How To Test Baking PowderBaking powder is activated by a combination of heat and moisture. Test baking powder by mixing 1 teaspoon of baking powder with 1/3 cup hot water. If the baking powder is fresh, the mixture should produce lots of bubbles. Be sure to use warm or hot water; cold water will not work for this test.
How To Test Baking SodaBaking soda is meant to produce bubbles when mixed with an acidic ingredient. Check baking soda by dripping a few drops of vinegar or lemon juice onto a small amount (1/4 teaspoon) of baking soda. The baking soda should bubble vigorously. If you don't see a lot of bubbles, it's time to replace your baking soda.
Baking Powder & Baking Soda Shelf LifeDepending on the humidity and how well the container is sealed, you can expect an opened box of baking powder or baking soda to retain its activity for a year to 18 months. Both products last longest if they are stored in cool, dry locations. High humidity can lessen the effectiveness of these leavening agents much more quickly. It's a good idea to test baking powder and soda before using them, just to be sure they are still good. The test is quick and simple and can save your recipe!
Baking Powder & Baking Soda InfoHow Baking Powder Works
How Baking Soda Works
Difference Between Baking Powder and Baking Soda
How To Substitute Between Baking Powder and Baking Soda
Easy Baking Powder Recipe