In natural dyeing processes, the fabrics always needs to be treated in some way prior to dyeing. This often involves ‘scouring’ to remove any fats and oils, and ‘mordanting’ where the fabric is soaked in a warm mordant bath containing metal salts which helps the dye to adhere to the cloth. Depending on the type of fabric, this can be a very lengthy process, but every step of the pre-dyeing process is essential in producing an even, vibrant and durable final colour.
Most of my dyeing follows the simple process of grinding the dried dye material to a fine powder, boiling it to extract the colour, and then heating the cloth in the resulting dye bath. The intensity of the resultant colour on cloth is dependant on ratio of dye material to the weight of the cloth submerged in the vat.
However, few natural dyes such as indigo and lichens cannot be extracted in this way.
Indigo pigment extracted from the plant matter has to be ‘reduced’ in a fermentation vat as it is insoluble in water. The indigo vat is living culture, and must be kept at an optimum temperature and regularly fed. The indigo colour only appears when the dye is oxidised, so when the cloth is dipped into the vat it emerges a greenish yellow colour, only turning blue as it oxidises. Through multiple dips, the blue pigment on the cloth slowly increases and intensifies.