|Traditional material||Cotton fiber|
Denim is an American shortened form of the French name Serge de Nîmes (" fabric from Nîmes"), which describes a robust cotton / hemp fiber material that was invented in Nimes and used there for the first time for clothing. World famous denim was its use for American jeans by Levi Strauss .
Denim is woven in a twill weave. Traditionally, a warp twill is used for denim in which only the warp thread is dyed with indigo , but the weft threads are undyed. In the past, ring spun yarns were mainly used, but due to the higher production speed, they were temporarily replaced by open-end yarns until, in the 1990s, ring yarns, due to their typical structure, played a major role in the fashionable aspect of modern jeans (cross-hedge optics) and replaced the open-end yarns again. Before weaving , the warp threads are given a color, which means that the yarn is only colored from the surface, but not completely. The threads are dyed either in a rope (rope) or fanned out next to each other (slasher). In doing so, they pass through the dyebath with the reduced soluble vat dye several times, only to be brought into contact with oxygen again and again in the air. Usually this happens five to seven times. The more frequently this process takes place, the deeper the blue coloration. However, the yarn is never completely dyed through, which is why jeans can be washed out so well and lightened by rubbing ( stone wash ).
After long periods of storage, denim articles often show yellowish spots that are lighter than the rest of the garment after washing. This is due to the degradation reaction of indigo to isatin by ozone , nitrous gases or UV radiation .