484

DYEING AND CALICO PRINTING.

cloth. The idea was good, but notwithstanding large sums of money havebeen spent to give this process a fair trial, requiring as it does complicatedmachinery, it has signally failed. Some of the causes of this failure are quiteunaccountable, so that the process was abandoned in despair, and has neverbeen worked for the last eighteen years. ■

We have now to turn our attention to an application of indigo known asChina blue, because the blue colour had a similarity to the well-known blue ofold China ware. It is produced by a process so extraordinary in its resultsthat it is impossible to conceive how or where it originated, and althoughthis application of indigo has now become obsolete, we cannot be justifiedin omitting to enter into some details on this subjedt.

The theory of China blue printing is exceedingly simple : the indigo, reducedto an impalpable powder, is thickened, and this mixture is printed on by meansof cylinders or blocks. After drying, the goods exhibit a more or less deepblue pattern, according to the quantity of indigo employed ; but this blue wouldnot resist even a rinsing in cold water. The next stage is therefore to reduceand dissolve the indigotin on the spot, and thereby to cause it to penetrateand combine with the fibre to be definitively fixed after a process of oxidation.These operations have to be performed so as to preserve the sharpness of thedesign and prevent any colour from running. The following means areresorted tor—The cloth is first passed through a tank containing milk of lime,next through one containing a solution of sulphate of iron, next through asolution of soda, and, lastly, through weak sulphuric acid, which, whiledissolving the oxide of iron, causes the precipitation of the white indigo, andaids also its oxidation. This is only an outline of the method to illustratethe theory ; the pradtice is essentially different, so as to secure success. Inthe first place, the printer begins his operation with the preparation of standardcolour in the following manner:—He takes 4 kilos, of very finely-pulverisedand sifted indigo (for this special purpose the Caraccas indigo is preferred,because, although it is less rich in colouring matter than Bengal or Javaindigo, it is more readily pulverised, and can be obtained in a powder as fineas the finest ultramarine) ; acetate of iron, 10 litres ; sulphate of iron, 1 kilo. ;water, 10 litres; Senegal gum, 6 kilos.: this mixture is well stirred and passedthrough a sieve, and whenever it is required for use, it is first well stirred.This standard colour serves to prepare the following colours, which are

employed for being printed on the cloth :—

Colours to be applied by roller or cylinder, beginning with ) 1 2 ^

the lightest and proceeding to the heaviest shades .. J

Standard blue; parts . .. 1 1 3 4

Acetate of iron liquor, at 7° Baume (sp. gr. 1-048), containing) 2 % ^ i

700 grms. of gum per litre.J

Gum-water, made up of 600 grms. to the litre. 16 2J 1 t

These shades may be varied in different ways, according to the desired pat-tern. Since the indigo has a tendency to settle to the bottom of the vesselfrom which it is supplied to the rollers, the liquid contained in that vessel hasto be stirred about now and then. If it happens that the pattern consists ofmore than one blue, the machine-printer has to take care that—after the firstcolour has been printed on and dried—he does not give too much colour tothe subsequent patterns, whereby the underlaying might become re-dissolved.