Place the sample in a metal ring of specified size, place a steel ball of specified size and weight on top, and immerse it in water (or glycerol). Heat at a rate of 5 ± 0.5 °C/min until the steel ball sinks to 25.4 mm. Record the temperature at this point, which is the softening point of the sample. Select the heating medium according to the estimated softening point. If the softening point is below 80 °C, use distilled water as the medium and adjust the initial temperature to 5 °C ± 0.5 °C. If the softening point is above 80 °C, use glycerol as the medium and adjust the initial temperature to 32 °C ± 1 °C.
The time from sample preparation to completion of the test should not exceed 240 minutes. For high softening point samples with a softening point between 120 °C and 157 °C, the brass ring and support plate should be preheated to 80 °C to 100 °C before the test. [1] The test should be conducted in an environment without significant air convection (ambient temperature 15 °C to 35 °C, humidity ≤ 85%).