Cream of Tartar Powder or potassium bitartrate, is created in the fermentation of grape juice which yields this sediment. It is an optional addition to the dye or mordant bath, used to acidify the bath, effecting a color change, and softening wool fibers. It creates brighter, redder shades when used with cochineal, madder and lac. When used with madder, it shifts the hue to orange. Warning it can inhibit the color development in logwoods and certain tannins dyes.