Baking bread is simple in theory, but mastering its complexities can take years. That's because the yeasts and bacteria that give bread its rise and its flavor are living organisms, and are sensitive to temperature, humidity and a wide range of other factors you might not be aware of. Bread machines address this by providing a closed environment with controlled, predictable levels of temperature and humidity. When you're baking bread on your own, you'll have to learn how to judge the dough's fermentation for yourself.

Fermentation is the name bakers and brewers give to the effect of yeasts. Those microscopic organisms digest the natural sugars found in the flour, as well as any additional sweeteners you've put in the bread. As byproducts, they produce alcohol and carbon dioxide. Brewers maximize alcohol production, keeping enough carbon dioxide to give the beer its fizz. Bakers maximize carbon dioxide, which helps the dough rise, but minimize alcohol production. In bread dough, alcohol gives the bread sour "off" flavors and affects the development of the dough's gluten. Whether your favorite bread rises quickly in a warm place, or slowly in a cool place, the baker's "finger test" will tell you when it's fermented enough.

Most recipes advise letting the bread ferment for a specified time, or until it doubles in bulk. That's a pretty vague guideline. A surer test is to press two fingers into the dough. If it's elastic enough that the mark of your fingers disappears, it hasn't fermented long enough. If your fingers leave a hole that stays unchanged, or if the dough sighs and collapses, you've left it too long. Ideally the mark of your fingers remains in the dough, but springs back partially. It's hard to visualize from a written description, but over time you'll come to recognize the different stages.

When you mix your liquids and flour to make the dough, proteins in the flour form long, stretchy strands called gluten. Those gluten strands act like hundreds of thousands of balloons, trapping the carbon dioxide produced by the yeast and causing the dough to rise. If the mark of your fingers disappears, that means the gluten strands are still strong and elastic, and have more stretch left in them. If the dough is soft and retains the mark of your fingers, that means the gluten strands are stretched to their limit. At that point, when you punch down the bread and knead it, you're compressing the gluten strands and making them springy again. When the bread rises once more, the newly strengthened gluten strands will hold it into its final shape.