Abstract: A rheometer 1, an example of which is shown in FIG. 1, comprising an upper die 2 and a lower die 3. Extending on the vertical axis of this die arrangement is a pneumatic cylinder shaft 6, which is connected to the heater element 4 and insulator layer 5 of the upper die 2. The lower die 3 is supported by a bearing 8 which allows a lower die to rotate about an axis which is in line with that of the pneumatic cylinder 6. A lower die 3 is caused to oscillate in a rotation manner of at a vertical axis in line with the pneumatic cylinder, which is also connected to a transducer 12 which measures the force needed to keep the upper die to substantially stationary as rotation occurs. Alternatively, a lower die 2 can be have substantially stationery while a rotor head 16 holds the material to be tested. This case the forces required to maintain oscillation of the rotor head 16 in the material are tested by the transducer 12.