1881.J on Indi(jo, and its Artificial Production. 591 



Printing Colour. 



Tako the above standard and dissolve in it immediately before 

 printing 1\ lb. xantliate of soda, stir well, and ready for use. 



For lighter shades reduce the above printing colour with tho 

 following : In 1 gallon white starch paste dissolve 1 lb. xantliato 

 of soda. 



Directions for use. — Print and dry as usual. Tlie pieces ought 

 not to be placed in immediate contact with drying cylinders, or 

 otherwise be subjected to heat above 100° C. The indigo-blue is best 

 developed by allowing the printed goods to remain in a dry atmo- 

 sphere and at an ordinary temperature for about 48 hours. Damp air 

 ought to be excluded as much as possible until the colour is fully 

 developed. Then the pieces may be passed through the ageing 

 machine, or steamed at low pressure if such treatment should be 

 required for fixing any other colour or mordant printed along with 

 the indigo-blue. 



After the blue is ready formed, the pieces are first thoroughly 

 washed in the washing machine and then boiled in the clean water, 

 or better, in a w-eak solution of hyposulphite of soda (1 lb. to 10 

 gallons), and at a full boil for half an hour in order to volatilise the 

 smell which would otherwise adhere to the goods. 



Clean in a soap-bath, at a temperature not above 40^ C. ; wash, dry, 

 and finish. 



Observations. — Wheat starch gives the best results in the colour, 

 then follows gum tragacanth. The colour is considerably reduced by 

 using gum Senegal, dark British gum, or calcined farina as thickening 

 materials. 



So far borax has answered best as an alkaline solvent of propiolic 

 acid, it may however be replaced in the above standard by acetate 

 of soda (from 1 to 1^ lb.) or by 6 oz. pearlash or soda. Any excess 

 of caustic-potash, or soda, destroys propiolic acid. 



The above standard keeps unchanged for any length of time, it is 

 likewise not sensibly altered by a small amount of xanthate of soda, 

 but when mixed with its full proportion of xanthate, as in the above 

 printing colour, it gradually loses strength after several hours. 



The xanthate ought therefore to be mixed with the standard 

 immediately before printing, and any colour remaining unused may 

 then be saved by mixing with the same a large proportion of 

 starch paste. 



Pro2)iolic acid may be printed along with aniline black, catechu 

 brown and drabs, and with alumina and iron mordants for madder 

 colours. 



After the indigo-blue is fully developed, the mordants are fixed in 

 the ordinary manner, dyed with alizarin, padded with Turkey-red oil, 

 steamed, and otherwise treated as usual. 



Indigo-blue, whether natural or artificial, suffers by prolonged 



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