Scientific American 13, 18.12.1847
For the Scientific American.
For a long period it had been considered impossible to dye a black, either on cotton or wool, without iron or copper for a basis, or mordaunt. Recent discoveries, however, have brought to light a better method of dyeing black than by any of the old plans, by using the bichromate of potash as a mordaunt, in place of the sulphates of iron or copper.
For a hundred pounds of clean white woollen yarn, use 3 lbs. of tartar, 3 of alum and 4 of bichromate of potash. Boil the yarn in this one hour, handling well, (cloth as well as yarn,) then take it out, wash and boil it one hour more in the liquor of 20 lbs. of logwood, when it will come out a most beautiful black. The bluer the shade that is wanted, the less chrome is used. The goods must be white, or some light color to make good black by this process. This color is not known to a great many practical dyers. It avoids that oxidising corrosiveness which weakens and impairs the strenght of fibre in those goods dyed with solutions of iron.