More Rhubarb Samples

For several years a collection of my naturally-dyed samples has been held at The Royal Institute for Cultural Heritage ( in Brussels, Belgium. This centre covers all aspects of Belgium’s artistic heritage and its laboratories carry out work on conservation techniques and materials, including the analysis of dyes on textiles from all periods and from all over the world. My samples are sometimes used in this analysis work, mainly for purposes of comparison.

Every now and then I receive a request for further samples and a few weeks ago I was asked for some more rhubarb samples, in addition to the ones they already have. The samples requested were to show the pinks and greys available from rhubarb root when the colour is extracted in an alkaline solution, using either washing soda or household ammonia.

As I couldn’t readily locate any suitable samples, I decided to produce some. I first soaked the chopped rhubarb root overnight in a solution of water and washing soda. By this time the liquid was deep red in colour and I added two alum-mordanted samples and two unmordanted samples. I left the samples to soak for about 24 hours, then I removed them. I dried one pair of samples away from the light and the other pair of samples was dried outdoors in direct sunlight. The samples exposed to the light dried to a greyish shade through a process known as photo-oxidisation.

The photo below shows the colours.









The upper two samples are alum-mordanted and the lower two are unmordanted. The pink samples were dried away from direct light and the greyish ones were dried outdoors in sunlight.

P.S. to the Kaltbeize AL mordant

I received a reply today from Karin Tegeler, the supplier of this mordant, and it would seem that I had understood perfectly the information supplied with it. (As all the information was in German, I wanted to be sure that my knowledge of German had been adequate.) The main advantage of this form of alum mordant would seem to be that it can be applied cold whereas, according to the comparative information supplied with this Kaltbeize, the more common alum mordants, such as alum sulphate and potash alum, cannot. (However, my experiments and the experiences of other dyers would suggest that alum sulphate can in fact be successfully applied without heat.) The information sheet suggests that each solution can be used at least 6 times before it is exhausted and that 100gms mordant powder should mordant about 1.5 kilos of fibres. I’m afraid I still don’t know why the ratio between the amount of water added and the quantity of mordant powder used seems to be the crucial factor when measuring quantities. Nor do I know whether its chemical name is aluminium formate, although further searches online for “aluminium formate mordant” seem to suggest that it must be.  But Frau Tegeler confirmed that a Kaltbeize mordant solution can continue to be used until there is insufficient liquid left to cover the fibres. However, I still think that 100gms/5 litres would probably be exhausted after 1.5 to 2 kilos of fibres had been mordanted in it, even if the level of the liquid was still fairly high. Frau Tegeler also told me that one customer had left her wool in the cold mordant bath for a year before getting round to dyeing it, but when she did dye it the results were excellent. Anyway, I think I should now stop asking questions and just enjoy using this mordant.

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 (,  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.

Anglo-Saxon Dye Experiments – Part 3



On the left of this picture (unfortunately rather dark) are two shades of blue from a woad fermentation vat, green from dyer’s broom yellow overdyed in the woad vat and purple from the lichen Ochrolechea tartarea. On the right are some browns from walnut leaves and hulls and alder bark and twigs. The black shades are from walnut, oak and alder plus iron water modifier.

Black can be achieved either by dyeing red, yellow and blue in succession over one another, and repeating the overdyeing until a suitable depth of black is reached, or by using the tannin/iron complex.

To use the tannin/iron complex, wool is mordanted with tannin, or dyed in a tannin-rich dye such as oak galls, oak or bramble leaves or alder bark, (or indeed a combination of several tannin-rich dyes), then modified in an iron solution. The depth of colour is best built up by repeatedly simmering the fibres in the iron solution, then airing them for about half an hour to allow the colour to develop. This process can be repeated until a rich black is achieved. Unfortunately, this method tends to weaken wool fibres over a period of time, so the dyed materials will gradually deteriorate. However, if you are not dyeing for posterity it is the simplest way to achieve black.



