of potash, forty per cent. copperas, and twenty per cent. tartar, and several times turned and agitated during the specified period while the entering temperature is maintained. Then the feathers are taken up, and the adhering liquid squeezed out by hand or by rolling them through a clothes wringer with rubber roller. In the meantime a logwood bath of medium concentration is prepared either with a fresh decoction or with extract of logwood and twenty per cent. Marsailles soap dissolved in it. The feathers are entered in this bath at hand-heat, diligently agitated for twenty or thirty minutes and, if necessary, while the temperature is raised to 200° F., laid down in the bath until the correct shade and a level dye are obtained. The feathers are then lifted, squeezed, very thoroughly rinsed in cold water, passed through starch and dried with frequent shaking, respectively beating upon the board or between the hands.
It occurs sometimes, that the stems of the feathers are imperfectly died and present light brown or gray places. This is attributable to insufficient scouring. In this case the defective portions of the stems must be scraped with a sharp penknife and dyed over. This operation, however, is difficult and requires much practice and a light hand, as too much scraping removes the horny glossy surface of the stem and, when dyed over, the only change effected is, that a dull black mark takes the place of the discolored or brown spot. Often, however, the defect can be remedied by touching the imperfect portions up with a feeble alcoholic solution of shellac, in which some nigrosine is dissolved. With properly scoured feathers this mishap does not occur.
Another trouble, however, which is not unfrequent with blacks, is that the feathers are over-dyed and become brownish black instead of black. But in this case the remedy is as simple as its occurrence is frequent; a quick passage through sulphuric acid diluted with water to 2° B. strips off the excessive dye and produces a good color. Besides, this operation gives the feathers a brilliant lustre. Many dyers, therefore, methodically avail themselves of this effect of sulphuric acid and deliberately over dye their feathers (See IV below) and then apply the sulphuric acid passage for the purpose of imparting the feathers that peculiar lustre. A passage through a solution of sodium chloride, of 2° B. strength, has the same effect as a passage in sulphuric acid 2° B.
For this purpose lay the feathers down in the warm sodium chloride solution, until the black cotton strings with which the feathers have been tied together, as in the beginning described, begin to turn gray. Then take up the feathers, rinse them very thoroughly in cold water, drain, starch and dry.
Sodium chloride can be prepared in a simple way as follows: rub one-half pound fresh chloride of lime in a porcelain mortar with a little water into a smooth milk, which pour into a bucket, dilute with cold water, and add, under stirring, the solution of one pound Glauber salt; let settle and use the clear liquid. Instead of Glauber salt (sodium sulphate), soda crystals (sodium carbonate) may be used; the latter, however, is a little higher in price and renders the solution strongly alkaline.