This standard specifies four methods for the determination of the
hardness of vulcanized or thermoplastic rubbers on flat surfaces
(standard-hardness methods) and four methods for the determination of
the apparent hardness of curved surfaces (apparent-hardness
methods). The hardness is expressed in international rubber hardness
degrees (IRHD). The methods cover the hardness range from 10 IRHD
to 100 IRHD. These methods differ primarily in the diameter of the
indenting ball and the magnitude of the indenting force, these being
chosen to suit the particular application. The range of applicability of
each method is indicated in Figure 1. This standard does not specify a
method for the determination of hardness by a pocket hardness meter,
which is described in ISO 7619-2.