If your baking powder is too old it won't do it's job and your recipes won't turn out. Buy your baking powder in small quantities. Write the date on the container and discard it after six months. To check baking powder for freshness add 1 teaspoon baking powder to 1/3 cup hot water. If it bubbles vigorously it's still good. If your baking powder is too old it won't do it's job and your recipes won't turn out. Buy your baking powder in small quantities. Write the date on the container and discard it after six months. To check baking powder for freshness add 1 teaspoon baking powder to 1/3 cup hot water. If it bubbles vigorously it's still good. 
