At any given moment, I have at least one open box of baking soda and one open canister of baking powder in my pantry, and I never, ever know how old they are. Unlike cheese or apples, neither of these leavening agents offers any visual cues as to when they have “gone bad.” They look the same no matter their age, but will just quit working, leaving flat, unleavened cakes, cookies, and quick breads in their wake. Luckily, there are two easy tests you can use to determine the efficacy of each.
As we’ve discussed previously, both baking soda and baking powder are chemical leavening agents, but they work in different ways. Baking soda is “pure sodium bicarbonate, an ionic salt with the chemical formula NaHCO3. It’s naturally alkaline (basic) with a pH of eight, and provides the ‘base’ portion of the acid-base reaction.” Baking powder, on the other hand, contains both acidic and basic ingredients, which are activated by introduction of water. To see if baking soda works, you have to introduce it to some acid; to test baking powder, add a little water.
To test your baking soda, pour three tablespoons of white vinegar into a bowl or cup, then stir in ½ a teaspoon of baking soda. For baking powder, add ½ a teaspoon of baking powder to three tablespoons of water. In either instance, if the solutions fizz, then the leavening agent is still good, and you can feel secure in proceeding with your baking endeavours. If they don’t fizz, it’s time to restock (and write the date on the new package this time) — though you can substitute one for the other if your leavening needs are dire and immediate. (You can also use either to clean and scrub with, provided the the cleaning does not hinge on a robust acid-base reaction.)
This post was originally published in 2014. It was completely rewritten and republished on May 3, 2021 to add more accurate information and to match current Lifehacker style guidelines.