DENIM GLOSSARY: OKI-NI EXPLAINS IT ALL
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 have compiled this handy guide explaining the key terms and breaking down the jargon so that you can better understand your denim.
Read our handy guide to learn the difference between sanforized and un-sanforized denim, to discover the workings of the indigo dying process, and to explore the various washes and laundry processes that are used to produce today's fantastic array of denim.
Be sure to browse our DENIM CATEGORY to see some of the season's finest denim, brought together here on oki-ni.
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.
Sanforization is the process of pre-shrinking fabric that limits the post-wash fabric shrinkage to under 1%. The process includes the stretching and manipulation of the denim cloth before it is washed. Raw, un-sanforized jeans will shrink between 7 and 10% after the first wash, and continue to shrink slightly up to the third wash.
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, but Levi's jeans remained shrink-to-fit for another three decades until the 1960s.
DYING: A PAINFUL PROCESS
The complexities of the dying process exist because each permutation alters the shade, or cast, of the denim that they produce. Depending on the dye used and the method of dying, 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.
However, many processes often need to occur before dye meets yarn to either help the dye bind to the yarn, or to partly keep the two apart to increase fading. Pigment dyes, for example, are dyes that do not easily bond with yarn fibres and therefore need to be held to the fabric by resins. They are available in almost any colour and are used extensively in the denim industry by fabric dyers who want to create fabrics that fade more easily. Similarly, mercerization is an industrial process that can increase the yarn's ability to adsorb dye. However, with denim it keeps the dye on the surface of the fabric, preventing it from fully penetrating the fibres.
Denim is a yarn dyed fabric, meaning that the individual yarns are dyed before they are woven into fabric. The other method of dying, garment dying, is performed on finished garments. If the pocket linings and labels of a piece of
clothing are the same colour as the fabric, chances are it has been garment dyed.
The three main industrial yarn dying processes are:
Rope dying, is the most popular and colour-consistent method, where 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 oxidize (react with the air). A typical machine allows six to eight dips.
Slasher dyeing, separates the individual yarns, laying them parallel to one-another across a cylinder or beam, with each moving through the dye process individually.
Loop dying, is similar to rope dying, except that instead of six or eight baths there is only one, meaning that the whole process must be repeated if you want to increase the depth of colour of the finished denim.
Other, more niche, dying processes are available including: ring dying, which is unique to indigo dying, where only the outer ring of the fibres in the yarn are dyed, leaving the inner core white; and hank dying, where yarns are loosely arranged in bundles, or hanks, that are then hung over a rung and immersed in a dye bath. These hanks are repeatedly dipped and then left to oxidize between each dip, giving the yarns a natural irregularity or patina (tarnishing caused by oxidisation) and cast. Although laborious, this method produces the richest colour-penetration, while the yarns also retain a softer feel.
The dye used it also a key part of the process, some manufacturers apply a sulphur dye before the customary indigo dye, which is known as sulphur bottom dyeing, 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 overdying can change the main cast or it can be applied to specific areas to create ‘dirty denim’.
In the denim industry 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 that 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).
There are many complex laundry techniques, which we will cover here, and wash development has become big businesses for denim companies, with the leading laundries coming from the US, Japan, and Italy.
The most straightforward methods involve either stone or sand to create abrasion. Taking sand paper to the denim, either before or after dying, produces a softer fabric. Sandblasting is this process reproduced on an industrial scale, where sand is literally 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.
One of the better-known abrasion processes is stone washing. Here, 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. 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.
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. Similarly, 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:
Atari – 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 traicks), on the front and back of the knees, the upper thigh, along the hem, on belt loops, and along pocket seams.
Iro-ochi – a term referring to the fading of indigo dye in denim. The term specifically relates to fading in exposed areas and not across the entire garment.
Tate-ochi – a term referring to occurrences of ‘Iro-ochi’(areas of fading, see above) forming in vertical lines in vintage denim. As the thread width is not uniform in 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.