25 October, 2006

Ancient Egyptian hair dye - technology finally catches up

Ever wondered why the people in Egyptian tomb paintings all seem to have such lovely lustrous black hair? Apart from the fact that the well-off wore wigs, of course. It turns out that the ancient world used a hair dye that - apart from the unfortunate drawback of being toxic - was several thousand years ahead of its time. I’m indebted to Philip Ball of Homunculus for an explanation of this ancient technology. Annoyingly, the American Chemical Society website with the original research report isn’t open-access and I haven’t got a subscription, but there’s enough information in the Homunculus post to work out the basics.

First, a little background on hair structure. Hair is made up mostly of a protein called keratin, which is the same material that makes up hooves, claws and fingernails. Each keratin molecule is a long slender thread coiled to form a cylindrical helix, exactly like a spring. This is why hair is flexible and will stretch before it breaks - the keratin molecules can uncoil and stretch out before springing back into their original shape, like a spring. Four of these keratin springs are twisted together to form a rope, called a protofibril, and eleven of these protofibrils are twisted together to form a thicker rope, called a microfibril. Microfibrils are packed together in long thin bundles called macrofibrils, the macrofibrils pack together to form long thin cortical cells, and the cortical cells pack together to form a single hair. There is a neat little animation here showing how all this works. The ropes are held together by chemical bridges between sulphur atoms in adjacent keratin molecules. You need a lot of these sulphur bridges to hold the many millions of keratin molecules together in a single hair, so hair contains a lot of sulphur. This high sulphur content is why hair and feathers smell so disgusting when burned - many sulphur compounds smell foul (hydrogen sulphide, the characteristic stink of rotten eggs, is a good example). The more sulphur bridges, the stronger the structure - so fingernails have more sulphur bridges than hair and are therefore stronger, even though they are made of the same keratin protein. Permanent wave and hair straightening products work by breaking these sulphur bridges and then reforming them while the hair is pulled into a different shape.

With me so far? Good. The ancient hair dye recipe is as follows: Mix lead oxide with slaked lime (a strong alkali) and water to make a paste. Rub this paste into the hair for three days. After this time, the hair will be dyed black throughout, and the dye won’t fade or wash out.

The alkali component of the dye breaks some of the sulphur bridges holding the keratin molecules together, and the sulphur then reacts with the lead oxide to form lead sulphide. Lead sulphide is a dense black substance that’s insoluble in water - it’s similar to the black corrosion that forms on silver jewellery. The clever part of the dye recipe is that the lead sulphide forms tiny crystals that attach to individual keratin microfibrils, deep within the structure of the hair. This makes the dye deep, long-lasting and permanent. It’s also something that materials science has only recently learnt how to do.

The drawback is that lead is poisonous. Homunculus comments that this rarely bothered people in the ancient world, since lead compounds were used in cosmetics (and paint, until very recently). This may be because life expectancy was shorter then, as he points out. Lead is a slow cumulative poison and it would probably have taken years to accumulate a lethal dose from face paint or eyeshadow, quite possibly more years than the average lifespan. It is also often very difficult to recognise the connection if the effects are delayed, as would be the case with chronic lead poisoning. If you have been using lead cosmetics for 40 years before you fall ill, your face paint or hair dye isn’t the first place you look for the cause of illness. It took Richard Doll years of rigorous epidemiological research to demonstrate a connection between smoking and lung cancer, and I don’t suppose he had a counterpart in Ancient Egypt. Moreover, the ancient Egyptians were great users of wigs, and some examples have even survived to this day - the British Museum has some in its collection (the link is to a picture gallery, click on page 6). A wig would only need to be dyed once as the dye would not grow out, so exposure to lead from a hair dye used on wigs would be much lower than the same dye used on natural hair. It seems quite possible to me that the lead hair dye might not be sufficient to cause poisonous effects if it was applied to wigs rather than to hair (unless there was some poor slave whose task it was to dye wigs all day, which would surely be a candidate for Worst Job in History).

12 comments:

Gabriele C. said...

Lol, I knew about the hair structure thing (my hairdresser explained it to me once) but not that the Aegyptians dyed their hair black.

Romans and Celts used lime based concoctions to dye their hair blond. And Roman women curled it with hot iron thongs, which doesn't sound good for the hair, either, especially since the procedure has to be repeated quite often.

Elizabeth Chadwick said...

Fascinating post Carla, thanks. I'm sure there's a great story/vignette in it somewhere!
Looking in A History of Private Life, Vol II, I see that a Medieval recipe for turning white hair back to blond was applying to it overnight a paste made of ashes of vine stems and ash trees boiled for half a day in vinegar. Not being a chemist or chemically minded I don't know what this would do to the hair. Make it smell I should think!

