When the seed pod has burst open, disclosing its treasure of snowy fibers, the time for hard and rapid work has begun. The problem of picking is sometimes a serious one. The crop must be gathered before rain or frost has had a chance to injure or destroy it, and there must be many laborers for the picking. Recently a machine which promises better than those previously tried has been invented for picking cotton and may revolutionize this part of the industry. When the crop has been gathered, before being shipped the seeds must be removed. This process of separating the fiber from the seeds is known as ginning. Until 1794 this was done by hand; then Eli Whitney invented the cotton gin, a machine which separates the fibers from the seeds by saws projecting through wire grating into a hopper. The cotton is put into the hopper, the fibers are caught by the revolving saw; but the seeds, being too large to go through the grating, are left behind. This gin is used for American cottons, except the long Sea Island fiber. This is ginned by the roller process, which consists merely in passing the fibers between rollers which do not allow the seeds to pass. The latter method has been employed in a rude way in India for many years.
By the hand process, five pounds of cotton could be picked from the seed by one person in a week. By the saw gin, five hundred pounds may be seeded in an hour, but this is too rapid for the best interests of the fiber. The cotton seeds are a valuable part of the cotton crop, although for a long time they were a waste product. Cotton-seed oil, used for cooking purposes, is obtained by pressing the seeds; cotton-seed meal, after the oil has been removed, furnishes cattle and poultry food; and the hulls are used as a fertilizer.
When the seeds have been removed, the cotton fiber is put into bales, varying in weight, but usually, in this country, of about five hundred pounds. These bales are compressed by a hydraulic press until they are very compact, are wrapped in burlap, bound with iron hoops, and then sent to market. A great deal of criticism has been made of the American cotton bale, because it often bursts open in transportation and because of the bulkiness. The cotton becomes dirty and absorbs a large amount of moisture if the conditions are right, and it is difficult to transport. An effort is now being made to improve the bales.
The manufacture of cotton differs in its details in different countries. In England, spinning, weaving, finishing, dyeing, weaving of fine goods, of coarse goods, prints, or ginghams are carried on by different firms. In this country there is much more centralization, one mill often carrying through all the processes from the raw fiber to the finished cloth and producing a variety of kinds of cloth. The processes necessary to perform the carding, spinning, and weaving of cotton into cloth by machinery are varied, and the machines for carrying them out are complicated. In order that they may be more easily understood, they may be grouped under six heads:
Opening and cleaning.
Preparation for carding and spinning.
Carding and spinning.
When the cotton reaches the factory it is much tangled, having been compressed for some time in the bales. It also contains a considerable amount of impurity - pieces of seeds, leaves, and sticks, as well as dust and dirt, collected on the way to the factory. The first thing necessary is to open the bales and pull this cotton apart. The tangled mass is thrown into a large hopper, where an apron covered with hooks pulls it apart. It is sent by compressed air to another machine, where the process is continued and a blast of air blows out the loose particles of leaves, dust, etc. From this, the scutching machine, the cotton comes out in a thick carpet-like lap, which must be of uniform thickness.
The fiber for medium and medium fine yarns is carded. When cotton yarn was manufactured by hand, this carding consisted of brushing the cotton on brushes made of wire bristles mounted on leather, until the fibers were smooth and parallel. The same result is now accomplished by machinery, large cylinders covered with short bristles revolving in contact with small cylinders likewise covered with bristles. The fiber comes out from this treatment in a very thin sheet, somewhat irregular, but with the fibers in a more or less parallel position. This lap is condensed into a soft rope or sliver by passing through a funnel. To make the slivers even and the fibers more parallel, several processes of drawing follow. The slivers are doubled several times and then drawn out; each time the process is repeated the sliver is drawn out finer, until at last the ropes are even and small enough for the final process of spinning. The strands from different stages in drawing are known as sliver, slubbing, intermediate, and roving.