 This picture shows some skeins dyed purple using the lichen Ochrolechea tartarea. They are lying on a piece of old woollen blanket, also dyed lichen purple. The shades are actually more purple in tone and deeper in colour than this photo suggests


 The lichen is steeped for several weeks in stale 4-week-old urine (or a solution of 1 part ammonia to 2 parts water), until the liquid becomes deep purple or almost black in colour. The solution should be stirred or shaken vigorously two or three times daily to incorporate oxygen. The liquid is then poured off and water added to make the dyebath. The fibres are then gently simmered in the dyebath for about 45 minutes, then left to cool in the dye liquid. This simmering  and cooling process can be repeated several times to increase the depth of colour.

In addition to the colours illustrated by my test samples, many more shades could be achieved by dyeing one colour over another. I think the experiments described in these three posts show that the early Anglo-Saxons would have been able to produce a wide range of colours without using mineral alum or other chemicals dyers tend to rely on today. One of my aims as a dyer is to achieve reliable colours using a minimum of manufactured chemicals and the results of these tests indicate that there is further scope for experimentation in this area.

Anglo-Saxon Dye Experiments – Part 2




This shows some of the range of shades from madder (Rubia tinctorum) on the left, and weld (Reseda luteola) and dyer’s broom (Genista tinctoria) on the right.





The shades on the left are from bramble leaves and sage leaves. On the right are some of the shades from wild madder (Rubia peregrina) & lady’s bedstraw (Galium verum)

  Most of the dyes were tested as follows:

The mordants used were clubmoss mordant, tannin mordant (oak gall or bramble leaf solution) and no mordant.  The modifiers used were clear vinegar (acid), wood ash water (alkali) and iron water. For the deepest black shades from tannin-rich materials, such as alder bark and oak galls, I used an iron water mordant followed by an iron water modifier. Too much iron does, of course, weaken fibres but iron water is slightly less harmful in this respect than the chemical ferrous sulphate. For a brownish purple shade from madder I used an iron water mordant followed by a wood ash water (alkaline) modifier. Where appropriate for comparison purposes, I also dyed some samples using wool mordanted with 10% alum.

For a further test with madder, I added chopped crab apples to the dyebath. I remembered reading about this some time ago, although I’m afraid I can’t recall where, and thought it worth trying out. I was pleased with the results, as this dyebath gave brighter, clearer shades than those from madder used alone and worked particularly well on unmordanted wool.

I was interested to note that yellows almost as bright and deep as those from a traditional alum mordant could be achieved from weld and dyer’s broom used on unmordanted wool and followed by an alkaline wood ash water modifier. Pretty olive green shades were achieved using an iron water modifier with weld, dyer’s broom, bramble leaves and sage leaves.In general, wood ash water proved useful to deepen and brighten shades. (Stale urine could also be used as an alkaline modifier, as it contains ammonia, but the aroma is perhaps less acceptable.)

To make wood ash water, remove the wood ash from a wood-burning stove, put it in a bucket or large lidded container and fill up with water. The leave the mixture to soak for several weeks. By this time the liquid will have become yellow in colour & feel “slick” or slimy to the touch. To use it as an alkaline modifier, remove the liquid without disturbing the ash sediment and soak the materials in it, adding more water as necessary. It’s better not to apply heat, as this may harm woollen fibres.

Unfortunately the photos don’t show the colours to their best advantage but I was pleased with the results of these tests, which indicated that the early Anglo-Saxon dyers would have been able to achieve a wide range of good, strong colours using only readily available materials and without using mineral alum as a mordant.

As far as light- and wash-fastness are concerned, I imagine these would have been of less importance to the Anglo-Saxons than they are to us today. Clothing was probably not washed as frequently and, if colours faded, clothing could be re-dyed relatively easily, especially as most of the dyes I used in my tests can be applied using little or no heat. As most garments were loose-fitting, a small degree of shrinkage might not have mattered too much. However, the classic dyes, madder, weld and woad, and the tannin-based dyes, such as walnut, oak leaves, oak galls, alder and bramble, all have reasonably good fastness properties, even when used without a mordant, so fading would not have been too much of a problem.

