Why baking soda and baking powder have different jobs
Read the leavener and the rest of the ingredient list together before making a substitution.
Baking soda is sodium bicarbonate. In a batter, an acidic ingredient such as buttermilk can react with it to release carbon dioxide. Baking powder supplies both bicarbonate and an acidic component in one mixture. Many powders are double acting: some gas is released on wetting, with more released as the batter heats.
Suppose a pancake recipe calls for both soda and powder. The presence of buttermilk helps explain the soda, and the powder can provide additional lift. Their different strengths and their effect on acidity mean that replacing both measures with the same total number of teaspoons of one product is not an equivalent recipe.
Read the label before you measure. Both powders may be fine and white, but a box marked bicarbonate of soda is the soda, not baking powder. If the required leavener is missing, look for the recipe developer’s tested substitution or choose a formula built for what you have. An extra splash of lemon juice or an extra spoon of powder also changes liquid, flavor or balance, so context matters.
