Perfect Japanese denim. Part II – coloring and weaving in custom style
Coloring.
As you know denim is produced by interweaving colored and uncolored cotton threads, that
is why it is necessary to color the threads before manufacturing fabric. The most common
and traditional color of customized denim is indigo. On the spectrum indigo is situated
between bleu and purple. Until 19th century the color was extracted from plants – the
most popular plant is called indigofera – and sometimes even from mollusks. Indigo is the
oldest color familiar to humans, it was used in ancient Greece, Rome, Mesoamerica, Egypt, Iran
and its country of origin is most probably India. Modern Japan preserves its ancient traditions
of indigo coloring. During historical Edo period (17-19 centuries) the use of silk for manufacturing
clothes was prohibited and it was back than quite difficult to color cotton fabrics with anything except for
indigo. In 1865 German chemist Johann von Bauer synthesized indigo from nitrobenzaldehyde and acetone. BASF
Company started to produce new color in commercial volumes. It is now called pure indigo to distinguish from
natural indigo. The first one has a more regular color, while the latter one has various shades received from
different additives. Indigo can’t be dissolved in water; when the thread is taken from the dying bath the color
reacts with oxygen and becomes insoluble. People in different countries used weird substances to dissolve indigo.
In Europe it used to be dissolved with addled urine which was in 19th century replaced by synthetic urea or carbamide
and turned the color into a yellow-green substance oxidizing and becoming blue. In Japan the technology of warming the
color in special ceramic baths with the cultures of thermophilic anaerobic bacteria was used. These bacteria could
educe hydrogen dissolving indigo. In Britain arsenic trisulphide was used and in China the picture was applied on fabric
with undissolved color and then oxidized in ferric sulphate. Today most tailor made jeans are manufactured with the use
of pure indigo, and denim creations colored with natural indigo are very expensive.
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High quality denim is colored with the use of rope dyeing technology. The threads are then gathered and bound
into long ropes which are then manually or with the help of special machines submerged into dyeing baths and
afterwards taken out for oxidizing. This process is usually repeated 20-25 times. That is why denim gets as a
result rich beautiful indigo color which is changed during jeans wear. Ring spun yarn then remains white in the
middle. The richness and intensity of coloring as well as next following dyeing of indigo is influenced by preliminary
and finishing yarn treatment with sodium hydrate or sulphur.
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Weaving.
Denim fabric represents an interweaving of warp threads (colored) and weft threads (uncolored), seen on the back. The
term selvedge means bright-colored threads of warp interweaved with uncolored fabric edge to prevent its stripping-down.
In old vintage models of made to measure jeans selvedge creates special charm and individuality. Weave direction also
influences the look of ready denim cloth. Left-hand-twill gives a smoother fabric structure. However, right-hand-twill
is nowadays used in manufacture of 90% of all denim. There is also the so-called broken twill technique. The twill type
is easily distinguished when you look on the threads’ direction on the right side of denim.
The fabric is also characterized by its weight. Thread count and thickness of the yarn can result into the weight of 17,
19 or even 21 ounces onto a square meter. However, the most widely used denim has a weight of 9-12 ounces.
Posted: 08.01.2010 by Stella Tornton
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