In materials science, quenching is the rapid cooling of a workpiece in water, oil or air to obtain certain material properties. A type of heat treating, quenching, prevents undesired low-temperature processes, such as phase transformations, from occurring. It happens by reducing the window of time during which these undesired reactions are both thermodynamically favourable and kinetically accessible; for instance, quenching can reduce the crystal grain size of both metallic alloys and plastic materials, increasing their hardness.