The material denim is a sturdy cotton warp-faced textile which differs from other textiles by having the weft pass under two or more warp threads. This particular weaving leaves the material with a diagonal ribbing that makes it distinct from cotton duck. The predecessor to denim, dungaree, has been produced in India for hundreds of years, with the most significant difference being that only the warp threads were pre-dyed. In denim, a dye can be applied to any of the threads before, during, or after production.
The most popular denim colour is indigo, created by dying the warp thread and leaving the weft thread white; this is what causes blue jeans to appear whiter on the inside than the outside. Different colours have come in and out of fashion over the years, although not all colours seem to work as well with the fading effect which denim gives, leaving various shades of blue as the most popular colour.
Almost all denim goes through the same creation process; cotton is harvested, typically by machine in the modern day. A cotton gin separates the cotton fibres from the seeds. The fibres are spun into yarn, some of which is dyed before it is put into a loom to be woven into a single piece. Once the entire piece of denim has been made, it will typically be sold to clothing manufacturers in bulk. Many denim manufactures use their own particular indigo colouring, considered by the companies themselves to be a trade secret, ensuring their brand has a unique look.