Significance and Use 4.1 The procedure described in this practice is intended to aid in evaluating the performance of house and trim paints to new, previously unpainted wood. 4.2 The relative durability of paints in outdoor exposures can be very different depending on the location of the exposure because of differences in solar radiation, time of wetness, temperature, pollutants, and other factors. Therefore, it cannot be assumed that results from one exposure in a single location will be useful for determining relative durability in a different location. Exposures in several locations with different climates which represent a broad range of anticipated service conditions are recommended. 4.2.1 Because of year-to-year climatological variations, results from a single exposure test cannot be used to predict the absolute rate at which a material degrades. Several years of repeat exposures are needed to get an “average” test result for a given location. 4.2.2 Solar radiation varies considerably as function of time of year. This can cause large differences in the apparent rate of degradation in many paints. Comparing results for materials exposed for short periods (less than one year) is not recommended unless materials are exposed at the same time in the same location. 4.2.3 It is recommended that at least three replicates of each material be tested. A statistical estimate of the number of replicates needed based on parameters known about the material can be found in Practice E122. 4.3 The Significance and Use section in Practice G7 addresses many variables to be considered in exterior exposure tests.Scope 1.1 This practice covers procedures to be followed for direct exposure of house and trim paints on new, previously unpainted wood and wood composite materials to the environment. When originators of a weathering test have the actual exposure conducted by a separate agency, the specific conditions for the exposure of test and control specimens should be clearly defined and mutually agreed upon between all parties. 1.2 This standard covers specimen preparation including the application of the test paint to the wood substrate. 1.3 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
