Copper bowls are the preferred vessel for whipping egg whites used in meringues and zabagliones. Using a copper mixing bowl produces a creamier foam that is more stable than the drier foam produced by whipping egg whites in a stainless steel or ceramic bowl.
Bain-Marie is the French term for "water bath" cooking, in which a container is placed in heated water to gently warm the food within. A bain-marie is similar to a double boiler, except the container in a bain-marie sits in the water itself. The bain-marie container is typically made of porcelain or ceramic rather than metal.