All denim is created through generally the same process: • Cotton fiber is spun into yarn • The warp yarn is dyed, while the weft is left white (usually) • The yarns are woven on a
shuttle loom or
projectile loom • The woven product is
sanforized Yarn production Traditional denim yarn is composed entirely of
cotton. Once cotton fibers are cleaned and combed into long, cohesive lengths of similar-length fiber, they are
spun into
yarn using an industrial machine. Throughout the creation of denim, washes, dyes, or treatments are used to change the appearance of denim products. Some yarns may substitute an
elastane component such as
Spandex/Lycra for up to 3% of the cotton, the woven form of which (typically called 'stretch denim') may have a
elasticity of up to 15%.
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. Before 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. 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. Denim fabric dyeing is divided into two categories:
indigo dyeing (Indigo dye is a unique shade of blue) and
sulfur dyeing (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. Indigo dyeing behaved differently from many other textile dyeing methods. Unlike many other dyes that fully penetrate the fibers of the material, indigo primarily adheres to the outer surface of the cotton yarns. This is what gives denim its distinctive aging characteristics. This happens because indigo is soluble in water and must be chemically reduced before dyeing; it is then rapidly oxidized when exposed to air. This results in the dye not fully reaching the core of the yarn, creating a layered structure with the outer parts of the yarn being colored, but the interior parts remaining lighter. This surface-level dyeing produces what is commonly referred to as a ring-dyed structure of the denim. Over time, as the denim is worn, the fabric reveals the cotton's inner layers. This process leads to the characteristic fading patterns seen in denim, which can vary depending on the movement and stress points of the denim as it is worn and used. Particular areas that show the most fading are the knees, seams, and pockets. Along with this, the method in which the indigo dye is applied to the cotton affects the appearance of the denim. Rope dyeing and slasher dyeing are two of the most common industrial techniques that are used. Each of which influences the color and consistency, as well as the production efficiency. While both methods rely on repetitions of dipping and oxidation cycles, there are differences in how the yarn is handled during the process, in which subtle variations in shade and the fabric's character can develop.
Weaving Most denim made today is made on a
shuttleless loom that produces bolts of fabric or wider, but some denim is still woven on the traditional
shuttle loom, which typically produces a bolt wide. Shuttle-loom-woven denim is usually recognizable by its
selvedge (sometimes written '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. The weight of denim can vary greatly, with a yard of fabric weighing anywhere from , with being typical. ==Uses==