A new alum mordant?

Recently I was given a link to a website in Germany, which was offering something called “Kaltbeize AL” or “cold alum mordant”. Naturally, my curiosity was aroused, especially as I had never come across a reference to this anywhere else. So I decided to find out more about this alum mordant, which would appear to be something new.

According to the information on the website (www.textiles-werken.de),  this form of alum mordant is suitable for wool and silk and is applied cold. Once made, the same mordant solution can apparently be used many times. The instructions seem to imply that the mordant is only exhausted when the liquid level has dropped too low to enable the fibres to be immersed in the solution.

I ordered some of this alum mordant from the website and decided to do some tests to compare it with my usual alum mordant.  I planned to follow the method given on the instructions accompanying the cold alum mordant and also to try out the same method with the aluminium sulphate I usually use to mordant wool.

As far as I was able to ascertain, this mordant would appear to be aluminium formate – something I’ve never come across before. It is apparently made using formic acid, rather than sulphuric acid or acetic acid – hence the name. But that is all I know about its chemical composition so, if anyone knows any more, I’d be grateful for further details.

Unlike with other alum mordants, where the amount of alum used is based on the weight of fibres to be mordanted, with this cold mordant it is the ratio of mordant powder to quantity of water added that would seem to be crucial. So once the solution has been made, no more than 20% more water should be added at any stage. The recommended proportions are 20gms mordant powder per litre of water, so to start with I made 5 litres of solution, using 100gms of Kaltbeize AL.  The alum powder is first dissolved in hand-hot water, then added to the pot, which is filled up with cool water to the appropriate level. According to the information given, 5 litres should be sufficient to mordant at least 1 kilo to 1.25 kilos of fibres in total, which is virtually the same as 10% alum – the percentage of alum sulphate I generally use. The fibres can be added in several batches. When the fibres are removed from the mordant, the advice is to squeeze any excess liquid back into the solution, so that as little liquid as possible is lost. (Actually, I found that, after mordanting about 1 kilo of fibres in three batches without adding any more water, the level of the liquid had dropped only slightly. So I would question whether the level of the liquid is really a reliable indicator of the continued viability of the mordant. I would be inclined to assume that after mordanting about 1 to 1.5 kilos per 5 litres of solution, the mordant is probably exhausted. But I may be wrong.)

The first batch of fibres should remain in the solution for at least 4 hours and subsequent batches should remain in the liquid for longer periods. I entered three batches, each weighing about 350gms, and the first batch steeped for 8 hours, the second batch for 12 hours and the third batch for 24 hours. However, the instructions are not specific as to timings and only give general guidelines. There is no limit to the length of time fibres can be left to soak, so they can be left in the mordant bath for several days or even weeks.

I followed exactly the same procedure with an aluminium sulphate solution, dissolving 100gms alum sulphate in hot water then topping it up to 5 litres. I mordanted three identical batches of fibres in this cold solution, so I could compare the results with those from the Kaltbeize AL mordant.

I dyed skeins from each batch from each of the two mordant solutions and the results were interesting. There was hardly any difference in depth of colour achieved from brazilwood when the two mordanting methods were compared. The colour from the Kaltbeize AL mordant bath was very slightly deeper on the fibres from the first batch, but after that the colours from each of the two mordant solutions were virtually identical. These experiments were very useful, as they illustrate clearly that alum sulphate can be used cold, providing the fibres are left in the solution long enough. I think in future I would probably leave the first batch of fibres in an alum sulphate solution for at least 12 hours to start with.

The question then was what to do with the remaining mordant solutions. Might there be some mordant potential left in them? As I’m the type of person who finds it difficult to throw anything away, especially if it might still be useful, I decided to add a further 500gms fibres to each solution. I left these fibres to soak for 36 hours. I then tested a sample of each in several different dyebaths and was surprised to find that they dyed well. This indicated that there had been enough alum remaining in both mordant solutions to mordant the added fibres perfectly satisfactorily. Now I have to decide whether to continue adding even more fibres or whether to assume that the alum is exhausted.

There are still some aspects of this cold mordant I’m not sure about. For example, would there be any difference in the results between 1 kilo of fibres mordanted for 4 hours in a fresh solution and 250gms of fibres mordanted for 4 hours in a fresh solution? Is it possible that the 250gms batch would have absorbed more mordant because the alum had to be divided between fewer fibres? Would my results have been different if I had added all my 1kg of fibres at the beginning, rather than dividing them into three batches?  The instructions suggest that each solution is sufficient for about six batches of fibres, but the weight of the batches doesn’t seem to matter. So does this mean that a 5-litre solution would mordant six batches weighing 1 kilo each? How does this mordant work if there seems to be no relation between the weight of the fibres added to the solution and the weight of the alum dissolved into the liquid? Why is the ratio of alum powder to water so important? Surely the mordant must be exhausted before most of the water has evaporated away? If anyone has answers to these queries, I’d love to read them.

