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-   -   Alizarin question...HELP! (http://www.turkotek.com/VB37/showthread.php?t=3352)

Paul Smith December 13th, 2014 08:31 AM

Alizarin question...HELP!
 
I've been in a discussion on a website devoted to the world of violins and luthiers and whatnot, and the topic came up asking about alizarin, a red dye which was first synthesized in 1868. They are using it as a component of violin varnish and were wondering about its light-fastness, etc. I cavalierly volunteered that along with all those evil aniline dyes, alizarin also must be fugitive to light and demonstrate all the bad behavior we despise in 19th-c. synthetic dyes. I posted images of the front and back of a piece of mine showing a potent raspberry shade on the back fading to a much more pleasing peach color on the front. I'll be honest--I assumed it was the same as aniline/azo, etc. dyes.

But I think I am completely wrong about this!
:nerd2:
As I did more research, I quickly realized that alizarin is the main "red" chemical component in madder root! It sure sounds like alizarin would behave as it does when it's in madder; that it is more similar to synthetic indigo, which it is my understanding is chemically identical to natural indigo.

So, hoping that someone might set me straight (Pierre?) on the pressing issue of my embarrassing ignorance in another forum, I also wondered how soon alizarin was adopted by rug weavers. Could this be a synthetic dye that was being used by weavers by 1880 or so and completely fooling us because it is essentially the same as madder?

Pierre Galafassi December 15th, 2014 03:09 PM

Hi Paul,

As your research has already shown, despite being one of the earliest synthetic dyes, Alizarin does not belong to any of those chemical families known for lousy light fastness on wool, like the so-called anilin dyes for example.


Alizarin is only one of about 20-30 natural red dyes belonging to a chemical family called the hydroxy-anthraquinones, which are found in various mixtures in just about all natural dyes of vegetal- and insect origin which our ancestors used to dye wool, silk and cotton, in red shades of decent fatnesses. (Besides, no, the hydroxy-anthraquinone family has no parenthood whatsoever with the chemistry of indigo. They are also applied by a completely different dyeing mechanism).

Together with pseudo-purpurin and purpurin, the alizarin molecule is the dominant hydroxy-anthraquinone in madder ( Rubia tinctoria)
It is only a secondary dye in the mix of hydroxy-anthraquinone red dyes which gives its coloring power to wild madder (Rubia peregrina) and exists only as a trace in Indian madder (Rubia cordifolia, Manjeet).
It is not found in the main red insect dyes (like the various cochineal origins or lac) in which other hydroxy-anthraquinones do the job.

When applied on alum-mordanted wool, a good light- and wet fastness is obtained with all these various mixes of hydroxy-anthraquinones.

Alizarin was the first natural hydroxy-anthraquinone molecule which was copied by 19th century chemists and the only one which was produced in very large quantities. It caused the quick disappearance of the cultures of madder and of Indian madder, all but eliminating the natural red dyes from industrial dyeing- and printing of cotton, wool and silk in Europe.
Only a few decades later, superior synthetic dyes appeared which cancelled synthetic alizarin as well from this industrial market.

Only a handful of scientists ever bothered to analyze the dye composition of a limited number of nineteenth century rugs , I can’t therefore tell whether synthetic alizarin took, or not, a large market share of the red shades in Asian carpet-making as well, during the second half of the nineteenth century. A few cases of red dyes containing pure alizarin (no significant traces of other hydroxy-anthraquinones) have been published so far, which probably indicate that some synthetic alizarine too found its way into Turkestan for example, but this does not tell us how much.

My wild guess is that this yurt-industry probably rather quickly adopted the first generation of bright, cheap and easy-to-apply tri-aryl-methan and azo synthetic dyes, which, as we well know, wreaked havoc with their very poor light- and/or wet fastness and triggered late but irate reactions from the authorities in Iran and Turkey. Before the end of the nineteen century, successive generations of better synthetic dyes appeared, specific for cotton or wool, which allowed to replace the lousy first generation and also achieved to push the natural red dyes into near oblivion.

Now, about the use of madder and alizarin in violin varnish:
I do believe that madder-root extracts were used to varnish violins already in the eighteenth century. I am ready to bet that the artisans used in fact an alum complex of the natural dye, a pigment which has a good inherent light fastness.
The same «alum complex» which a wool dyer creates inside the fibre when he applies a hot decoction of madder-root to an alum-mordanted wool yarn. There is no reason to believe that alizarin would not do the job well. Actually it is highly probable IMHO that violin makers have been trying it a long time ago. I would be surprised, though, to learn that modern pigments would not be technically superior. I suppose that Filiberto has a much better knowledge of these ancient pigments for painting and varnish, than I do.

