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.


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.


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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