Elastomers are found in all mechanical pressure gauges or thermometers. They provide a secure sealing between the individual components. In detail, these are the flat gasket at the window, and with pressure gauges additionally the blow-out device on the rear of the case and the vent valve for pressure compensation.
However, the sealing materials used in standard designs cannot durably withstand very low ambient temperatures. They become brittle over time and lose their sealing properties. This results in the case filling escaping. This, in turn, leads to the formation of condensation and the frosting of the window.