A nonreactive pan or container is one that is made from material that will not create a chemical reaction with ingredients and alter the flavor or color of the food (acids such as vinegar or tomatoes, for example, can react with aluminum pans). Good choices for nonreactive containers include glass, glazed ceramic, and enamel (not chipped). For cookware, choose stainless steel, enamel (not chipped), glazed ceramic, or heat-safe glass. Copper is a reactive metal that is great for whipping egg whites, but, like aluminum, can react with other ingredients when subjected to high heat, causing unwelcome changes in food. These two metals conduct heat really well, so some lines of cookware use a layer of copper at the bottom (where the pan meets the heat source) but a nonreactive metal to hold the food.