Raising agent Bicarbonate of soda is the chemical substance which causes scones to rise in the oven. It activates immediately on the addition of a liquid which is why scones must be quickly mixed and put straight in the oven. If used alone without a neutralizing acid substance the resulting scones would have a very unpleasant taste. So cream of tartar, which is acidic, is used together with bicarbonate of soda. The most convenient way to add both of these ingredients to the mixture is to use baking powder, a substance containing both the alkaline bicarbonate of soda and an acid reacting powder such as cream of tartar.
