This standard is the core methodological standard for determining the International Rubber Hardness Degree (IRHD). Its core content includes a total of eight specific methods for measuring "standard hardness" on flat surfaces and "apparent hardness" on curved surfaces within the range of 10 to 100 IRHD. The standard specifies the selection of corresponding test methods based on factors such as sample thickness and test surface (flat or curved), with the main differences lying in the diameter of the spherical indenter used and the applied force value. The method explicitly does not apply to measurements taken with portable hardness testers. The International Rubber Hardness Tester is the specialized testing instrument designated by this standard. Its principle involves measuring the indentation depth of a specific spherical indenter under specified conditions to determine the hardness value.