P.S. It is important to remember that good light fastness on one substrate (wool for example) says nothing about the light fastness of the same dye on another substrate (cotton for example, or wood surface). The mechanism of light-degradation is complicated and influenced in positive or in negative, among many other things, by the chemical structure of the substrate.
Best regards
Pierre

Filiberto Boncompagni December 15th, 2014 04:51 PM

Alas, your supposition is wrong, Pierre. I had to reach for my old books on the chemistry of restoration. :rainy_day:
I found that natural Alizarin was the main component of the lacquer “Lacca di Robbia” (a.k.a. Madder Lake, Garanza, Rose Madder), it was used since ancient Egypt and, besides being quite stable, like all organic colorants was sensible to light.

“Alizarin Crimsom” was the name for the artificial variety used since the half of the 19th century and, yes, it had more stability and light fastness than the natural Madder Lake.
Regards,

Filiberto

Lloyd Kannenberg December 15th, 2014 06:35 PM

Hello Paul, Pierre and Filiberto,

In the movie "The Red Violin" the color was supplied by the blood of the (deceased) wife of the violin maker. I do not know if there is any relation between the chemistry of hemoglobin and that of madder, but isn't venal blood supposed to be a darker red than arterial blood? Perhaps some experiments are in order.

Season's greetings!

Lloyd Kannenberg

Paul Smith December 15th, 2014 06:40 PM

Thank you!
 
I knew I could count on the generosity of the Turkotek team to shine a light on my struggle. Thank you for your responses. I have returned to the other forum to confess my ignorance. Balance is again restored to the universe.

Yes, it's true that natural madder pigments were an old source for red tones in violin varnish, I think going back into the 17th century. Interesting that alum plays a role in both the pigment and the dye. From what a few of the luthiers have said, the method of preparing the pigment with the proper use of alum is crucial in making it lightfast. It is also interesting to find out that synthetic alazarin did at least to some degree make it into Central Asia, because I am pretty sure that I would be fooled by this color visually if I saw it. I probably am already fooled by something hanging on a wall here.

Paul Smith December 15th, 2014 06:59 PM

The Red Violin
 
My luthier friends were pretty amused about several features of "The Red Violin." Apparently blood added to varnish would make it brown, not red, and it would destroy the transparency of the varnish. The other parts they liked were the scenes in the lab with all the cool technical gear and everyone wearing white coats and looking very scientific. I have been told in no uncertain terms that there is no such laboratory, and that no one in the trade would ever dress like that. And it has also been impressed on me that serious experts could not possibly be fooled by such a ruse. Personally, I loved the film, and thought it was cool that they showed how the violin was modernized through the years, though the one flaw in that was that when the violin was dug up by the Roma folks, it was in its original "baroque" condition, but then when they handed it over to the English Paganini-esque fellow (Frederic Pope), the neck had been grafted and the instrument was in its modernized form. Nah, the Roma wouldn't have done that--it would have come to Pope in baroque form and he would have had it altered.

Filiberto Boncompagni December 15th, 2014 08:01 PM

Hi Paul,
Yeah, I liked the movie too but I was never convinced by the blood-in-the-varnish part, for the reasons you quoted. Glad to hear I wasn’t alone.
Regards,
Filiberto

Steve Price December 15th, 2014 08:12 PM

Hi Lloyd

Hemoglobin and alizarin have nothing in common except being red.

The color difference between arterial and venous blood is due to hemoglobin having different colors when it's carrying oxygen (arterial blood) and after it's unloaded oxygen (venous blood).

Regards

Steve Price

Rich Larkin December 15th, 2014 10:28 PM

Don't mind me, folks. I'm just feeling a little faint.

:vomit:

Pierre Galafassi December 18th, 2014 08:01 AM

Quote:

Originally Posted by Paul Smith (Post 18888)
My luthier friends were pretty amused about several features of "The Red Violin." Apparently blood added to varnish would make it brown, not red, and it would destroy the transparency of the varnish..



Hi Paul,

Your luthier friends are right: the mix of blood and madder/alizarin would turn the violin lacquer brown, or even black after a while.
For at least two reasons, one being the fact that hemoglobin is an iron complex of less than perfect stability. Thus, some iron will eventually shift allegiance and form a more stable brown-black metal-complex with the hydroxy-anthraquinones of madder.

As Steve indicated, hemoglobin and alizarin do not belong to the same chemical families.

Hemoglobine is, structurally speaking, related to another natural pigment, of vital importance too, the green chlorophyll magnesium-complex.
Another interesting cousin of hemoglobin is a group of stable modern synthetic dyes (and pigments) called phtalocyanines: Copper- or nickel complexes which color wool and cotton in beautiful bright turquoise- or green shades. (These synthetic dyes are from time to time utilized in modern Persian rugs, IMHO a not-so-bright idea:thumbsdown:).

Best
Pierre


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