Here's another handy reducing agent to try with your indigo vats!
Are you tired of waiting a while for your indigo vats to produce a flower and want to jump into dyeing as fast as you can?
Then Sodium Hydrosulfite is the one for you! Think of this reducing agent like choosing premium gas for your sleek vehicle. It will give you a quicker reaction, better color performance (especially on silks and wools) and doesn't leave any leftover residue (or flower) which has to constantly be skimmed off the top.
Sodium Hydrosulfite also tends to have a longer shelf life than other reducing agents, so if you keep it in a cool, dry place and take care not to expose it to oxygen, it can last you a while!
Sodium Hydrosulfite can also be used as a discharging agent to help remove color from fabric, or create neat patterns, or as a step in reverse tie-dye.
You can adjust it's strength anywhere from 3-5% per dry weight of fabric. It must be used in equal parts with Soda Ash and used on the stovetop at a rolling boil. This means for 1 pound of fabric you would use 22 grams (about 1 1/2 Tablespoons) for a 5% strong solution.
Heat to 185ºF, add fabric and continue heating. Color removal works best at a rolling boil.
Keep fabric moving for 10 to 20 minutes or until color has left as desired. Wash with mild detergent in cool water.
Note: not all dyes are fully susceptible to color removal. Results may vary. Test first whenever possible - not all fabrics will go back to being white!