Nothing is worse than being in the middle of making your favorite pizza dough recipe, suddenly realizing you only have baking soda when it actually calls for baking powder. While it is important to understand that these two ingredients are not directly interchangeable, they are related. Fortunately with a few simple modifications, you can be confident that your dough will rise to delicious perfection.
Food Science 101
The main role of baking powder or baking soda in a recipe is to leaven your batter or dough. Think of adding vinegar to baking soda as a kid. That same reaction is what causes dough or batter to rise. With baking soda, an acidic ingredient is needed in the recipe to get that chemical reaction to take place. In baking powder, those acids are incorporated into the mix as tartaric acid and sodium aluminum sulfate. When you add water, it hydrates everything and causes the reaction to occur without needing extra acid in your recipe.
In order to substitute baking soda for baking powder in any recipe, you need to add extra acid to make your dough rise, and to neutralize the alkalinity of the baking soda. Alkalinity in food contributes to extra browning while cooking via a process called the Maillard reaction. The Maillard reaction is a contributing factor in the browning and flavor development in most cooked foods, but extra alkalinity speeds up the process and can make your pizza dough brown too quickly on the outside before the inside is done.
Double the Action
Most baking powder today is double acting, which means that when you add liquid to it, one of the acids dilutes and reacts with the base very quickly, while one doesn't dilute and react until it's heated up. That means that as it's cooking, more acid is dissolving and creating even more bubbles. It isn't possible to recreate this at home with baking soda, but you can modify your recipe to make it function as a substitute when you are in a bind.
Getting a Rise Out of Pizza Dough
For each teaspoon of baking powder in a recipe, use 1/4 teaspoon baking soda with a generous 1/2 teaspoon cream of tartar. If you want to keep some of this for later, add 1/4 teaspoon of cornstarch per teaspoon of mix and store in a sealed container to prevent moisture from getting in and causing a premature reaction. Remember that this won't be a double acting compound, but it will do the job.