ISO 7884-5:1987 Glass viscosity and viscosity fixed points - Part 5: Determination of working points with a sunken rod Viscometer - The standard specifies a method for measuring the working point of Glass using a sunken rod Viscometer. Working point refers to the temperature at which the viscosity of the melt reaches a specific level during processing, when the Glass can maintain both sufficient flowability and appropriate structural Stability. The standard describes in detail the use of the sunken rod Viscometer, specimen preparation, heating conditions and data calculations to ensure test accuracy and repeatability. This method is widely used in melt state control, molding and mass monitoring in the Glass industry, providing an important technical basis for the production and processing of Glass products.