Full definition
A handheld instrument that measures the indentation hardness of elastomers and plastics by pressing a calibrated spring-loaded indenter into the material surface and reading the resistance to penetration on a 0-100 scale. Type A (ASTM D2240): for soft to medium-hard elastomers (20-90 Shore A range covers most industrial rubber, seals, and gaskets), uses a truncated cone indenter. Type D (ASTM D2240): for hard rubber, rigid plastics, and hard polyurethane (>90 Shore A), uses a sharp cone indenter. Test procedure: apply durometer firmly to flat specimen surface (minimum 6 mm thick), read after 1 second (ASTM) or 3 seconds (DIN 53505). Minimum of 5 readings averaged. Temperature: 23 ± 2°C. Calibration: verify against standard test blocks. Digital durometers improve repeatability. Hardness is the most commonly specified and tested property of rubber products — it appears on virtually every rubber data sheet and purchase specification. Per ASTM D2240 and ISO 48-4.