I don’t know. But how are those beautiful colours in old carpets or Egyptian Coptic textiles like the one in the image above still holding their brightness?

Or even earlier, this rug, now in the Hermitage which dates to 400BC?

In my search for sustainable natural dyeing I came across the fermentation method as practiced by Manfred Bierber. The carpet pictured above also seems to have been made using the same technique. I don’t know if the same goes for ancient Egyptian textiles.

Usually, dyeing with madder involves heating madder with water and mordanted wool. What if the heating part could be bypassed? That would save energy. Maybe too it would give a deep, long-lasting dye. I tried ‘solar dyeing’ in the distant past. That worked but took several months and didn’t achieve strong colours.

Manfred Bierber’s Facebook site has some really remarkable results, mainly using madder which involve fermenting wool and then adding dye (https://www.facebook.com/share/qfkY39VNnXKFRgse/). I am really impressed with the results he gets: deep, deep reds and beautiful purples. Unfortunately, I couldn’t find really detailed methods of what he does now but he does guide people to this site: https://www.exoriente.de/ My German is abysmal, I am ashamed to say. This article by Manfred particularly useful: Bieber, M. Das Kavacık-Projek. In Anatolische Dorfteppiche (eds. Plötz, R.) 37‒55 (Niederrheinisches Museum für Volkskunde und Kulturgeschichte, 1988). I managed to get a copy through interlibrary loan. What I could glean (I hope I’ve got it right), is that his method is based on studies of Anatolian carpets.

Studies showed that the makers of these carpets were able to get deep, lasting colours through fermentation. There is more information in this book, which I managed to get hold of. It wasn’t cheap!

Various observations of carpet makers in the early 20th century showed that fermentation was carried out by mixing sourdough starter with wheat bran and then adding wool and madder. The wool was left in the fermenting mix for at least 10 days. It seems that the acid produced by fermentation destroyed the fats in the wool cuticles making it easier for the dye to be absorbed deeper into the wool fibres.

Studies of carpets dyed using the fermentation method are also discussed in the 2017 paper by Meyer et al. Both ancient wool and modern samples were examined.

To get a purple, an iron sulphate mordant is used post-dyeing with the madder (though the 2017 paper suggests that the mordant is added during the madder dyeing process as the mordant has completely penetrated the wool fibres). Wood ash is used as a modifier post-dyeing. The iron sulphate changes the madder dye to a blackish hue, but the wood ash changes this to a purple. I have tried searching for more information on the purple with madder. There is something called ‘Amish purple’ which also uses iron sulphate.

I was also able to find some useful information by Suzanne Deckel. She also suggests that the fermentation process produces heat which aids dye take-up.

I’m also the ex-curator of the Egypt Centre museum of Egyptian antiquities in Swansea, so naturally looked at studies of ancient Egyptian textiles. The 1st Millennium CE textiles have beautiful decorations in dyed wool. One such is Harvard Museum 1975.41.28 which dates from the 5th to 6th centuries CE. While it has been shown that purple in ancient Egyptian textiles was often produced through a mixture of indigo/woad and madder, analysis of this item showed at least some of the purple areas to be dyed with madder only (https://harvardartmuseums.org/article/unraveling-the-production-secrets-of-an-egyptian-textile) . I haven’t been able to find out if any of the ancient Egyptian textiles show evidence of fermentation or not.

But first, just to get the deep red without heating the brew. I thought I would experiment. I took 7000ml tap water, 200 grams wheat bran, 200ml sourdough starter, 20 grams aluminium sulphate . All was put in stainless steel container. The room temperature fluctuated between 16.5 and 17.5 degrees. There were lots of bubbles at first. The wool (c.20 grams) was added on day 3. By day 10, the bubbles significantly reduced. 1tbs of fresh sourdough added plus 3 tbsp of not very fresh ground madder. The container was put outside in the sun to warm up and bubbling resumed. When bubbling slowed again I added 20 grams of wheat bran to the mix. The wool took the colour though not strongly. This could be as the madder is a year or so old. I left it in the brew for 20 days but it seemed to stop taking up colour so I removed it.

Well I wasn’t terribly successful:

Trying to cold mordant this with iron sulphate didn’t work at all! But I didn’t really expect this as there was probably not enough madder dye was present to bring out purple, or more likely, the initial addition of alum in the initial brew kept the colour orange.

But onward and upward. A few questions are going through my mind. While heating over a stove may not have been used on Anatolian wool, I wonder, was the temperature higher? Should I have left the wool in longer before adding the madder? Maybe my madder was just too old? Perhaps the water was too acidic (I have read that alkaline modifier could be added to increase the redness). But I shall try again with fresher madder and perhaps a touch of wood ash to increase alkalinity. I will also try using a mordant after the fermentation.

This was the second experiment.

I would be delighted if anyone can steer me in the right direction!