in order to initiate the leavening process). In some variations, the dry ingredients are in a bowl and the wet ingredients are heated sauces in a saucepan off-heat and cooled. During the chemical leavening process, agents (one or more food-grade chemicals—usually a weak acid and a weak base) are added into the dough during mixing. These agents undergo a chemical reaction to produce carbon dioxide, which increases the baked good's volume and produces a porous structure and lighter texture. Yeast breads often take hours to rise, and the resulting baked good's texture can vary greatly based on external factors such as temperature and humidity. By contrast, breads made with chemical leavening agents are relatively uniform, reliable, and quick. Usually, the resulting baked good is softer and lighter than a traditional yeast bread. Chemical leavening agents include a weak base, such as baking soda (sodium bicarbonate) plus a weak acid, such as cream of tartar, lemon juice, or cultured buttermilk, to create an acid–base reaction that releases carbon dioxide. (Quick bread leavened specifically with baking soda is often called "soda bread".) Baking powder contains both an acid and a base in dry powdered form, and simply needs a liquid medium in which to react. Other alternative leavening agents are egg whites mechanically beaten to form stiff peaks, as in the case of many waffle recipes, or steam, in the case of cream puffs. Nevertheless, in a commercial process, designated chemical leavening acids and bases are used to make gas production consistent and controlled. Examples of acid—base combinations include: Almost all quick breads have the same basic ingredients: flour, leavening, eggs, fat (butter, margarine, shortening, or oil), and liquid such as milk. Ingredients beyond these basic constituents are added for variations in flavor and texture. The type of bread produced varies based predominantly on the method of mixing, the major flavoring, and the ratio of liquid in the batter. Some batters are thin enough to pour, and others thick enough to mold into lumps. Mixing methods There are three basic methods for making quick breads, which may combine the "rise" of the chemical leavener with advantageous "lift" from other ingredients: The stirring method (also known as the quick-bread method, blending method, or muffin method) is used for pancakes, muffins, corn bread, dumplings, and fritters. It calls for measurement of dry and wet ingredients separately, then quickly mixing the two. Often the wet