Is soy milk a mordant?

Jenny Dean (1) doesn’t think so.  She says…”I am rather puzzled by the many references I have seen recently to soya milk/soymilk “mordant”as I would not describe soya milk as a mordant, rather as an assistant in certain dyeing and fabric patterning processes. In my understanding, soya milk has the same purpose in Japan as buffalo milk has on the Indian Sub-Continent – in both cases the milk solution is used as a binder or sizing agent, applied to fabric before mordanting or dyeing, in order to increase absorption and to prevent wicking and improve the sharpness of the outlines when painting or printing mordants, pigments and dyes on fabrics. Unlike a true mordant, soya milk solution does not form a chemical bond. I have never known soya milk solution to be traditionally applied to yarns rather than to fabrics and as far as I know it is not commonly used on woollen fibres.”

In the past I have tried to mordant cotton fabric with soy milk on the understanding that it somehow  makes the cellulose fibres “mimic” protein fibres, thus allowing a better bond between the fibres and the dye molecules.  The results have been unconvincing but it might be that my use of store bought soy milk is the problem.  How much soy is in supermarket soy milk?  Are there other additives in the supermarket soy milk product that are counter productive to dyeing?

A visit to the exhibition of artist Helen Coleman: Windfall-Chemistry of the Dyepot  at CASM in Mandurah, Western Australia (3), alerted me to the fact that one can make soy milk from soy beans and that this is effective in natural dyeing on cotton.

A bit of research yielded an easy recipe for soy milk by an expert, John Marshall, ( 2) and I discovered that soy beans are relatively inexpensive (A$2.99 per kilo) at my local Asian grocer.


So I made some. The process is not instant but simple.  It’s just repetitive. However, one factor in this might have been that I used my Thermomix rather than a food processor.  It may be that the bowl of a food processor would offer a bigger volume so that more water could be added to the beans in one step than I could manage, thus reducing the processing iterations.

I had been gifted an old pure cotton sheet.  It was a simple matter to rip it into many rectangular pieces about 30cm x 60cm.  (Sorry sheet!)

Before I considered any dyeing, I took some of the pieces of fabric and subjected them to the time-honoured practice of flour pasting, crackling, and over-painting with acrylic paint.  I wanted to test whether over-dyeing with natural dyes would produce additional complexity in the fabric , or merely obscure the paint patterning.

For this first experiment I only dipped the fabric pieces (both the virgin and the acrylic painted ones) once, rather than soaking, removing, dipping a couple of times more then drying,  as Jenny Dean (1) recommends.  Also, although I squeezed the fabric out , there was undoubtedly an unevenness in the distribution of the soy milk across the fabric when it had dried.

This is where the pseudo-scientific method ends and the truly subjective reporting begins.

Why?  Because I forgot to include a control…..

However, I got results which convinced me on the basis of past experience that treating cotton fabric with properly prepared soy milk enhances colour take up. Mind you, Jenny Dean may be right. My colour was better than non-soy-assisted fabric results but perhaps not as good as if I had subsequently mordanted with alum.  I am still learning and I do not yet understand how one would mordant with alum without removing the soy?

Anyway, no one reads a blog that doesn’t have photos.  So here are some:


Cotton, soy milk treated, covered with iron-dipped geranium, casuarina,  and eucalyptus leaves and steamed for two hours


Cotton pre-treated with soy milk, steamed with purple carrot puree, then steamed with iron-soaked grevillea



Cotton, pre-teated with soy milk, steamed with hibiscus (Alyogine huegeli) above a bath of acacia.

Left above: Cotton treated with flour paste, crackled, painted with rose acrylic , dried then treated with soy milk then wrapped with iron-soaked leaves, including one large rhubarb leaf.

Right  above: Cotton pre-steamed with pureed purple carrot then treated with soy milk then wrapped with iron-soaked geranium and peppermint leaves.


Cotton treated with soy milk, processed  with flour paste and burnt sienna acrylic paint, dried then put in bath of acacia bark


I have concluded that pre-soaking in properly made soy milk does help enrich the dyeing results on cotton.

It also seems possible to pre-paint cotton fabric with various acrylic painting techniques and then do some natural dyeing over the top with resultant richer texture.

In future blogs I will try to show the differences between dyeing by steaming  frozen plant material; boiling fabric in “solutions” of the same material; and  wrapping and steeping fabric in thawed material over time….

(1) accessed 3 Dec 2018

(2) accessed 22 Oct 2018 and 3 Dec 2018

(3) accessed on 3 Dec 2018


This entry was posted in Natural dyeing, soy milk, soy milk mordant for cellulose fibres. Bookmark the permalink.

7 Responses to Is soy milk a mordant?

  1. Leena Ruoppa says:

    thank you for your inspirational posts dealing with natural dyeing! Have you tried to mordant cotton fabric with alumn first and then soak it into soymilk?

    • Margaret Ford says:

      No, Leena, I haven’t done that. Do you think it would be better than soy milk alone? I can’t work out the chemistry but somehow I’m doubting the value of doubling up like that?

  2. leenairene1 says:

    Hi, I´m asking that, because you write up there:
    I am still learning and I do not yet understand how one would mordant with alum without removing the soy?
    Perhaps it would be worth experiment to use both? I`m not an expert on chemistry either and I don´t understand how soy actually works on cellulose fibers.

  3. VLF says:

    It would be a great experiment, I was searching to see if it had been done when I found this post. I would be interested in the results!

  4. Earthchild Sarah says:

    Just add the alum to the dye bath with cream of tartar. 1/4 alum and 1/16 cot per dry weight of fabric.

  5. Judy says:

    Thank so much for posting your experiments! I experimented with soy milk and indigo powder to make a “paint” on soy milk soaked cotton, as per the Maiwa earth pigments handout. ( I did not steam just cured for 2 weeks. The results were disappointing as only a charcoal colour appeared, not indigo. I was also wondering if I needed to pretreat the cotton with alum, but have not tried this yet. I thought I might try to spray soy milk on an alum mordanted cloth. I also wondered if the results would have been better if I had steamed the cotton after curing. So MANY many variables!

  6. Karen Reisle says:

    I’ve had great success using soy milk as a mordant for cotton, rayon, and linen fabrics that I have eco-printed. It brings out different colours from the plant material than alum does. I have only used commercial soy milk so far and not made my own……. yet.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s