How to mordant linen and cotton fabrics successfully

I have received a lot of emails the last couple of weeks, asking about  how to mordant linen and cotton fabric. After repeatedly answering the same question over and over again, I thought why not post it on the blog?

There are several different methods of mordanting cellulose fibres, but I found the following technique the most practical. Many other recipes require Alum acetate, which I personally avoid using. I like to use what I have at hand and this recipe works a treat. Keep in mind that you will need time. This can be done within 4-5 hours or over a couple of days if you choose the non heated version. 

You can find a tip section at the end of this article - a shorter version of the text below.

There are several different tannin rich plants that can be used, each slightly different from the next. Tannin will always leave a slightly yellow buttery colour behind. Tara and Oak Gall less so than Myrobalan. If you are planning on light colours, I would leave out the Myrobalan. Another little trick - if you add your fabric to a 2-5% iron after bath, your fabric will turn grey to dark grey/black once it has been mordanted with a tannin rich dye. The richer in tannin the darker the results. If that is the colour you require - leave out the Alum/Soda Ash Step. Alum brightens dyes, which might not be what you are looking for when going for black.


Before we start, if you want to dye your fabric with Indigo - no mordanting is required. You only need to scour your fabric. 

Indigo dyed double layered organic cotton

Double layered organic cotton dyed in an Organic Indigo Vat


Scouring cotton                      scoured cotton

Before (left) and after (right) scouring single layered organic cotton

(Please note that some fabrics come already scoured in which case you can skip this step.)


  • A pot big enough to hold your fabric
  • 1 tsp of Soda Ash (or 1% of w.o.f.( w.o.f. stands for weight of fibre))
  • 1/2 -1 tsp of organic washing up liquid
  • Heat resistant rubber gloves
Wet fabric thoroughly.
Dissolve the Soda Ash in a little hot water and add to the pot, followed by the washing up liquid.
Add the fabric to the pot and stir.
Bring pot to the boil and keep at a light simmer for an hour. Stirring regularly. 
Remove fabric, let cool and give it a good rinse.

Mordanting cellulose fabrics succesfully.

 A 2 step process, please read through the entire instructions first.

Step 1:


10-60% Tannin rich plant like Myrobalan (10% of the weight of fabric (w.o.f.)) other options would be Oak Gall and Tara.


1.Fill a plastic or stainless steel vessel with hot water (40-50 d. Celcius/100-120F) to a 30:1 ratio (water:fabric)

2. Add tannin and stir until dissolved or evenly distributed

3. Add fabric, immerse fully for 1-2 hours. The bath will cool down, which is totally fine. Stir occasionally.

4. Use rubber gloves when removing fabric, squeeze fabric. Rinse very lightly or better spin it out using a centrifugal spinner or washing machine. Tannin is bound to the fibre only by affinity and can be removed if rinsed aggressively.

5. Save mordant for future use.

6. Don't let it dry before moving on to Step 2.

Step 2:

Alum 12% (w.o.f.) Dissolved in enough boiling water, cool.
Soda Ash 1.5% (w.o.f.) Dissolve in enough boiling water, cool.

1. Combine the two solutions while stirring. It will bubble, so make sure your vessel is big enough.

2. Bubbles will subside quickly and you should be left with a clear liquid. Add additional hot water as described above (Steps 3 and 5 from above).

3. Rinse the textile well, to make sure any unattached mordant is rinsed off.

4. The textile may be dyed immediately or dried for future use.


*Too hot and the tannin will oxidize, which is fine, if you want a potentially darker colour. For overdyeing, it is best to keep the colour as light as possible.
** You can also use cold water instead of hot, but it will require a 12h or overnight soak 
***Any tannin can be used with this recipe, but for lighter results use Oak Gall or Tara.


  • Astrante

    I have access to a sumac bush. I am wondering if it is possible to use the leaves fresh or dried to mordant cotton ?

  • Jennifer Lienhard

    Hello Patricia, I sent you an email, concerning your comment. Thanks!

  • Jennifer Lienhard

    Hello Leah, yes it does, just give the yarn a good long soak before mordanting (24-48h). Because it is twisted into thread, it will take longer for the water/mordant to penetrate. Once thoroughly soaked, add to the tannin for 24h followed by Alum Soda Ash for another 12-24h, if you want the tannin to be properly locked in. I hope that answers your question. x

  • Leah Rosenthal

    Will your methods work on spun cellulose yarns (cotton, flax, thistle, etc)?

  • Patricia Pelletier

    I am natural dying for the first time this summer. I successfully have dyed cotton fabric after a red sumac Tanin bath and using alum and an iron mordant ( separately). My first attempts used factory cotton in which I scoured twice.
    My second attempt used recycled cotton fabric that I scoured twice and the used red sumac Tanin and an alum bath. This time the cotton turned blue/grey and dark blue? I can’t figure out what happened? I am using stainless steel pots and it is almost like iron got into it. Any ideas

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