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Old June 18th, 2018, 08:58 AM   #1
Kay Dee
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Default Colour change from light exposure

Thought some folks might be interested to see the colour change from light exposure to some chemical dye colours in a Tibetan rug (made circa 1930).

Top image is bottom of rug, bottom image the pile side.


Last edited by Kay Dee; June 18th, 2018 at 07:25 PM.
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Old June 18th, 2018, 02:03 PM   #2
Danielle Duperreault
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Interesting! The colour changes in that Tibetan rug are really dramatic. It is very helpful to see actual before-and after comparisons.
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Old June 18th, 2018, 02:32 PM   #3
Rich Larkin
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Very interesting. Notwithstanding what I have learned from Pierre and others, I persist in making judgments-at-a-glance on the original circumstances of certain colors. Probably evidence of weak character. In any case, in regard to this rug, I would mark the mid-light blue indigo (possibly having gotten into the sulphonic blue process) and the lovely-looking variety of pink to the far right, very nice.
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Old June 18th, 2018, 06:30 PM   #4
Pierre Galafassi
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Hi Kay,

Interesting!
An irresistible provocation
All these shades could have been done either with natural or with synthetic dyes.
Let’s not forget that nearly all natural coloring substances have a very poor light fastness on wool, silk etc.. (the very few ones suitable for textile dyeing have been selected by our admirable ancestors over millenaries) and that this was also the case for many (but not all) synthetic dyes invented during the last quarter of the 19th century.

Do you know how long these samples have been exposed to light?

Assuming that it was a long time:

Red #1. Seems to feature a reasonable lightfastness. If the shade which I can see on my monitor is correct, it is more likely to be a synthetic dye than a natural one.

Green #2. My guess: Wool dyed with indigo and over-dyed with a yellow of medium light-fastness. Synthetic or natural. Part of the yellow has faded, the blue has not . The blue element could also have been a synthetic dye of the amino-anthraquinone family (introduced first during the early decades of the 20th century and featuring good- to outstanding lightfastness).

Pale blue #3. Could be either Saxon blue, as Rich guessed. A sulfonated indigo, first synthesized 3 centuries ago and featuring poor light-fastness, poor wet-fastness and poor build-up (The dye, not Rich!).
Or it could be a very early synthetic blue (Triaryl-methane Victoria blue?).
Such a very pale shade, correctly dyed with indigo, would not have faded as much as that IMHO.

Blue-black #4. The shade-shift from a neutral black to a bluish-black may suggest that the dyeing was made with Indigo, over-dyed with a bit of yellow and a bit of red, both of medium/poor light fastness. They could have been either natural or synthetic. Alternatively it could have been wool from a black- or grey sheep, dyed with indigo. It seems that these poor beasts did not get a light-fast coat.

Pink #5. A natural- or early synthetic red of medium-low light fastness. As there is still some trace of red left on the pile, it does not seem to be a very early Triphenyl-methane synthetic red (Which would have quickly turned beige and then white or a trace grey). It is rather a so-called ‘azo’ synthetic red.
If it is was a natural dye, it could have been a local variety of lichen/fungi red, similar to Orchil / Rocella or it could have been a variety of madder dyed on un-mordanted wool.

Just guessing but fun.
Pierre
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Old June 19th, 2018, 06:16 AM   #5
Kay Dee
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Quote:
Originally Posted by Pierre Galafassi View Post

Do you know how long these samples have been exposed to light?

Assuming that it was a long time:
First, thanks very much for you concise description of the various colours and what they could be, etc.

As to your question, the rug was made circa 1930's so it has been 'exposed' as it were for more or less for 80 / 90 years.

And again, THANKS for your input! ( = Pierre!)
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Old June 20th, 2018, 05:33 AM   #6
Kay Dee
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Default Another 'light exposure' colour change example

Note in the below Baotou rug circa 1900-1920, the rug's mauve / purple secondary border has turned to 'white' on the pile side, the only colour change in the rug. Still, a beautiful rug though IMO. (Unfortunately I do not have a photo of the complete rug pile side or I would post it. )

I'd be interested in Pierre's thoughts on this.

