A laboratory testing machine for measuring the plasticity of raw rubber or unvulcanized rubber compounds. A knurled steel rotor disc winch is centrally embedded iii the heated rubber specimen firmly held in a cavity under pressure is caused to rotate at a low speed (2 rpm). The resistance offered by the plastic rubber mass to the rotation of the rotor disc is the measure of the plasticity of the rubber. The machine is also used to determine the scorch characteristics of rubber mixes.