Method and apparatus for refining glass in a melting tank

A method of manufacturing glass comprising feeding glass forming material into one end of a glass melting tank, melting the material in a melting zone of the tank adjacent an inlet end of the tank, refining the molten material at a refining zone downstream of the melting zone, and conditioning the molten glass in a shallow conditioning zone adjacent an outlet end of the tank so that the molten glass leaves the tank ready for use in a forming process, said method further comprising passing the molten glass from an inlet end of a glass melting tank through a wide body portion including said refining zone and subsequently through a substantially narrower channel, including said shallow conditioning zone and a deeper intermediate zone leading from said refining zone to said conditioning zone, towards the outlet end, said refining zone and said intermediate zone being sufficiently deep for forward and return flow of molten glass to take place, enforcing temperature gradients within the melting, refining and intermediate zones and enforcing forward and return flows of molten glass in the melting. refining and intermediate zones, limiting the downstream position of the return flow at a step in the base of the narrow channel at the juncture of said intermediate and conditioning zones, and further physically slowing up the forward flow of the upper levels of molten glass into the intermediate zone by flow control means, whereby the glass enters the shallow conditioning zone at a temperature suitable for conditioning and flows in the direction of the outlet with substantially no return flow in the shallow conditioning zone.