To make self raising flour, add 2 teaspoons of baking powder to one cup of plain flour. To make equivalent baking powder from other ingredients, follow these recommendations.
1 teaspoon of baking powder= ¼ teaspoon bicarbonate of soda + 5/8 teaspoon cream of tartar.
1 cup self-raising flour = 2 teaspoons of baking powder or 1/2 teaspoon bicarbonate of soda + 1 ¼ teaspoons cream of tartar to 1 cup of plain flour.
1 teaspoon baking powder= ¼ teaspoon bicarbonate of soda + ¼ to ½ cup molasses, honey or golden syrup.
1 cup sour milk= 1 cup minus 1 tablespoon fresh milk+ 1 tablespoon vinegar or lemon juice.
1 teaspoon baking powder= ¼ teaspoon bicarbonate of soda + ½ cup buttermilk, sour milk, yoghurt or sour cream. Decrease liquid in the recipe by about ½ cup or by a 1/3 cup for a thick yoghurt or sour cream.
Source: Perth Diet Clinic, Nigella
In other words, in order for baking soda to function properly, you need to make sure:
- that your batter contains a liquid ingredient (such as water or milk)
- that your batter contains an acidic ingredient (such as yogurt, buttermilk or lemon juice)
- that you heat the batter to a temperature of 80°C/175°F
