The Book of Household Management by Mrs. Beeton

566. THE VESSELS USED FOR BOILING should be made of cast-iron, well

tinned within, and provided with closely-fitting lids. They must be kept scrupulously clean, otherwise they will render the meat cooked in them unsightly and unwholesome. Copper pans, if used at all, should be reserved for operations that are performed with rapidity; as, by long contact with copper, food may become dangerously contaminated. The kettle in which a joint is dressed should be large enough to allow room for a good supply of water; if the meat be cramped and be surrounded with but little water, it will be stewed, not boiled.