Baking Powder and Bicarbonate of Soda

Baking powder is a mixture of cream of tartar and sodium bicarbonate. In baking, when liquid is added, cream of tartar (an acid) reacts with sodium bicarbonate (an alkali), and releases bubbles of carbon dioxide, causing the cake or bread to rise. Most commercial brands are double-acting: they produce bubbles when activated first by liquid, then by heat. Don’t be too heavy-handed when using it as too much will taint the cake with a slight soapy flavour. Replace every 6 months — to see if it’s still active, stir some into hot water — it should bubble vigorously. Bicarbonate of soda (baking soda) is also a rising agent, but needs an acid such as buttermilk or sour cream to activate it. Bicarbonate of soda starts acting as soon as liquid is added, so cook the mixture quickly.