International Standards Shore A Hardness:
ASTM D 2240  -  DIN ISO 48-4  -  DIN ISO 7619-1 (withdrawn)  -  ISO 48-4  -  JIS K 6253-3  -  VDA 671 002  -  a.o.


Shore A hardness measurement is a method for determining the hardness of elastomers and thermoplastic elastomers in the scale range 20 to 90 (normal hardness range). The measuring time is 1sec., 3sec. or 15sec. depending on the specification and or material. The measurement is ideally performed on a flat, smooth material surface. The Shore A hardness is an important parameter for the characterization of elastomers and TPEs and helps in the selection of materials for various applications.

When determining the indentation hardness by the durometer method (Shore hardness), a spring-loaded indenter with standardized geometry is pressed into the material for a defined measuring time and the indentation depth is measured. The scale for Shore hardness in general ranges from 0 (very soft) to 100 (very hard). The hardness is determined by the reaction of the elastomer to the generated indentation. The reaction is complex and depends on the following factors:

  • Young's modulus of the elastomer or TPE
  • Viscoelastic properties of the elastomer or TPEs
  • Thickness of the specimen
  • Geometry of the indenter
  • Spring force
  • Speed of the pressure increase
  • Time span after which the hardness is distinguished (measuring time)

Due to these influencing variables, a direct comparison of durometer hardnesses (Shore A, Shore D, etc.) with IRHD hardnesses (micro IRHD, IRHD N, etc.) is not meaningful.