That Indigo is a vat dye is common knowledge. It must be reduced first
and dissolves only in alkaline solutions. For dyeing wool one needs slightly
elevated temperatures - the higher the pH of the dye vat the more active it is,
the higher is the amount of fibre damage. A master dyer has to balance these
two vectors which are opposed to each other.
Indigo is formed by oxidation of an easily water-soluble precursor, Indoxyl. If two molecules of Indoxyl combine by oxidizing a solution of Indoxyl compounds either
are formed (simplified, as quite some more compounds may occur). In
addition the presence of Indoxyl changes the behaviour of ready Indigo in the
vat to a big extent. From long researches with woad we came to the conclusion
that the way Indigo is deposited on and in the fiber is changed to a remarkable
degree if Indoxyl is applied together with other reducing auxilliaries that one
can obtain from woad. A visual impact like in the very early (pre-16th century)
pieces we could get only with Indoxyl compounds.
From this point of view we state here that according to what we have seen this particular blue in this kilim must have made using woad! Whether woad was used as a primary source of the dye, which is possible, or used as an auxilliary in vatting natural Indigo we do not know. Both is possible to obtain this visual impact. - Whatever: this blue differs from any blue hue that we have seen in any Anatolian kilim until today.
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