Direct Weathering exposes specimens directly to the elements. Specimens are mounted on aluminum exposure racks capable of handling various dimensions and evaluated per industry standards. Factors that affect exposure findings include specimen backing, orientation and test duration.
Under Glass Weathering specimens are mounted under or behind glass. Specimens usually are samples of test materials used inside a building or automobile. Test materials are exposed in cabinets, which protects them from rainfall while letting sunlight pass through a sheet of glass. The glass filters the sunlight, removing (at a minimum) shorter ultraviolet wavelengths in solar radiation. Enclosures are either well-ventilated or sealed, depending on customer requirements. Some of the factors that affect exposure findings include glass type, specimen backing, orientation, and test duration.