How to Prepare Fiber/Fabric for Natural Dyeing - themazi

How to Prepare Fiber/Fabric for Natural Dyeing

Fibers and fabrics must be properly prepared for natural dyeing.  If they are not properly prepared, this can lead to uneven uptake of dye and poor wash and light-fastness.  There are lots of myths about natural dyeing circulating on the internet so we will try to dispel some of them here too! 

The most commonly used fibers/fabrics for dyeing are protein or cellulose based.  These are used mainly because most petroleum based fibers such as polyester do not take up natural dyes well.  Protein fibers include silk and wool, cellulose include cotton, linen, hemp and bamboo. Whichever you use, the preparation process involves these steps:

What is Scouring in Natural Dyeing? 

  • scouring - cleaning really well to remove grease, any substances used in the manufacture of the fibres or detergents/conditioners used to wash them

What is Mordanting in Natural Dyeing? 

  • mordanting - preparing the fiber/fabric with a substance to allow the dye to fix, or ‘bite’.  The word mordant comes from the French ‘mordre’ - to bite.  

Here we will explain some methods of scouring and mordanting, which are different depending on whether you are using protein or cellulose fibers.  These are not the only ways, but these are commonly used, tried and tested, and are the processes used to obtain the results shown in lots of the photos on our themazi website.


Just because something is ‘natural’ it doesn't necessarily mean it is safe!  We recommend you read all the safety notes provided with any products you use in your natural dyeing processes, wear gloves and a mask when appropriate, for example when working with anything that is an irritant or is finely powdered.  Work in an outdoor or very well ventilated space.  Do not use equipment for cooking after you have used it for dyeing.  

How to prepare protein fibers?

Scouring - Soak fiber/fabric for two hours in warm water to which you have added a little pH neutral detergent, rinse well and leave to dry. 

Mordanting – Weigh your fiber/fabric. For every 100g silk, you need 8g alum (potassium aluminium sulphate, PAS).  For wool, you need 8g alum and 7g cream of tartar for every 100g fiber/fabric.  Dissolve the alum (and cream of tartar for wool) in a heatproof container with a little boiling water, stirring.  To a pan containing enough cold water to cover the fabric easily, add the alum and the fabric, which should be wet.  Bring the mixture to a very gentle simmer, turn off the heat and leave to cool in the mordant overnight. Wring out very well.  You can now use it straight away, or leave it to dry, and dampen again when you are ready to use it.   

How to prepare cellulose fibers?

Scouring - simmer the fiber/fabric for 90 minutes in a large non-reactive pan with a tablespoon of sodium carbonate (soda ash) and rinse, or put through the hottest cycle in your washing machine with a tablespoon of sodium carbonate (soda ash) in the drum.  You will be amazed at the gunk that you see coming out if you do it in a pan! 

Mordanting  Tannin/alum method: 

Weigh your fiber/fabric. For every 100g, you need the recommended amount of tannin.  This is shown in our themazi product descriptions on our website.  The tannins that impart the least colour of their own to fibers are our oak gall tannins, and these are very rich tannin sources, but we have several other tannins available too including sumac, pomegranate and acorn.  Most tannins can be applied by soaking with the fiber/fabric in hot water and leaving to cool overnight, but you will see more detail under each themazi product.

Next, for each 100g of the fiber/fabric you will need 15g alum (potassium aluminium sulphate, PAS) and 2g sodium carbonate (soda ash).  These should each be dissolved separately with boiling water.  In a container big enough to accommodate your fiber/fabric easily, add some hot water - from the tap/faucet is hot enough.  Then add each of the alum and sodium carbonate solutions carefully - it will fizz when the two are mixed.  Add the damp tannin-prepared fiber/fabric, and leave for several hours or overnight, stirring occasionally.  

The fiber/fabric can be treated a second time with the tannin mixture from the first step if you wish.  You can now dye straight away, or leave it to dry, and dampen again when you are ready to dye. 

Are all Oak Gall are the same in term of tannin and Mordanting?

Read exclusive experiment from Catharine Ellis. 

Myth busting

Vinegar and salt are not mordants for natural dyeing.

Most natural dyes need a mordant to fix them properly, although some dyes such as onion skin don’t require a mordant.

Most berries, red cabbage, beets, black beans and purple carrots make stains, not dyes, and these are not colour-fast, even with a mordant.  Don’t bother to dye with them, eat them instead, yum yum!

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Hi can you tell me if Butterfly Pea Flower powder or tea is stable to use as a fabric dye, if so which is best cellulose or protein and what type of mordant procedure would you suggest? Thank you


Thank you so much. xxxx

Audrey Reiss

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