Denim is a rugged cotton twill textile, in which the weft passes under two (twi- "double") or more warp fibers. This produces the familiar diagonal ribbing identifiable on the reverse of the fabric, which distinguishes denim from cotton duck. Denim has been in American usage since the late eighteenth century. The word comes from the name of a sturdy fabric called serge, originally made in Nîmes, France, by the Andre family. Originally called serge de Nîmes, the name was soon shortened to denim. Denim was traditionally colored blue with indigo dye to make blue "jeans," though "jean" then denoted a different, lighter cotton textile; the contemporary use of jean comes from the French word for Genoa, Italy (Gênes), where the first denim trousers were made.
A similarly woven traditional American cotton textile is the diagonal warp-striped hickory cloth that was once associated with railroadmen's overalls, in which blue or black contrasting with undyed white threads form the woven pattern. Hickory cloth was characterized as being as rugged as hickory wood—not to mention the fact that it was deemed to be worn mainly by "hicks"—although neither may be the origin of that term [from a nickname for "Richard"]. Records of a group of New Yorkers headed for the California gold fields in 1849 show that they took along four "hickory shirts" apiece. Hickory cloth would later furnish the material for some "fatigue" pantaloons and shirts in the American Civil War.
The word dungarees, to identify heavy cotton pants such as overalls, can be traced to a thick cotton country-made cloth, Dongari Kapar, which was sold in the quarter contiguous to the Dongari Killa, the fort of what was then known as Bombay (Hobson Johnson Dictionary). The word entered English with just this meaning in 1696 (OED). Dongri Fort was rebuilt in 1769 as Fort George, Bombay, where the first cotton mill was established in 1854. Dyed in indigo, the traditional cloth was used by Portuguese sailors and cut wide so that the legs could be swiftly rolled up when necessary. Thus, dungarees have a separate history.
Dry or raw denim, as opposed to washed denim, is a denim fabric that is not washed after being dyed during its production. Over time, denim will generally fade, which is often considered desirable.
Most denim is washed after being crafted into an article of clothing in order to make it softer and to eliminate any shrinkage which could cause an item to not fit after the owner washes it. In addition to being washed, non-dry denim is sometimes artificially "distressed" to achieve a worn-in look.
Much of the appeal of dry denim lies in the fact that with time the fabric will fade in a manner similar to factory distressed denim. With dry denim, however, such fading is affected by the body of the person who wears the jeans and the activities of their daily life. This creates what many enthusiasts feel to be a more natural, unique look than pre-distressed denim.
To facilitate the natural distressing process, some wearers of dry denim will often abstain from washing their jeans for more than six months, though it is not a necessity for fading. Often, enthusiasts will just hang their unwashed denim to help get rid of the smell.
Selvage denim (also called selvedge denim) is a type of denim which forms a clean natural edge that does not unravel. It is commonly presented in the unwashed or raw state. Typically, the selvage edges will be located along the out-seam of the pants, making it visible when cuffs are worn. Although selvage denim is not completely synonymous with unwashed denim, the presence of selvage typically implies that the denim used is a higher quality.
The word "selvage" comes from the phrase "self-edge", the natural edge of a roll of fabric. In this case, denim made on old-style shuttle looms. These looms weave fabric with one continuous cross thread (the weft) that is passed back and forth all the way down the length of the bolt. As the weft loops back into the edge of the denim it creates this “self-edge” or Selvage. Selvage is desirable because the edge can’t fray like lower grade denims that have separate wefts which leave an open edge that must be stitched. Shuttle looming is a more time-consuming weaving process that produces denim of a tighter weave resulting in a heavier weight fabric that lasts.
Shuttle looms weave a more narrow piece of fabric, and thus a longer piece of fabric is required to make a pair of jeans (approximately 3 yards). To maximize yield, traditional jean makers use the fabric all the way to the selvage edge. When the cuff is turned up the two selvage edges, where the denim is sewn together, can be seen. The selvage edge is usually stitched with colored thread: green, white, brown, yellow, and red (red is the most common). Fabric mills used these colors to differentiate between fabrics.
Most selvage jeans today are dyed with synthetic indigo, but natural indigo dye is available in smaller niche denim labels. Loop dying machines feed a rope of cotton yarn through vats of indigo dye and then back out. The dye is allowed to oxidize before the next dip. Multiple dips create a deep dark indigo blue.
In response to increased demand for jeans in the 1950's, American denim manufacturers replaced the old shuttle style looms with modern projectile looms. The new looms produced fabric faster and wider (60-inches or wider), yet lighter and less durable. Synthetic dyeing techniques along with post-dye treatments were introduced to control shrink and twist.
Bonded Logic UltraTouch is a home insulation, to replace fiberglass, made from the remnants of fabric used in making blue jeans.