GRAY DYE. The gray dyes, in their numerous shades, are merely various tints of black, in a more or less diluted state, from the deepest to the lightest hue.
The dyeing materials are essentially the tannic and gallic acid of galls or other astringents, along with the sulphate or acetate of iron, and occasionally wine stone. Ash-gray is given for 30 pounds of woollen stuff, by one pound of gall nuts, # pound of wine-stone (crude tar tar), and 21 pounds of suiphate of iron. The galls and the wine-stone being boiled with from 70 to 80 pounds of water, the stuff is to be turned through the decoc tion at a boiling heat for half an hour, then taken out, when the bath being re freshed with cold water, the copperas is to be added, and, as soon as it is dissolved, the stuff L9 to be put in and fully dyed.
Pearl-gray is produced by passing the stuff first through a decoction of sumach and logwood (two pounds of the former to one of the latter), afterwards through a dilute solution of sulphate or acetate of iron ; and finishing it in a weak bath Of weld containing a little alum. Nouse
gray is obtained, when with the sauie proportions as for ash-gray, a small quan tity of alum is introduced.
For several other shades, as tawny gray, and slate-gray, the stuff must receive a previous blue ground by dipping it in the indigo vat ; then it is passed first through a boiling bath of sumach with galls, and lastly through the same bath at a lower temperature after it has received the proper quantity of solution of iron.
For dyeing silk gray, fastet, logwood, sumach, and elder-tree bark, are employ ed instead of galls. Archil and anuotto are frequently used to soften and beau tify the tint.