Manufacture of flat glass

Claim 1

In a method of producing float glass having a predetermined surface characteristic, comprising continuously forming and advancing a ribbon of glass along a bath of molten metal, maintaining the advancing ribbon sufficiently hot to be susceptible to surface modification utilizing a molten metal body, maintaining a current conducting first molten metal body against the upper surface of the ribbon, passing a controlled electric current through the glass between the first molten body and the bath to effect surface modification of the ribbon, and continuing the advance of the surface-modified ribbon along the bath, and wherein a vapour originating from the current conducting first molten metal body is engendered, the improvement comprising: maintaining against the modified surface of the advancing ribbon downstream of said first body an ancillary molten metal body, electrically isolating said ancillary molten metal body to maintain that body electric current-free, maintaining the electric current-free ancillary body at a lower temperature than the first body, spacing the ancillary body downstream of said first body by a distance which locates the ancillary body beyond the region of condensation of vapour originating from the first body, and, without passing current through said ancillary body to effect surface modification of the ribbon, cleansing the modified glass surface of any metal of said first body which is present on the modified surface of the ribbon by absorbing that metal with said electric current free ancillary molten metal body while not engendering vapour therefrom.