Abstract: A high-temperature furnace for melting materials, e.g. silicon, wherein the furnace comprises a vessel having a wall which defines an inner chamber. A crucible containing the material to be melted is positioned inside of the chamber and heating means is arranged around the crucible. An insulation package is provided in the chamber for protecting the vessel wall from the heat generated by said heating means. Specifically, the package comprises a support ring of insulation mounted in the chamber, a sleeve of insulation supported on the ring and extending upward between the heating means and the vessel wall, a catch tray adapted to receive any material which may leak from the crucible during heating mounted through the support ring, and a top and a lower layer of insulation to thermally seal the crucible within the package during heating.