Full definition
Standard Test Method for Rubber Property — Durometer Hardness — the universal standard for measuring the hardness of elastomers and plastics by indentation using a handheld durometer. Defines multiple scales for different material hardness ranges: Type A (the most widely used for rubber — truncated cone indenter, 0-100 scale, covers 20-90 Shore A for all common elastomers), Type D (sharp cone indenter, for hard rubber and rigid plastics above 90 Shore A), Type M (micro hardness for thin rubber), and Type O (soft sponge rubber). Test procedure: press durometer firmly and squarely against flat specimen surface (minimum 6 mm thick, 12 mm diameter), read after 1 second (ASTM standard timing — note: DIN 53505 specifies 3-second reading, which gives slightly different values). Record to nearest whole number. Minimum 5 readings averaged, at locations separated by ≥6 mm. Calibrate against standard test blocks. Temperature: 23±2°C standard. Hardness is the most frequently specified, tested, and QC-verified rubber property — it appears on every rubber data sheet and is the primary incoming inspection test. Per ASTM D2240-15(2021). Equivalent: ISO 48-4 (Shore methods), ISO 48-2 (IRHD method).