Baking powder

A common guide is 1–2 teaspoons for every 150 g of flour. Too much can make a cake rise rapidly and then sink, or leave a bitter, soapy taste.

Yes, but you generally need about three times as much baking powder as baking soda, and the result may taste different. For a closer substitute for 1 teaspoon of baking powder, mix ¼ teaspoon bicarbonate of soda with ½ teaspoon cream of tartar.

It releases some gas when it gets wet and more as the batter heats in the oven. This gives the mixture a second lift during baking, so get it into the oven promptly but don’t worry if it sits briefly while you finish preparing the tin.

Stir ½ teaspoon into a small glass of hot water. It should fizz vigorously; if it barely bubbles, replace it.

Keep it tightly sealed in a cool, dry cupboard, away from steam and damp. Always use a dry spoon, as moisture can start the reaction before it reaches your mixture.

Not as a like-for-like swap: baking powder raises dough quickly, while yeast ferments it and develops the flavour and texture of yeasted bread. Use a quick-bread or soda-bread recipe designed for baking powder instead.

Yes. It gives pancakes a lighter texture; whisk it into the dry ingredients first, then stir the wet and dry mixtures together just until combined. A few small lumps are better than overmixing, which can make pancakes tough.