50

DYEING AND CALICO PRINTING .

passed through the liquors employed in the process of bleaching it becomesnecessary to discharge the fluid, and this operation is effe&ed by squeezingrollers or squeezers. These are rollers generally worked under steam-power,the upper one being caused to bear upon the cloth by its own weight, or bymeans of a weighted lever. There are many varieties of these machines,the description of which belongs, however, to mechanical engineering, and isnot an essential of the chemical processes of bleaching.

When squeezed, sometimes effected over rollers heated by steam, the cloth,if required for printing, needs no further operation, but if intended for themarket it must be “ finished,” that is, starched and calendered. Manybleachers prefer to prepare their own starch from flour, as they thus avoid thedrying process, for which the manufacturer of the starch must be paid. Thestarch is coloured with blue, generally ultramarine. It is disseminated overthe cloth by means of rollers dipping into the starch, other rollers removingthe excess. The starch need not be pure ; fine clay or gypsum is sometimesemployed as well. The pieces of cloth are occasionally artificially weightedwith sulphate of baryta during the finishing, or with silicate of soda. TheobjeCt of such an addition is to render the cloth solid in appearance. Thecalendering machine is really an ironing machine, surface and gloss beingimparted to the cloth by means of heated rollers. The pieces when calenderedand finished are subjected to hydraulic pressure.

Bleaching Muslins.

Muslins are bleached in the same manner as other cotton goods: Mr.Barlow employs solutions of the same strength, and does not consider thatmuslins need any special treatment. Only in cases where goods havecoloured threads woven into them or colours printed on them must greatcaution be used ; then it is desirable to employ weak solutions, repeating theoperation often rather than allowing it to be continued for a length of time.It is possible to perform the entire bleaching in one operation, but then thegoods would be made rotten : a certain strength of bleaching solution or sodaleaves the fibre unattacked, while a more concentrated solution destroys thefibre as well as the colouring matters. It is often required to bleach thewhite ground of printed goods, where the ground has taken up sufficientcolour to deteriorate the brilliancy of the white, and which soap would bepowerless to remove. A solution of bleaching-powder at half a degreeTwaddle is then employed. The liquor should be tested with a piece ofTurkey-red dyed stuff; if too strong the colour will be discharged.

Muslins when finished and dried without motion become very hard, rigid, andrough to the touch ; they are therefore stretched during drying, the lines ofselvage being moved backward and forward so that the weft threads ma)'rub against each other and not become united. This method of drying impartsthe peculiar spring or elasticity to muslins.

Bleaching Cotton Stockings.

We shall from time to time in the progress of this work give descriptions 10technical terms of processes which have been found advantageous for specialpurposes. These descriptions will differ from the rest of the work in being