HOW TO MORDANT COTTON OR OTHER CELLULOSE FIBRES

Cellulose fibres can be fully dried and stored before dyeing. Fibres do not need to be re-mordanted between dyes. Once a fibre has been mordanted it can be dyed and then overdyed without any further mordanting.

INITIAL STEPS

  1. Weigh the fibre dry, record the weight, then scour.

  2.  Choose your tannin – The tannin bath must always be done first.

  3.  Choose one of the alums from the mordant process below.

THE TANNIN PROCESS

  1. Measure tannin to the recommended WOF for the tannin you are using. Dissolve in hot water.

  2. Fill the kettle with enough hot water 120°F - 140°F  (48°C - 60°C) to cover the fibres.

  3. Add your chosen tannin, stir.

  4. Add the scoured, wet fibres.

  5. Let soak for 1-2 hours. Stirring occasionally (cover kettle so it stays warm).

  6. Remove the fibre and very gently rinse and wring – or spin out in a centrifuge (Spinnex), or the spin cycle of a washing machine. In order not to have to re-wet-out your fibres, do not allow fibre to dry before proceeding to the alum mordant.

    You can let the fibres steep in the tannin bath for an additional 8-24 hours. Steeping may give deeper colours, but always test your fabric-water-pot combination when steeping for more than a couple of hours.

THE MORDANT PROCESS

Note: For more effective mordanting on fibres such as linen we mordant twice with alum. For example we will mordant once with alum at 15% WOF and then again with a fresh mordant bath of alum at 10% WOF. Or we will do a tannin/alum/alum mordant to achieve slightly richer colours.

For the procedures below you do not “cook” the fibre. Begin with very hot tap water 48°C - 60°C (120°F - 140°F). It is not necessary to heat the bath again to maintain temperature.

Alum – Aluminum Potassium Sulfate

  1. Fill the kettle with enough hot water 120°F - 140°F  (48°C - 60°C) to cover the fibres.

  2. Measure soda ash at 2% WOF. Dissolve in hot water and add to the kettle.

  3. Measure alum at 15% WOF. Dissolve in hot water and add to the kettle.

  4. Add wet fibre (already treated with tannin) to your kettle.

  5. Let soak for 1-2 hours (cover the kettle so it stays warm).

  6. Now the fibre may be:   a. Rinsed and remordanted

                                  b. Rinsed and dyed

                                  c. Left to steep for an additional 8-24 hrs and then rinsed

                                  d. Rinsed and dried, to dye later.


Aluminum Acetate

Note: Some dyers omit the initial tannin process when using Aluminum Acetate. In our experience we have found keeping the tannin process results in superior lightfastness.

(see our recipe for homemade alum acetate)

  1. Measure aluminum acetate at 8% WOF. Dissolve in hot water and add to the kettle.

  2. Add wet fibre (already treated with tannin) to your kettle.

  3. Fill the kettle with enough hot water 120°F - 140°F  (48°C - 60°C)   to cover the fibres. Stir.

  4. Let soak for 1-2 hours (cover the kettle so it stays warm) or steep overnight.

  5. Chalk (fix) the fibre. Aluminum acetate must be fixed prior to dyeing. In some cultures this is known as dunging (as cow dung is used, which is high in phosphates). To 5 litres of warm water add 50g of chalk (calcium carbonate). Fully wet the fibre and wring out. Rinse thoroughly after chalking. These solutions may be kept and refreshed after every 10kg of fibre.

    As an alternative to chalking you may use 100g of wheat bran to 5 litres of warm water. The wheat bran needs to soak for about 30 minutes before adding your fibre. The wheat bran option is sometimes preferable for processes using thickened mordants. Rinse thoroughly afterwards.

  6. Now the fibre may be:

    1. Dyed immediately

    2. Dried completely for dyeing at a later date.

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