Not sure your baking powder still works? Drop 1 tsp into 1/3 cup hot water; if it bubbles vigorously, it may still have enough potency for baking

A flat cake or spread-out cookie is often blamed on a bad recipe, but the real reason could be hiding in your pantry. According to Penn State Extension, mixing a teaspoon of baking powder into a third cup of hot water is a good way to test its potency. If the mixture bubbles vigorously, it still has enough potency to make a good recipe. If it doesn't bubble much, the baking powder may have lost potency and should be replaced. Most people don't learn this trick until they have already made a disappointing cake or cookie that turned out flatter than expected. Although it's not difficult, this trick can be very helpful when you've already added eggs, butter, and vanilla to a mixing bowl.

Why baking powder loses its lifting power over time

Baking powder contains an acid and baking soda as dry ingredients, which react together to produce carbon dioxide when moistened, making the batter rise when baked. When moisture is introduced and the powder is heated, it produces this gas. Leaving it in a pantry for months can add enough moisture to react with the mixture and produce carbon dioxide. Plunging a wet spoon into the mixture adds moisture every time you use it. According to Michigan State University Extension, opened baking powder generally loses its effectiveness within 6 to 12 months, since it has already been exposed to moisture and its potency may be lost before the printed date due to a wet or dirty utensil. The print date on the container is just a guide. Baking powder left near a stove, where moisture is more likely, may last less than that kept in a closed cupboard.

How to run the hot water test at home

This test takes less time than preheating an oven. Here's the simple procedure: bring some hot water, nearly boiling, because heat activates the reaction, and measure one teaspoonful of baking powder into a small bowl, then add a third-cupful of hot water and watch the fizzing action for a few seconds. A good batch will fizz vigorously, like a chemistry-class demonstration, while a poor-quality batch will show little or no reaction.

What a weak result means for your bake

A failed test is usually a failed batch of your favorite treats. Instead of light, fluffy, airy delights, you end up with something heavy, compact, and underbaked. The reason? The leavening agent failed to rise the dough or batter properly. In other words, the baking powder was defective. The solution is to replace it with fresh baking powder, since baking soda alone isn't a suitable substitute because it needs an acid to release carbon dioxide.

Storing baking powder so it lasts longer

Where you store the baking powder in the kitchen matters almost as much as its age. Heat and moisture are the main enemies of any baking powder kept in a domestic environment. Store baking powder in a closed, dry cabinet, away from the stove and dishwasher, since heat and steam from cooking can gradually reduce its potency. Always measure the powder with a dry spoon, because even a small amount of moisture can start the process that heat begins in the freshness test. Close the lid after each use, and try to use it within the period indicated on the label rather than keeping it on your shelf for many years. For general storage guidelines for various kitchen items, including baking powder, the U.S. Department of Agriculture offers an app called FoodKeeper.

A quick check for baking soda too

Baking soda needs a similar test but with vinegar instead of water. Mix 1/4 teaspoon of baking soda with 1 tablespoon of vinegar in a small bowl. If it bubbles up and reacts, it's still good for baking. If it barely reacts at all, it's lost most of its leavening power but can still be used to absorb odors in your fridge.

Make this test part of your regular baking routine

A heavy cake or muffin that refuses to rise could be caused by something other than bad technique; your baking powder or baking soda could be to blame. Test it in a hot water bath first, before you pull out your mixing bowl. It's faster than preheating your oven and can save you from ruined eggs and a disappointing result.