The aim in making meat stock is to produce a full-flavored liquid with enough gelatin that it will also become full-bodied when reduced. Meat is an expensive ingredient, an excellent source of flavor, and a modest source of gelatin. Bones and skins are less expensive, poor sources of flavor, but excellent sources of gelatin. So the most flavorful and expensive stocks are made with meat, the fullest bodied and cheapest with bones and pork skin, and everyday stocks with some of each. Beef and chicken stocks taste distinctly of their respective meats, while veal bones and meat are valued for their more neutral character, as well as their higher yield of soluble gelatin. Cartilaginous veal knuckles and feet give especially large amounts. Typically, the meat and bones are cooked in between one and two times their weight in water (1–2 quarts or liters per 2 lb/1 kg solids), and yield about half their weight in stock, thanks to gradual evaporation during cooking. The smaller the pieces into which they’re cut, the more quickly their contents can be extracted in the water.