Homemade Baking Powder (single acting)

2 measure cream of tartar
1 measure baking soda

Mix together and use immediately. If you want to mix ahead of time and store no longer than one month, add 1 measure cornstarch. The cornstarch will help keep the other ingredients from absorbing moisture (this is what is used in manufactured baking powder).

If you have a recipe that calls for double acting baking powder, just use twice the amount.

To check and see if the baking powder in your pantry is still active, stir 1 teaspoon into one-third cup hot water. There should be immediate vigorous bubbling. If no bubbling or bubbling is sporadic, the baking powder is past its prime. Homemade baking powder starts to fizz and release carbon dioxide the minute it is added to liquid. It is very important that the oven be preheated and baking pans be ready before mixing batter. Mix quickly and put in oven right away.

To test baking soda's effectiveness: mix 1/4 teaspoon baking soda with 2 teaspoons of vinegar. The mixture should bubble immediately.