The dried wool may be in a partially matted con dition. If so, it must be opened out and the whole material brought into a uniformly 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 Soo 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.
For certain classes of wool, notably Buenos Aires, still another preparing operation is essential at this stage—that is, the removal 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 carboniz ing agent), draining off the dilute acid by means of the hydro extractor, and then heat-drying in a temperature of about 25o° 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 carbon ized. 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 series of three burring rollers rotating in an opposite direction, the projecting rails of which knock the burrs off the wool. The burrs fall on a grating
and are ejected, with a certain amount of wool adhering to them, by another rotating cylinder. With wools not too burry the worsted spinner largely depends upon burring rollers placed upon the first cylinder of the "carder," and possibly to one or other of the patent pulverizing processes applied further on in the card. In the latter process a complete pulverizing of the burrs is aimed at, this being effected by the introduction of specially constructed pulverizing rollers between the first doffer and the last swift of the carding engine. Wooled skins are now successfully deburred by a recently introduced machine—an Australian invention.
(A. F. B.) Wool in the United States.—The three types of wool pro duced in the United States are usually classified as fine, medium and long. Fine wools come from Merino and Rambouillet sheep or crossbreds which show a preponderance of Rambouillet or Merino blood. They vary from 1. to 4 in. in length. The 1920 Census showed that 42.2% of the purebred sheep were of the fine wool breeds. The fineness, crimp, elasticity and good felting qualities of such wools make them suitable for a wide range of uses. They are well adapted to the making of choice woollen and worsted yarns, from which many different fine-textured goods, such as suitings, dress goods and broadcloths are manufactured.
Medium wools, which are coarser than the fine wools, but not usually as coarse as the long wools, come largely from the South down, Hampshire, Shropshire, Oxford and Dorset breeds; known as Down breeds. Wool from many different kinds of crossbred sheep similar to the Down breeds is also included as medium wool. The length of medium wool varies from 2 to 5 inches. According to the 1920 Census 54.1% of purebred American sheep belonged to medium wool breeds. This kind of wool does not usually possess the elasticity or such well-defined crimp as the fine wools. While it is used in the manufacture of woven fabrics of nearly every description, it is particularly well adapted for blankets, tweeds, and flannels, as well as suitings. It also makes very choice knitting yarns.
The long wools, or "coarse wools" come from Lincoln, Lei cester, Cotswold and Romney sheep. This wool is usually coarser than the medium wool, very lustrous, and varies from 5 to 15 in. in length. The 192o Census showed that only 3.7% of purebred American sheep were of the long wool breeds. Long wools are used for the most part in the manufacture of bright, lustrous yarns for linings, mantel fabrics, braids and dress goods.