After scouring and rinsing well, prepare a warm bath (100-120° F.) with
five per cent., of the weight of feathers, bisulphate of soda, to which
add solution of Victoria blue and of extract of archil, according to
sample. Acid violet may be used, but requires a temperature near the
boiling point, which ought to be avoided wherever possible in dyeing
ostrich feathers. To be on the safe side, make the solutions of the
dyestuffs of medium concentration, use only the clear of them, or
better filter the same, and add it slowly and gradually first in small
doses, finally by drops, for which purpose the use of a burette with
squeeze-cock is recommendable.