Now, fold your bias tape over to the back side, encasing the raw edge. Pin as you go. Bias tape folded over to the back side: This is what my pinning looks like. I slip the pins under the bias tape on the top side and make sure it catches the bias on the back.
Baking Powder. Baking powder on the other hand, is actually a combination of baking soda plus another acid, in the presence of an inert stabilizer (a fancy term for an inactive ingredient that keeps the mixture from reacting), which is often a bit of cornstarch.
Recipes that call for both baking soda and baking powder is usually due to the fact that the recipe has some acid and is needing neutralized by the baking soda, but possibly not enough to do the amount of leavening desired. The baking powder picks up the slack.