Anglo-Saxon Dye Experiments – Part 1


  These are the classic dyes: madder, weld and woad.






 I have always been interested in researching the dyeing methods of the past. The Anglo-Saxon period (cAD450 – AD1066) is one that particularly interests me, especially the early Anglo-Saxon period (AD450 – AD700).  There is much evidence that, even at this relatively early stage in our history, craftspeople were highly skilled and capable of remarkable levels of craftsmanship, including textiles woven using a variety of sophisticated and complex weaving techniques. The Anglo-Saxons had a variety of naturally-coloured sheep breeds, ranging from beige and brown to grey and black, so some colour patterns could be achieved without the use of dyes. However, dyes were necessary to achieve truly bright shades and to extend the colour palette.

One thing that is still not clear is whether the dyers of the early Anglo-Saxon period would have had access to alum mordants.  Alum shale was not discovered in England until the 17th century and before then alum had to be imported, mainly from the Mediterranean. Most experts seem to doubt that mineral alum would have been available widely, if at all, in England during the early Anglo-Saxon period, although it is certainly possible that the necessary trade routes may have been established. Nevertheless, it is perhaps unlikely that a product like alum, that had to be imported, would be readily available to everyone, and most probably more humble dyers would have had to manage without it.  So what colour range could they have achieved without using an alum mordant?  And what alternative mordants or fixatives might they have used?  These considerations formed the basis for my experiments.

The purpose of my tests was to investigate some of the range of shades available to dyers of the period, using only materials to which they would have had easy access.  So as my main mordants I used aluminium extracted from clubmoss (see below for more details) and tannin from oak galls, with iron water, vinegar and wood ash water as colour modifiers. As wool would have been the main fibre used by most people, I limited my tests to wool only. Linen and hemp were also used in the period but they appear to have usually been left undyed.

To prepare the tannin mordant, I simmered 50gms of oak galls for about 30 minutes, strained off the liquid and then simmered the fibres in this solution for 30 minutes. This oak gall solution can be stored and re-used several times. As a result of this mordanting  process the fibres become light brown in colour and this sometimes has an effect on the colours dyed on a tannin mordant, making them darker or duller.

Although mineral alum may not have been available, excavations at the later Viking Age (Anglo-Scandinavian) site in York (9th – 11th centuries)indicate that dyers there probably used a mordant prepared from clubmoss, which has the ability to accumulate aluminium from the ground in which it grows. However, as the particular clubmoss species found (Diphasium complanatum) is not native to Britain, it is thought likely that it was brought by the Vikings themselves, who were probably familiar with its use as a mordant. Diphasium complanatum is not the only clubmoss capable of absorbing aluminium and it is possible that the Anglo-Saxons may have also used a native species of clubmoss as a source of aluminium for mordanting. Based on this possibility, I decided to try this as part of my experiments. Extracting aluminium from clubmoss is not easy and I would recommend it only for research purposes.  I used fir clubmoss, imported from Europe as I did not have access to any locally, but the extraction process takes several days, during which time the liquid has to be kept fairly hot, and application to the fibres takes a similar length of time. I used a recipe from Scandinavia that I happened to come across in a dyeing book from Germany, “Farben aus der Natur” by Gretel Fieler. (Recipe details below) Using alum-mordanted wool and unmordanted wool as controls, my tests with madder indicated that I did indeed manage to mordant my wool samples with aluminium from clubmoss. The resulting shades were very close to those achieved on an alum mordant and certainly redder in tone than the shades produced on unmordanted wool. But more about that later.

Recipe for clubmoss mordant (Lycopodium selago) : Use 100% clubmoss, chop it into small pieces, then pour water over it and heat the mixture to 40C. Keep at this temperature for 3 days, then boil up the mixture once briefly, strain off the liquid and leave to cool. Then add the wool and heat slowly to 40C. Repeat this heating process daily for 3 days. Allow to cool, then remove the wool and rinse.