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Old June 20th, 2018, 12:46 PM   #7
Pierre Galafassi
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Hi Kay,

This shade was most probably dyed with one of these triphenyl-methan and triaryl-methan dyes ( called at the time ‘aniline’ dyes) which closely followed Perkin’s discovery of ‘mauveine’ (1).
If you are lucky it could even be mauveine, who knows. This would make your rug a genuine collector piece.

Fuchsine (Magenta) , Britannia violet, Malachite green or Victoria blue were some of the most famous members of this very early family of synthetic dyes. These dyes were characterized by a color-strength and by a brightness which the leading natural dyes were not able to match, nor could they compete with the dyeing cost of these newcomers.
These dyes did indeed jump-start the highly lucrative synthetic dyestuff industry, mainly in Germany, France, England and Switzerland, but destroyed the economy of many regions for which the production of natural dyes were vital.

These precursors were however also technically inferior in several ways to the traditional natural dyes. Their lightfastness, especially, was absolutely lousy. They were banned in Persia (if I remember well ca. 1900) and also in the Ottoman Empire. Not sure whether these bans were really respected though, given the weakness of the Qajar and Ottoman rulers, at the time

Soon the young industry discovered a very large number of other families of synthetic dyes, then often specifically developed for a given fiber and featuring much improved fastnesses and dyeing properties. They eliminated whatever was still left from the traditional production of natural dyes.

Most synthetic dyes created in this very early phase have disappeared from the market a long time ago, including mauveine and fuchsine, but a few of them are still manufactured: for example Victoria blue & Malachite green, because they found a market niche (dyeing of PAN fiber) in which they featured decent properties.


(1) Mauveine is not a triphenyl-methane dye, but its light-fastness properties are just as lousy. Funnily, a number of rug dealers call these very early dyes ‘analine dyes’. Quite fitting, I’d say.

Best regards
Pierre
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Old June 21st, 2018, 07:09 AM   #8
Kay Dee
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Thanks again Pierre!
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Old July 24th, 2018, 04:06 AM   #9
Jeff Sun
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Hi Kay-

It is my experience as well is that the Uber-Orange and Blinding Pink in Tibetan rugs often fade to more pleasing tones.
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Old August 7th, 2018, 10:08 AM   #10
Kay Dee
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Quote:
Originally Posted by Jeff Sun View Post
Hi Kay-

It is my experience as well is that the Uber-Orange and Blinding Pink in Tibetan rugs often fade to more pleasing tones.
Pardon delay in reply Jeff but have been away.

Be careful saying you find some 'faded' colors more pleasing, as I do at times, as your are stepping on dangerous ground there.

Last edited by Kay Dee; August 7th, 2018 at 01:14 PM.
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Old August 9th, 2018, 12:17 AM   #11
Lloyd Kannenberg
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Hi All,

Someone (I forget who) suggested that 18th century Chinese weavers must have been aware of the extreme light sensitivity of brazilwood dye, and therefore took its fading into account in designing their rugs. Who really knows? But I wouldn’t dismiss the idea out of hand.

Lloyd Kannenberg
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Old August 9th, 2018, 02:02 AM   #12
Jeff Sun
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Quote:
Originally Posted by Lloyd Kannenberg View Post
Hi All,

Someone (I forget who) suggested that 18th century Chinese weavers must have been aware of the extreme light sensitivity of brazilwood dye, and therefore took its fading into account in designing their rugs. Who really knows? But I wouldn’t dismiss the idea out of hand.

Lloyd Kannenberg
Maybe that was the case SOMETIMES. But I have seen clear cases where the weaver clearly wasn't thinking that far ahead.
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Old August 9th, 2018, 06:55 AM   #13
Kay Dee
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Quote:
Originally Posted by Jeff Sun View Post
Maybe that was the case SOMETIMES. But I have seen clear cases where the weaver clearly wasn't thinking that far ahead.
Jeff, while I tend to agree with you, I have collected upwards of a thousand (or more?) photos of Chinese and Tibetan rugs over the years, and sometimes ya just gotta wonder, as the the more muted colours of some of the 'faded aged' seem so much more pleasing (at times), repeat at times, than the garish beasts some obviously were when made.
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