Carla said...

Gabriele - strictly speaking the lime treatment is a bleach rather than a dye because it works by dissolving the hair pigment (melanin) in the alkaline lime and so removing it. Apply too much and it dissolves most of the rest of the hair, too - I wonder if all these fierce lime-washed Celtic warriors found they went prematurely bald because of the damage the lime had done to their hair?

Elizabeth - well, vine black is a recognised pigment, made by burning vine shoots in a closed container. My guess is that the vinegar releases this or some similar plant pigment from the vine stem ashes (vinegar is quite a good solvent), then some of the pigment sticks to the hair as a dye. Since the hair's already white it has no natural pigment of its own for the dye to have to cover up, so it would probably need only a small amount of pigment to alter the colour. Natural blond hair has the same pigment (melanin) as black hair, just a lot less of it, so it's quite possible that a small amount of a black pigment might make hair look blond. Or sort of blond :-)
Has a re-enactment group ever tried this, do you know? I wouldn't want to try it on hair that was still attached to the owner (!), but one could try it on cut hair, like dyeing cloth, and see if it produced a colour that resembled blond.

Elizabeth Chadwick said...

A re-enactment group probably has (!) but I don't know of anyone personally.
Your explanations makes it sound perfectly feasible as a hair colour. I don't quite know where I'd get anyone brave enough to try it out. My own hair is already ummm...bottle blond, so a strand test wouldn't be much good. However, it's something to think about. I have access to the raw ingredients (we have a vine in the greenhouse and ash trees nearby). All I need now is someone cooperative with white hair of a suitable length!

Carla said...

Do re-enactment groups share experience with each other, by the way? E.g. if someone in Regia was thinking of trying out a method for medieval hair dye, or for making shoes, or making chain mail, would they try contacting other groups (say, Angelcynn) or experimental archaeologists or whatever to ask if someone else had already tried it and what their experience had been? Or if you tried out, would there be a way for you to share the results? Apart from happeneing to mention it to someone at a show, or posting it on your blog. It might be a quack remedy that happened to be written down - I'm sure there were plenty of ineffective health and beauty products touted in the Middle Ages just as there are now - or it might sort-of work. I shouldn't think it would be anything like as effective as the Egyptian nanocrystal dye because the recipe sounds like it would just be a surface pigment (like modern hair dye), rather than forming by a chemical reaction right in the hair microstructure. So it would probably fade and/or wash out.

Elizabeth Chadwick said...

I'm not aware of any official path to share findings Carla, but the UK re-enactment community tends to be a fairly tight-knit one with a lot of informal inter-communication. For e.g. several members of our branch of Regia, Conroi de Vey, are also members of Angelcynn. Others are members of Conquest. Someone else does 14thC too. I've been to a Re-enactor's fair in Warwick this afternoon and constantly kept bumping into people and traders I know. So, although there is no 'official' arena for dissemination of information and research (as far as I know, I coul be wrong), there is a fairly strong but informal 'ask so and so' structure at work. It would be useful to coordinate and formalise such research, I agree.
I have a professional medievalist friend who has some recipes for hair dyes. She was going to ferret them out for me re something I was curious about in my own novel research, but we've both been too busy. I'll have to chase her up and see what the recipes are.

Bernita said...

Here, I think they have various listserves where experimentation/research is shared but I suspect it's fairly casual.

Carla said...

Elizabeth - I'd be interested in the exact details of the recipe if you and/or your friend have time to look them up. I've got mildly interested in the possible chemistry and am wondering whether the ashes of ash trees in the recipe might be acting as a neutraliser for the acid in the vinegar, as wood ash (of any kind) is a traditional source of alkali. I.e. am wondering if there is some pigment in the vine stems that is soluble in acid (vinegar) but precipitates out (onto the hair) when the pH is returned to neutral or alkaline by adding wood ash. If this were the case, I'd expect the recipe to boil the vine stems in vinegar and then add the ash tree ash as a second step. If the ingredients all go in together, then it would be more consistent with the ash tree ash acting as a source of pigment (rather than a source of alkali), and the pigment would be deposited on the hair just by the paste drying out overnight. (Or it might be something else altogether - I'm not a professional chemist! - or it might be a quack rememdy that doesn't actually work).

Bernita - that sounds similar to the informal channels that Elizabeth described.

Smitten said...

Carla, you are a fucking fabulously fascinating chick. I LOVE your blog. From Egyptian hair dye to mincemeat recipes. You're an original, that's for sure. xxx

Carla said...

Well, smitten, I don't know quite what to say to that, except thank you, and I hope you carry on reading and enjoying my ramblings :-)

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Maddy1994 said...

Did you know eygptians created marshmallows..........that might explain why they also had dentists!!!