ings which go to making a successful
dyer and colourist is the grasping of this fact by careful
observation, and working accordingly. Dyers will find much assistance
in acquiring a knowledge of colour and colour mixing from the two
little books on _Colour_, by Mr. George H. Hurst, and the _Science of
Colour Mixing_, by Mr. David Paterson, both issued by Messrs. Scott,
Greenwood & Co., the publishers of the present work.

#Black on Wool.#--Until within a comparatively recent time black was
dyed on wool solely by the use of logwood, combined with a few other
natural dye-stuffs, such as fustic, indigo, etc., but of late the
researches of colour chemists have resulted in the production of a
large number of black dyes obtained from various coal-tar products.
These have come largely into use, but still, so far they have not been
able to entirely displace logwood, chiefly on the score of greater
cost, the use of the natural dye still remaining the cheapest way of
producing a black on wool; although the blacks yielded by some of the
coal-tar black dyes are superior to it in point of intensity of colour
and fastness to scouring, acids and light, as well as being easier to
dye.

Blacks may be obtained from logwood by several methods, either by
previous mordanting of the wool or by the stuffing and saddening
methods, or by the one-bath process. The following recipes will (p. 084)
show how these various methods are carried out in practice:--

_Chrome Logwood Black_.--The wool is first mordanted by boiling for
one and a half hours with 3 lb. bichromate of potash and 1 lb. of
sulphuric acid, working well the whole of the time. It is not
advisable to exceed the amounts of either the bichromate or the acid
here given, these quantities will result in a full bloomy black being
obtained, but any excess gives rise to greyish dull blacks, which are
undesirable. After mordanting rinse well with water, when the goods
will be quite ready for the dye-bath.

The dyeing is done in a bath made from a decoction of 40 lb. of good
logwood. It is perhaps preferable to start cold or only lukewarm,
raise to the boil and work for one hour, then lift, rinse well, and
pass into a boiling bath made from 1 lb. of bichromate of potash and
1/4 lb. of sulphuric acid for half an hour. This extra chrome bath
fixes any colouring matter which may have been absorbed by the wool
but not properly fixed by the mordant already on, it leads to fuller
shades which