The Food Lab: Better Home Cooking Through Science

get a light, tall, fluffy interior. Let the batter sit for half an
hour, and you get a dense, gummy interior with few
bubbles. But wait a minute, there are still some bubbles in
there, right? Where did those come from?
Well, pretty much all baking powder is what is referred to
as “double-acting.” Just as the name indicates, it produces
gas in two distinct phases. The first occurs as soon as you
mix it with water; the second occurs only when it is heated
(see “Experiment: Double-Acting Baking Powder,” here).
This second rise in the skillet makes for extra-light and
fluffy pancakes.