A glass container is provided that includes a tube, a circular bottom, and a longitudinal axis. A curved glass heel extends from an outer end the bottom to the first end of the tube. The two-dimensional distance h(x,y) between a contact plane and the outer surface. The two-dimensional distance is measured in a direction parallel to the axis. The slope magnitude of the outer surface at the given position x,y is given by

√{square root over ((dh/dx).sup.2+(dh/dy).sup.2)}.

The 75% quantile of values that have been determined for the term

√{square root over ((dh/dx).sup.2+(dh/dy).sup.2)}×d1/h(xy).sub.delta

for all given positions x,y within a circular area having a radius of 0.4×d2/2 and that correspond to the centre is less than 4100 μm/mm. The adjacent positions x,y increase stepwise by 200 μm, and h(x,y).sub.delta=h(x,y).sub.max−h(x,y).sub.min, h(x,y).sub.max is a maximum value for h(x,y) and h(x,y).sub.min is a minimum value for h(x,y) being determined in that circular area.

A glass container is provided that includes a tube, a circular bottom, and a longitudinal axis. A curved glass heel extends from an outer end the bottom to the first end of the tube. The outer surface has a topography defined by a function ĥ(x) that is an azimuthal average of a distance between a contact plane and the outer surface at any given position located on a circle having the centre and the radius |x|. The values ĥ for ĥ(x) are determined for a plurality of circles the radius of which increases stepwise by 500 μm starting with a circle around the centre having a radius of 500 μm. The values ĥ are determined in a range from x=−0.4×d2/2 to x=+0.4×d2/2, d2 having a size such that at least 4 values ĥ are determined and can be fitted with a curvature function

[00001]$\hat{h}\left(x\right)=\frac{-c\times x^2}{1+\sqrt{1-c^2\times x^2}}+h_0.$

A process for preparing a glass container that includes: providing a glass tube with a first portion, a second portion, and a longitudinal axis (L.sub.tube); holding the first portion in a first clamping chuck and the second portion in a second clamping chuck; rotating the glass tube around the longitudinal axis (L.sub.tube); heating, via a heater, the glass tube above a glass transition temperature; separating the first and second portions from one another by pulling apart along the longitudinal axis (L.sub.tube) while the heated glass tube is still rotating by moving the first and the second chucks away from each other; and moving the heater, while moving the first and second chucks away from each other, so that the heater follows a mass that remains at a circular end region of the first and/or second portion.

A method for thermally treating an annular region of an inner surface of a glass container produced from a borosilicate glass tube is provided. The annular region is disposed at a tubular portion of the glass container and is disposed adjacent to a glass container bottom. The method includes: forming the glass container bottom from the glass tube; heating the annular region of the inner surface of the tubular portion to a treatment temperature T.sub.Beh above the transformation temperature T.sub.G, wherein the annular region is adjacent to the glass container bottom; maintaining the treatment temperature T.sub.Beh for a certain time period; and cooling the glass container to room temperature.

A perforated quartz glass tube includes a jacket tube containing a quartz glass material, a plurality of cylindrical glass tubes which are inserted into a pore region of the jacket tube along an axial direction of the jacket tube, and contain a quartz glass material having a softening point higher than a softening point of the jacket tube, and a gap member which is inserted into a gap between the cylindrical glass tubes and a gap between the jacket tube and the cylindrical glass tube, and contains a quartz glass material having a softening point lower than a softening point of the cylindrical glass tube.

A perforated quartz glass tube includes a jacket tube containing a quartz glass material, a plurality of cylindrical glass tubes which are inserted into a pore region of the jacket tube along an axial direction of the jacket tube, and contain a quartz glass material having a softening point higher than a softening point of the jacket tube, and a gap member which is inserted into a gap between the cylindrical glass tubes and a gap between the jacket tube and the cylindrical glass tube, and contains a quartz glass material having a softening point lower than a softening point of the cylindrical glass tube.

A method for controlling alkali emissions of a glass element during hot forming is provided. The method includes the steps of: heating the glass element using one or more burner units each providing a burner flame to provide a heated glass element; sensing light emissions of a total light emitting area of the heated glass element and the burner flame of the one or more burner units via one or more sensor units; providing one or more signals of the one or more sensor units of the light emissions; comparing the one or more signals with one or more reference signals; determining, based on the comparing step, determined alkali emissions of the glass element; and controlling the one or more burner units based on the determined alkali emissions to adjust the alkali emissions of the glass element to a pre-given interval.

A method for producing ceramizable green glass components provided, as well as apparatus for performing such method and ceramizable green glass components producible by such method. The method is a redrawing process in which a preform is heated, in a deformation zone, to a temperature that enables redrawing of the glass. The deformation zone is particularly small, which permits redrawing of the ceramizable green glass bodies while avoiding ceramization during the redrawing. The method provides plate-like or sheet-like green glass components that have a particularly smooth surface.

Provided is a small-diameter chalcogenide glass material having excellent weather resistance and mechanical strength and being suitable as an optical element for an infrared sensor. The chalcogenide glass material has an unpolished side surface, a pillar shape with a diameter of 15 mm or less, and a composition of, in terms of % by mole, 40 to 90% S+Se+Te and an inside of the glass material is free of stria with a length of 500 m or more.

Provided is a small-diameter chalcogenide glass material having excellent weather resistance and mechanical strength and being suitable as an optical element for an infrared sensor. The chalcogenide glass material has an unpolished side surface, a pillar shape with a diameter of 15 mm or less, and a composition of, in terms of % by mole, 40 to 90% S+Se+Te and an inside of the glass material is free of stria with a length of 500 m or more.