Cream of Tartar – Cream of Tartar is a white powder often used in baking to help stabilize meringue. It is a byproduct from the sediment left behind in winemaking – another use for a waste product! In natural dyeing, cream of tartar is used to acidify the dye bath to as a color changer. It’s also used in mordanting to soften wool fibers. As well, I’ve read that it helps aluminum sulfate bind more strongly to the fibers. Depending on the dye, it will shift cochineal, madder and lac to brighter, redder colors. With madder, it will shift the hue to orange and with cochineal the color will become a bright red. It can inhibit the color development in logwoods and certain tannins, so it is rarely used with these dyes.