Abstract: The invention provides an improved furnace structure and methods of melting material in furnaces, particularly aimed at reducing the start up time for such furnaces. The furnace (2) defines a container for the molten metal having a maximum depth of molten metal in that container during use. A flow generator (30) for the molten metal within the furnace is fed through a first conduit (32) and supplies material back to the furnace through a second conduit (36). The first conduit entrance is provided in the upper 60% of the maximum depth of the molten metal in the container and/or the second conduit exit is provided in the lower 25% of the maximum depth of the molten metal in the container. The flow generator may receive material preferentially from around the periphery of the container and/or direct material towards the centre of the container. The inlet and outlet to the flow generator may be angled downwards towards the container.