ASTM D2319 Standard Test Method for Softening Point of Pitch (Cube-in-Air Method)
10. Procedure
10.1 Suspend the hooks with the test specimens in place from the supporting ring on the oven cover with the tips of the hooks pointing toward each other from the left and right sides of the thermometer as viewed through the windows. The feet of the hooks shall lie along an imaginary horizontal line through the center of the windows.
10.2 Insert the thermometer through a cork in the central hole in the cover so that the bottom of the bulb is level with the bottom edges of the cubes, and the ends of the feet of the hooks are close to, but do not touch, the bulb.
10.3 Center the oven on the heat source and place the shield around it so that the two are concentric.
10.4 Preheat the oven if necessary and, when equilibrium is established, adjust the heating rate so that the temperature rises at 5 °C/min [10 °F/min]. The maximum permissible variation from this rate shall be +/- 1.0 °C/min [+/- 2 °F/min] for the final 50 °C [90 °F] below the softening point.
10.5 Maintain a written record of the temperature to 0.25 °C [0.5 °F ] for each minute over the last 50 °C [90 °F]. Average these readings algebraically. The average shall not deviate more than +/- 0.5 °C [+/- 1 °F] from the 5 °C/min [10 °F/min] over this interval. Reject any test in which the rate for any minute in this interval is outside the range from 4 °C to 6 °C [7 °F to 11 °F], or the average is outside the range from 4.5 °C to 5.5 °C [8 °F to 10 °F].
10.6 The softening point is the average of the thermometer readings (with no correction for emergent stem) when the two cubes touch the pan. Estimate the readings to 0.25 °C [0.5 °F]. If the individual values differ by more than 1.5 °C [2.7 °F], reject the result and repeat the test.
