Regular all-purpose flour is just that: flour, in its simplest form. Flour is made of milled wheat, which is then enriched with vitamins and minerals in accordance with Canadian food law. But that’s it. It contains no other ingredients.
Self-rising (or self-raising) flour is different from all-purpose flour because it has baking powder and salt already added to it. It is best used in recipes that call for it, as using it instead of regular flour in a recipe without modifying the recipe may yield unexpected results. Using it in a recipe that calls for all-purpose flour will mean you must decrease the leavening agents called for in the recipe, which can be difficult to calculate accurately.
It’s most commonly called for in recipes for biscuits, scones and tea loaves from countries other than Canada and the United States. In the U.S., it’s a common ingredient in breading for fried chicken.
Self-rising flour can be found in the baking aisle of most grocery stores – the Brodie brand is generally easy to find. However, if your recipe calls for self-rising flour and you don’t have any on hand – or you can’t be bothered buying a bag when you only need a cup – you could use all-purpose flour plus 1 1/2 tsp baking powder and 1/2 tsp salt per each cup of flour called for in the recipe. It’s also not a bad idea to stir the three ingredients together to get a good mix