Handy Mom puts cream of tartar to work.

Once, in an exhausting bout of holistic housecleaning, Handy Mom stumbled on a variety of other uses for Cream of Tartar, that innocent looking jar of white powder in her spice cabinet. She always knew that this stuff
(better known to scientists as the acid salt "potassium hydrogren tartrate") was what you add to egg whites to poof them up when making a meringue (it has something to do with cream of tartar's ability to prevent crystals from forming during the baking process). But Handy Mom also learned cream of tartar has a host of other uses.
-Jane Hawes

Cleaning metals: Make a paste of cream of tartar and vinegar (or lemon juice) and use on aluminum, copper and brass.

Cleaning greasy pots and pans: With a mixture of 2-1/2 cups baking soda, 1-1/2 cups salt and 2 tablespoons of cream of tartar.

Cleaning the ring around the bathtub: Slather a paste of cream of tartar and hydrogen peroxide on the tub surface, let dry, then wipe clean; works especially well for older porcelain tubs.

Making play dough: Mix 1 cup flour, 1 cup salt, 1 cup water, 1 tablespoon vegetable oil, 1 tablespoon cream of tartar, and 3-5 drops of food dye.

Folk remedy for rheumatism and gout: Because it helps dissolve uric acid in the bloodstream (a major cause for both conditions), Livestrong.com claims that drinking a half-teaspoon of cream of tartar dissolved in 8 ounces of water is supposed to help.