Provided is an alkali-free glass substrate having a high strain point and excellent bubble count, and a method for manufacturing the alkali-free glass substrate. The method includes: a batch preparing process of preparing a raw material batch so as to obtain alkali-free glass containing, in mass %, 50 to 80% of SiO.sub.2, 15 to 30% of Al.sub.2O.sub.3, 0 to 4.5% of B.sub.2O.sub.3, 0 to 10% of MgO, 0 to 15% of CaO, 0 to 10% of SrO, 0 to 15% of BaO, 0 to 5% of ZnO, 0 to 5% of ZrO.sub.2, 0 to 5% of TiO.sub.2, 0 to 15% of P.sub.2O.sub.5 and 0 to 0.5% of SnO.sub.2 as a glass composition; a melting process of melting the prepared raw material batch; a fining process of fining the molten glass; and a forming process of forming the fined glass into a sheet shape. The raw material batch is melted such that a bubble enlarging temperature of the obtained glass is lower than a maximum temperature of the fining process.

Provided is an alkali-free glass substrate having a high strain point and excellent bubble count, and a method for manufacturing the alkali-free glass substrate. The method includes: a batch preparing process of preparing a raw material batch so as to obtain alkali-free glass containing, in mass %, 50 to 80% of SiO.sub.2, 15 to 30% of Al.sub.2O.sub.3, 0 to 4.5% of B.sub.2O.sub.3, 0 to 10% of MgO, 0 to 15% of CaO, 0 to 10% of SrO, 0 to 15% of BaO, 0 to 5% of ZnO, 0 to 5% of ZrO.sub.2, 0 to 5% of TiO.sub.2, 0 to 15% of P.sub.2O.sub.5 and 0 to 0.5% of SnO.sub.2 as a glass composition; a melting process of melting the prepared raw material batch; a fining process of fining the molten glass; and a forming process of forming the fined glass into a sheet shape. The raw material batch is melted such that a bubble enlarging temperature of the obtained glass is lower than a maximum temperature of the fining process.

An energy-efficient device for refining a glass melt to produce a glass and/or a glass ceramic is provided. The device includes a refining crucible defined at least by lateral walls with a metallic lining as a melt contact surface, so that a melt refining volume is defined by a base surface, a top surface and a circumferential surface; at least one heating device that conductively heats the lining by an electric current in the lining, so that the melt is heated through the lining, the heating device and the lining are connected to one another by a feeding device. The feeding device establishes contact with the lining so that an electric current runs from the top surface to the base surface or from the base surface to the top surface, at least in sections of the lining.

A method of producing a melt includes contacting a first heating element directly with an inside of a solid-liquid mixture layer including a batch raw material of glass and a mixture of solid and liquid phases denatured from the batch raw material to apply thermal energy to the solid-liquid mixture layer by heat transfer from the first heating element, supplying the batch raw material from the above of the solid-liquid mixture layer, and continuously producing a liquid phase melt with a bulk density greater than that of the solid-liquid mixture layer in a lower layer in contact with the solid-liquid mixture layer.

A method of producing a melt includes contacting a first heating element directly with an inside of a solid-liquid mixture layer including a batch raw material of glass and a mixture of solid and liquid phases denatured from the batch raw material to apply thermal energy to the solid-liquid mixture layer by heat transfer from the first heating element, supplying the batch raw material from the above of the solid-liquid mixture layer, and continuously producing a liquid phase melt with a bulk density greater than that of the solid-liquid mixture layer in a lower layer in contact with the solid-liquid mixture layer.

A method of making an electrode assembly for a furnace includes providing a heating element within the furnace. The method further includes providing a power feedthrough having an end portion that extends into the furnace to couple with the heating element. The power feedthrough includes a conductive member for transmitting electricity to the heating element. The method includes cleaning an exterior surface of the conductive member proximate the end portion of the power feedthrough. The method further includes a step of applying an electroless nickel plating to the exterior surface of the conductive member for preventing corrosion of the conductive member within the furnace. The method also includes connecting the end portion of the power feedthrough to the heating element.

A method of making an electrode assembly for a furnace includes providing a heating element within the furnace. The method further includes providing a power feedthrough having an end portion that extends into the furnace to couple with the heating element. The power feedthrough includes a conductive member for transmitting electricity to the heating element. The method includes cleaning an exterior surface of the conductive member proximate the end portion of the power feedthrough. The method further includes a step of applying an electroless nickel plating to the exterior surface of the conductive member for preventing corrosion of the conductive member within the furnace. The method also includes connecting the end portion of the power feedthrough to the heating element.

A glass substrate of the present invention has a temperature at a viscosity at high temperature of 10.sup.2.5 dPa.Math.s of 1,650° C. or less, and an estimated viscosity Log η.sub.500 at 500° C. of 26.0 or more calculated by the equation Log η.sub.500=0.167×Ps−0.015×Ta−0.062×Ts−18.5.

A sealing system for isolating the environment inside a vitrification container from the outside environment comprises a vitrification container with a lid. The lid comprises two or more electrode seal assemblies through which two or more electrodes may be operatively positioned and extend down through the lid into the vitrification container. The electrodes may move axially up and down through the electrode seal assemblies or lock into place. The electrode seal assemblies each comprise a housing having two halves with recessed ring grooves. Sealing rings with a split may be placed into the grooves. Gas galleries may be machined or cast into the housing such that they are adjacent to the ring grooves. The gas galleries distribute gas onto the external faces of the sealing rings causing a change in pressure resulting in the sealing rings compressing onto the electrodes and forming a seal.

A sealing system for isolating the environment inside a vitrification container from the outside environment comprises a vitrification container with a lid. The lid comprises two or more electrode seal assemblies through which two or more electrodes may be operatively positioned and extend down through the lid into the vitrification container. The electrodes may move axially up and down through the electrode seal assemblies or lock into place. The electrode seal assemblies each comprise a housing having two halves with recessed ring grooves. Sealing rings with a split may be placed into the grooves. Gas galleries may be machined or cast into the housing such that they are adjacent to the ring grooves. The gas galleries distribute gas onto the external faces of the sealing rings causing a change in pressure resulting in the sealing rings compressing onto the electrodes and forming a seal.