Tempering is the controlled feeding or discharging of heating or cooling energy in order to reach a constant temperature within a medium. This can be achieved using a thermostat and a tempering bath or a heatable magnetic stirrer.

During tempering, it is important to have short heating and cooling periods along with precise temperature control. Mediums can be tempered in open or closed systems.

Tempering can be used in most all laboratories. Preparative work in schools requires samples to be tempered to exact temperatures. Medical exam samples have to be adjusted to fit the person's body temperature. The cosmetic industry requires precise tempering in order to ensure that all germs are killed. Defined temperatures are a prerequisite for chemical reactions. There is an infinite list of tempering variables.