I saw a Land o' Lakes baking magazine at Costco today, and I thought I'd pick it up to see if there were any useful recipes or tips. I found one about pie pans (use glass) and one about cookie sheets (use shiny).
But I also learned the difference between baking powder and baking soda. I knew the powder had other ingredients—cream of tartar and cornstarch—but I didn't know when a recipe would call for one over the other.
Use baking soda in anything with sour ingredients. So if the recipe calls for sour cream, vinegar, or buttermilk, use baking soda.
Good thing I'd chosen, by instinct only, to subtitle my book: "A Celebration of Flour, Sugar, Butter, Eggs, Vanilla, Baking Powder, and a Pinch of Salt." Soda would not have worked.