IRHD = International Rubber Hardness Degree

The International Rubber Hardness Degree according DIN ISO 48 – Part 1 is, beside the Shore hardness, another test method for the measurement of the rubber hardness. IRHD shows the resistance of a rubber specimen against the intrusion of a ball with a diameter of 2.5 or 5.0 mm respectively under a defined pressure.
We differentiate between sub-ranges soft and normal.

If the rubber products are very small you can apply the IRHD measurement according DIN ISO 48 – Part 2. You will use a small ball with a diameter of 0.4 mm.

Sub range IRHD range Diameter measuring ball Specimen thickness
soft from 10 to 35 IRHD 5,0 mm 10-12 mm
normal more than 35 IRHD 2,5 mm 6 bis 10 mm
IRHD normal from 35 to 90 IRHD 0,4 mm 1,5 bis 2,5 mm

The standard test specimens are platens with plat, parallel top and bottom surfaces.