This is an early model of a hardness tester for the International Hardness Degree scale micro, IRHD-M, manufactured by Wallace Co in UK.

When asking Wallace about the manufacturing year, they replied that they never seen a photo of such an old instrument. They estimated the manufacturing to mid-60-ies.

The instrument measures Rubber hardness by measuring the indentation of a ball with the diameter of 0,395 mm pressed into the rubber. It is a downscaling from the IRHD-N scale with six times and is used for test samples with a thickness around 2 mm.

The instrument was a little tricky to use and required good experience of the operator to avoid variation of the results.

The hardness tester is specified in ISO 48.

In this early model an amplifier with a “magic” eye was used to find the exact hardness value. It was also possible to use headphones to listen to the tone and find the dip in the frequency of the tone.

This instrument was earlier very common in the rubber laboratories and is now on display in the Elastocon museum.

Owner history: SCANIA AB

Göran Spetz