Littlefox, Re: Indigo

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Posted by Nick on August 8, 2002 at 15:17:51:

I did some searching, and found some very interesting information on
the indigo dye process at a molecular level. Here's what i've got:

"The indigo molecule is not very water soluble, nor is it drawn
toward the cellulose fibers in cotton thread. It can, however, easily
gain electrons from a reducing agent to produce the soluble leuco-
base form (see figure), which, because of its molecular shape and
polarity, is drawn toward the cellulose strands. The problem is, the
leuco-base form is yellow, not blue. Furthermore, because the leuco-
base is water soluble, it would readily wash out. So this leuco-base
form, once attracted to the cotton fibers, must give electrons back
to form the insoluble, blue indigo form. This is usually accomplished
by exposing the treated cotton to oxygen in air and to some source of
heat or strong light. But, if the leuco-base is converted back to the
indigo, which has very little attraction for the cotton fibers, then
what keeps your blue jeans blue? The answer lies in the fact that,
once oxidized back into indigo, the bulky molecules are essentially
trapped inside the three-dimensional polymer network of the cotton
and have little chance for escape."

I'm not sure if that would work on skin, becuase the molecules are
quite large and unlikely to penetrate in the first place, but it
gives some insight. Also, skin is not a cellulose, rather, a keratin.
But i know that there are ways of dyeing silk (also a keratin fibre)
with indigo as well.

The picture above illustrates the paragraph... I'm going to give
somebody a ring to find out what exactly the terps are doing to the
hennotannic acid molecules, and maybe we can replicate it with the


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