ASTM_D_358_-_98.pdf

Designation:D 358 98Standard Specification forWood to Be Used as Panels in Weathering Tests ofCoatings1This standard is issued under the fixed designation D 358;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon(e)indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1.Scope1.1 This specification designates woods for weathering testsof exterior solvent-borne or water-borne paints and othermaterials of similar purpose.Such tests may include eitheroutdoor exposure tests or accelerated laboratory tests.It is thepurpose of this specification to minimize the influence ofvariation of wood of a given species on test results.1.2 The values stated in inch/pound units are to be regardedas the standard.The values given in parentheses are forinformation only.2.Referenced Documents2.1 ASTM Standards:D 3924 Specification for Standard Environment for Condi-tioning and Testing Paint,Varnish,Lacquers,and RelatedMaterials23.General Considerations3.1 A variety of different species should be used for testingfinishes because of the wide variations in the anatomy and thedensity between wood species.The factors have tremendousinfluences on finish performance.Latewood band width anddensity are especially important to finish performance,andthese parameters vary significantly between wood species.Cedar and redwood have relatively low proportions of hardsummerwood distributed in narrow bands and contain extrac-tives that discolor some paint films.Southern pine has a largeproportion of hard summerwood in wide bands.3.2 The angle between the growth rings and the surface ofthe specimen is very critical to finish performance.Commer-cial practice utilizes the following classification system.Boards in which growth form an angle of less than 30 with thewide surface of the piece are said to be flat-sawn or flat-grained;those with the rings intersecting at angles between 30and 60 are termed bastard-sawn;and those with angles greaterthan 60 are termed quarter-sawn,edge grain,or vertical grain.3.3 Some industrial processors of wood products may uti-lize wood at moisture levels significantly higher than theequilibrium moistures cited in this specification.In thesespecific cases,appropriately higher moisture content panelsmay be prepared for testing of factory applied finishes.WESTERN RED CEDAR4.Species4.1 The material for test panels shall be western red cedar(Thuja plicata).5.Weight per Volume5.1 When the wood is in equilibrium with air at 60 to 65%relative humidity and 70 6 1F(21 6 0.5C)it shall weigh 22to 23 lb/ft3(350 to 370 kg/m3)or at 50 6 5%relative humidityand 73.5 6 3.5F(23 6 2C),which are specified inSpecification D 3924 as standard conditions for testing paintand related coatings,it shall weigh 21.4 to 22.4 lb/ft3(343 to359 kg/m3).NOTE1The density requirement is to eliminate wood specimens thatvary greatly from the average for that species.Either set of conditions maybe used to establish the density.At 60 to 65%relative humidity wood hasa moisture content of approximately 12%while at 45 to 55%relativehumidity it contains 9 to 10%.The former is closer to the moisturecontent of wood exposed to most exterior climatic conditions.6.Character of Wood6.1 The wood shall be heartwood having edge grain andshall be free of knots and other defects.The color of the woodshall be uniform across each panel with no streaks that areexcessively light or dark.The number of annual growth ringsper inch along the radius of the log from which the wood wasobtained shall not be less than ten.The surfaces shall besmoothly planed and sanded thoroughly with 150 grit sandpa-per within two weeks of testing.7.Thickness of Panels7.1 The minimum thicknesses(Note 2)in proportion towidth(across the grain)shall be as follows:Panel Width,in.(mm)Minimum Thickness,in.(mm)1This specification is under the jurisdiction of ASTM Committee D-1 on Paintand Related Coatings,Materials,and Applications and is the direct responsibilityD01.52on Factory-Coated Wood Products.Current edition approved May 10,1998.Published August 1998.Originallypublished as D 358 33.Last previous edition D 358 93.2Annual Book of ASTM Standards,Vol 06.01.1AMERICAN SOCIETY FOR TESTING AND MATERIALS100 Barr Harbor Dr.,West Conshohocken,PA 19428Reprinted from the Annual Book of ASTM Standards.Copyright ASTMLess than 3(less than 75)38(10)3 to 6(75 to 150)716(11)Over 6(over 150)34(19)NOTE2Minimum thicknesses in proportion to width(across thegrain)do not apply to panels made of clapboard or siding of commercialtypes,which shall be used as regularly marketed.WHITE PINE AND PONDEROSA PINE8.Species8.1 White pine wood shall be northern white pine(Pinusstrobus).Western white pine(Pinus monticola),or sugar pine(Pinus lambertiana).Western white pine is some