CHAPTER III.
SIZING MATERIALS, MIXING, AND MACHINERY.
In a weaving mill there is no more important process than sizing, and on its satisfactory management depends the quality and quantity of work turned off, and probably the success of the concern. This is exemplified by the anxiety of a manufacturer to get hold of those recipes well known as obtaining good results. The sale of a shirting, domestic, drill, or heavily sized cloth, absolutely depends on the satisfactory sizing, whilst the cost of making it is regulated by the production of the looms. This has been known in many instances to vary 2s. per loom per week, in the use of a good mixing and a bad one. Cotton warp will not weave well without the previous application of some strengthening substance. In the loom the tension on the threads is great, and whilst distended—and therefore in the most favourable condition for being chafed—the healds with alternate vertical motion, and the reed with reciprocating horizontal motion, rub the threads so severely as to fray them to pieces, unless sized. This point was recognised and counteracted, even in the hand loom days, as mentioned in Chapter I.
In sizing, the objects are to press into the thread a mixture of suitable ingredients, so as to strengthen the yarn, smoothen it, and lay the fibres which project from the surface of the thread, thus increasing the strength, and at the same time reducing the amount of fluff at weaving; also to give to the yarn and cloth the requisite appearance of toughness, strength or body, known technically as the “feel.” It is in the sizing that the “boardy,” “leathery,” “clothy” feels or grip are produced.
Another very important object of this process is the introduction into low classes of cloth of an additional weight of foreign substances. We have not here to deal with the debated and debateable point of its honesty or otherwise, but how the object may best be attained; so long as heavily sized pieces will be bought, so long will they be made, and no blame can, at all events, be attached to the manufacturer. He profits not by the weight, unless unscrupulous, for the price obtained for the piece of cloth is not based on the total weight, but on the amount of cotton contained in it. Frequently the state of the market allows a greater profit out of pure sized goods.
The percentage of size put on cotton goods is calculated according to the increase of weight on the warp only. Thus if the warp in a piece of cloth be composed of 10lbs. of cotton covered with 4lbs. of size, the warp will have been sized to the extent of 40 per cent. The amount of size on cotton warps varies from 3 to 200 per cent. In those classes of goods which are intended for dyeing or bleaching, and which are generally sold by the counts of yarn, it is obviously not wise to add foreign matter to be washed out again, but in those exported goods which have to be made of a fixed weight, or certain feel, heavy sizing is adopted. In the chapter treating of cloths, fuller information on this point is given. Up to 20 per cent. are termed light sized goods, from this to 50 per cent. medium, and above 50 per cent. heavily sized.
Yarn for Warps.
The selection of suitable yarn is obviously important. Warp yarn is generally stronger than weft, and the hardness is obtained by extra twisting of the thread: owing to this peculiarity, warp yarn is generally called “twist.” For heavy sizing purposes, a soft spun twist is advisable, and one made out of the harder and wiry stapled cottons. Brazilian is of this character, and is often mixed with American for “shirting” warps. The spongy and size-absorbent properties are obtained at the expense of the strength of the yarn, and therefore a good sizing twist often winds badly. The colour of the warp yarn is not important, and therefore whiter cottons are often reserved for weft. Fine twists are spun out of longer and finer cottons forming a close spun thread, which is used for better classes of cloth lightly sized. Strength and elasticity are great advantages in twist, and these properties should be obtained and preserved for the last process of weaving.