This International Standard specifies four methods for the determination of the Vicat softening temperature (VST) of thermoplastic materials:
method A50 using a force of 10N and a heating rate of 50K/h;
method B50 using a force of 50N and a heating rate of 50K/h;
method A120 using a force of 10N and a heating rate of 120K/h;
method B120 using a force of 50N and a heating rate of 120K/h.
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.