Chapter 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.