The ISO 7884-3-1987 standard specifies the method of measuring the viscosity of Glass using the fiber elongation Viscometer, which is a key technical specification for viscosity measurement of Glass materials. This method calculates the viscosity value of Glass at different temperatures by measuring the elongation behavior of fiberglass under specific conditions. The standard is applicable to the evaluation of material flow characteristics and processing performance in Glass production and research and development, covering experimental equipment, operation procedures, result calculation and test conditions. This standard provides a unified technical basis for the viscosity test of Glass materials, which helps to improve the scientific and conformity of Glass quality control and process optimization.