用煤粉制备的铅笔状试样在炉内的钢罐中以恒定速率加热，温度监测系统之前已使用两种已知熔点的参考金属进行校准。连续观察试样上岩钉水平的变化，并记录煤的膨胀特性。

A test piece, in the form of a pencil, prepared from powdered coal is heated at a constant rate in a steel retort positioned in a furnace, the temperature monitoring system having been previously calibrated using two reference metals of known melting points. The change in level of a piton resting upon the test piece is observed continuously, and record is produced which is characteristic of the swelling properties of the coal.