Denim can be confusing stuff. Over the 130-year lifespan of the humble jean there have been countless methods of producing denim, each with their own intricacies and quirks. That's why we've compiled this handy guide, explaining the key terms and breaking down the jargon so that you can better understand your denim.
Discover the difference between sanforized and un-sanforized denim, understand the workings of the indigo dyeing process, and explore the various washes and laundry processes that are used to produce today's range of denim.
Honey, I Shrunk The Jeans
The first and most important thing that you need to know with jeans is if they are sanforized or un-sanforized.
Sanforized Denim which has undergone a pre-shrinking process that limits post-wash fabric shrinkage to under 1%. This includes the stretching and manipulation of the denim cloth before it is washed.
Developed in the late 1920s by the American chemist Sanford Cluett and patented by Sanforize Co. in 1928, the process was reportedly first used by Erwin Mills in 1936 to make denim for overalls marketed under JC Penney's Big Mac label. Lee jeans were made from Sanforized fabric soon afterwards.
Un-sanforized Raw, un-sanforized jeans will shrink between 7 and 10% after the first wash, and continue to shrink slightly up to the third wash. All Levi's jeans remained shrink-to-fit until the 1960s.
Depending on the dye used and the method of dyeing, denim can have a black, brown, grey, green, red, or yellow cast to it. However, many processes often need to occur before dye meets yarn, either to help the two bind, or to keep them apart to increase fading. Below are some of the most common terms you might come across.
Denim is a yarn dyed fabric, meaning that the individual yarns are dyed before they are woven into fabric.
The other method of dyeing, garment dyeing, is performed on finished garments. If the pocket linings and labels of a piece of clothing are the same colour as the fabric, it's probably garment dyed.
Pigment dyes don't bond easily with yarn, so need to be held to the fabric by resin. Available in almost any colour, they're used in the denim industry by dyers who want to create fabrics that fade more easily.
This is the most popular and colour-consistent dyeing method. A group of un-dyed yarns are twisted together and dyed as a single unit, called a rope. The rope runs through a long machine where the yarn is dipped into the indigo and pulled out to oxidise (react with the air). A typical machine allows six to eight dips.
Similar to rope dyeing, but in loop dyeing there is only one bath instead of six to eight, meaning that the whole process must be repeated if you want to increase the denim's depth of colour once finished.
This separates the individual yarns, laying them parallel to one-another across a cylinder or beam, with each moving through the dye process individually.
Ring dyeing is a more niche method which is unique to indigo dyes. Only the outer ring of the fibre is dyed, leaving the inner core white.
Yarns are loosely arranged in bundles (hanks) which are hung over a rung and immersed in a dye bath. These hanks are repeatedly dipped and left to oxidise between each dip, giving the yarns a natural irregularity (or patina). Although laborious, this method produces the richest colour-penetration, while the yarns also retain a softer feel.
Sulphur Bottom Dyeing
Some manufacturers apply a sulphur dye before the customary indigo dye to create a grey or yellow vintage-look cast.
At the other end of the scale, colour can be applied to the fabric after the indigo dye. This process of overdyeing can change the main cast or it can be applied to specific areas to create ‘dirty denim’.
An industrial process that can increase the yarn's ability to absorb dye. However, with denim it keeps the dye on the surface of the fabric, preventing it from fully penetrating the fibres.
Tarnishing of the yarn caused by oxidisation.
A laundry is a manufacturing company that takes unwashed jeans and processes them in order to change the cast and hand (feel) of the denim, but also to re-create the naturally occurring wear patterns which occur wherever the denim is creased or rubbed. Typically, these natural wear patterns occur on the thigh and crotch (called whiskers), on the ankles (stacks), and on the back of the knees (honeycombs).
Using sandpaper on the denim (before or after dyeing) produces a softer fabric. Sandblasting is this process reproduced on an industrial scale, where sand is fired at high pressure onto the fabric. A slightly more high-tech version of this is micro-sanding, where fabric is pulled over a series of abrasive or chemically-coated rollers, which creates a soft, sueded hand to the fabric.
Stonewashing One of the better-known abrasion processes is stone washing. A 20-yard roll of fabric is put into a 250-pound washing machine along with pumice stones. The fabric and stones are then rotated – the longer the rotation the lighter in colour the denim becomes. The denim is then rinsed, softened, and tumble dried.
Enzyme Wash A more efficient and less damaging laundry technique is the enzyme wash. Here, naturally occurring enzymes are used to eat away at the cellulose in cotton, which also removes the indigo of the dye. Enzyme washes cause the fabric less trauma and produces stronger fabric that lasts longer.
River washing Combinations of both enzyme and stone washing produce the most drastic results. River washing introduces pumice stones first and then enzymes, in a two-stage process, to produce a dramatic vintage-effect.
Acid wash The iconic acid wash is created by soaking the porous pumice stones in chlorine and then stone washing as normal. The result is a heavily contrasted finish with unique patterns.
Lost in Translation
Denim, like so many things, is big in Japan, and there are a number of specialist Japanese terms for denim characteristics that simply do not translate. Here are some of the main ones.
A term describing the selective fading of the ridges and creases on a pair of jeans. The most common areas for Atari are along the side seams (called train tracks), on the front and back of the knees, the upper thigh, along the hem, on belt loops, and along pocket seams.
A term referring to the fading of indigo dye in denim. It specifically relates to fading in exposed areas, and not across the entire garment.
A term referring to occurrences of ‘Iro-ochi’ which form in vertical lines on vintage denim. As the thread width is not uniform with vintage denim, the colour tends to fade the most where the thread is the thickest. This creates a white, or severely faded, line of up to several centimetres along a single vertical indigo thread.