ise the black will have a
tendency to assume a greenish tone that is not at all desirable. This
greening becomes more marked when from 7-1/2 to 10 lb. of fustic is
used, or if alum be added to the mordant along with the bichromate of
potash.

Chrome blacks are the best blacks which can be obtained from (p. 086)
logwood. They have, however, a tendency to turn green on exposure to
the weather, which tendency seems to be most prevalent in those blacks
in which sulphuric acid has been used as the acid constituent of the
mordanting bath. The greening may be reduced to a minimum by adding to
the dye-bath about 1 to 2 lb. of Alizarine. Another plan which has
been followed is to give the wool a bottom with 5 to 6 lb. of camwood
or peachwood, then mordanting and dyeing us usual.

_Logwood Black on Wool_.--Boil first for one hour with a decoction of
8 lb. camwood, then lay down for fifty minutes in a boiling bath of
3 lb. bichromate of potash, 1 lb. alum, 1 lb. tartar. It is a good
plan to allow the goods to hang overnight.

The dye-bath is prepared with 45 lb. logwood, 8 lb. fustic, 4 lb.
sumac. Dye one hour at the boil, wash and dry.

_Indigo Black_.--This is sometimes called woaded black, and has an
excellent reputation as a fast black. It is dyed by first giving the
wool a medium blue bottom in the indigo vat by the method of vat
dyeing, which will be described later on, and then dyeing by either
the second or third recipe given above. The use of sulphuric acid is
rather to be avoided in dyeing an indigo vat with chrome and logwood,
as the chromic acid set free during the process is likely to attack
and by destroying the indigo to materially reduce the intensity of the
blue bottom. Or, after blueing in the vat, the black may be dyed or
topped on by the process with copperas, which will be described below.

_Iron Logwood Black_.--Mordant the wool by boiling one and a half to
two hours in a bath made with 5 lb. copperas, 2 lb. bluestone, 2 lb.
alum, and 10 lb. argol. The dyeing is done in a bath of 50 lb.
logwood.

It is not advisable to use more argol than is here given, for (p. 087)
although a little excess will not materially affect the beauty or
brilliancy of the resulting shade, yet such excess is wasteful, and
makes the dyeing cost more than it otherwise would. On the other hand,
too little will cause the shade to become greyish in tone and wanting
in solidity. The copper sulphate (bluestone) added incre