A process for melting material to be treated includes placing material to be treated in a container that may include an insulating lining, heating the material to be treated and melting the material to be treated, preferably allowing the melted material to cool to form a vitrified and/or crystalline mass, and disposing of the mass. The mass is either disposed while contained in container or removed from container after cooling and disposed. Heat loss and melt-surface disruptions can be minimized with an engineered overburden material, which covers at least a portion of an exposed surface of the material to be treated.