It's neither a cream nor related to tartar sauce, but it is an extremely useful ingredient in baking. Cream of tartar, whose chemical name is potassium bitartrate, is actually an acidic salt produced as a byproduct of winemaking. Its primary purpose is culinary, but when combined with other products -- such as vinegar -- it can also be used around the house.
Adding one-eighth of a teaspoon of cream of tartar per egg to whipped egg whites will help "stabilize" the whites. This makes them fluffier and better able to retain air and hold onto their shape when baked. It is most often used when making meringue, and can also help keep the egg whites looking extra bright and white. The delicate nature of angel food cake and souffle also benefits from cream of tartar's stabilizing properties.
If you want smooth, creamy-looking icings or candies, cream of tartar can help. Add a pinch of cream of tartar to cooked sugar to prevent the sugar from sticking to itself and forming crystals, which can make a finished product look rough. Some examples of sweets that get their smoothness in part from cream of tartar are:
Baking Powder Substitute
When you're out of baking powder, add two parts cream of tartar to one part each of cornstarch and baking soda for an effective baking-powder substitute. Dissolving cream of tartar in water triggers the baking soda and helps make your baked product rise naturally in the oven.
Cream of tartar is particularly useful around the home. Make a paste with lemon juice and cream of tartar to remove stubborn laundry stains. A paste of water and cream of tartar can help rejuvenate scratched dishes and clean aluminum pots and pans, while a hydrogen peroxide-cream of tartar paste is said to effectively remove stains from tubs, sinks and toilet bowls.