Dyeing Shibori Arashi (Japanese tie die) with natural indigo extracted from wild Dyer's Woad (Isatis Tinctoria).
The woad plant is the original source of indigo dye and has been used for thousands of years. It grows wild in Northern California and is listed as a Noxious Weed by the state because it spreads rapidly and overtakes pasture land.
The woad plant has green leaves, yellow flowers and black seeds. There is no hint of blue, but the leaves contain an indigo precursor that can be extracted and chemically reacted to form Indigo. The first year leaves are collected from the plants growing in my neighborhood. The leaves are soaked in hot water (60C). After 20 minutes, the water is a fluorescent yellow-green. The leaves are removed and the pH is raised to about pH 10 with washing soda (Sodium Carbonate). The water immediately turns deep green. The solution is oxidized by pouring back and forth between buckets. The foam on the top starts green, then turns blue as the indigo forms. The insoluble indigo drops out of solution forming a sludge in the bottom of the bucket. This sludge is extracted, and dried to be added to the dye vat later.
The dye vat contains indigo which has been reduced to the soluble 'Leuco Indigo' by high pH and a reducing agent which strips oxygen from the solution. 'Leuco Indigo' is clear yellow and water soluble which allows it to soak into the fibers. When the cloth is removed from the vat, it immediately starts to oxidize turning from yellow to the blue indigo. Once the cloth has fully oxidized, the blue is permanent.
The indigo extracted from Dyer's Woad is chemically the same as the artificial indigo in blue jeans.