As far as dyestuffs were concerned, for blues I used woad (Isatis tinctoria) and for purples I used the lichen Ochrolechia tartarea. Lady’s bedstraw (Galium verum) and wild madder (Rubia peregrina) were used for orange and coral shades, and weld (Reseda luteola) and dyer’s broom (Genista tinctoria) for yellows. Madder (Rubia tinctorum), the source of red dye, is a little more problematic. Although madder was available and used during the Roman period, it seems to have disappeared for a while with the departure of the Romans from Britain, suggesting that the dyestuff, rather than the plant, had been brought by the Romans. There is evidence, however, that cultivated madder was in use by the 7th century, so I included it in my tests. Various tannin-rich materials, such as alder, bramble, oak and walnut, were used for browns and black. Walnut, although not native to Britain, was probably introduced by the Romans and there is some evidence that walnut would have been available during the period.

The test results were interesting and provided a wide range of strong colours.


This image shows a selection of colours from my tests.






 In Part 2, I will start to describe the experiments in more detail.

More about Mordants



Recently I was asked some rather probing questions about the various names given to alum and the other chemicals used for mordanting. So since then I’ve been working on supplying some answers but, as my understanding of chemistry is limited to what I need to know as far as dyeing is concerned, I realise how many gaps there are in my knowledge. However, I hope the following information may be helpful.



For a detailed explanation of the history of alum production I’d recommend Dominique Cardon’s book “Natural Dyes”, published by Archetype Publications. This is a huge, scholarly work and, although it is costly to buy, it is well worth the expense if you are looking for an all-encompassing reference book.

Alum is not poisonous but it should be handled with care and not ingested. The 4 types of alum used by dyers are: aluminium sulphate, potassium aluminium sulphate (or potash alum), ammonium aluminium sulphate (or ammonium alum). – (Note: sometimes these last two are written with the word “aluminium” first) – and aluminium acetate. As far as I understand it, the different names refer to the different methods used in the processing of alum to refine it. In the early days of production, refining was necessary to make sure the alum was free from iron contamination and this was mainly done using either potassium or ammonia (or stale urine which contains ammonia). Pure aluminium sulphate (without the potassium or ammonia) contains the highest proportion of aluminium of the 3 sulphates, but by only a small margin, and is a later 19th century development, resulting from improved methods for removing the iron from alum shales. All the three aluminium sulphates mentioned above can be used for mordanting, although ammonium alum is less commonly used as a mordant. Aluminium acetate is used to mordant vegetable fibres and silk only.

The alum available in the past in chemists’ shops in the UK tended mainly to be ammonium alum, used, I think, for pickling and for applying to the skin in poultices. The aluminium content of ammonium alum is slightly lower than that of the other two aluminium sulphates, but not sufficiently lower to make a significant difference. The other alum sulphates may occasionally have been available in chemists’ shops but  alum in any form is rarely available over the counter in chemists or pharmacies in the UK now. It may sometimes be possible to buy aluminium sulphate in garden stores as a soil treatment and as long as it doesn’t have any iron contamination (usually in the form of specks of brown in it) it is fine to use as a mordant.

The difference between aluminium sulphate and aluminium acetate is that the former is processed using sulphuric acid and the latter using acetic acid. Alum acetate is usually used for mordanting vegetable fibres and silk only, not animal fibres such as wool, mohair etc.


I think the alum sulphate most suppliers sell for mordanting is probably potash alum, although it is often simply described as alum. In the 1990s, when I had my mail-order business selling dyes and mordants etc, I supplied aluminium sulphate (iron free), and not potash alum. The reason for this is simple – when I took over the business, the previous owner recommended that I should continue to supply granular aluminium sulphate (iron free), purchased from the wholesalers in 50kg sacks, as this is what she had supplied. So this is what I did. Since then, I have always used aluminium sulphate myself, so when I mention alum sulphate in my writings that’s what I mean, not potash alum. But it really doesn’t matter which of the three forms of alum sulphate a dyer uses. However, it does matter that dyers understand the difference between alum sulphate & alum acetate & what each is used for.


