As a textile, cotton is popular for its versatility, comfort and reusable qualities. Companies manufacture the material using variations of the same technologies that have been implemented in production for years, such as spinning and weaving. In its natural state, cotton contains a variety of impurities that must be eliminated before the material can be processed. Generally these purification methods include bleaching and ginning, techniques that are commonly categorized as part of the preparatory process.
The Pre-treatment/Preparatory Process
The Ginning Method
Due to oils, plant seeds, insects, and a variety of other contaminants, it is essential that cotton is treated, and this is typically done by the ginning process. The traditional ginning method involved the removal of impurities using hand and foot devices. The current method involves a series of dryers, where moisture reduction takes place, and gin stands, which are used to extract contaminants with circular blades, and by separating raw fibers away from impurities via the spaced ribs of the machinery.
The Bleaching Method
Bleaching brightens cotton from its natural off-white color and also removes additional impurities from the material. The process generally involves a peroxide treatment, such as alkaline hydrogen peroxide. In recent years, researchers have developed specific enzymes that are used to help breakdown the bleach/waste water, which could pose as a toxic threat. Because the water used for bleaching may originate from various different sources, manufacturers must monitor and ensure that the water itself does not further contaminate the cotton that is processed during the bleaching cycle. For instance, water with excess salt can leave spots and must be pre-processed before it can be implemented in the treatment cycle.
Cotton Manufacturing Processes
Cotton Spinning
Originally, cotton spinning was processed with the aid of a spindle, bobbin or spinning wheel. The process is essentially the twisting of the fibers to create a yarn, which is usually completed before the weaving process can take place. One process generally associated with spinning includes cotton ring spinning. This technique is used to tighten and twist the yarn to the appropriate count so that it may be further processed. The traditional form of ring spinning involves using a frame and a spinning bobbin, which rotates at high speeds.
According to manufacturers, open end spinning has gradually begun to replace the traditional ring spinning in recent years as the former process does not require a bobbin and is capable of processing thicker yarns. Additionally, some cotton processers have implemented the use of the air vortex spinning process, a method that uses compressed air currents and is fast in production time.
Cotton Weaving
The traditional cotton weaving process required a manually operated loom. Today, there are multiple variations of loom technologies, including plain weave and twill weave. Plain weaving generally produces durable thick fabrics that are often used in upholstery furnishings whereas twill weaving produces a ribbed aesthetic, and is commonly associated with denim jeans. Essentially, the weaving process involves entwining the warp, the fabric that runs vertically across the loom, with the weft, which runs horizontally. Both large looms and circular machines are employed to create woven fabrics for artisan and industrial products. Before cotton can be processed through the weave loom, it is treated to prevent the warp yarns from ripping. Treatment of the yarn includes coating the fabric with a starch paste, which varies according to the thread, as natural cotton and synthetic blends react differently.