Provided is a glass material that can satisfy both high Faraday effect and high light transmittance at wavelengths used. A glass material containing, in terms of % by mole of oxide, more than 40% Tb.sub.2O.sub.3 and having a percentage of Tb.sup.3+ of 55% by mole or more relative to a total content of Tb.

The development of cracks or breakage in a glass material during production of the glass material by a containerless levitation technique is reduced. A glass material is obtained by heating a levitated block 12 of glass raw material to melting by irradiation of the block 12 of glass raw material with laser light to thus obtain a molten glass and then cooling the molten glass. A first irradiation step and a second irradiation step are performed. In the first irradiation step, the levitated block 12 of glass raw material is heated to melting by irradiating the block 12 of glass raw material with the laser light. In the second irradiation step, an intensity of the laser light being applied to the molten glass is reduced and irradiation with the laser light is then stopped.

The development of cracks or breakage in a glass material during production of the glass material by a containerless levitation technique is reduced. A glass material is obtained by heating a levitated block 12 of glass raw material to melting by irradiation of the block 12 of glass raw material with laser light to thus obtain a molten glass and then cooling the molten glass. A first irradiation step and a second irradiation step are performed. In the first irradiation step, the levitated block 12 of glass raw material is heated to melting by irradiating the block 12 of glass raw material with the laser light. In the second irradiation step, an intensity of the laser light being applied to the molten glass is reduced and irradiation with the laser light is then stopped.

Provided is a method that enables a crystal-free glass material to be stably produced by a containerless levitation technique. A glass material 30 has a first surface 31 facing a forming surface 10a and a second surface 32 located on a side opposite to the forming surface 10a. The first surface 31 includes a central portion 31a and a peripheral portion 31b located outside of the central portion 31a. Gas is jetted through a gas jet hole at a flow velocity and a flow volume at which a glass material satisfying R.sub.2<R.sub.3<R.sub.1 is formed where R.sub.1 represents a radius of curvature of the central portion 31a, R.sub.2 represents a radius of curvature of the peripheral portion 31b, and R.sub.3 represents a radius of curvature of the second surface 32.

An apparatus for making a profiled tubing includes a mandrel adapted for positioning proximate a tubing. The mandrel has a nozzle section with a select cross-sectional profile that will define a final cross-sectional profile of the tubing. The nozzle section has a feed chamber for receiving a gas and a porous circumferential surface through which the gas can be discharged to an exterior of the mandrel. The gas when discharged to the exterior of the mandrel forms a film of pressurized gas between the porous circumferential surface and the tubing. A method of forming a profiled tubing using the apparatus is disclosed. A sleeve formed from the profiled tubing is also disclosed.

An apparatus for making a profiled tubing includes a mandrel adapted for positioning proximate a tubing. The mandrel has a nozzle section with a select cross-sectional profile that will define a final cross-sectional profile of the tubing. The nozzle section has a feed chamber for receiving a gas and a porous circumferential surface through which the gas can be discharged to an exterior of the mandrel. The gas when discharged to the exterior of the mandrel forms a film of pressurized gas between the porous circumferential surface and the tubing. A method of forming a profiled tubing using the apparatus is disclosed. A sleeve formed from the profiled tubing is also disclosed.

A production apparatus that continuously produces plate glass, includes a molding member configured to mold molten glass to form a glass ribbon, wherein the molding member is (i) constituted with graphite or includes a portion constituted with graphite, and/or (ii) supported by a support member containing graphite, wherein in a case of (i), the molding member is surrounded by a fence, and in a case of (ii), the support member is surrounded by the fence together with the molding member, and wherein a space surrounded by the fence is adjusted to have an oxygen concentration of less than or equal to 100 ppm.

A production apparatus that continuously produces plate glass, includes a molding member configured to mold molten glass to form a glass ribbon, wherein the molding member is (i) constituted with graphite or includes a portion constituted with graphite, and/or (ii) supported by a support member containing graphite, wherein in a case of (i), the molding member is surrounded by a fence, and in a case of (ii), the support member is surrounded by the fence together with the molding member, and wherein a space surrounded by the fence is adjusted to have an oxygen concentration of less than or equal to 100 ppm.

Provided is a method that can manufacture a glass material having excellent homogeneity by containerless levitation. With a block (12) of glass raw material held levitated above a forming surface (10a) of a forming die (10) by jetting gas through a gas jet hole (10b) opening on the forming surface (10a), the block (12) of glass raw material is heated and melted by irradiation with laser beam, thus obtaining a molten glass, and the molten glass is then cooled to obtain a glass material. Control gas is jetted to the block (12) of glass raw material along a direction different from a direction of jetting of the levitation gas for use in levitating the block (12) of glass raw material or the molten glass.

Provided is a method that can manufacture a glass material having excellent homogeneity by containerless levitation. With a block (12) of glass raw material held levitated above a forming surface (10a) of a forming die (10) by jetting gas through a gas jet hole (10b) opening on the forming surface (10a), the block (12) of glass raw material is heated and melted by irradiation with laser beam, thus obtaining a molten glass, and the molten glass is then cooled to obtain a glass material. Control gas is jetted to the block (12) of glass raw material along a direction different from a direction of jetting of the levitation gas for use in levitating the block (12) of glass raw material or the molten glass.