n The resistance of a material to penetration by a sharp steel point under a known load with an instrument called the Barcol Impressor. Direct readings are obtained on a scale from 0 to 100. The instrument has often been used as a way of judging the degree of cure of thermosetting resins and harder materials. The ASTM test, www.astm.org, is referred to as “Indentation Hardness of Rigid Plastics”. See Indentation Hardness.