which it is a superb dye. The
varying shades of indigo of butchers' coats, sailors' collars, and
French porters' blouses always give us pleasure.

CHAPTER XI

THE DYEING OF SILK

Silk is covered with a natural gum which has to be removed before the
dyeing process can begin. This is done by boiling for one hour or more
in a bath containing soap, 2 to 8 ozs. to the pound of silk according
to the amount of gum on the silk. It is then well washed, and is ready
for mordanting.

The mordants mostly used are _Alum_, for most of the bright colours.
_Tin_, for brightening some colours, and as a separate mordant for
others. _Iron_, for black dyeing. _Chrome_, for certain browns such as
catechu.

The principal Alum mordant is Acetate of Alumine, prepared as follows:
Let 3 lbs. Alum and 3 ozs. chalk be dissolved in 1 gallon of warm
water in an earthenware pan, add the chalk slowly to the Alum. Add 2
lbs. white acetate of lead, stir occasionally during 24 to 36 hours.
Let it remain 12 hours at rest. Decant and preserve the clear liquor,
being careful not to stir up the sediment. Pour 2 gallons of water on
the sediment, and stir occasionally for 12 hours. Let it rest 12
hours. Decant the clear and add to the first lot. Bottle for use. It
keeps about three weeks. Of the mordant 2 parts are diluted with 1 of
water, and the silk is well worked in this for 10 minutes, after being
wetted down. Steep for 12 hours, wring out and dry. Wet down again and
return to the Alum liquor, work for 10 minutes, steep 12 hours, dry.
When thoroughly dry, wash well in several changes of water before
dyeing. For less bright colours one mordanting may be sufficient.

The mordant is used for successive batches of silk until exhausted;
the fresher the mordant, the better for brighter colours. Silk should
be dyed as soon after it is dried as is convenient.

Another Alum mordant. Dissolve 25 per cent of Alum in hot water and
add 6 per cent carbonate of soda crystals. Fill up a jar with water
and steep silk in it over-night. It must be washed before dyeing.

RECIPES FOR DYEING

(1) INDIGO VAT FOR BLUE

Silk is dyed in a similar manner as described for wool, but requires
stronger vats and longer dips to obtain the same depth of colour. See
page 33.

(2) INDIGO EXTRACT FOR BLUE

Dye at a temperature of 40 to 50 deg.C. with as much Indigo Extract
dissolved in the bath as is required for the desired depth of shade.
If the silk has been fir