Baking powder is a leavening agent, most frequently used in recipes like cakes, quick breads and pancakes. You’ll often see baking powder advertised as double acting. Unlike baking soda, baking powder frequently adds an additional ingredient, usually an acid, to bicarbonate of soda. This results in a higher rise in baked goods, because the rise begins at room temperature, instead of when foods are baked.

The most common combination of acids and alkalines that produce baking soda are cream of tartar and sodium bicarbonate. Sodium bicarbonate activates at high temperatures, but combining it with an acid like cream of tartar activates it earlier. Not all recipes require baking powder, and in fact some baked goods can be ruined by the double rise mechanism. When a recipe calls for baking soda, using baking powder can create too much rise. Similarly, substituting soda for powder may result in flatter baked goods.

What you can do, if you’ve run out of baking powder is combine baking soda and cream of tartar to make your own soda. One part baking soda is added to two parts cream of tartar. For instance, in a recipe that calls for 3 teaspoons of baking powder, you would use two teaspoons cream of tartar and one teaspoon of baking soda.

Baking powder may also contain a small amount of cornstarch, which helps to keep the ingredients from absorbing moisture. This is largely unnecessary when mixing up a small substitution batch. In the 20th century, concern arose regarding the aluminum content in baking powder, especially as related to the potential for later development of Alzheimer's disease. If you are concerned about this possible risk, you can find numerous brands of baking powder that are aluminum free. If you're having trouble finding a brand that is aluminum-free, try your local natural or health food store.

Since baking powder begins to activate at room temperature, you’ll note many recipes for baked goods that tell you to have all ingredients at room temperature. Many ignore this advice, and still produce fine baked goods. Yet if you’re trying for a high, light cake, you have to pay attention to these instructions. Essentially, you want the rising process to begin before the cake every reaches the oven.

You should also note that recipes containing acids like lemon juice and buttermilk will activate baking powder more quickly and render it more effective. Often you’ll see baking powder recommendations of about a teaspoon of powder to a cup of flour. This amount should be lower when high acid content foods are added. If you note they are still the same, you may be adding too much baking powder to your mixtures. The amount of baking powder required in a recipe that contains about a cup of lemon juice or buttermilk usually decreases by a half.