This square-shaped blown and molded glass apothecary jar has a baked enamel baroque-style blue and yellow cartouche on its front. It is labeled TART TARTAR in black, with the first letter in each word in red. Tartar, also known as cream of tartar, or potassium bitartrate is a byproduct of the wine making process, crystallizing from the pulp and skins of grapes called must, in the fermenting barrel. Tartar was used as a diuretic and as a cathartic.