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Accelerated test for measuring the water resistance of coatings were preformed in test cabinets where the sides of the cabinets are covered with test panels and inside is filled with saturated air at test temperature. Adjusting inside temperature of the cabinet by at least 10ºC higher than outside temperature, condensation of the water vapour in cabinet atmosphere, on the coated surface facing inside is accomplished. Hence, a thin boundary layer is deposited on the coated side of the panel, throughout the test. Condensing humidity tests are carried out at temperatures between 40ºC and 60ºC and for 5 to 20 days.
See Also Non-condensing humidity test
In non-condensing humidity test panels are suspended in the constant temperature cabinets. The air inside the cabinet should be saturated. In this stage, condensation leads to formation of random water films on panels which are also at the same temperature with the inside air. Calling this test non-condensing should not be misleading. Difference between condensing and non-condensing humidity test is, a continuous film formed on panels in the former test whereas random (from place to place or time to time) film formation is seen on the latter test. Temperature and humidity of non-condensing humidity test can be kept in the same range in condensing humidity test. In these tests, it is advisable to evaluate performance of a coating with respect to reference paint.
See Also Condensing humidity test