Under the stimulus of necessity and risk, combined with the hope of advantage, a great deal of skill and attention have been of late years bestowed upon the question of sizing, and especially upon the composition of the size. The latter of course depends upon its pnrpose : whether the end to be accomplished is light, medium, or heavy sizing. These terms may be defined to mean :— 1. "light sizing": that which is requisite to lay down the loose fibres of the threads, and to enable the yarn to withstand the friction and strain incident to the operation of weaving; 2. " medium sizing " : in which a larger quantity is put upon the warp than is requisite for the above purpose, and in order to procure to some extent the peculiar feel remarked upon above ; 3. " heavy sizing in which the yarn is loaded to the extent of its capacity to carry the burden, consistently with retaining its adaptability for weaving. In the first case, the weight of the warp will be increased from 5-10 per cent., according to the strength of the cloth into which it has to be woven ; in the second, 25-30 per cent. may be added ; and in the last, this proportion will probably be doubled.
The materials that enter into the composition of size vary according to the requirement and opinion of the manufacturer. In all cases, however, they may be classified under the following heads :—Starchy matters, to lay the fibres of the yarn, and to induce close coherence ; fatty sub stances, to reduce the harshness resulting from the former ; mineral matters, generally used to procure "feel" and weight ; and chemicals, chiefly introduced for antiseptic purposes. The starchy matters generally in use are wheat-flour ; farina, or potato-flour ; rice-flour ; sago ; and maize, or Indian corn-flour. The two first are in most extensive use. The fatty substances introduced for softening purposes are chiefly soap, tallow, coconut-, palm-, olive-, and castor-oils. Sometimes, a small proportion of white wax is introduced. Of mineral substances used for weight-giving purposes, China-clay is the most common : that of a white hue is the best (see Clays—China-clay). Soap stone, or French chalk, has also been introduced for sizing purposes in this capacity, but has not met with much favour. The " chemicals " or salts used in sizing are primarily for the purpose of keeping the yarn moist and pliable, whilst passing through the process of weaving. This they do, owing to their power of absorbing moisture from the atmosphere. The principal ones hitherto used have been chloride of magnesium and chloride of calcium. In some cases, they are used in excess of the above requirement, for obtaining weight, but this is exceedingly dangerous, unless a powerful antiseptic, such as chloride of zinc, is used in combination therewith. Without this, if other neces
sary conditions are favourable, mildew or other fungoid growth is liable to be developed.
For light sizing, whereby a pure cloth results, the following recipes give the prescribed quantities of ingredients used by numerous manufacturers : (1) Flour, 280 lb., or 1 sack (fer mented); soft soap, 5 lb. ; tallow, 8 lb.; used at 14° Tw. (2) Flour, 280 lb., or 1 sack (fermented); curd soap, 10 lb. ; tallow, 12 lb. ; used at 16° Tw. (3) Sago, 180 lb. ; water, 360 gal. ; coconut oil, 22 lb. These, especially the two first, will serve for medium sizing by the addition of China clay to one-third the weight of flour, and proportionate quantities of the chlorides of magnesium and zinc. For heavy sizing, the composition is materially altered in its proportions. (4) Flour, 5 sacks, or 1400 lb. ; China-clay, 10 bags, or 1240 lb. ; tallow, 200 lb. ; chloride of magnesium, 24 gal. at 56° Tw. ; chloride of zinc, 10 gal. at 92° Tw. ; blue, 1 oz. ; used at 42° Tw. (5) Flour, 1 sack, or 280 lb. ; China-clay, 21 bags, or 560 lb. ; tallow, 100 lb. ; chloride of magnesium, 20 gal. at 56° Tw. ; chloride of zinc, 2 gal. at 92° Tw. ; blue, 5 dwt. (6) Farina, 180 lb. ; China-clay, 580 lb. ; tallow 251h. ; dulcine, 8 gal. ; chloride of magnesium, 14 gal. at 56° Tw.; chloride of zinc, 6 gal. at 92° Tw. ; blue, 2 dwt. Dulcine is a mixture of glycerine, gum, and Chinese wax, in various proportions. The above mixtures, for heavy sizing, are used at a high degree of specific gravity, generally 38° to 44° Tw. If light sizing be required, it can be attained by simply reducing the strength of the above mixtures 20°-25° Tw.
• The following is a recipe used with advantage in making " shirting," a description of cloth largely exported from this country to India, China, and adjacent markets :—Flour, 840 lb. con taining 12 per cent. of gluten, fermented at 21°-27° (70°-80° F.), aged for 6 weeks, and made to 34° Tw., is mixed cold with 225 lb. solution of chloride of zinc at 90° Tw., and 112 lb. solution of chloride of magnesia at 56° Tw., the whole kept at 27° (80° F.) ; 896 lb. China-clay, mixed with water, and boiled for one day ; 193 lb. tallow ; 24 lb. wax ; 10 lb. cheap fat is melted and run into the clay, and the mixture is boiled for another day. The flour at 27° (80° F.) is run into the clay at boiling heat, and allowed to cool ; 200 lb. farina is mixed with water, and heated to 65° (150° F.) for 6 hours, then run into the other mixture, the whole being heated to 65° (150° F.). It is then ready for use.