Science, Tech, Math › Science Baking Powder Shelf Life How long does baking powder last? Share Flipboard Email Print Baking powder has a relatively short shelf life compared with other baking ingredients. Dave King, Getty Images Science Chemistry Chemistry In Everyday Life Basics Chemical Laws Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated December 08, 2017 Did you know that baking powder has a shelf life? Unopened baking powder remains good indefinitely, but once you open a container of baking powder its potency starts to wane. The ingredient in the baking powder that would react with liquid in your recipe reacts instead with water vapor in moist kitchen air. You can slow this process by making certain your baking powder is tightly sealed when you aren't using it. Test Baking Powder It's a good idea to test baking powder before using it in a recipe. Mix a bit of warm water into a small amount of baking powder. If you see bubbles of carbon dioxide form, then your baking powder is good. If no bubbles are formed or the reaction seems weak, it's time to replace your baking powder. If you only get a few bubbles from the reaction with warm water, but can't get fresh baking powder in time to make the recipe, you can either use a bit more baking powder or else make homemade baking powder from baking soda and cream of tartar.