Types of customized denim and the technologies which help it to create a worn look. Part II
Let’s continue our story about techniques that help customized jeans to create a worn look. The next stage we are
going to take a closer look on is bleaching. This procedure is unessential; it all depends on eventual type of
denim and the result we want to achieve as a ready product. Nowadays customers prefer to buy blue and dark blue
customized denim and bleaching is not practiced on it. However, there are still fans of classical light blue
denim, and this color can be hardly achieved without bleaching. Sometimes also potassium permanganate and hydrogen
peroxide are being used as well as glucose bleaching which is becoming very popular. However, the only way to
achieve a classical rich light-blue color or a so-called bleach color is to use the technology of sodium hypochlorite.
All other variants are far from perfection and besides are much more expensive.
However, the use of sodium hypochlorite brings numerous problems with it. Chloride is toxic and environmentally
detrimental, besides it destroys the structure of cotton fabrics. That is why bleaching is carried out in mild
conditions at a temperature of 50-55° C and special dosage is being chosen so that the reaction takes up 10-20
minutes. For classical denim cloth the concentration of sodium hypochlorite is 10% of the dry product weight. On
different factories different technologies of indigo dyeing and different dye mixtures are being used, that is
why after bleaching fabrics of different shades and color intensity are being achieved.
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Another disadvantage of sodium hypochlorite is its instability. That is why
jeans of different color can be found even in one batch. Besides, sodium hypochlorite
can also cause yellowish shade of made to measure jeans. However, indigo dyed fabrics
lose their color, bleach out and become yellow under the influence of light or because of
environmental pollution with nitrogen oxide and ozone. All these unfriendly factors make
indigo oxidize very quickly and irretrievably. However, all descendants of indigo dye are water
soluble; that is why one can get rid of the yellowish shade just by washing his or her jeans.
There are even special softeners to be found, which apart from their direct action also help to
protect denim fabrics from ozone influence. Another reason of jeans becoming yellow are chloride
rests on the surface of denim. Exposed to direct sun rays they can also cause yellow shade. Moreover,
in this case it is not that easy to get rid of, because the structure of fabric is destroyed irretrievably.
The best solution of the problem is the use of optical bleachers which create a bright light-blue color of
jeans and prevent them from getting a yellowish shade. This procedure can be carried out immediately before
softening.
Posted: 13.01.2010 by Stella Tornton
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