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.
Size Mixing.
Mixing is performed in becks—wooden tanks fitted with dashers, constantly revolving and stirring the mixture. To each beck pumps are attached so as to force the size to another beck to complete the mixing process; or, if the mixing is ready for use, to pump it to the size box of the slasher frame.
A set of becks generally consists of four—two about 4 by 8 feet, and two each 4 feet square, while for heavy sizing a copper or copper-lined boiling pan is used. This latter is fixed at a higher level than the becks for convenience in transferring the boiled size to the becks.
Considering that a mixing made from a fixed quantity of certain ingredients is not generally used for percentages ranging more than 15 per cent., and that different mixings are required all the way up to 150 or 200 per cent., whilst at the same time not more than two or three manufacturers may use exactly similar mixings even for the same degree of weighting, it will readily be seen that the mixings employed in the cotton trade are innumerable. This difference has been caused by the jealous care taken by a sizer to preserve to himself the recipe of his own mixing, and rightly so. Thus, new mixings have had to be adopted by new firms, the correct quantity of each ingredient having to be fixed by repeated experiments; and as the true properties of each substance have not been, and are not yet, well understood among manufacturers according to scientific investigation, the differences of opinion, and consequent differences of recipes, are very great. Nor is it to the ingredients that these opinions are confined, but to the order of putting each into the beck, the times of fermenting and boiling, and many other details.
It is somewhat difficult to satisfactorily determine beforehand the amount of weight which can be obtained from a mixing. An instrument, really a hydrometer, but often, from the name of its inventor, dubbed a “Twaddle,” is sometimes used; but unless a fixed temperature is always taken, these instruments are not reliable, as a mixing twaddles differently at different heats. Indeed, from the varying results obtained, a twaddle cannot be said to be of much practical use in sizing. A better system, perhaps, is to take the proportion of solid or semi-solid matters in a mixing as against the weight of water, and compare it with the ratio of another mixing which is known to give a certain percentage. Thus, if one mixing of 3lb. of solid matter to a gallon (10lb.) of water gives 25 per cent., then a mixing with 6lb. solids to the gallon may roughly be said to put in 50 per cent. Heavy liquids, such as zinc and solution of magnesium chloride, will have to be reckoned partially as liquids, in consequence of the evaporation which will take place on drying at the cylinders; and the softeners, from their inability to retain liquids as well as the starches, will not be calculated as having the same weighting power. Magnesium may be reckoned as having one-third of its weight in solids, and zinc at one-half.
For Light Sizing.—Taking a pure size, say 8 to 10 per cent., farina and wax or tallow is generally used as being the cheapest, and at the same time most suitable mixing. The ingredients are generally combined in the same beck that they are boiled in; for 10 per cent. the following may be used: 200lb. farina, 20lb. wax, 200 gallons water. By the addition of clay, the same may be made serviceable up to 25 per cent.
For Medium Sizing, say 50 per cent.—Flour, clay softener and chlorides are used—say flour 480lb., clay 224lb., tallow 60lb., chloride of magnesium (so-called anti) 5 gallons, zinc 2 gallons, soda 8lb., water 150 gallons in all. It is mixed as described for 100 per cent.