Rhubarb mordant part 2

I have long last concluded my first test of using rhubarb leaves as mordant instead of chemical ones. (even though they are in fact toxic, they are natural. Or, as MotherOwl points out below, even though they are natural, they are in fact toxic!)

And I have to say, it’s not really worth the effort. Not only does it not help the wool take up the dye any more than an unmordanted skein, in fact sometimes I could hardly see the difference. It also doesn’t add to lightfastness, both of which are the whole point of mordanting in the first place.

I tried both wool and cotton and none had better results than the other for me.


Top to bottom and left to right: Alum + rhubarb simmer not boil, boiled rhubarb + iron, boiled rhubarb, rhubarb + madder, rhubarb + weld, rhubarb + french marigold.

The alum mordanted, rhubarb dyed skein was also a handsome yellow in itself for sure, although it has faded a bit in just a month even without light. Without mordant they are a varying shade of beige depending on how hard you heat the dyebath. The madder is also quite alright, although not any kind of red exactly.

It did have one redeeming feature though: I really liked the shade I got from overdyeing with woad. From historical textiles we can see that some yellows fade away, leaving a once green section of fabric blue, but I’m not really expecting anything I make to live for 600 years. I’ll be forgotten and the line will die out when I do. It’s a patchy dye job because the vat had too little water and too much yarn, so I believe the darkest strands are the “truest” had it been done properly.


Check also under comments in my first post for additional info.


Ikke den helt store gevinst efter min mening, hvilket vi også debatterede under foregående indlæg. Garnet bliver ikke lysægte eller optager farve i samme grad som med alun, de gule farver kan knap nok ses ovenpå selve rabarberfarven som bliver mørk beige hvis man koger den. Det brunlige garn på billedet er krap, og den er vel ok, den grønne er overfarvet med vaid, og blev ret god, bortset fra jeg havde for lidt vand i gryden, så den er lidt skjoldet.

15 thoughts on “Rhubarb mordant part 2

  1. Ja så vil jeg nøjes med at spise mine rabarbere i kager og kompot, bruge frøene til farve og smide bladene på komposten. Og så kan det godt være at plantegifte er naturlige, men det bliver de ikke mindre farlige af.
    Det er godt at få afslutningen på sådanne forsøg. Der er megen viden, der bliver væk, når man ikke deler ud af sine erfaringer.

    1. jeg synes det er mindst ligeså vigtigt at dele sine fejltagelser, og ikke kun sine glansnumre. Hvordan skal vi ellers blive klogere allesammen? Det er også derfor jeg laver eksperimenterne selv, i stedet for at bare læse i en bog at xx plante er xx grader lysægte. Og så er der et helt andet aspekt. Alle de der opskruede perfektionismekrav vi lever under i disse dage slår os jo ihjel indefra. Så jeg går og øver mig i at være synligt sårbar og indrømme når jeg kvajer mig.

      1. Ja det der med at stole på bøger kan være misvisende. De skriver mere eller mindre af efter hinanden allesammen, og det er næsten umuligt at stoppe kæden igen.
        Og ja, lad os vise nullermænd og mislykkede projekter frem, og smile ad og lære af hinandens fejl istedet for at grine af hinanden.

  2. I wonder why it is so often mentioned as a mordant, if it doesn’t add anything useful in terms of colour fastness or how much the yarn absorbs dye? Perhaps the ratio of rhubarb to yarn plays a role? I once read a master’s thesis research about using willow as a mordant (in the wonderful sounding Department of Home Economics and Crafts in the Helsinki University, where they seem to do quite a bit of research on natural dyes), and I seem to remember there was an optimum ratio at which it would work best, and it was quite high (perhaps 200-400%).

    But given that rhubarb leaf mordant is toxic anyway, it really would need to perform incredibly well to be worth the trouble. And as a colour modifier, it looks quite similar to tannin, doesn’t it, which is less toxic (I think). But I agree the woad-rhubarb combo looks lovely.

    1. Until somebody comes up with a foolproof formula, and it aint’ gonna be me, this is a dead project for me. Incidentally I just got a few old dye books home from the library and she mentions rhubarb root – perhaps you’ve heard some say it can yield red? Well, it’s also a waste of time she writes, because the rhubarb in question is not the one we have and eat, but some exotic variety (other latin name). Typical example of how old knowledge turns into half-baked tales and treated as truth.

  3. lovely. so much chemistry happening, all very alchemical, too. that said, i’m here for the colors! i find them all to be calming and beautiful, like a spring bubbling up out of the green forest floor.

  4. I have also tried rhubarb leaf mordant, but I used it with Eucalypts, expecting it might modify the colours. It didn’t–but then in my samples, neither did alum, even though other dyers report that it can. I do wonder about the ratio… and had never heard of willow mordant! Thanks for running these experiments, I’m glad to have your findings 🙂

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