Indigo is an organic pigment derived from plants and used for millennia across cultures. It it also one of the more complicated dyes to prepare. Where we work, the dehydrated indigo cake is usually bought from growers in the Istmo region of Oaxaca. It takes a minimum of three days to prepare before it is ready to dye the yarn. Steps include grinding the cake into powder, then adding it, with leaves, to filtered wood ash water. All steps must be carefully monitored for pH values and other factors.
The organic purple dyes from this area of Mexico are derived from sea snails (purpura patula). Indigenous people have long collected the snails sustainably, while respecting the land, sea and moon cycles, and conserving the environment. They pick them from rocks on the coastline during low tide and return the snails unharmed after extracting the dye. The snails produce an initially colourless secretion, which can be rubbed onto a skein of cotton. Contact with the air turns it yellow, green, and ultimately purple. In the 1980s, a foreign company came into the area and harvested the snails year-round, greatly reducing their numbers until a law was introduced forbidding them. Today only Indigenous dyers are allowed to work with the snails. Garments made from yarn using this dye are difficult to find and highly sought after.