CHAPTER VII.
OPERATIONS FOLLOWING DYEING: WASHING, SOAPING, DRYING.
After loose wool, or woollen yarns or piece goods of every description have been dyed, before they can be sent out for sale they have to pass through various operations of a purifying character. There are some operations through which cloths pass that have as their object the imparting of a certain appearance and texture to them, these are generally known as finishing processes, of these it is not intended here to speak, but only of those which precede them but follow on the dyeing operations.
These processes are usually of a very simple character, and common to most colours which are dyed, and here will be noticed the appliances and manipulations necessary in the carrying out of these operations.
Squeezing or Wringing.--It is advisable when the goods are taken out of the dye-bath to squeeze or wring them according to circumstances in order to express out all surplus dye-liquor, which can be returned to the dye-bath if needful to be used again. This is an economical proceeding in many cases, especially in working with many of the old tannin materials, like sumac, divi-divi, myrobalans, and the modern direct dyes, which during the dyeing operations are not completely extracted out of the bath, or in other words the dye-bath is not exhausted of colouring matter, and therefore it can be used again for another lot of goods simply by adding fresh material to make up for that absorbed by the first lot.
Loose wool and loose cotton are somewhat difficult to deal with by squeezing or wringing, but the material may be passed through a pair of squeezing rollers such as are shown in figure 24, which will be more fully dealt with later on.
Yarns in Hanks.--In the hand-dyeing process of hank-dyeing the hanks are wrung by placing one end of the hank on a wringing-horse placed over the dye-tub, and a dye-stick in the other end of the hank, giving two or three sharp pulls to straighten out the yarn and then twisting the stick round; the twisting of the yarns puts some pressure on the fibres thoroughly and uniformly squeezing out the surplus liquor from the yarn.
Hank-Wringing Machines.--Several forms of hank-wringing machines have been devised. One machine consists of a pair of discs fitted on an axle, these discs carry strong hooks on which the hanks are placed. The operator places a hank on a pair of the hooks. The discs revolve and carry round the hank, during the revolution the hank is twisted and the surplus liquor wrung out, when the revolution of the discs carries the hank to the spot where it entered the machine, the hooks fly back to their original position, the hank unwinds, it is then removed and a new hank put in its place, and so the machine works on, hanks being put on and taken off as required. The capacity of such a machine is great and the efficiency of its working good.
Mr. S. Spencer, of Whitefield, makes a hank-wringing machine which consists of a pair of hooks placed over a vat. One of the hooks is fixed, the other is made to rotate. A hank hung between the hooks is naturally twisted and all the surplus liquor wrung out, the liquor falling into the vat.
Roller Squeezing Machines for Yarn.--Hanks may be passed through a pair of indiarubber squeezing rollers which may be so arranged that they can be fixed as required on the dye-bath. Such a pair of rollers is a familiar article and quite of common and general use in dye-houses.