Take 3-1/2 gallons of caustic soda lye of spec. grav. 1·15.
3-1/2 lbs. of ground indigo.
5 lbs. of precipitated protoxide of tin (as above).
Boil the mixed ingredients for ten minutes, take them from the fire, and
add, first, 3 lbs. of Venice turpentine; then 11 lbs. of gum.
Put this mixture into the colour trough, print with it, and after two
days wash in the dash-wheel; then pass it through a soap bath, along
with a little soda, to brighten the blue, and to take off its greyish
tint.
The use of the turpentine is easily explained; it serves to exclude the
atmospherical oxygen, and prevent the regeneration of the indigo blue,
before it is spread upon the cloth.
After the application to white calico of a similar blue, into which a
little acid muriate of tin has been put, the goods are dipped for ten
minutes in thin milk of lime, shaking the frame all the time. They are
then washed, and cleared with a soap boil. The following colour remains
long in the deoxidized state from its containing 8 ounces of indigo, 10
ounces of hydrated protoxide of tin, and 1-1/2 pounds of solution of
muriate of tin, to 2 quarts of soda lye of 1·15, thickened with 2-1/2
pounds of gum. This blue may be applied by either the block or the
cylinder.