Dyeing of textiles
Practical Action
The principal difficulty in dyeing mixed yarns and fabrics is to achieve the same colour in
both fibres. Cotton fibres may, for instance, absorb dyes rapidly, while the wool fibres will
have to be boiled over an extended period to reach the same depth of shade. This could
lead to significant damage to the material. In this case a chemical compound would need
to be used to restrain the rate at which the cotton fibre takes up the dyestuff.
The amount of dyestuff which is used is usually given in the recipe. It is usually quoted as a
percentage weight of the fabric to be dyed. Box 2 demonstrates a typical, simple recipe for
dyeing using natural dyestuff, in this case onion skins.
Box 2
Recipe for dyeing wool with onion skins
Fabric: applicable to wool or other animal (protein) fibres.
You will need:
100 grams of natural wool
30 grams of onion skins (use only the dry, brown, outer skins)
8 grams of alum (the mordant)
7 grams cream of tartar (the assistant)
Some liquid detergent (the scouring agent)
A water supply*
If a larger quantity of wool is to be dyed, increase the quantities proportionally.
Weigh the wool. All weights given are relative to the dry weight of the wool. Skeins of wool
are tied loosely in several places to prevent tangling. In this case the recipe calls for 30%
dyestuff i.e. the weight of the dyestuff is 30% that of the fabric to be dyed.
The wool should be scoured. This means getting the wool completely clean. For this the
wool is soaked overnight in a liquid detergent solution. Rinse the wool well and gently
squeeze out the excess water. Use lukewarm water and avoid sudden changes in the
temperature of the water which cause the wool to felt or mat.
Next the skein will be mordanted. Dissolve the alum and cream of tartar in a little hot water
and then add this solution to cool water in the mordant pan. Immerse the wetted yarn and
then place the pan on the heat source. Slowly raise the temperature to 82oC (180oF) and
simmer for 45 minutes. Leave to cool, then remove the wool and rinse well.
To prepare the dyebath, place the onion skins in the dyepan and cover them with water.
Slowly heat the dyebath to boiling point. Simmer for about 45 minutes by which time all
the colour should have been extracted from the onion skins. Remove from the heat, allow to
cool and then strain off the liquid form the skins.
The dyeing process is then carried out. The mordanted, thoroughly wetted fabric is placed
into the now cool dyebath. Replace the heat under the dyebath, bring the temperature up to
boiling point and then immediately reduce the heat to 82oC (180oF) and simmer for 45
minutes or until the wool is the required colour. Remember that wool is darker when wet
than when dry. Remove the wool from the dyebath if no further uptake of dye is required, or
allow the fabric to cool with the liquid in the dyebath. Do not cool quickly with cold water.
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