If I lived in Germany and had easier access to this new Kaltbeize AL mordant, and if I knew exactly what it is and how it works, I would certainly consider it as an alternative to alum sulphate. However, the high cost of postage to the UK, added to the cost of the mordant, makes it rather expensive. And if I can get similarly good results from alum sulphate used cold in the same way, there would seem little point in incurring the extra cost. But I’d still like to know more about aluminium formate.

9 Responses to “A new alum mordant?”

  1. Pia says:

    This is very interesting description of this Kaltbeize AL. I have never heard about it before and would be also curious to know more about it. Thanks for sharing your experiments about this.

  2. Hanne says:

    Hello Jenny,

    Why don`t you ask Karin Tegeler , who owns the shop, where you bought the “Kaltbeize” , for more informations? Karin is an excellent artist in dyeing with mushrooms and dyeing with indigo! I`m sure, she can tell you more about the “Kaltbeize” and I`m sure that she will help you! Karin “knows” the stuff, that she works with! In Germany many dyers are using this “Kaltbeize”.
    You can write Karin over her Homepage. I`m sure, she can understand your language.

    Good Luck! Hanne from Switzerland, who has 2 of your dyeing books an one booklet of Karins. And who uses these books very much! Thanks for your knowledge!

  3. Martine says:

    Hallo Jenny,
    i have taken a five day workshop natural dying with Karin Tegeler last year and am using this Kaltbeize since then. I’m very happy with it, because being a felter means i dont like to heat my wool twice.
    I have a bucket with Kaltbeize and use it for months. Leave my wool sometimes in the solution for days.
    Why dont you talk to Karin about it. She’s a marvellous dyer, a very nice lady and very concerned about our environment.

  4. Caroline says:

    Hi Jenny,

    Thanks for writing about Kaltbeize AL. I had seen the website last year but the information there was so vague that I wasn’t sure about ordering any. If you do any more experiments please let us know.

  5. Helen Melvin says:

    Hi Jenny thank you -again-for a fascinating post. I think Kalbeize sounds a good way to mordant cold. I mordant silk cold using potassium aluminium sulphate but not usually wool so I am hot foot off to the website to try it! I too feel a bit baffled as to the concentration issue .

  6. Thoma says:

    Hi Jenny,
    I think it’s acetate of alumnia (I hope that’s correct in English), (C4H7AlO5) in German called “essigsaure Tonerde”, an old folk remedie, which you use for medical appliance because it’s antiseptic and astringent.
    Karin Tegeler gave a recipie with that time ago in a German magazine called “Lavendelschaf”, where she writes a lot about dying with plants and mushrooms and because she’s a felter she publishe that important method.
    I’m not sure, if she had the mentioned Kaltbeize in her shop in those days, therefore I bought it in a pharmacy and added water as requested. But I think her shop version is cheaper.
    Due to lack of time I only tried it once some weeks for some experiments. I liked the handling very much.
    The good thing is, you put your wool and silk in and that’s it – no heating, no simmering, just a big plastic cask (the size you have or wish – depending on the amount of wool you want to mordant) standing around in the corner. If you don’t have time for dyeing, you leave the material there.
    As the others said: Ask her for further information.

    • Jenny Dean says:

      I’m grateful for all these comments. I have contacted Karin Tegeler for more information & am awaiting her reply. The Kaltbeize is not “essigsaure Tonerde”, which is I think alum acetate, as Essigsaure is acetic acid. According to the notes accompanying the Kaltbeize, it is made using Ameisensaure which is formic acid.
      I’ll post on my blog any useful information I may receive.


  7. that’s a lot of information – you do have the same questions as I have, but i’am not expirenced enough to do research. The only thing I have found untill so far by google on ‘ameisensaure’ that it is also a part of the plant achillea millefolium… thanks for this interesting post! xDorie

  8. claudia says:

    Hallo Jenny,

    at first excuse my bad english, I left school to long ago.
    But I only would like to write you, that I also use the Kaltbeize very often, it is so easy to use. Especially if I dye before spinning it is very good for sensitive wool, like australian merino.
    I also have your dying book.
    best wishes
    claudia from germany