The Varitherm Wax Bath comprises a resin tank which holds the paraffin wax, surrounded by an electrically heated, thermostatically controlled water jacket. The temperature control may be set to maximum in order to provide rapid melting of the solid wax when the unit is first switched on.

After almost all of the wax is melted, the temperature control is normally set to approximately 50° C so that the paraffin is just in its molten state. The latent heat of fusion of the wax is released as the wax solidifies, therefore, applying heat to the treatment area at constant temperature.

In normal treatment several layers of wax are applied and further heat is released from the wax into the skin. Another consequence of the solid layer of wax is that moisture is prevented from being lost from the surface being treated. At the end of treatment, when the wax is peeled off, the skin is left moist and soft.