1、Designation: D6686 01 (Reapproved 2008)2Standard 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 o
2、f last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1NOTEAn editorial change was made in 3.1.1 in June 2008.2NOTEEditorial changes were made in 6.2 and 8.1 in October 2010.1. Scope
3、1.1 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 parenthesis are for information only.1.3 This standard does
4、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 and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standa
5、rds: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
6、 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 conta
7、in 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 preva
8、lent to a high degree in cedar, redwood, oakand 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
9、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
10、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 29.5C (65 to 85F) and 40to 60 % relative humidity.7. Reagents and Materials7.1 Wood PanelsSuch as cedar, redwood, oak
11、, 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, photo-graphs, or paints for this test method, an agreed-
12、upon controlpaint (7.2) should be included as one of the test paints.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
13、panel because of1This 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 June 1, 2008. Published June 2008. Originallyapproved
14、in 2001. Last previous edition approved in 2001 as D6686 - 01. DOI:10.1520/D6686-01R08E02.2For 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 Sum
15、mary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.different growth rates, grain angles, colors and species ofwood. If necessary, panels may be sanded to remove raisedgrain. Substrates with areas of rough sp
16、ots should be avoided,as they will bleed through more readily. Divide substrate intostrips at least 15.2 cm (6 in.) wide or as agreed upon betweenthe purchaser and the seller and label the back of each test areawith paint designation. The control paint should be placed nearthe middle of the panel.8.
17、2 Prepare the cabinet as described in Practice D4585.8.3 Prepare paint brush as described in Practice D5068.8.4 Prime all edges of the panels with an appropriate primerand allow to dry according to manufacturers recommenda-tions. The backside of the panels must also be primed if thepanels are to be
18、placed fully inside the chamber.8.5 Measure the density of the test paint in accordance withTest Method D1475, and then using a brush, apply sufficientweight of test paints to achieve the desired spreading rate.Since dry time is critical, paints should be applied as quickly aspossible, so that the a
19、verage dry time is as close to the specifieddry time as possible for each test paint. If a second coat (selfprimed) is to be applied, allow the first coat to dry in theconditioned room for four h (dry time may affect results) or asagreed upon between the purchaser and seller. If appropriate,apply se
20、cond coat or topcoat over the entire substrate withenough grams to achieve the desired spread rate. Stain block-ing is highly dependent of film thickness; therefore, it isessential that the test paints be weighed on accurately, particu-larly for small test areas. The amount of paint in grams require
21、dfor a specific spread rate can be determined from the followingequation:g 5 A*W!/S!*3.15where:A = area, square inches,W = weight per gallon, lb./gal, andS = spreading rate, square feet/gal.Or the following metric equation:g 5 Am*D!/Sm!*1000where:Am= area, square metres,D = density, g/mL or kg/L, an
22、dSm= spreading rate, square metres/L.8.6 Allow the panels to dry in the conditioned room for 246 1 h (dry time may affect results) or as agreed upon betweenthe purchaser and seller. Immediately place the panels on thechamber with the painted sides facing toward the humidity orplace backprimed panels
23、 fully inside the chamber if agreedupon between the purchaser and seller.All panels should be runsimilarly. If the panels are placed on the chamber, fill all spacesin the specimen rack with test boards or blanks. Close allcracks between boards to prevent water vapor loss and tem-perature variation.
24、Larger cracks may be closed with tape ormetal strips. If the panels are placed inside the chamber, makesure panels are placed at an angle to avoid water spotting andrun off onto the test areas.8.7 Adjust the thermostat to maintain the desired tempera-ture of the saturated air and water vapor mixture
25、. Cabinettemperature of 39C (100F) is suggested. To ensure adequatecondensation on face down panels, maintain at least a 11C(20F) temperature differential between the room and theinside of the chamber.8.8 After 16 6 1 h, or an exposure time agreed uponbetween the purchaser and seller, carefully remo
26、ve the panelsand allow to dry for 24 h.8.9 Quantitatively rate each paint using the ASTM ScoringSystem 0-10 with 10 being no tannin stain and 0 a severe stain.8.10 Check CIELAB values using a spectrophotometer.Report L* and b* values. In this test b* values are mostimportant. Lower b* values general
27、ly indicate better tanninblock resistance. Higher b* values indicate a yellower orbrowner color. L* values, measuring whiteness versus dark-ness, are also important. Significant differences in either L* orb* values is 0.5 units. Five readings per test area should betaken, ranging from the top portio
28、n to the bottom part, andaveraged together. The average of multiple measurementsshould minimize differences in grain pattern. Readings shouldnot be taken over any obvious defect which is not a truereflection of the test area, such as a knot or any other defect.9. Report9.1 Report the following infor
29、mation:9.1.1 Substrates used, test paints, topcoat, spreading rates,dry time of first coat, dry time of topcoat, vapor temperatureand exposure time of topcoated panel to humidity. Report if thepanels were placed face down or fully inside the cabinet.9.1.2 Subjective results based on 0-10 scale.9.1.3
30、 L* and b* values and specify both illuminant andstandard observer.10. Precision and Bias10.1 It is not possible to specify the precision and bias inTest Method D6686 for measuring the tannin stain resistance ofcoatings because of the varying degree of tannin stains presentin the test substrates.11.
31、 Keywords11.1 stain blocking; tannin stain; wood extractives; woodstainD6686 01 (2008)22ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of
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34、nts have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or m
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