Figure 1. Some cotton products.
Figure 2. Flax and jute products.
Textiles are fabrics made from natural or synthetic fibers, whether knitted, woven, bonded, or felted. Archaeological evidence from caves in Mexico and the American southwest reveals that fibres were already being used more than 10,000 years ago. Apart from using flax, jute, hemp, and other fibers to make ropes, nets or sacks, early man made crude fabrics by pounding the fibrous tissues of certain trees and plants into flat sheets of “bark-cloth”, such as the Polynesian tapa still made today. By 3000 BC cotton was being spun into yarn and woven into cloth in India while the manufacture of linen was well developed in Egypt even earlier.
|Flax. Linum sp.|
Types of fibers
Fibers from different parts of a plant have varying characteristics. Bast fibers come from the inner tissues beneath the bark of dicotyledons (plants having two seed leaves). Made up of long overlapping cells, they are bedded in a cementing material that must be removed before the fibers can be peeled apart. Bast fibres are known as "soft tissues" and are particularly flexible. They can be made into rope or twine or woven into coarse, heavy-duty sacking. Jute, hemp, and flax are most commercially important and flax can also be woven into a soft, fine fabric known as linen.
By soaking, or retting, the long stems in water, the material binding bast fibers together is partially decomposed by microorganisms in the water. The stems are then beaten and passed through rollers that separate the softened fibers from the mucilaginous matter. Jute fibers are stripped away by hand. Leaf fibers, mostly obtained from perennial plants, are part of the vascular structure of leaves. They have a stiff texture and are much shorter than bast fibers. In a process called decortications, rolling machines crush the leaves, scrape off non-fibrous matter and wash it away with jets of water. These "hard fibers" are generally too stiff to be made into fabrics. Their major use is as cord, twine, brush bristles, and coarse sacking. The most important leaf fibers are sisal, henequen, and abaca.
Seed fibers grow as fine hairs on the seeds of certain plants. Each individual fiber is a single, elongated cell. Cotton, coir, and kapok are the only seed fibers of any major commercial value. Of the three, only cotton is suitable for spinning into fine yarn (see Figure 1). Kapok is mainly used as stuffing or insulation, and coir is made into ropes, sacks, and brushes.
The fibers are prepared and spun (see spinning) into yarn. This is then formed into fabric by weaving or other methods. Finishing processes include bleaching; calendering; mercerizing; dyeing (see dye), brushing, sizing, fulling, and tentering. Chemical processes are used to impart crease-resistance, fireproofing, stain-resistance, waterproofing, or nonshrink properties.
Manufacture of textiles
Carding is a process used in textile manufacture whereby the fibers are laid out parallel to each other, then gathered into strands (card slivers) about 25 millimeters (1 inch) thick. This process may be followed by combing, where the fibers in the sliver below a certain length are removed, those remaining being set more accurately parallel.
|Two-handed spinning wheel or Saxon
Spinning is the ancient craft of twining together fibers from a mass to form strong, continuous thread suitable for weaving. The earliest method was merely to roll the fibers between hand and thigh. Later two sticks were used: the distaff to hold the bundle of fibers, and a spindle to twist and wind the yarn.
Mechanization began with the spinning wheel, invented in India and spreading to Europe by the fourteenth century. The wheel turned the spindle by means of a belt drive. In the fifteenth century the flyer was invented: a device on the spindle shaft that winds the yarn automatically on a spool.
Improved weaving methods in the Industrial Revolution caused increasing demand which provoked several inventions. The spinning jenny, invented by James Hargreaves (c.1767), spun as many as 16 threads at once, the spindles all being driven by the same wheel. Richard Arkwright's water frame (1769), so called from being water-powered, had rollers and produced strong thread. Then Samuel Crompton produced a hybrid of the two – his mule – which had a movable carriage, and was the forerunner of the modern machine. The other modern spinning machine is the ring-spinning frame (1828) in which the strands, drawn out by rollers, are twisted by a "traveler" that revolves on a ring around the bobbin on which they are wound.
Weaving is making a fabric by interlacing two or more sets of threads. In "plain" weave, one set of threads – the warp – extends along the length of the fabric; the other set – the woof, or weft – is at right angles to the warp and passes alternately over and under it. Other common weaves include "twill," "satin," and "pile." In basic twill, woof threads, stepped one warp thread further on with each line, pass over two warp threads, under one, then over two again, producing diagonal ridges, or wales, as in denim, flannel, and gabardine. In satin weave, a development of twill, long "float" threads passing under four warp threads give the fabric its characteristically smooth appearance. Pile fabrics, such as corduroy and velvet, have extra warp or weft threads woven into a ground weave in a series of loops that are then cut to produce the pile. Weaving is usually accomplished by means of a hand- or power-operated machine of loom. Warp threads are stretched on a frame and passed through eyelets in vertical wires (heddles) supported on a frame (the harness). A space (the shed) between sets of warp threads is made by moving the heddles up or down, and a shuttle containing the woof thread is passed through the shed. A special comb (the reed) then pushes home the newly woven line.
Bleaching is the process of whitening materials by sunlight, ultraviolet radiation, or chemicals that reduce or oxidize dyes into a colorless form. Hydrogen peroxide is used to bleach wool, silk, and cotton; hypochlorites, including bleaching powder (see below), are used for cotton; and sodium chlorite for synthetic fibers. Sulfur dioxide bleaches are impermanent. Careful control of pH is essential.
Bleaching powder is a white powder consisting of calcium hypochlorite and basic calcium chloride, made by reacting calcium hydroxide with chlorine. It is used for bleaching and as a disinfectant, but in time loses its strength.
Calendering is a process used in the manufacture of textiles, rubber, some plastics, and especially high-grade quality paper. The substance concerned is passed between a series of pairs of heated rollers, which squeeze it to form a smooth textured sheet.