Hint: Keeping Baking Powder Dry

Kitchens are humid, hot environments at times. This is a bad place to store baking powder because moisture in the air quickly kills its leavening power. A simple fix that greatly extends the lifespan of a can of baking powder is to store it along with an open box of baking soda, tightly sealed together in a zip top heavy plastic bag. Excess moisture is absorbed by the baking soda, sparing the baking powder from loss of action. Moisture has no effect on the baking soda, which remains a useful leavening (and alkalizing) agent when combined with the acids in foods such as buttermilk.