Wool

Scouring.

The washing which a fleece may have received on the live sheep is usually not sufficient for the ordinary purposes of the manufacturer. On the careful and complete manner in which scouring is effected much depends. The qualities of the fibre may be seriously injured by injudicious treatment, while, if the wool is imperfectly cleansed, it will dye unevenly, and the manufacturing operations will be more or less unsatisfactory. The water used for scouring should be soft and pure, both to save soap and still more because the insoluble lime soap formed in dissolving soap in hard water is deposited on the wool fibres and becomes so fixed that its removal is a matter of extreme difficulty. In former times stale urine was a 'favourite medium in which to scour wool; but that is now a thing of the past, and a specially prepared potash soap is the detergent principally relied on. Excess of uncombined alkali has to be guarded against, since uncombined caustic acts energetically on the wool fibre—especially in the presence of heat—and is indeed a solvent of it. A soap solution of too great strength leaves the wool harsh and brittle, and the same bad result arises if the soapy solution is applied too hot.

The scouring of wool has passed through many changes during the past fifty years, but to-day the principle upon which all scour ing machines are based is that wool naturally opens out in water. The mechanical arrangements of the machines are such as to en sure the passage of the wool without undue lifting and "stringing"; to obviate the mixing of wool grease, sand, dirt, etc., once taken out of the wool with that wool again; to give time for the thorough action of the scouring agents, so that neither too strong a solution nor too great a heat be employed ; and to allow of the ready cleansing of the machines so that there is no unnecessary waste of time. In England the recognized type of merino wool-washing machine is the fork-frame bowl. Three to five of these machines are employed. The "scour" is strongest and hottest in the first bowl (unless this is used as a "steeper") as the wool at first is protected from the caustic by the wool-fat, etc., present. The last bowl is simply a rinsing bowl. With modern "nip rollers" botany wool is sufficiently dry to be passed on directly—say by pneumatic conveyers—to the carding. This the worsted spinner does, thereby saving time and money. The woollen spinner, however, may require the wool for blending, and so may require it dry and in a fit state for oiling. He, therefore, will employ one or other of the drying processes to be immediately described. For English and cross-bred wools more agitation in the scouring bath may be desirable. If so, the eccentric fork action machine is employed, in which the agitation of the bath is satisfactorily controlled by the setting of the forks which propel the wool forward. An average

wool will be in the scouring liquor about eight minutes, the tem perature will vary from F to IIon F, and the length of bath through which it will have passed will be from 48 to 6o ft.

It is interesting to note that the "emulsion" method of wool scouring as described above is practically universal in England. In the United States of America the "solvent" method is largely in use. The agent employed—say benzene—is recovered by volatil izing and condensing, thus being used over and over again.

Wool Drying.

The more gently and uniformly the drying can be effected the better is the result attained; over-drying of wool has to be specially guarded against. By some manufacturers the wool from the squeezing rollers is whizzed in a hydro-extractor, which drives out so much of the moisture that the further drying is easily effected. The commonest way, however, of drying is to spread the wool as uniformly as possible over a framework of wire netting, under or over which is a range of steam-heated pipes.

A fan blast blows air over these hot pipes, and the heated air passes up and is forced upwards through the layer of wool which rests on the netting, or downwards, as the case may be. In either case, unless the wool is spread with great evenness, it gets un equally dried, and at points where the hot air escapes freely it may be much over-dried. A more rapid and uniform result may be obtained by the use of the mechanical wool drier, a close chamber divided into horizontal compartments, the floors of which have alternate fixed and movable bars. Under the chamber is a tubular heating apparatus, and a fan by which a powerful current of heated air is blown up the side of the chamber, and through all the shelves or compartments successively, either following or opposing the wool in its passage through the machine. The wool is introduced by a continuous feed at one end of the chamber; the strength of the blast carries it up and deposits it on the upper shelf, and by the action of the movable bars, which are worked by cranks, it is carried forward to the opposite end, whence it drops to the next lower shelf, and so on it travels till at the extremity of the lower shelf it passes out by the delivery lattice well and equally dried. Another drying machine in extensive use is what is known as the "Jumbo dryer." This consists of a large revolving cylinder or churn which turns over the wool—as a churn turns butter—and owing to its inclination passes it from one end to the other. A hot air blast follows the wool through the machine.