When temperatures drop to or below freezing temperature, military vehicles are no different than a family car. Vehicle windows form a layer of ice on the inside from freezing condensation preventing one from driving. The area where frost shields used to be installed kept the windows clear.
Car shields were plastic rectangles with a raised adhesive strip around the entire edge (picture on left). They were placed on the inside of car windows and prevented condensation from forming and becoming frost.
Frost shields were first used commercially in the winter of 1926 – 27, long before front and rear window defrosters were invented. The first shields were a thin piece of glass that came with a rubber gasket and glue. It was not until the late 1940s that celluloid (plastic) versions were advertised.
In 1937 it became law in Manitoba that windshield (front windows), rear window and front-row side windows had to be fitted with frost shields from December 1st to March 31st. As windshield defrosters became more commonplace in the 1950s and rear window defrosters in the 1970s, the demand for frost shields diminished. However, their use is still mandated (in place) in Manitoba’s Highway Traffic Act. As one might suspect based on its cold winters, Winnipeg was a hub for manufacturing frost shields.
Frost shields are still used in construction equipment, helicopters and other equipment. The only company known to still manufacture them is in Brandon, Manitoba as of 2013–Custom Tarps and Filters.
Tool used to remove frost shields in the CSS Museum.