Email to Harper How To Test Baking Powder List of Ingredients To test the freshness of baking powder, just mix 1 tsp. of the baking powder with 1/3 cup hot water. If it doesn't foam, it's not fresh. Recipe
To test the freshness of baking powder, just mix 1 tsp. of the baking powder with 1/3 cup hot water. If it doesn't foam, it's not fresh.