Channeling Julia

Baking often involves foods that rise.

When we fill a pan, we must be aware that the final volume of the baked goods will be larger than the initial volume.

This is particularly true of recipes that use baking powder (or baking soda and an acid such as Cream of Tarter) as an ingredient. Baking powders are rapid acting and give off gases as soon as they are mixed with water, but they also create gas as they are heated (that's why they are called double acting). Cakes and quick breads will typically expand in volume to 150% as they cook (more or less depending on the recipe. This is why you will see notes like 2/3 full in a recipe.

Yeasts require much more time to rise. The yeast metabolizes sugars and starches to grow and carbon dioxide is the by product that makes the dough rise. The yeast may double or triple in volume. Large gas pockets may burst and change the volume. This is controlled by kneading the dough several times as the dough rises. Folding the dough reduces the size of the air pockets and gives a finer texture. If you've ever toured a large commercial bakery you can't help but remember the huge tubs where dough rises the first time and seen the big gas bubbles in the dough. The common grocery store loaf of bread has risen three times, twice in a tub and once in the pan just before baking. This is why white bread has such a fine texture compared to french bread (which only rises twice).