Pad in the preceding chamois liquor of the spec. grav. 1·007; dry in the
hot-flue; wince well in chalky water at 160° F., and then dye by wincing
in the following liquor:--
Dissolve 5 ounces of prussiate of potash, in 25 gallons of water heated
to 90° or 100°, adding 2 ounces of sulphuric acid; afterwards rinse, and
brighten in a very dilute sulphuric acid.
10. _Green_ is given by padding goods, previously dyed in the indigo
vat, in a solution of acetate of lead containing a little glue; and then
padding them in a warm solution of bichromate of potash; finally rinsing
and drying.
III. Resist pastes or reserves; these are subservient to the cold indigo
vat, and they may be distributed under four heads; 1. fat reserves; 2.
reserves with bases of metallic salts; 3. coloured reserves capable of
assuming different tints in the dyeing; 4. reserves with mordants, for
the cloth to be afterwards subjected to a dyeing bath, whereby variously
coloured figures are brought up on a blue ground, so as to resemble the
mineral called _lazulite_; whence the name _lapis_ or lapis lazuli.
1. The fatty resists are employed in the printing of silk; which see
_infra_.
2. With regard to reserves the following general observations may be
made. After printing-on the paste, the goods must be hung up in a
chamber, rather humid than too dry, and left there for a certain time,
more or less, according to the nature of the reserve. In dipping them
into the blue vat, if the reserve be too dry, it is apt to swell, scale
off, and vitiate the pattern. This accident is liable to happen also
when the vat is deficient in lime, especially with deep blues.