Cream of tartar: the cream of tartar used together with alum in some mordanting recipes is potassium bitartrate (or potassium hydrogen tartrate). It was originally made from the salt deposits that formed on wine casks & could be either white or red, depending on the type of wine for which the cask was used. The culinary cream of tartar sold in supermarkets may sometimes be sodium pyrophosphate, which is slightly less effective than potassium bitartrate but still fine to use. Some dyers mordant wool and other animal fibres using alum without cream of tartar, although in some sources an alum + cream of tartar mordant is recommended as preferable to get good strong colours from cochineal & other insect dyes. I have found that mordanting animal fibres using 10% alum sulphate, without cream of tartar, gives me good results with all dyes, including cochineal, but the mineral content of my local water may also play a part in this. 


Washing soda (or soda crystals) is sodium carbonate. Soda ash is also sodium carbonate but with the water content largely removed. However, as washing soda can be bought in supermarkets and hardware stores, it may be easier to obtain than soda ash and is equally effective. In all the recipes in my books I use washing soda/soda crystals rather than soda ash.


Iron is harmful if ingested and should be handled with care. It is usually supplied in the form of ferrous sulphate (or iron sulphate), which is a green powder. (Incidentally, when it gets damp it turns brownish but this doesn’t seem to make any difference to its viability). It may also be called copperas or green vitriol. Iron sulphate is also sometimes available in garden stores as a treatment for plants showing iron deficiency and it is sometimes cheaper to buy it this way, if you can find it. Home-made iron water (called iron liquor in the USA) is technically probably ferrous acetate, because it’s made using acetic acid, but I avoid the chemical term, as I’m not sure how accurate it is when used to describe a home-made product. Home-made iron water can be used instead of ferrous sulphate as a mordant or colour modifier and some writers suggest that iron water may be less corrosive on fibres than ferrous sulphate solutions.


Copper is toxic and should be handled with care and not ingested. It is usually supplied as copper sulphate, a blue powder, and is also known sometimes as blue vitriol or blue copperas. Home-made copper water (copper liquor) is technically probably copper acetate (see comments on iron acetate above) & is occasionally called verdigris. Verdigris is the green deposit that sometimes forms on copper piping etc and I think this is what is dissolved into the solution when making copper water. Copper water can be used instead of copper sulphate as a mordant or colour modifier.



Before disposing of any liquids containing chemical residues, make sure they are well diluted with water. Iron and alum are the most common elements in the earth’s core and disposing of mordant or dye bath remains containing these chemicals should not present any problems, especially as they are used in very small quantities and most of the chemical content should have been absorbed by the fibres anyway. I usually pour solutions containing small residues of iron and alum around acid-loving plants, such as broad-leaved evergreens or blueberries. Otherwise remains may be poured down the drain or disposed of on the ground in an isolated spot, away from children, pets and septic tanks. Copper is toxic so should be handled with particular care but it should be safe to pour residues containing copper on the ground in an isolated spot as described above. Some dyers prefer to avoid using copper because of its toxicity and it is certainly possible to achieve excellent results and a wide colour range without the use of copper.


I do not use chrome or tin as they are toxic, difficult to handle safely and disposal of chrome and tin residues may present problems.


For more information, Helen Melvin (Fiery Felts) has written at length about mordants and alum on her blog. (   However, wherever one goes for information, one tends to find different mordanting & dyeing recipes, as dyeing can be a highly personal craft. So in the end the choices are individual ones. My aim is to make good, reliable results as simple to achieve as possible – probably because I’m an impatient person & I don’t see the sense in making things so complicated that one is deterred from even making a start.

But that doesn’t mean that my methods are better than anyone else’s, so try out different recipes and select the ones that suit you best and give results that you like.

