Scour and rinse the feathers well; for dark shades unbleached grays
may be used. Prepare a feebly acidulated bath with sulphuric acid, at
a temperature near the boiling point; add turmeric freely and Guinea
green G less. Enter the feathers and manipulate at the same temperature
for fifteen or twenty minutes, according to the desired tone, re-enter
and dye to shade.
By varying the proportions of the three dyestuffs, a great variety of
green-brownish modes can be produced, which approach medium and dark
bronzes the more the fast brown predominates in the composition of the
color.