It deals with a viscometric fixed point (value of temperature) at the viscosity η=1014,5dPas.
This limit presents the highest temperature into use of a glass component. Above this limit temperature inner mechanical stress are gradually reduced. Consequently the characteristics change permanently, but not irreversibly.
It deals with a viscometric fixed point (value of temperature) at the viscosity η=1013,0dPas. At this temperature the desired tension release appears quickest possible without leading on to a shape change of the structural component in case of slow cooling down, too.
The two points can be determined with beam bending.
(Samples: massive glass pieces, 30x20x4 mm or bigger respectively bar-shaped pieces from 5 mm)