Scour and rinse the feathers well; grays must be bleached as near to
white as possible, and these ought only to be dyed dark shades of
red. Prepare a bath with twenty per cent., of the weight of feathers,
bisulphate of soda, and see, as in all cases, that it is well
crystallized and dry. (Never use the article when it looks decayed,
forms lumps or is moist). Add four to six per cent. azo red, according
to the shade wanted, raise the temperature to 170° F., enter the
feathers and work to shade; take out, starch and dry.