Alum Mordanting Again

As I have used up almost all my alum-mordanted yarns, it is time to replenish my stock. So this week I have been mordanting wool with alum, following my usual methods. (For details of these, see the post “Alum Mordants”)

As I explained in the above post, I now use 10% alum sulphate without cream of tartar for mordanting wool. (i.e. 10gms alum  – or 2 rounded teaspoons- per 100gms wool.) As I find it easier to measure out liquids rather than powders, I usually make a solution of 100gms alum dissolved in one litre (1000mls) water.  At this dilution, 10% means I use the same quantity of alum solution in mls as the wool weighs in gms. (i.e. to mordant 500gms of wool I need 500mls of alum solution).  To save time later, I tend to make several litres of alum solution at once, as any remaining solution can be stored indefinitely for use at a later date. (See note below for storage advice) The crucial thing to remember when making the alum solution is to make sure that all the alum has dissolved completely. I find it best to add the boiling water gradually, stirring well as I proceed. When I want to use the solution I always shake the bottle well first, just in case some alum has sunk to the bottom.

I have done tests with most dyestuffs and can see little, if any, difference in the depth of colour achieved on wool using a 10% alum mordant, when compared with the results achieved from the same dyebath using wool mordanted with a higher percentage of alum. As one of my aims as a dyer is to reduce as far as possible the quantity of chemicals used, without compromising the quality of the results, I can see no point in using a higher percentage of any chemical than is necessary for good results. However, I would also add that each dyer will tend to have his or her preferred mordanting methods and whatever gives the desired results, without causing harm to humans or the environment, is the best method for the individual dyer in question.  Indeed, the number of different alum mordanting recipes available is remarkable and must be bewildering for a beginner. Dyeing books written in the early to middle 20th century tend to advocate the use of a higher percentage of alum than is necessary or desirable, often as much as 30%, but in more recent books the percentages recommended tend to be lower. In today’s environmentally- and safety-conscious world, where dyers have recognised the need to use the smallest quantities of  chemicals possible, the abundance  of different alum mordanting recipes available would seem to indicate that more people are experimenting to find the recipes that best suit their individual needs.

I don’t work with silk very often, although I do sometimes mordant and dye silk skeins for a friend who is a silk weaver.  My preferred mordant for silk is now 5% alum acetate. In Japan, alum acetate is widely used as a mordant for silk and I find this recipe gives excellent results, although the 10% alum sulphate recipe I use for wool is also effective. 

For vegetable fibres I also use 5% alum acetate, as this is so much simpler than the alum/tannin/alum method I used in the past and gives excellent results.

To return to today’s mordanting: After stirring 600mls alum solution into the water in the pot, I added 600gms of well wetted wool. I started off by raising the heat gradually then simmered the wool in the alum solution for about 45 minutes. Unfortunately, the pot was rather full & the lid doesn’t fit very well, so the mordant bath overflowed during the simmering process and left my work surface swimming in water. After mopping up the liquid and squeezing as much as possible back into the pot, I then turned off the heat and left the skeins to steep overnight. I then removed them, squeezed the excess liquid back into the pot and dried all the skeins except those I want to dye in the next few days. These I left damp in a plastic bag, so I wouldn’t need to wet them out again.

I then added a further 600mls alum solution to the used mordant bath and added a further 600gms of wool. In order to avoid flooding my work surface again, this time I gradually raised the temperature to simmering point, keeping a close watch on the pot all the time, then immediately turned off the heat. I left this batch of yarns to steep in the mordant solution for about 36 hours, moving the yarns around gently from time to time. It doesn’t really matter which method one uses, as both are equally successful. In fact, it’s also possible to apply an alum mordant to wool fibres without heating the solution at all, as long as the fibres are allowed to steep in the cool solution for 3 to 4 weeks and are moved around in the pot regularly. However, when mordanting wool, I prefer to apply heat, at least to start with, mainly because wool tends to absorb liquids better with heat and I feel the results are therefore likely to be more reliable. This is also why a hot indigo dye vat is recommended for wool, whereas cotton, linen and other vegetable fibres can be successfully dyed in a cool vat. However, if wool is left for a longer period in a cool vat, it will gradually absorb the colour. Silk, whilst technically an animal fibre, seems to fall between the two fibre categories and tends to react equally well in both hot and cool vats.

Storage advice: Alum solutions can be stored in glass or strong plastic containers, with well-fitting lids.  However, I don’t recommend the rather flimsy opaque plastic milk containers as they may absorb, rather than store, some of the solution. I know that when I used these milk containers to store woad solution, I ended up with dark blue containers & rather less blue pigment for dyeing than I had expected.

