This section is from the "Henley's Twentieth Century Formulas Recipes Processes" encyclopedia, by Norman W. Henley and others.
The preparation of non-poisonous colors for dyeing fabrics and eggs at home constitutes a separate department in the manufacture of dye-stuffs.
Certain classes of aniline dyes may be properly said to form the materials. The essence of this color preparation consists chiefly in diluting or weakening the coal-tar dyes, made in the aniline factories, and bringing them down to a certain desired shade by the addition of certain chemicals suited to their varying characteristics, which, though weakening the color, act at the same time as the so-called mordants.
The anilines are divided with reference to their characteristic reactions into groups of basic, acid, moderately acid, as well as dyes that are insoluble in water.
In cases where combinations of one or more colors are needed, only dyes of similar reaction can be combined, that is, basic with basic, and acid with acid.
For the purpose of reducing the original intensity of the colors, and also as mordants, dextrin, Glauber's salt, alum, or aluminum sulphate is pressed into service. Where Glauber's salt is used, the neutral salt is exclusively employed, which can be had cheaply and in immense quantities in the chemical industry. Since it is customary to pack the color mixtures in two paper boxes, one stuck into the other, and moreover since certain coal-tar dyes are only used in large crystals, it is only reasonable that the mordants should be calcined and not put up in the shape of crystallized salts, particularly since these latter are prone to absorb the moisture from the air, and when thus wet likely to form a compact mass very difficult to dissolve. This inconvenience often occurs with the large crystals of fuchsine and methyl violet. Because these two colors are mostly used in combination with dextrin to color eggs, and since dextrin is also very hygroscopic, it is better in these individual cases to employ calcined Glauber's salt. In the manufacture of egg colors the alkaline coloring coal-tar dyes are mostly used, and they are to be found in a great variety of shades.
Of the non-poisonous egg dyes, there are some ten or a dozen numbers, new red, carmine, scarlet, pink, violet, blue, yellow, orange, green, brown, black, heliotrope, etc., which when mixed will enable the operator to form shades almost without number.
The manufacture of the egg dyes as carried on in the factory consists in a mechanical mixing of basic coal-tar dye-stuffs, also some direct coloring benzidine dyestuffs, with dextrin in the ratio of about 1 part of aniline dye to 8 parts of dextrin; under certain circumstances according to the concentrated state of the dyes, the reducing quantity of the dextrin may be greatly increased. As reducing agents for these colors insoluble substances may also be employed. A par also of the egg dyes are treated with the neutral sulphate; for instance, light brilliant green, because of its rubbing off is made with dextrin and Glauber's sal in the proportion of 1:3:3.
For the dyeing of eggs such color mix tures are preferably employed as contain along with the dye proper a fixing agent (dextrin) as well as a medium for this superficial mordanting of the eggshell The colors will then be very brilliant.
Here are some recipes:
Blue . .
. Marine blue B. N.
. Brilliant green 0.
Red . .
Pink . .
. Eosin A........
Methyl violet 6 B
. Naphthol yellow
Very little of these mixtures suffices for dyeing five eggs. The coloring matter is dissolved in 600 parts by weight of boiling water, while the eggs to be dyed are boiled hard, whereupon they are placed in the dye solution until they seem sufficiently colored. The dyes should be put up in waxed paper.