ASTM D7787/D7787M-13(2022) PDF

SIGNIFICANCE AND USE 5.1 Natural weathering tests can take several years and accelerated weathering evaluations often run for cycles requiring several weeks or months before obtaining useful data. Correlating wood panels selection with desired weathering performance characteristics assists a coatings experimenter in maximizing information in the desired time frame. 5.2 Because of the long time spans required for exposure testing, it is critical to plan a reliable experiment while controlling as many variables as possible. For this reason, selection of experimental panels made from representative wood species or composites, grades of lumber and surface types that are expected to be painted is very important. 5.3 This practice may be used for any types of exterior architectural coating intended for use on wood or wood composite substrate such as exterior house paints, primers, wood stains, or waterproofers. SCOPE 1.1 This practice offers guidelines for selecting wood or wood composite substrates for the evaluation of specific weathering performance characteristics of architectural coatings such as exterior paints, primers, and deck finishes. 1.2 Procedures include selecting wood species and choosing individual wood test panels through visual examination of the wood characteristics. 1.3 This practice is intended to cover the most commonly employed wood substrates used in weathering studies of architectural coatings. It is not intended to serve as a comprehensive guide for all wood species that may be employed for the purpose of evaluating weathering performance characteristics of architectural coatings. 1.4 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. 1.5 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. 1.6 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.