A perfect mordanting

from Gaia Gualtieri - 23 October 2013

Gaia Gualtieri

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A perfect mordanting is the secret for achieving the best dyeing

The mordanting process, in  fact,  is the necessary procedure to prepare the fibers for dyeing with natural dyes in order to facilitate bonding between the fibers and natural dyes, and making them stable.

The perfect mordanting

Clearly, as well as the dyeing with natural dyes, mordants can also be made on both fibers, of yarns, fabrics and artifacts. And also remember that the natural dyes (unlike synthetic ones) dye only natural materials.

As you know, when dealing with natural dyes we can only ask for our well-known and trusted consultant, Paola Barzanò. She explained patiently how to achieve a perfect mordanting.

The perfect mordanting

It is a process made using mordants, especially mineral or synthetic salts (such as potassium alum), but also vegetable materials (such as tannins). Depending on the type of natural fiber to be dyed, the techniques for mordanting may vary.

In order to perform this process on animal fibers (and/or yarns and fabrics obtained by them) made of a protein base more similar to natural dyes, only one bath should be used.

In order to perform the mordanting process on vegetal fibers (and/or yarns and fabrics obtained by them) less  similar to natural dyes, it is necessary to do it twice to obtain a more stable colour.

To this end, in the mordanting of vegetable fibers tannins (plant substances present for example in the bark of plants such as oak and chestnut)  give a colour of variable intensity to the fibers, depending on the type of tannin used. The gallnut of the oak is the most neutral and widely used tannin for dyeing fibers with light colours so that it interferes less with the colour bath.

Mordanting animal fibers (such as wool and silk)

Natural animal fibers (and/or yarns and fabrics obtained by them), thanks to their protein composition, which is similar to the dyeing extracted from plants and insects, need an easy mordanting process, in one bath only. Hereafter there is an explanation of the different steps of the mordanting process for all colours, except for indigo and woad.

  • Weigh the dry material (fiber, yarn or tissue).
  • Rinse with water and neutral soap.
  • Weigh the potassium alum: you have to calculate a 20 to 1 ratio compared to the weight of the material you wish to dye. Please note that in order to guarantee shine to the red tones you have to add to potassium alum also a 5% (compared to the weight of the dry material) of cream of tartar in the mordanting bath.
  • Dissolve your potassium alum in a liter of warm water and make sure that the salt crystals are completely melted.
  • Pour the compound obtained in a pot filled with water (keeping the bath ratio at 20/1) and bring to 80°C (176°F).
  • Completely soak the material in the mordanting bath first, then – in order to avoid the formation of air bubbles– slowly immerse your material.
  • Stir it from time to time to let the fiber absorb the mordant in a uniform way.
  • Let the material sit in the mordanting bath for about one hour at 80° C (176°F).
  • Let the material cool down in its mordanting bath, then rinse it thoroughly in warm water to avoid thermal shocks. The material is now ready for the dye bath.

Mordanting vegetal fibers (such as bamboo, hemp, cotton and ramie)

Mordanting natural animal fibers (and/or yarns and fabrics obtained by them), is a process composed of two or three different baths.

Steps are:

  • Weigh the wet material.
  • Rinse it with neutral soap and water.
  • Leave it to dry completely.

First mordanting bath

  • Weigh 2% of gallnut powder (tannin) compared to the weight of the dry material.
  • Dissolve the gallnut extract in a liter of hot water.
  • Pour the liquid in a pot filled with water and bring to 80°C (176°F)
  • Completely soak the material in the mordanting bath forst, then – in order to avoid the formation of air bubbles- slowly immerse your material.
  • Stir it from time to time to let the fiber absorb the mordant in a uniform way.
  • Let the material sit in the mordanting bath for at least one hour at 80° C (176°F).
  • Let the material cool down in its mordanting bath, then rinse it thoroughly in warm water to avoid thermal shocks.
  • Let the fabric dry.

Second mordanting bath

  • Weigh your potassium alum: calculate a 20 to 1 ratio compared to the weight of the dry material.
  • Add 6% sodium carbonate compared to the dry material.
  • Dissolve the potassium alum in about one liter of hot water and when it is well melt add the washing soda.
  • Pour your compound in a pot filled of water (bath ratio 20/1) previously brought to 80°C (176°F)
  • Wet again the material you have processed with the mordant (first mordanting bath)
  • Completely soak the material in the mordanting bath first, then – to avoid the formation of air bubbles- slowly immerse your material.
  • Stir it from time to time to let the fiber absorb the mordant in a uniform way.
  • Maintain the mordanting bath temperature at 80°C (176°F) for at least one hour.
  • Let the material cool down in its mordanting bath, then rinse it thoroughly in warm water to avoid thermal shocks.
  • Let the fabric dry. The material is now ready for the dye bath.

