Denim

Most denim yarn is composed entirely of cotton. Some denim yarn may use an elastic component such as spandex for up to 3% of the content to allow the final woven product to stretch. Even such a small amount of spandex enables a stretching capacity of about 15%.

Denim was originally dyed with indigo dye extracted from plants, often from the genus Indigofera. In South Asia, indigo dye was extracted from the dried and fermented leaves of Indigofera tinctoria; this is the plant that is now known as "true indigo" or "natural indigo". In Europe, use of Isatis tinctoria, or woad, can be traced back to the 8th century BC, although it was eventually replaced by Indigofera tinctoria as the superior dye product. However, most denim today is dyed with synthetic indigo dye. In all cases, the yarn undergoes a repeated sequence of dipping and oxidation — the more dips, the stronger the color of the indigo.[10]

Prior to 1915, cotton yarns were dyed using a skein dyeing process, in which individual skeins of yarn were dipped into dye baths. Rope dyeing machines were developed in 1915, and slasher or sheet dyeing machines were developed in the 1970s; both of these methods involve a series of rollers that feed continuous yarns in and out of dye vats. In rope dyeing, continuous yarns are gathered together into long ropes or groups of yarns – after these bundles are dyed, they must be re-beamed for weaving. In sheet dyeing, parallel yarns are laid out as a sheet, in the same order in which they will be woven; because of this, uneven circulation of dye in the dye bath can lead to side-to-side color variations in the woven cloth. Rope dyeing eliminates this possibility, because color variations can be evenly distributed across the warp during beaming.[10][11]

Denim fabric dyeing is divided into two categories: indigo dyeing and sulfur dyeing. Indigo dyeing produces the traditional blue color or shades similar to it. Sulfur dyeing produces specialty black colors and other colors, such as red, pink, purple, grey, rust, mustard, and green.

Denim under a microscope.

Selvedge identifier visible in white at the interior of a pair of jeans

Most denim made today is made on a shuttleless loom[12] that produces bolts of fabric 60 inches or wider, but some denim is still woven on the traditional shuttle loom, which typically produces a bolt 30 inches wide. Shuttle-loom-woven denim is typically recognizable by its selvedge (or selvage), the edge of a fabric created as a continuous cross-yarn (the weft) reverses direction at the edge side of the shuttle loom. The selvedge is traditionally accentuated with warp threads of one or more contrasting colors, which can serve as an identifying mark.

Although quality denim can be made on either loom, selvedge denim has come to be associated with premium products since final production that showcases the selvedge requires greater care of assemblage.[13]

The thickness of denim can vary greatly, with a yard of fabric weighing anywhere from 9 to 32 oz,[14] with 11 to 14 oz being typical.[15]

Denim fibers from an old pair of jeans through a microscope

Natural fading on a worn pair of selvedge jeans. Sometimes referred to as 'whiskers' or 'honeycombs'

Over time dry denim will fade, considered fashionable in some circumstances. During the process of wear, fading will usually occur on those parts of the article that receive the most stress. On a pair of jeans, this includes the upper thighs, the ankles, and the areas behind the knees.[15]

To facilitate the natural distressing process, some wearers of dry denim will abstain from washing their jeans for more than six months.[16] Most dry denim is made with 100% cotton and comes from several different countries.

Patterns of fading in jeans caused by prolonged periods of wearing them without washing are a way of "personalizing" the garment.[17] Such patterns include:

• honeycombs – meshes of faded line-segments that form behind the knees[18]
• whiskers – faded streaks that form radially from the crotch area[18]
• stacks – irregular bands of fading above the ankle caused by according of the fabric due to contact with the foot or shoe[19][20]
• train tracks – fading along the out-seams due to abrasion[20]

AMC Gremlin with Levi's trim and upholstery

As jeans grew in popularity in the early 1970s, "one of the most creative carmakers of the era, AMC, took note."[21] Starting with the 1973 model year, American Motors (AMC) offered a regular production option consisting of a Levi's interior trim package.[22][23] American Motors had an objective of offering fashion interiors for its cars and the Levi's trim was "designed to appeal to young men and women who enjoy the casual look in clothes and cars.[24] Over the years it was available on the Gremlin, Hornet, and Pacer.

Although the car's jean material looks just like the real thing, AMC used spun nylon that was made to imitate denim. This was because real denim fabric is not tough enough for automobile use and cannot pass fire resistance safety standards.[25] The copper rivets were the actual versions and the seat design included traditional contrasting stitching with the Levi's tab on both the front seat backs. The option also included unique door panels with Levis trim and removable map pockets, as well as "Levi's" decal identification on the front fenders. The Levi's trim package option was $134.95, but only $49.95 extra if ordered together with the "Gremlin X" appearance option.[26] The Levi's interior upholstery was available through the 1978 model year AMC Gremlin.[27] It has become one of the best-known options on the Gremlins.[28]

A Levi's trim package was also available by AMC on most Jeeps, including the CJ series, the full-size Cherokee (SJ), and the J series pickup trucks from 1975 through 1977.[29] This consisted of denim-colored-and-textured vinyl upholstery and a matching canvas top.[30] This option was available on all CJ models in blue or tan, and was the standard trim on the top-level Renegade versions.[31] The Levi's association was removed in later years with the upholstery trim named "Denim vinyl" through 1980.[32]

Between 1973 and 1975 Volkswagen produced the Jeans Beetle, which had denim interior trim and special exterior graphics for sale in Europe.[33] This concept was repeated in some later models.[34]