The dyeing of goods composed of silk and cotton is generally done in winch dye-vats, in some cases also on the jigger.
METHOD OF DYEING.
The direct colours are as a rule dyed in a soap-bath with addition of phosphate of soda, Glauber's salt or common salt and a little soda.
The addition of these salts effects a better exhaustion of the baths; they are therefore principally used for dark and full shades, whilst pale shades are dyed with the addition of soap only or in combination with phosphate of soda. Dark or pale shades may thus be produced at will by selecting the
proper additions, but the fact should not be overlooked that the greater exhaustion of the baths not only increases the depth of shade of the cotton but also causes the silk to absorb more dye-stuff. Too large a proportion of salt would cause the dye-stuffs to go on the fibre too quickly and thus make the dyeing liable to turn out uneven.
A large proportion of soap counteracts the effects of the salts, causing the dye-stuff to go on less quickly and tending to leave the silk lighter than the cotton, in some cases even almost white, a property which is valuable in many cases, especially as enabling the silk and cotton to be dyed in different colours to obtain shot effects.
It is thus obvious that a general method applicable in all cases cannot be given; it will vary according to the effect desired, and partly also depend on the material to be dyed.
The following particulars may serve as a guide for the first bath:—
For pale shades each 10 gallons dye-liquor should contain 3¼ to 6½ oz. soap and 4 to 7 drs. soda or 3¼ to 6½ oz. soap, 4 to 5½ drs. soda and 3¼ to 6½ oz. phosphate of soda.
For medium and dark shades each 10 gallons dye-liquor may contain 3¼ to 6½ oz. soap, 4 to 7 drs. soda, 3¼ to 6½ oz. phosphate of soda and 6½ to 13 oz. cryst. Glauber's salt.