A furnace for melting vitrifiable materials having a compartment (1) for the melting/refining of the glass and which is provided in its upstream part with at least one opening (12) to be supplied with vitrifiable materials (10) with the aid of a charging device positioned facing and in the downstream part a discharge opening (17) for the molten glass issuing into one or more successive, downstream compartments (18, 19) for leading the molten glass to the forming zone. The melting of the vitrifiable materials takes place in the melting/refining compartment (1) essentially via a plurality of burners (16) with an oxidizer constituted by oxygen. It is designed to operate without any air introduction into the melting/refining compartment (1) coming from the downstream compartment or compartments.