Cream of Tartar
Cream of Tartar, also known as potassium bitartrate, is a sediment that is produced in fermenting grape juice. It is an optional addition to the dye or mordant bath and is used to acidify the dye bath to effect a color change and to soften wool fibers. It will dramatically shift the color of cochineal, madder, and lac from their fuchsia and burgundy red shades to a brighter, redder shade. With madder, it will shift the hue to orange. It can inhibit the color development in logwoods and certain tannins, so it is rarely used with these dyes.
The Earthues cream of tartar is Food Grade. Use 6% wog.