from 170 deg. to 180 deg. F. will usually be found hot enough to
dye good shades.

Indigo extract is not much used by itself in dyeing blues on wool, but
it is extensively employed along with other dye-stuffs to produce an
immense variety of shades--drabs, greens, fawns, greys, lilacs, etc.,
of which some examples will be given later on.

_Indigo Blue_.--Prepare a bath with 10 lb. indigo extract, 5 lb.
sulphuric acid, and 10 lb. Glauber's salt. Work just under the boil to
shade.

_Sky Blue_.--The dye-bath contains 1 lb. indigo extract, 2 lb.
sulphuric acid, and 10 lb. Glauber's salt. Work at about 160 deg. F. to
shade.

#Dyeing Wool Blue with Logwood.#--This method of dyeing blue on wool has
lost much of its importance since the introduction of the artificial
dyes, but it is still employed when a blue fast to milling is wanted.
Logwood gives dark navy blue shades. The process is as follows: The
wool is first mordanted by boiling for one and a half hours in a bath
of 3 lb. bichromate of potash and 2-1/2 lb. of tartar. The operation
must be so carried out that the non-oxidising green chrome mordant is
developed on the fibre, and therefore the boiling must be thorough. In
place of tartar, argols and oxalic acid are frequently used, while
lactic acid or lignorosine might be employed. The dyeing is done (p. 152)
in a bath of 20 to 25 lb. logwood, or 5 to 8 lb. logwood extract;
the bath is started cold, heated slowly to the boil, and kept at that
heat for one to one and a half hours. Between the mordanting and
dyeing the wool should be well rinsed.

DYEING BLUE WITH COAL-TAR DYES.

The blue dyes derived from coal tar are very numerous, direct, basic,
acid and mordant blues being known. The direct and basic dyes are very
little used, but the acid and mordant dyes are extensively employed,
as is indicated in the following recipes.

#Dyeing with Direct Dyes.# _Pale Blue_.--Prepare a dye-bath with 1/2 lb.
Sulphon Cyanine and 10 lb. Glauber's salt. Enter the goods, and work
at the boil for one hour, then lift, wash and dry.

_Black Blue_.--Prepare a dye-bath with 3 lb. Sulphon Cyanine, 5 lb.
Glauber's salt, and 5 lb. acetate of ammonia; work at the boil for one
hour. Sulphon cyanine works well with other dye-stuffs, and gives
shades which are fast to milling.

#Dyeing with Acid Dyes.# _Bright Blue_.--Prepare a bath with 2 lb. borax
and 1 lb. Alkali Blue B. Enter the wool at about 170 deg. F., then heat
to the boil