Editing Denim (section)

===Dyeing===
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, the 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.<ref name="Bojer">{{cite web |last1=Bojer |first1=Thomas Stege |title=How Denim Is Made: Indigo Dyeing |url=https://www.denimhunters.com/how-denim-is-made-indigo-dyeing/ |work=Denimhunters |access-date=2 September 2019 |date=16 December 2016 |archive-date=3 September 2019 |archive-url=https://web.archive.org/web/20190903003208/https://www.denimhunters.com/how-denim-is-made-indigo-dyeing/ |url-status=dead }}</ref>

Before 1915, cotton yarns were dyed using a skein dyeing process, in which individual [[hank (textile)|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. 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 dye circulation in the 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.<ref name="Bojer"/><ref>{{cite news |last1=Mercer |first1=Harry |title=Rope Dyeing Vs Slasher (Sheet) Dyeing |url= https://www.denimsandjeans.com/denim/manufacturing-process/rope-dyeing-vs-slasher-sheet-dyeing/3117 |archive-url= https://web.archive.org/web/20161012171205/https://www.denimsandjeans.com/denim/manufacturing-process/rope-dyeing-vs-slasher-sheet-dyeing/3117 |url-status=dead |archive-date=12 October 2016 |access-date=2 September 2019 |work=Denims and Jeans |date=19 May 2011 |via=Archive.org}}</ref>

Denim fabric dyeing is divided into two categories: [[indigo dye]]ing (Indigo dye is a unique shade of blue) and [[sulfur dye]]ing (Sulfur dye is a synthetic organic dye and it is formed by sulphurisation of organic intermediates, this contains nitro or amino groups). Indigo dyeing produces the traditional blue color or shades similar to it. Sulfur dyeing produces specialty black and other colors, such as red, pink, purple, grey, rust, mustard, and green.