The go to mordant for protein fibres, wool and silk, may also be used for cellulose fibres with a pre tannin mordant bath. Potassium Alum provides a base for long lasting bright colour.
Potassium Alum Sulphate, is used at 10-12% of the dry weight of Fabric (WOF ) To increase depth of colour the percentage can be increased up to 20%.
HOW TO
Weight dry fibres or fabric
Weigh out the percentage of Potassium Alum Sulphate required @ 10-12%
Dissolve alum in warm water, in a stainless steel pot, deep enough in which fibres / fabric may move freely and literally bathe. Make sure during the first hour to stir the pot at 10 - 15 mins intervals, keep your items moving, so that fibre is not floating but fully saturated, and no air bubbles are caught between layers of fabric.
Air bubbles will impeded the uptake of alum, and therefore create inconsistency of colour, creating unwanted patches or spots.
Minimum mordant time 24 hours. For good long lasting colour soak for 72hrs. Make sure your pot is out of direct sunlight and lidded to prevent any other organic materials from entering and marking your goods.
Please take the necessary precautions to protect yourself, gloves, goggles and respiratory mask, even aprons, to avoid coming into contact with fine dust, also found when weighing out granulated substances. Working in a well ventilated area is best.
