Ingredients

　　

Need some, have none

Step 1

For every cup of flour in the recipe, mix 2 teaspoons cream of tartar, 1 teaspoon baking soda, and 1/2 teaspoon salt. Use this right away; it won’t be effective for more than a day or so.

　　

Uncertain quality

Step 2

Stale baking powder can ruin whatever you’re making, but old powder isn’t necessarily stale. Here is a simple test: Put 1 teaspoonful in a cup of hot water. If it bubbles a lot, it’s good. If it doesn’t, throw it out.

　　How to Repair Food, Third Edition