If you find yourself without baking powder, make your own using baking soda. Baking soda requires an acid to activate its leavening properties, and that's what baking powder is -- baking soda combined with an acidic powder. Mixing baking powder with liquid activates its leavening ability. You can make your own baking powder if you have baking soda and one or two other ingredients, and it will be fresher than store-bought baking powder, too.
Things You'll Need
Cream of tartar
Sift 1/4 cup cream of tartar, 2 tbsp. cornstarch and 2 tbsp. baking soda into the bowl.
Stir the mixture thoroughly.
Store your homemade baking powder in an airtight container in a cool, dry place. Use it just as you would commercial baking powder.
If you don't have cornstarch, add an extra 2 tbsp. cream of tartar instead.
To substitute directly for baking powder in a recipe, mix 1/4 tsp. baking soda and a scant 3/4 tsp. cream of tartar per tsp. baking powder into the dry ingredients. Alternatively, use 1/4 tsp. baking soda, 1/2 tsp. cream of tartar and 1/4 tsp. cornstarch.