Cochineal works best with silk or wool but cotton can also be used. 25 grams of cochineal will dye a pound (450 grams) of wool a good red, and another pound or two pink. When you take the first batch of fibre out of the dye bath, you can add more fibre for paler but still beautiful colours.
Make sure the fibre is well scoured and washed before dyeing. Soak the fibres in water overnight or for a couple of hours before dyeing. You need to mordant your fibre with alum (see Mordants section) before cochineal dyeing and you can obtain several different types of red with cochineal by using different mordants. It is important to use soft water when dyeing with cochineal.
Dyeing with Cochineal
Boil about a pint of soft water, pour it over the ground cochineal and leave the powder to soak overnight. The next day, add more soft water to your dyeing vessel leaving enough space for the fibres. Heat the cochineal to near boiling for 15 to 20 minutes.
Let the water cool a little and then filter the dye bath through a coffee filter reserved just for cochineal. Add the mordanted fibres, aiming for no more than 100 grams of fibre (dried weight) per 10 litres of water. Leave the fibres overnight, or simmer the fibres gently at low temperature for about 40 minutes. Remove the fibres from the dye bath and let them dry and cure for a couple of day before washing them.