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Created page with "==Introduction== Hardness is a measure of how resistant solid matter is to various kinds of permanent shape change when a compressive force is applied. Some materials (e.g. metals) are harder than others (e.g. plastics, wood). Hardness is dependent on ductility, elastic stiffness, plasticity, strain, strength, toughness, viscoelasticity, and viscosity. There are three main types of hardness measurements: scratch, indentation, and rebound. Within each of these classes of..."
