4.1 Pellet hardness is related to several carbon black characteristics. Among these are mass strength and attrition. The subsequent level of dispersion obtained in some mixed compounds containing the carbon black may be affected by pellet hardness. Acceptable pellet hardness must be agreed to by the user and the producer.

Note 1: Test Method D5230 is the preferred standard for testing of individual pellet hardness. It is recognized that Test Method D3313 relies on operator judgement, thus adding an additional source of variation for this test.