Special strength-testing methods have been established for refractory ceramics, which are of a mostly heterogeneous composition. The Refractoriness under Load (RUL) and Creep in Compression (CIC) identify the deformation resistance of a test piece under a defined load and temperature/time factors. The modulus of rupture at high temperatures (HMOR) is determined with a hot modulus of rupture tester. The melting behavior of these heterogeneous ceramics is determined indirectly through comparison with so-called Seger cones (PCE – Pyrometric Cone Equivalent). These all conform to the pertinent instrument and applications standards, e.g. ISO 1893, ISO 3187, ISO 5013, DIN EN 993-7/8/9/12/14/15, DIN 51048, DIN 51053, DIN 51063, DIN 51046, ISO 8894-1, ISO 8894-2, ASTM C1113.