And now, it’s time to play with colours. Let us know the results you get. We bet they will be fantastic!

If you liked this article maybe you would also enjoy Natural dyes: 10 gold rules to dye

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10 Comments for A perfect mordanting

  1. LEta

    If the Gallnut bath is heated up too hot will it produce a tint onto the cellulose fiber? I ask this because I just recently used gallnut for a tannin on my fabric before my alum mordant bath. After the gallnut bath my fabric had a greyish-tan color on it. The recipe I went by suggested getting the heat up to 200degrees F and letting sit for 45 minutes or longer for a deeper shad in your dye .via this website: http://maiwahandprints.blogspot.ca/2013/01/natural-dyes-mordants-part-3.html . I do not want this tint on my fabric, it seems to have saddened the fabric, although I have not put color onto it yet. OK thanx for sharing! 😀

  2. Gaia Gualtieri

    Dear LEta,
    thank you for your interesting question and we are sorry if we are responding only now, however we were closed for a few days for vacation. Also, before we responded to your question we wanted to ask the opinion of Dr. Barzanò which took a few extra days.
    When we use tannins as a mordant wtih vegetable fibers it is inevitable that the white fabric takes the color of the tannin because tannin isn’t colorless. That is why the color of the tannin will contribute to the color of the next dye bath, darkening it slightly.
    To limit the mordant effect of the tannin, that is, to obtain the least possible color variation in the fabric to be dyed, we reduce the percentage of tannin. For example, we use 2% of tannin instead of 5-10%. Be careful however, because while the interference with the color will be minimal, the stability of the final color will be reduced, because tannin makes colors more solid and stable.
    Therefore you have to weigh the costs & benefits (the costs being the variations in color and the benefits being the greater solidity of colors). To make this decision we suggest carrying out various tests on the fabric/fiber so as to obtain the desired result with an acceptable stability, as according to our standards.
    I hope to have provided you with the information you needed. If you have any more questions, feel free to write to us again.

  3. Anita

    Thank you for your explanation on natural dyeing.
    There is only one thing not correct: wool should never be cooled in its mordant bath. It should be transferred into a bath of water a little cooler.
    Kind regards,
    Anita

  4. Gaia Gualtieri

    Dear Anita,
    actually this is the process Mrs Barzanò follows and as far as we have experienced it works perfectly. Yet it can be there are other different ways, and even better ones. Thanks for sharing your experience with us. We will treasure it.

  5. Paula

    Good.morning to all,

    I just discovered you in Pinterest. Thanks for sharing all this precious information on the dyeing natural fibers. I am so happy to discover a very well explained process of mordant, however whee I am living actually (somewhere in west Africa ) I can’t find easily all the products required for mordanting cotton. Is there any substitutes I could use ? Concerning second bath mordant for cotton you mention caustic soda can you please indicate the pourcentage?

    Thanks again for the so wonderful articles.
    Kind Regards
    Paula

  6. Annalisa Chelli

    Hi Paula,

    thanks for writing us. So glad to know you appreciate our blog.

    Concerning your questions:

    1 – as a substitute for gallnut powder you can use Cherry plum/Mirabolano
    2 – for the second mordant bath we suggest you, in this case, sodium carbonate/washing soda. Pourcentage 8% sodium carobonate/washing soda and 20% alum

    Hope I helped you.

  7. Paula

    Dear Annalisa,
    Thank you so much for taking your time to answer the questions of a beginner and sorry to not having replied before, a little busy with other aspects of live .
    I am going to make few tests and will revert with results.
    Have a fruitful day.
    Kind Regards
    Paula

  8. Autumn

    I am working on hammered leaf prints, hoping to incorporate them into a quilt. Can this mordant process be used on fabric that ALREADY has the dye on it? Thank you so much!

  9. Gaia Gualtieri

    Hi! You can use this process on unbleached fabrics. We have tested it and it works perfectly.

  10. Autumn

    I forgot to add that I’m working on unbleached cotton fabric!!

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