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Difficulties in Discerning the Difference between Natural and
Synthetic Dyes
From dye expert Pierre Galafassi 's posts on Turkotek,
February 3 and 4, 2012.
For the full discussion, go to
http://www.turkotek.com/VB37/showthread.php?t=1203
A) All shades feasible with natural dyes can be matched
perfectly with recipes based on synthetic dyes (even old ones,
say even older than 1920)
B) Making decision on whether a shade is dyed with synthetical or
natural dyes on a mere picture requires a lot of faith in fairy
tales. There are only a few exceptions like an infamous orange, a
teeth-grinding poison green, a fluorescent pink etc.. which appear
now and then on carpets and which are obvious and criminal synthetical dyes.
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There is indeed no doubt... that some of the early synthetic dyes,
in particular the so-called «aniline dyes» (triphenyl-methan dyes )
are easy to identify even in pictures, because of their absolutely
lousy light-fastness, far worse than any natural dye traditionally
used for rugs.
It is also true that other early synthetic dyes, mainly some red and
magenta so-called «acid" dyes, are notorious for their poor wet
fastness (bleed), worse again than traditional natural red rug dyes
(Correctly applied madder, lac and cochineal reds do not run under
the wet conditions to which rugs are supposed to be exposed,
including cold washing).
These lousy synthetic dyes appeared on the market during
the second half of the nineteenth century (ca.1860 onwards) and were
gradually replaced by better dyes even before the end of that
century. First, by better «acid» dyes, then from 1920 onwards by
so-called «migrating 1/1 chrome complex-» dyes, which rapidly
achieved over 90% of the market for rug dyes. Both the wet-fastness
and the light-fastness of this later generation of carpet dyes are
good, at least as good as the best natural dyes and mostly superior.
These 1/1 chrome dyes are not significantly brighter than the usual
natural carpet dyes and shrieking shades cannot be produced with
them even by mistake.
Several carpet-producing regions actually banned by law, with severe
penalties, the most disastrous early synthetic dyes.
Now, sure, a handful of these lousy «anilin» ancestors are still
produced (for other uses) and one can still buy them, not only on
markets in Pakistan or India, but also in Europe or USA. I still
fondly remember an epochal joke using 100 g of the «anilin dye»
called Victoria Blue when I was a (mischievous») kid. (This was long
ago of course, but still well into the twentieth century).
It is true too that modern «acid dyes» for polyamide (suitable
for wool) do feature, in part, very bright shades. However, their lightfastness is now comparable and mostly better than the one of
natural dyes (thus no fade) and their wet fastness is superior to
the ancestor’s (hardly any risk of bleed).
These modern «acid» dyes are not supposed to be used for carpet
wool, but they probably are nevertheless used, for various possible
reasons like greed (they are cheaper than 1/1 Cr complex), the
weaver’s taste for shrieking shades, ignorance etc..
Even with such modern bright "acid" dyes, well chosen and
used in «trichromy» by a competent dyer (I assure you, for having
worked with them during 35 years, that most are competent), one can
match perfectly all shades obtained with natural dyes. In that case,
no experienced eye, only HPLC or TLC will give up the fraud. As many
experienced rug purchasers and dealers know, the little
ahem...forgery...is even sometimes perfected by the weaver by an
addition of cheap spent fibers of natural dyes to the dye-bath. Some
fibers remain attached to the wool and are supposed to prove a
dyeing with natural dyes.
When the proper technical analysis is done, even among persons
with an experienced eye, there are more than a few surprises. One
of the causes of «surprises», as often mentioned... is that one
takes as a fact that when a dye fades or bleeds on a rug it is,
without any possible doubt, a synthetic dye. Unfortunately this
«fact» is wrong:
- Some (few) recipes with natural dyes can bleed and some others can
fade (just give a look at some «polonaise» Safavid rugs).
- The synthetic dyes most used since the early twentieth century by
industrial dye-houses and serious artisans neither bleed nor fade.
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For an exhaustive
discussion of rug dyes, see Pierre Galafassi's Turkotek Salon, WOOL
DYEING HISTORY, WITH FOCUS ON DYEING OF RUGS. Be sure to
read the discussion threads that follow the essay.
http://www.turkotek.com/salon_00129/salon.html
For a detailed discussion of red carpet dyes, see the Turkotek
Salon discussion conducted by Pierre Galafassi on THE QUEST FOR THE
BRIGHT SALOR RED. Color samples displaying the differences between
madder and cochineal reds are included. Go to:
http://www.turkotek.com/mini_salon_00026/salon.html. A
discussion follows the essay.
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