Sizing Materials.
Many points distinguish a good size-mixing from a bad one, and the leading qualifications for a suitable one are adhesive properties—it is no use sizing warps if the substance falls off at the loom—good colour, and uniform consistency. Mealy cloth is often produced by lumpy size. Yarn, even with a heavy coat of size, should remain tenacious, pliable and smooth.
The number and variety of sizing substances render it impossible to adequately describe the properties and use of each. Mention is only made of those of greatest use and importance; yet the list is sufficiently long. They may be divided into four classes—those for forming the basis or body of the mixing or adhesive substances, those for rendering the dried size pliable, weight-giving substances, and antiseptics. In the adhesive substances, flour is of first importance for medium and heavy sizing. This is manufactured by grinding a portion of the wheat grain, and the qualities used in sizing are of the better sort, fully equal to those used for bread-making. For giving body and adhesiveness to the size, flour is valued, but is found a rather expensive substance, and rather inclined to mildew. To remove this latter disadvantage, and also to render flour more suitable for the purpose for which it is intended, most manufacturers steep it in water for periods varying from three days to as many months. Practical men and sizing specialists generally agree, however, that from two to three weeks is the best length of time for fermentation. On judging the quality of flour, comparisons of colour and stiffness after boiling are made; in the latter case equal quantities of each sample should be taken and treated similarly, both as to amount of water taken and time allowed for boiling. The best test, however, and one that applies to all sizing substances, is whether it “goes far” or not in actual use.
Farina is the ground starch of the potato, and largely used in light sizing on account of its cheapness and convenience for mixing. It requires the use of a softener with it, generally tallow or wax, to counteract a harshness which it gives to the twist when used alone.
Two other vegetable substances—sago and rice flours—are used for very light sizing, especially for fine reeds or coloured work.
Softeners.—Unless some ingredient with a more or less greasy nature be mixed with the above substances in sufficient quantities, the warp is so brittle and harsh as to break frequently in the loom. The substance most frequently used is tallow (refined animal fats). This is somewhat expensive, yet its softening properties in heavy sizing are often introduced into the mixing. The quantity of tallow to each bag of flour or clay varies according to the quantity of other softeners used. In using tallow care must be taken to obtain it hard and free from grit; much wear of clacks and rams may be attributed to gritty matter in this and other ingredients, especially in china clay.
Wax is a softener used for light sizing with farina. It is of two kinds: Japan wax, a vegetable substance, of rather yellow colour, and paraffin wax, clear and semi-transparent, obtained from mineral oils. A high melting point of wax is a great desideratum, to ensure the mixture hardening thoroughly on the warp—110° is considered a fair temperature for wax to bear before melting. For softness, castor oil and glycerine are occasionally adopted, as is also Irish moss.
Soap.—A mixture of animal and mineral substances is not generally used, although a good softener, its frothy nature when boiling rendering it difficult to deal with. Soap and chloride of magnesium (so called anti.) should not be used together, as their action on each other tends to make the size lumpy. One important property of soap, or rather alkali contained in it, is that it kills any acid developed in the mixing. Soda has a similar and stronger tendency. Chloride of magnesium, muriate or chloride of zinc have softening properties, but those substances will be more fully mentioned in the next group.
Weight-giving Material.—Next to flour no substance enters into heavy mixings in such quantity as china clay. This is a white earthy matter found in Devon and Cornwall. After having all stony substances washed out it is dried and packed in bags for shipment to Runcorn and other small ports in the neighbourhood of cotton manufacturing districts. In selecting good qualities, colour and smoothness should be borne in mind. To use this material to advantage a good knowledge of other materials is required, so that such ingredients may be used with clay as to keep the size on the yarn at the loom. When clay is boiling it is somewhat dangerous to lift up the lid of the boiling beck, this substance having an unpleasant property of spurting up, possibly on the face or hands of an attendant.
Metal size is that containing the chlorides of the metals, magnesium and zinc. Chloride of magnesium, a mineral salt obtained in Germany, is valued as a weighting and softening compound. It has the peculiar property of attracting moisture to itself, always causing cloth or any substance containing it to feel damp. This substance is melted out of its solid form into a liquid by the application of steam, and is afterwards stored in a lead-lined tank. Muriate of zinc, or chloride of zinc, is a substance of importance for weighting, and is also valuable in checking the growth of mildew.
Mildew, as may be seen under a microscope, is a species of fungus—a vegetable growing under certain conditions favourable to its development. If warp or cloth is sized or finished damp, then stored in a dry room for a considerable time, mildew may be expected, unless antiseptics have been used. An antiseptic is a substance tending to destroy vegetable life, and of antiseptics muriate of zinc and carbolic acid are the most suitable for sizing purposes. As chloride of magnesium does not prevent mildew, indeed, its use being rather favourable to the development of that evil, the name anti, or antiseptic, usually given to it is misleading. It is very important that a manufacturer should take every precaution to prevent mildew by the use of real antiseptics, especially when using such sizing materials as flour, tallow, or any other which readily mildews. It may be mentioned that the maker of the cloth is liable for any damage done in this respect, if the cause can be found in defective sizing, even though the growth may not be seen until the goods have arrived abroad.
The before-mentioned chlorides are greatly dependent on the weather, and also on the situation of a shed, for their good weaving properties. In case of east winds, extremely dry or cold atmospheric conditions, or in a dry shed twist sized with magnesium, zinc or china clay, is rendered brittle first. Numerous other materials are used by a few manufacturers, but they do not require an extended notice. Dividing them into the four classes previously mentioned, we may refer to:—1st, maize, starch, tapioca, dextrin, and gum; 2nd, oils, compositions, spermaceti, curd soap, Irish moss, cocoanut oil; 3rd, French chalk, Epsom salts; whilst soda is used to prevent iron-mould, and blue to take away a yellow tinge from the size mixing.