Baking powder contains bicarbonate of soda and tartaric acid with a dried starch or flour to absorb any moisture during storage. It has a limited shelf life. To make your own: combine 15ml/1tbsp bicarbonate of soda with 30ml/2tbsp cream of tartar. Measure carefully as too much or too little can upset a recipe's balance.
Use: A raising agent used in cakes, biscuits and breads. When mixed with liquid, baking powder releases carbon dioxide gas bubbles that cause a bread or cake to rise.