2 to 4 per cent of the wool. It is then washed well and
immediately dyed. Wool mordanted with chrome should not be exposed to
light, but should be kept well covered with the liquid while being
mordanted, else it is liable to dye unevenly. An excess of chrome
impairs the colour, 3 per cent of chrome is a safe quantity to use for
ordinary dyeing. It should be dissolved in the bath while the water is
heating. The wool is entered and the bath gradually raised to the
boiling point, and boiled for 3/4 of an hour.

COPPER

(_Copper Sulphate, Verdigris, Blue Vitriol, Blue Copperas,
Bluestone._)

Copper is rarely used as a mordant. It is usually applied as a
saddening agent, that is, the wool is dyed first, and the mordant
applied afterwards to fix the colour. With _cream of tartar_ it is
used sometimes as an ordinary mordant before dyeing, but the colours
so produced have no advantage over colours mordanted by easier
methods.

CHAPTER III

BRITISH DYE PLANTS

On the introduction of foreign dye woods and other dyes during the
17th and 18th centuries, the native dye plants were rapidly displaced,
except in some out of the way places such as the Highlands and parts
of Ireland. Some of these British dye plants had been used from early
historical times for dyeing. Some few are still in use in commercial
dye work (pear, sloe, and a few others); but their disuse was
practically completed during the 19th century, when the chemical dyes
ousted them from the market.

The majority of these plants are not very important as dyes, and could
not probably now be collected in sufficient quantities. Some few,
however, are important, such as woad, weld, heather, walnut, alder,
oak, some lichens; and many of the less important ones would produce
valuable colours if experiments were made with the right mordants.
Those which have been in use in the Highlands are most of them good
dyes. Among these are Ladies Bedstraw, whortleberry, yellow iris,
bracken, bramble, meadow sweet, alder, heather and many others. The
yellow dyes are most plentiful and many of these are good fast
colours. Practically no good red, in quantity, is obtainable. Madder
is the only reliable red dye among plants, and that is no longer
indigenous in England. Most of the dye plants require a preparation of
the material to be dyed, with alum, or some other mordant, but a few,
such as Barbary and some of the lichens, are substantive dyes, and
require no mordant.