Soy Milk Mordant: Dyeing from Nature

Soy Milk Mordant

Using soy milk as a mordant is very effective for cellulose fibres. Using soy milk adds protein to your cellulose fibres, which allows dyes to adhere more strongly to said fibres. 

You can use store-bought unsweetened soya milk, which is easily accessible; or you can make your own soy milk. Homemade milk will probably be more concentrated than store-bought milk, so it can be used for a larger quantity of fibres. 

To make soya milk for mordanting ONLY (makes 1 litre): 

  • Soak 125g soya beans in 1 litre water overnight
  • Blend this mixture in a blender until smooth.
  • Strain the milk through a woven fabric (like muslin or cheesecloth)
  • Add the pulp that’s left in the cloth after straining back into the blender with some fresh water and blend again.
  • Strain the second batch of milk into the container with the first batch.
  • Repeat this process a couple more times and discard any solids.

* Again, do not consume this as it has not been properly processed for drinking.

Using soy milk mordant:

  • You can dilute your soy milk in a bucket with water at a 1:5 ratio, for example you can use a 1 litre carton of store bought soy milk mixed with 5 litres of water.
  • Pre-wet your fibres and add them to your bucket of soy milk mordant. 
  • Make sure that there is enough of your mixture to completely cover your fabric, add extra water if need be. I have also found that weighing your fabric down so that it stays submerged is beneficial. 
  • The most important part of mordanting with soy milk is to ensure that the fibres receive an even coating of diluted milk.
  • Leave the fibres to soak in the milk for about 12 hours. Stirring and flipping the fibres a couple times during this period.
  • Remove the fabric from the mordant, squeezing out the excess milk. If you have access to a washing machine, put your fabrics in on a spin cycle to remove the excess milk so that only a light and even coating remains on the fibres.
  • For yarns: do not place them in the washing machine, just gently squeeze out the excess milk 
  • An uneven coating of soy milk may result in patchiness when dyeing.
  • Hang your fibres to dry and store your soy milk mordant somewhere cool to be reused. 
  • Once your fibres are dry, dip them briefly in your soy milk mordant (without rinsing off first layer) and remove excess milk again by squeezing or spinning the fibres.
  • Allow fibres to dry and repeat the previous step 1-3 more times.
  • It is recommended to wait approximately a week before dyeing your fibres to allow the soybean protein to bond to the fibres.


  • If your soy milk mordant begins fermenting, dispose of it and make a new batch.
  • If using a washing machine to spin excess soy milk out of your fabric, it’s recommended to put your washing machine on a rinse cycle afterwards to avoid any residue buildup. 
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