Gluten free baking requires a good knowledge of baking powder and bi-carb soda (baking soda in the US). The further you delve into gluten free using alternative gluten free flours the more you need to supplement recipes with baking powder or bi-carb soda. Here is a guide to what they are and their purpose in your gluten free cooking.
Let us first rule out baking soda, which is actually the American name for what we in Australia call bi-carbonate soda. When cooking from American websites it is very easy to read baking soda and automatically go for the baking powder (believe me I know!), the results won't be disastrous but bicarbonate of soda will provide one closer to the intended goal!
Bi-carb soda and baking powder are both rising agents, they create the air bubbles you see when stirring, whipping or in some cases just adding it to your mixture. They also give the rise to your recipes when they are cooked.
Bicarbonate of soda is a pure rising agent. When mixed with moisture and an acidic ingredient a chemical reaction will make the ingredients rise. An acidic ingredient needs to be present, such as lemon juice, vinegar or honey.
Baking powder, contains bicarbonate of soda but it is pre-mixed with the acidic ingredient, cream of tatar so you simply need moisture to activate it. If you don't have any baking powder in the pantry you can make your own by mixing two parts cream of tartar with one part bicarbonate soda.
Historically in Australia we just use self-raising flour (which has raising agent already added) unless more rising agent is specified, but as a gluten free group we know that some recipes and just the pursuit of a great gluten free flour blend mean that sometimes we choose not to buy pre-mixed gluten free flour. This is the reason the need for baking powder and bi-carb soda is greater in gluten free cooking.
Bicarbonate of soda has a slightly tangy taste, to reduce the chance of it clumping always sift into the other ingredients. Baking powder has a neutral taste and it often used with other more neutral ingredients.
Always be sure to check the baking powder and bicarbonate of soda are themselves gluten free. Good brands in Australia that are readily available at supermarkets are Wards Baking Powder (clearly marked gluten free) and McKenzie's Bicarbonate of Soda (which isn't marked gluten free but is such by ingredient).
Hopefully this answered that fizzing question, happy baking!