The killed skins are immersed in the mordanting solution, and allowed to remain the required length of time. They are then thoroughly rinsed to remove any excess of the mordant, and are hydro-extracted. Under no circumstances should mordanted skins be permitted to dry, for they would be unfit for use again.
The dyebath is next prepared by dissolving the necessary quantity of the dye, varying from 0.1 gm. to 10 gms. per liter. Then if the solution must be neutralized, the ammonia is added and the temperature of the bath is brought to 30–35° C. by the addition of cold water. This temperature is maintained throughout the dyeing operation. To the solution is added the oxidizing agent. Ordinary commercial peroxide of hydrogen containing 3% by weight is the usual oxidizer, although perborates have been suggested. 15–20 parts of peroxide of hydrogen for every part of dye are added, and the dye solution brought to the proper dilution. As soon as the dyebath is ready, the skins are entered, and worked for a short time to effect even penetration. They are then left in the dyebath for 2–12 hours or longer according to the depth of shade. After being satisfactorily dyed, the furs are rinsed thoroughly, hydro-extracted and dried and finished. Where the dye is to be applied by the brush to the tips of the hair, stronger dye solutions are used, the brushed skins being placed hair together and let lie for about 6 hours in order to permit the color to develop, after which the furs are dried and drum-cleaned.
Some shades, particularly black, have a tendency to rub off slightly. In order to overcome this, the dyed furs, after rinsing, are treated with a cold solution of 1⁄2 part of copper sulphate per 1000 parts of water, for 3–4 hours, then without rinsing, hydro-extracted and dried. Furs which have been tipped are brushed with a 1–2% solution of copper sulphate and dried. Care must be taken in this after-treatment, for the use of too strong a solution of copper sulphate, or too prolonged action of such a solution will materially alter the shade of the dyed fur.
A few typical formulas will serve to illustrate the general methods of employing the Oxidation Colors:
Brown Sable Imitation on Unsheared Rabbit
The skins are killed with soda, soured, and washed, then mordanted with
| Bichromate of soda | 2 | grams |
| Copper sulphate | .25 | grams |
| Cream of tartar | 1 | gram |
| Water | 1 | liter |
for 24 hours. Then washed, and dyed for 24 hours with
| Fur Brown 2G[3] | 3 | grams |
| Hydrogen peroxide | 45 | grams |
| Water | 1 | liter |
Wash and dry the skins, then brush the tips with