Thiourea dioxide is a reducing agent for indigo and other vat dyes and is an excellent substitution for sodium hydrosulfite in color stripping and discharge. It is safer to use, has a greater strength, and has a better shelf life. It can be used for stripping cellulose fiber or bleaching wool or silk. It must be used in a well ventilated area or outside.
Sequoia comes from Californian Coastal Redwoods. The dyestuff occurs in minute quantities in the seed cones, and only reaches useable quantities as a byproduct of seed collection and reforestation programs. Sequoia yields rich purple browns when dyed at 15% WOF. Shades achieved are beautiful but with moderate lightfastness.
Mordanting: use alum mordant at 15% WOF for protein fibres. For cellulose mordant with tannin at 8% WOF and then alum at 15%, or alum acetate at 8%.
Dyeing: the dyestuff may be added directly to the dyebath. Add dye material to dye pot and cover with water. Bring up to about 60ºC (140ºF) and hold for an hour. Add fibres and continue cooking for another 1-2 hours.