The first of the “Big Three” leavening methods is chemical leavening. It’s the latest of the three to arrive on the baking scene, having been invented right about the time of the First Industrial Revolution, some 230 years ago. As its name implies, it involves using chemicals to create “seed” bubbles (usually of carbon dioxide) in wet doughs or batters. I say “seed” bubbles because just as with microbes, chemical leaveners can only push a bread up so far. They can initiate the process certainly, but the real heavy lifting is done by steam. And if that sounds like mechanical leavening to you, it’s a because it is. Mechanical (or steam) leavening is part of every leavening method. Whether alone or teamed with others, it is the true engine of bakery.