ASTM_D_6686_-_01_2019.pdf

Designation:D668601(Reapproved 2019)Standard Test Method forEvaluation of Tannin Stain Resistance of Coatings1This standard is issued under the fixed designation D6686;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()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method is an accelerated procedure to deter-mine the effectiveness of latex coatings at preventing themigration of tannin stains from wood substrates.1.2 The values in SI units are to be regarded as the standard.The values in parentheses are for information only.1.3 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety,health,and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.4 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade(TBT)Committee.2.Referenced Documents2.1 ASTM Standards:2D1475 Test Method for Density of Liquid Coatings,Inks,and Related ProductsD4585 Practice for Testing Water Resistance of CoatingsUsing Controlled CondensationD5068 Practice for Preparation of Paint Brushes for Evalu-ation3.Terminology3.1 Definitions:3.1.1 tannin stain resistance,nthe ability of a coating toprevent the migration of tannins or other wood-based chromo-spheres to the surface of a film.4.Summary of Test Method4.1 This test method utilizes a condensation test chamber todetermine the tannin stain resistance of latex paints.The testpaints are applied to substrates that contain tannin extractivesand are placed on or in the test chamber.CIELAB L*and b*values as well as subjective ratings are recorded after exposure.5.Significance and Use5.1 Tannins and other chromophoric extractives are natu-rally occurring materials in wood and wood-based substrates.Tannins are prevalent to a high degree in cedar,redwood,oak,and to a lesser degree in white and yellow pine.Tannins arealso present in varying amounts in wood composition products.These extractives are solubilized and darkened in color byaqueous coatings,resulting in unsightly yellow or browndiscolorations.This test method is designed to show therelative ability of paints to prevent tannin bleed-through.Typically,cedar or redwood panels are used for this test.6.Apparatus6.1 Test Chamber,as described in Practice D4585.6.2 Test Substrate,15.2 by 121.9 cm(6 by 48 in.)substrateor of a size agreed upon by the purchaser and seller of thecoating being tested.6.3 Paint Brush,nylon/polyester brush of good quality.6.4 Spectrophotometer.6.5 Electronic Balance.6.6 Conditioned Room,at 18 to 29.5 C(65 to 85 F)and 40to 60%relative humidity.7.Reagents and Materials7.1 Wood PanelsSuch as cedar,redwood,oak,white pine,yellow pine,or other substrate as agreed upon between thepurchaser and the seller of the coating being tested.7.2 Control PaintAn agreed-upon paint of known tanninstain resistance.7.3 Test PaintsSince there are no standard panels,photographs,or paints for this test method,an agreed-uponcontrol paint(7.2)should be included as one of the test paints.1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings,Materials,and Applications and is the direct responsibility ofSubcommittee D01.42 on Architectural Coatings.Current edition approved April 1,2019.Published April 2019.Originallyapproved in 2001.Last previous edition approved in 2013 as D6686 01(2013).DOI:10.1520/D6686-01R19.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade(TBT)Committee.1 8.Procedure8.1 Choose a substrate with a consistent grain pattern.Patterns vary greatly from panel to panel,so try to select aboard that has consistent wood grain across the length of thesubstrate.Results may vary from panel to panel because ofdifferent growth rates,grain angles,colors,and species ofwood.If necessary,panels may be sanded to remove raisedgrain.Substrates with areas of rough spots should be avoided,as they will bleed