Color pusher. Dye absorption leveler.
Glauber’s Salts have numerous uses. It is used in the dyepot as a leveling agent, that is, it helps make the dyeing a more even prospect. It also tends to encourage the dye to move towards the fiber more uniformly, keeping dyes that strike really fast (like osage orange) from missing large portions of the fiber in it’s enthusiasm.
The DyeWorks recommends Glauber’s Salts when the dyestuff (usually madder) is taking it’s sweet time and could use a little extra encouragement. Glauber’s Salts are dissolved in boiling water, a tablespoon at a time, and strained into the dyepot for desired results.