Thermally treating a glass sheet by holding the glass sheet between first and second gas bearings, the glass sheet having first and second major surfaces on opposite sides thereof and an edge surface surrounding the sheet and connecting the first and second major surfaces, the glass sheet being held with the first major surface adjacent to the first gas bearing and the second major surface adjacent to the second gas bearing, a glass of the glass sheet having a glass softening temperature, and, while holding the glass sheet between the first and second gas bearings, maintaining the glass sheet at a viscosity (t) for a time t such that the value of the expression (30 MPa times the integral from 0 to t of t/(t) with respect to t) is within the range of from 10 to 10.sup.6.

Thermally treating a glass sheet by holding the glass sheet between first and second gas bearings, the glass sheet having first and second major surfaces on opposite sides thereof and an edge surface surrounding the sheet and connecting the first and second major surfaces, the glass sheet being held with the first major surface adjacent to the first gas bearing and the second major surface adjacent to the second gas bearing, a glass of the glass sheet having a glass softening temperature, and, while holding the glass sheet between the first and second gas bearings, maintaining the glass sheet at a viscosity (t) for a time t such that the value of the expression (30 MPa times the integral from 0 to t of t/(t) with respect to t) is within the range of from 10 to 10.sup.6.

According to one embodiment, a method for thermally treating glass articles may include holding a glass article at a treatment temperature equal to an annealing temperature of the glass article 15 C. for a holding time greater than or equal to 5 minutes. Thereafter, the glass article may be cooled from the treatment temperature through a strain point of the glass article at a first cooling rate CR1 less than 0 C./min and greater than 20 C./min such that a density of the glass article is greater than or equal to 0.003 g/cc after cooling. The glass article is subsequently cooled from below the strain point at a second cooling rate CR.sub.2, wherein |CR.sub.2|>|CR.sub.1|.

According to one embodiment, a method for thermally treating glass articles may include holding a glass article at a treatment temperature equal to an annealing temperature of the glass article 15 C. for a holding time greater than or equal to 5 minutes. Thereafter, the glass article may be cooled from the treatment temperature through a strain point of the glass article at a first cooling rate CR1 less than 0 C./min and greater than 20 C./min such that a density of the glass article is greater than or equal to 0.003 g/cc after cooling. The glass article is subsequently cooled from below the strain point at a second cooling rate CR.sub.2, wherein |CR.sub.2|>|CR.sub.1|.

To provide a method for forming molten glass, capable of easily improving the forming accuracy of molten glass. One embodiment of the method for forming molten glass of the present invention comprises a supplying in which molten glass having a temperature of at least the softening point is discharged in a strip shape and supplied on the surface of molten metal, and a transporting the glass ribbon supplied on the surface of the molten metal, wherein the transporting includes a cooling the glass ribbon being transported, in a region on the upstream side in the transport direction, so that the temperature of the glass ribbon becomes lower than the softening point in the entire width direction.

To provide a method for forming molten glass, capable of easily improving the forming accuracy of molten glass. One embodiment of the method for forming molten glass of the present invention comprises a supplying in which molten glass having a temperature of at least the softening point is discharged in a strip shape and supplied on the surface of molten metal, and a transporting the glass ribbon supplied on the surface of the molten metal, wherein the transporting includes a cooling the glass ribbon being transported, in a region on the upstream side in the transport direction, so that the temperature of the glass ribbon becomes lower than the softening point in the entire width direction.

Method and apparatus are provided for the controlled transport of glass sheets (13) or glass ribbons (15) undergoing heating and/or cooling (e.g., thermal tempering) by conduction more than convection. The controlled transport is achieved by applying a gas-based force (17,19,21) to the glass sheet (13) or glass ribbon (15). The gas-based force (17,19,21) can move the glass sheet (13) or glass ribbon (15) in a desired direction and/or cause it to acquire a desired orientation. The gas-based force (17,19,21) can also cause the glass sheet (13) or glass ribbon (15) to retain a desired position and/or a desired orientation. The gas-based force (17,19,21) can be applied to the glass sheet (13) or glass ribbon (15) continuously or intermittently. Systems for transitioning a glass sheet (13) or a glass ribbon (15) between a heating zone (27) and a quench zone (31) are also discussed.

A workpiece conveyance apparatus having: a conveyance path on which the workpiece moves; a gas flotation section that gas-floats the workpiece over the conveyance path; a movable holding section that holds the workpiece to move on the conveyance path along with the workpiece; and a treatment region conveyance path that is located on the conveyance path, and has a treatment region where predetermined treatment for the workpiece is performed, wherein the movable holding section has at least two or more holding sections along a movement direction of the conveyance path, each of the holding sections is capable of switching between release of holding and holding for the workpiece during movement of the workpiece, operation for releasing holding of the workpiece by the holding section on the treatment region conveyance path, and holding the workpiece on the conveyance path other than the treatment region conveyance path.

A method for manufacturing a float glass includes a step of melting a glass raw material, a step of forming the glass melted in the melting step into a glass ribbon while floating the glass on a molten metal, and a step of annealing the glass ribbon. In the forming step, a gas or a liquid containing a molecule having a fluorine atom present therein is blown to the glass ribbon having a viscosity of from 1.010.sup.4 to 2.510.sup.10 Pa.Math.s.

A method for manufacturing a float glass includes a step of melting a glass raw material, a step of forming the glass melted in the melting step into a glass ribbon while floating the glass on a molten metal, and a step of annealing the glass ribbon. In the forming step, a gas or a liquid containing a molecule having a fluorine atom present therein is blown to the glass ribbon having a viscosity of from 1.010.sup.4 to 2.510.sup.10 Pa.Math.s.