Principles and Practice of Fur Dressing and Fur Dyeing

by William E. Austin

	Chrome	Copper	Iron	Direct
Rodol D	brown black	coal black	coal black	brownish black
Rodol P	red brown	dark brown	grey brown	light brown
Rodol 2G	yellow brown	yellow brown	yellow brown	dull yellow
Rodol 4G	light brown	light brown	reddish brown	pure yellow
Rodol A	...	blue black	...	blue black
Rodol Grey B	greenish grey	greenish grey	mouse grey	...
Rodol Grey R	greenish grey	brownish grey	mouse grey	...

All these shades are produced by dyeing in a bath containing a neutral solution of the dye. Sometimes the dye comes in the form of a salt of a mineral acid, like hydrochloric or sulphuric acid, in which case a sufficient amount of an alkali, usually ammonia, is added to liberate the free base. According to the Cassella Co., German manufacturers of the Furrol brand of fur dyes, the dyeing can also be carried on in slightly alkaline or in slightly acid solution, a different series of shades being obtained in each instance. Ammonia is used to render the bath alkaline, and formic acid to make it acid. The most customary practise, however, is to use neutral solutions of the dyes.

For preparing the mordant solutions much smaller quantities of the metallic compounds are used than in the case of the vegetable dyes. With chrome mordants cream of tartar is always employed as an assistant, and occasionally also with copper and with iron mordants. With copper, and also with iron mordants no addition is made at all, or sometimes a small quantity of acetic acid is added. The temperature of the mordant solution is kept about 30° C., and the duration of the mordanting varies from 2–24 hours according to the depth of shade desired. The concentration of the solution may also be varied, it sometimes being just as well to use a strong mordant solution and less duration of mordanting. Chrome may be combined with copper, and iron may be combined with copper, but chrome and iron do not go together as mordants. Some typical average mordanting formulas are as follows:

Chrome mordant.
Bichromate of soda	2.5	gms.
Cream of tartar	1.5	gms.
Water	1	liter

Copper mordant.
Copper sulphate	2	gms.
(Acetic acid 50%	2	gms.)
Water	1	liter

Iron mordant.
Ferrous sulphate	2	gms.
(Acetic acid 50%	2	gms.)
Water	1	liter

or,

Iron pyrolignite 30%	10	gms.
Water	1	liter

Chrome-copper mordant.
Bichromate of soda	2	gms.
Copper sulphate	0.25	gms.
Cream of tartar	1.0	gms.
Water	1	liter

Copper-iron mordant.
Copper sulphate	2	gms.
Ferrous sulphate	2	gms.
(Acetic acid 50%	2	gms.)
Water	1	liter