The dyeing of textile fabrics . Another method of dyeing with Indigo, but one whichyields fugitive colours, and is applicable only to the animalfibres, depends on the fact that Indigo treated with strongsulphuric acid becomes changed into sohible indigotin-di-sulphonic acid (Indigo Extract). Animal fibres attractand are dyed with this compound when they are simplysteeped in its hot and slightly acidified solutions. Vat-blue is largely employed, particularly in woollen 296 DYEING OF TEXTILE FABRICS. [Cbap XIII. dyeing, as the blue part of compound shades, , browns,drabs, itc. The. same may
The dyeing of textile fabrics . Another method of dyeing with Indigo, but one whichyields fugitive colours, and is applicable only to the animalfibres, depends on the fact that Indigo treated with strongsulphuric acid becomes changed into sohible indigotin-di-sulphonic acid (Indigo Extract). Animal fibres attractand are dyed with this compound when they are simplysteeped in its hot and slightly acidified solutions. Vat-blue is largely employed, particularly in woollen 296 DYEING OF TEXTILE FABRICS. [Cbap XIII. dyeing, as the blue part of compound shades, , browns,drabs, itc. The. same may be said of Indigo Extractor Indigo Carmine blue, with regard to wool and silkdyeing. Indeed, this colouring matter possesses c^iiainadvantages over the majority of blue colouring can be associated with other acid colouring mattei^,and it dyes verj^ level shades. Its only drawback is itsextremely fugitive character. 233. Indigo Grinding Mills.—One of the firstnecessities in employing Indigo in dyeing is to have it. Fig. 81.—Indigo Grinding Mill. thoroughly well ground. When required for making In-digo Carmine it must be ground in the dry state, but forthe indigo-vat it may be mixed with water, by whichmeans the grinding is considerably facilitated. The oldest form of giinding machine is the stampingmill, provided with an arrangement for passing theground Indigo through fine sieves. At jiresent the millsgenerally employed consist of cast-iron vessels, in whichthe Indigo is ground either by the rolling of heavy cannonballs, or of iron cylinders. The ball mills are said togive the finest powder ; the cylinder mills the greatestyield within a given period. Fig. 81 represents a section Chap. Xm.] INDIGO. 297 of one of tlie best forms of ball mills. It consists of astrong iron box enclosing several heavy cannon balls,which are pushed round by means of a pair of revolvingarms. Sometimes the bottom of the box is flat, andheavy blocks of sand-stone are substituted for ball
Size: 2024px × 1235px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1880, booksubjectdyesanddyeing, bookye
