1.1 This International Standard specifies four methods for the determination of the Vicat softening temperature (VST) of thermoplastic materials: Method A50 using a force of 10 N and a heating rate of 50 °C/h Method B50 using a force of 50 N and a heating rate of 50 °C/h Method A120 using a force of 10 N and a heating rate of 120 °C/h Method B120 using a force of 50 N and a heating rate of 120 °C/h 1.2 The methods specified are applicable only to thermoplastics, for which they give a measure of the temperature at which the thermoplastics start to soften rapidly.