its allotted receptacle. Sorting is very far removed from being a mere
mechanical process of selecting and separating the wool from certain
parts of the fleece, because in each individual fleece qualities and
proportions differ, and it is only by long experience that a stapler is
enabled, almost as it were by instinct, rightly to divide up his lots,
so as to produce even qualities of raw material. Cleanliness is most
essential if the wool sorter is to keep his health and not succumb to
the dread disease known as “anthrax” or “wool-sorters' disease.”
Certain wools such as Persian, Van mohair, &c., are known to be very
liable to carry the anthrax bacilli, and must be sorted under the
conditions imposed by government for “dangerous wools.” Ordinary or
non-dangerous wools are perfectly harmless from this point of view.
The washing which a fleece may have received on the live sheep is not sufficient for the ordinary purposes of the manufacturer. Scouring. 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 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 detrimental result arises when the soapy solution is applied too hot.
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Fig. 7.—Qualities of Wool in a Lincoln Fleece. |
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The numbers indicate the quality of wool taken from the respective sections of the fleece. Thus the finest quality—44's—is found on the shoulders, while the coarsest “britch” is found on the hind-quarters of the sheep. |
In former days, when the method of hand-scouring prevailed, the wool to be washed was placed with hot soap-sud in a large scouring “bowl” or vat, and two men with long poles kept stirring it gently about till the detergent loosened and separated the dirt and dissociated the grease. The wool was then lifted out and drained, after which it was rinsed in a current of clean water to remove the “scour” and then dried. These operations are now performed in scouring machines. Many firms now steep the wool previous to the true scouring operation, the object being to scour the wool with its own potash salts, to obtain wash-waters so fully charged with the potash salts that these salts, &c., may be readily extracted and put to some good use, and lastly to save the artificial scouring agent employed in the true scouring operation. The scouring of wool has passed through many vicissitudes during the past fifty years, but to-day the principle upon which all scouring machines are based is that wool naturally opens out in water. The mechanical arrangements of the machines are such as to ensure the passage of the wool without undue lifting and “stringing,” to obviate the mixing of wool grease, sand, dirt, &c., 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, &c., 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 conveyors—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 temperature will vary from 120° F. to 110° F., and the length of bath through which it will have passed will be from 48 to 60 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, for the two points aimed at are quantity of production and cheapness. Quality is sacrificed to quantity and cheapness results from the ease with which the agent employed—say carbon disulphide—is recovered by volatilizing and condensing, thus being used over and over again.
Botany wools should leave the wool-washing machine in a fit condition to be fed immediately on to the carder, provided that the first cylinders are clothed with galvanized wire. Cross-bred and English wool, however, require artificially 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 Wool drying. 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 this case, unless the wool is spread with great evenness, it gets unequally 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 side 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. In this and in all drying machines it is more important to get the moisture laden air away from the wool than to develop a great heat.
The dried wool may be in a partially matted condition. If so, it must be opened out and the whole material brought into a uniformly Teasing. free and loose condition. This is effected in the Willey, which consists of a large drum and three small cylinders mounted in an enclosed frame. The drum is armed with ranges of powerful hooked teeth or spikes, and is geared to rotate with great rapidity, making about 500 revolutions per minute. The smaller cylinders, called workers, are also provided with strong spikes; they are mounted over the drum and revolve more slowly in a direction contrary to the drum, the spikes of which just clear those of the workers. The wool is fed into the drum, which carries it round with great velocity; but, as it passes on, the locks are caught by the spikes of the workers, and in the contest for possessing the wool the matted locks are torn asunder till the whole wool is delivered in a light, free and disentangled condition. It is a debatable point as to whether willowing should precede scouring. Some scourers always willow prior to scouring, while others never subject the wool to this operation, which is advantageous in some cases and not in others.
For certain classes of wool, notably Buenos Aires, still another preparing operation is essential at this stage—that is, the removal Barring. of burrs or small persistently adherent seeds and other fragments of vegetable matter which remain in the wool. Two methods of effecting this—one chemical, the other mechanical—may be pursued. The chemical treatment consists in steeping the wool in a dilute solution of sulphuric acid (or other carbonizing agent), draining off the dilute acid by means of the hydro extractor, and then heat-drying in a temperature of about 250° F. The acid leaves the wool practically uninjured, but is concentrated on the more absorbent vegetable matter, and the high heat causes it to act so that the vegetable matter becomes completely carbonized. The burrs are then crushed and the wool washed in water rendered sufficiently alkaline to neutralize any free acid which may remain, and dried. The same burr-removing effect is obtained by the use of a solution of chloride of aluminium, a method said to be safer for the wool and less hurtful to the attendant workmen than is the sulphuric acid process. For mechanical removing of burrs, a machine something like the Willey in appearance is employed. The main feature of this apparatus is a large drum or swift armed with fine short spikes curved slightly in the direction in which it rotates. By a series of beaters and circular brushes. the wool is carried to and fed on these short spikes, and in its rotation the burrs, owing to their weight, hang out from the swift. The swift as it travels round is met by a
