Cream of tartar plus baking soda, the principal ingredients in commercial baking powders, undergo a chemical reaction when they come in contact wth moisture: They produce carbon dioxide gas, which leaves dough. In recipes that call for beaten egg whites, a bit of cream of tartar added midway during beating will help stabilize the peaks os they don't deflate.
A sharp-edged cookie cutter or biscuit cutter works best for shaping the dough. A drinking glass or other cutter with rounded edges will compress the sides of the scones and inhibit proper rising.
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