My answer: Rose’s question was originally two-part asking how to test baking powder and baking soda for freshness. Last week we talked about baking powder so this week we’ll have information for how to test baking soda.
Put a few tablespoons of white vinegar into a small bowl and add a teaspoon of baking soda. It should bubble up furiously, and the foaming should take several moments to subside. The more bubbles, the more potent the baking soda. If there is no reaction or if you end up with only a handful of small bubbles, you need to replace your baking soda. Here’s a site that will tell you everything you need to know about baking soda and more. Keep in mind that baking soda that fails the test can still be used for household cleaning, freshening drains, etc. Thank you, Rose, for your question and for your interest in Ask Cynthia a Question.