In dyeing leather, aniline or coal-tar colors are generally used. These dyes, owing to their extremely rapid action on organic substances, such as leather, do not readily adapt themselves to the staining process, because a full brushful of dye liquor would give a much deeper coloration than a half-exhausted brush would give. Consequently, to alter and to color leather by the staining process results in a patchy coloration of the skin. In the dyeing operation a zinc shallow trough, 4 to 6 inches deep, is used, into which the dye liquor is put, and to produce the best results the contents of the trough are kept at a uniform temperature by means of a heating apparatus beneath the trough, such as a gas jet or two, which readily allows of a heat being regulated. The skins to be dyed are spread out flat in the dye trough, one at a time, each skin remaining in the dye liquor the time prescribed by the recipe. The best coloration of the skin is produced by using 3 dye troughs of the same dye liquor; each of different strength, the skin being put in the weakest liquor first, then passed into the second, and from there into the third dye liquor, where it is allowed to remain until its full depth of color is obtained. Very great skill is required in the employment of aniline dyes, as if the heat be too great, or the skins remain too long in the final bath, "bronzing" of the color occurs. The only remedy for this (and that not always effectual) is to sponge the skin with plenty of cold, clean water, directly it is taken out of the final dye bath. The dyed skins are dried and finished as before.

Leather Brown

Extract of fustic.... 5 ounces

Extract of hypernic. . 1 ounce

Extract of logwood... 1/2 ounce

Water.............. 2 gallons

Boil all these ingredients for 15 minutes, and then dilute with water to make 10 gallons of dye liquor. Use the dye liquor at a temperature of 110° F.

Mordant

Dissolve 3 ounces of white tartar and 4 ounces of alum in 10 gallons of water.

Fast Brown

Prepare a dye liquor by dissolving 1.5 ounces fast brown in 1 gallon of water, and make a 10-gallon bulk of this. Use at a temperature of 110° F., and employ the same mordanting liquor as in last recipe.

Bismarck Brown

Extract of fustic.....     4 ounces

Extract of hypernic. .     1 ounce

Extract of logwood.. .       1/2 ounce

Water..............     2 gallons

Preparation

Boil all together for 15 minutes.

Method of Dyeing

First mordant the skins with a mordanting fluid made by dissolving 3 ounces tartar and 1/2 ounce borax in 10 gallons of water. Then put the skins into the above foundation bath at a temperature of 100° F. Take them out, and then put in 1 ounce of Bismarck brown, dissolved in boiling water. Put the skins in again until colored deep enough, then lift out, drip and dry.