No one knows for sure where cotton plants were first cultivated---scientists have found ancient cotton cloth in Mexico, Pakistan and Egypt. Until the Industrial Revolution, cotton was picked, processed and woven by hand. With the invention of the cotton gin in the late 18th century, cotton fibre production multiplied more than fifty times in the first ten years. Today, cotton generates more than £78 billion in total revenue for United States businesses.
Picked cotton must be turned into yarn before it can be woven into fabric. The cotton fibres, called lint, are sent to a textile mill's carding machine, which rearranges fibres into a weblike arrangement. This web is funnelled into a single strand of fibre and blended with several other strands for strength. Called a "sliver," this new rope of fibre is spun to make it smaller and tighter, forming yarn.
Cotton yarns are placed vertically on a mechanical weaving loom. The machine weaves horizontal rows of yarn across the vertical yarns, creating woven fabric. Different types of cotton fabric require different weaves; most use a basic over-and-under weave structure. Sturdier fabrics like denim use a tighter weave. Differently coloured skeins of yarn are used during the weaving process to create striped, gingham or checkered prints.
Cotton yarns can also be knit into fabric instead of woven. Machines create long rows of yarn loops knit together with perpendicular rows of more loops. The end result is similar to that of weaving---vertical and horizontal lines of loops are connected, forming a flat surface of fabric.
Once the fabric is woven or knitted, it is passed through an industrial version of an iron---metal plates that smooth wrinkles, disperse threads and remove lint. The fabric needs to be flat and smooth to absorb the dye or chemical treatment that follows. Once it's flat, the fabric is pretreated with hydrogen peroxide to remove any natural colour and make the dyeing process easier.
Dyeing and Printing
The smoothed fabric is dipped into a vat of single-colour dye and squeezed through padded rollers. If the fabric is scheduled to have a print, it then passes beneath a roller that's engraved with the print and implanted with dye. On such a roller, up to ten colours can be printed at once. Once all colour has been imparted, the fabric is then sent to an oven where the heat will sear the dye into place.
Special finishes can be applied to make the fabric water-resistant, shrink-resistant or flame-retardant. Some finishes are for appearance only, making the fabric matt or glossy. Machines apply the finishes with sprayers, brushes and rollers. Once any desired finishes have dried, the fabric is ready to be shipped to the user. Approximately 57 per cent of cotton fabric is used for clothing, with the remainder being used for home furnishings and industrial products such as tarps, book binding, zipper tape and medical supplies.