I use the strong plastic gallon/5 litre containers in which things like cider, apple juice, vinegar, detergent etc are sold & have found these ideal. (My husband tells me he thinks these are actually made from some sort of nylon, which is non-absorbent.) Otherwise, the clear strong plastic bottles in which water & juices are sold are also suitable.  Containers for household bleach would also be OK, as long as they are thoroughly washed out first, and they have the added advantage of child-proof tops. Large glass bottles which contained pickled onions, gherkins etc would also be fine & if the neck is too wide, I use a funnel to make pouring easier. As long as the containers are well washed out, it doesn’t really matter if they still smell of whatever they contained, as any aroma is unlikely to be transferred to the materials being treated in whatever solution was stored inside them.

I usually store all my solutions in a brick-built outbuilding, which doesn’t get much natural light. In general, store solutions in a cool place, away from direct light & make sure they are clearly labelled, preferably in indelible pen. For extra security I usually fasten a plastic label round the neck, as I’ve found that snails tend to make their way into the outbuilding and sometimes eat away at my paper labels.

What do I do with all my dyed samples?

This is a question I am frequently asked and I’m afraid that the majority of my samples remain in cupboards until required for talks or displays. Some of them are fixed into sample books, of course, or made into display boards. But believe me, I really do have a large amount of dyed yarns, so when I can no longer find space for them all, I take some of them to the knitting workshops I occasionally lead and invite students to help themselves. It is a real pleasure to tip out the contents of bags and boxes onto the table and watch as students select the colours they find most to their taste.

When I do get round to using my dyed yarns, I like to design my own knitwear & chart my own multi-coloured patterns, sometimes for cushions or bags and sometimes for jackets. However, complicated patterns are usually for jacket borders and cuffs only, as I rarely have the patience to knit an entire garment in charted, stranded knitting. However, I plan to knit a jacket using only colours from mushrooms and I have been experimenting with colour designs.

img_17201This is a sample of a design I charted and then knitted using only colours achieved from Cortinarius semisanguineus used without a mordant



img_1725This is part of a sample knitted from a design I charted using colours from Cortinarius semisanguineus achieved on alum-mordanted wool.

This is the design I plan to use as an all-over pattern for my next jacket.

                                                                                                                                                             img_17332This is a close-up of a section of the design above.






This cushion was knitted using only yarns dyed with madder. Some of the skeins have been modified for colour variations. The purple shade was achieved using an iron mordant followed by a washing soda modifier.  The recipe is in my latest book “Colours from Nature”. For more details click on “My Books” on the home page.


This is another cushion knitted using only yarns dyed with madder. The patterns on both cushions are traditional Turkish sock designs. This one uses a typical Turkish sock technique of working the pattern design itself in the same colour throughout and changing the background colour.

Fungi in the Garden

Now that I am aware of the potential pleasures of dyeing with fungi, I keep my eyes open for anything in the garden that may be a possible source of dye colour. I’ve been told that the darker the fungus is in colour, the more likely it is to contain useful dye pigments, so I must bear this in mind, as I don’t want to waste time or fungi by collecting indiscriminately.

I think this mushroom, found growing under some pine trees, is Russula sardonia and I suspect that it will not be useful in the dyepot. However, as there are two largish clumps of it in the garden, I tested a small quantity and found that my suspicions had been correct. The dyebath produced only a pale beige tone on both alum-mordanted and unmordanted wool.

img_1585I think this is Giant Club Fungus (Clavariadelphus pistillaris). It was growing on the stump of an elm tree in our garden.  As it is brown in colour, I thought it might be worth trying it in the dyepot.


img_1658These are the results of the Giant Club Fungus dye tests.

Left to right: No mordant. alum mordant, no mordant + iron. Whilst the colours are not remarkable, the grey from the iron modifier is an attractive and useful shade. However, as this shade can easily be obtained from other sources (e.g. oak galls + iron), I shall probably not be using this fungus again for dyeing.