MECHANICAL TREATMENT OF COTTON.—Ae a preliminary to B detailed description of tho pro cesses and machinery used in the various stages of the treatment of cotton, for the production of yarn, and afterwards of textiles, the subject will be rendered more easily intelligible by drawing up a scheme representative of the general procedure ; this will also afford an opportunity of defining the principal technical terms used, and will remove any confusion arising from their occasional employment in wide, restricted, or otherwise varying senses.
Cotton Spinning.--This term, as previously indicated, is employed to describe in the aggregate all the operations involved in transforming raw cotton into yarn : that is, into a single twisted strand, or thread composed of cotton fibre. The word " spinning" has also a more limited signification, being used to denote, as will subsequently be seen, the concluding process of the series.
The manipulation, mechanical and otherwise, that cotton undergoes in being converted into yare, from the state in which it is gathered from the plant, may be outlined as follows:— 1. " Ginning."—This is usually performed in the vicinity of the cotton plantation ; the object being to remove the fibre from the seed of the plant, and partially to cleanse it from foreign matters.
2. "Packing" or " Baling."—After ginning, the lint is in a loose state, and unfit for convenient transport to distant markets . hence it is necessary to compress it into less space, which is ordinarily performed hy means of hydraulic presses. The package leaves the press in the well-known form technically called a " bale," in which state it passes through the markets into the hands of the spinners.
3. " 1V1ixing."—Is the blending of different varieties of raw cotton, in order to secure economical production, uniform quality and colour, and an even thread, in any desired degree. Mixing is, in a measure, imperatively necessary, in order to neutralize the irregularities of growth, and imperfect classification, found more or less in all cottons. It is the first operation in a cotton mill.
4. " Willowing."—This is a process of opening and cleaning cotton, which, except in the Oldham district, is not much used in modern mills, and is retained chiefly for opening and cleansing low cottons, waste, &c.
5. " Opening."—In consequence of the heavy pressure to which cotton is subjected in packing, the fibres become strongly matted together ; the opening process is to loosen them, and to remove a portion of the foreign substances present. It is the present equivalent of willowing.
6. " Scutching."—Hos a twofold object: viz. the further extraction of impurities, and the formation of a " lap," which is a web or sheet of cotton formed in the machine, and wound upon a small roller. In this web, the fibres lie in all directions.
7. " Carding."—The foregoing processes have dealt with the cotton in bulk. In carding, the operation of opening if3 continued ; but the material is treated in its individual fibres, which are taken from the lap, further cleansed, and laid in a position approximately parallel to each other, forming a thin film, which is afterwards condensed into a " sliver "—a round, soft, and untwisted strand of cotton.
8. " Combing."—Is used for the production of fine yarns, or those of very high quality. Its object is to obtain uniformity in the length 'of the fibres undergoing preparation ; to accotnplish this, all those shorter than the required standard are combed away, and rejected.
9. " Drawing."—In this operation, several slivers, the product of the carding process, are combined, and attenuated to the dimensions of one of the component parts; the objects are to render the new sliver more uniform in thickness, and to place the fibres more perfectly in parallel order.
10. " Slubbing."—Is a process by which a further combination of the slivers is effected, and the objects of drawing are more perfectly accomplished. The drawing or attenuation of the strand is now carried so far that it becomes necessary to twist it slightly, in order to preserve its cohesion, and rounded form.