The low temperature test called Gehman was first published in 1947.

Gehman S .D., Woodford D.E., Wilkinson C.S. Low temperature characteristics of elastomers.
Ind. Eng. Chem. 1947 Sept., 39 p. 1108.

Test method

In the test method the stiffness of the rubber material is measured by twisting a rubber test piece to measure the torsional stiffness. This is done by connecting a rubber strip in series with a calibrated spring steel wire with known stiffness. The sample and the spring is then rotated 180° and the twist will be divided between the spring and the rubber strip. The angle between the steel spring and the rubber strip is measured and as the stiffness of the spring is known, the stiffness of the rubber strip can be calculated. See figure 1.

Normally the stiffness is measured at laboratory temperature (23 °C) and then compared with the stiffness at lower temperatures. The results are shown as 2, 5, 10 and 100 times the stiffness at 23 °C. If the dimensions of the test piece are known the torsional modulus in MPa can be calculated.


Wallace Instruments in UK has manufactured the classical instrument shown in the photo and the standard ISO 1432 was written for this instrument. In 2012 the standard was revised including a more general description allowing also modern computerized instruments to be used.

The instrument in the photo is a gift from Superior seals in UK to Elastocon museum.

Owner history: Superior Seals, UK

Göran Spetz