Full definition
International standard for the determination of hardness of vulcanized or thermoplastic rubber, covering both the Shore method (per ISO 48-4, using type A and D durometers — equivalent to ASTM D2240 methodology) and the IRHD method (International Rubber Hardness Degrees, per ISO 48-2). The IRHD method uses a dead-weight indentation system (spherical indenter, calibrated mass) providing more precise and reproducible measurements than the spring-loaded Shore durometer, particularly at the extremes of the scale (very soft <30 and very hard >85). IRHD values and Shore A values are numerically similar in the 40-80 range but diverge at extremes. IRHD advantages: operator-independent (dead weight vs manual force), better precision at extremes, micro-hardness version for small/thin specimens (ISO 48-2 Annex A). IRHD is specified in European and ISO rubber product standards, while Shore A (ASTM D2240) dominates in the Americas. For commercial specifications: "hardness 65±5 IRHD/Shore A per ISO 48/ASTM D2240" covers both. Per ISO 48-4:2018 (Shore method) and ISO 48-2:2018 (IRHD method). Complementary: DIN 53505 (German Shore method, 3-second reading).