1、BSI Standards PublicationPD CEN/TS 16498:2013Paints and varnishes Coating materials and coatingsystems for exterior wood Assessment of tannin stainingPD CEN/TS 16498:2013 PUBLISHED DOCUMENTNational forewordThis Published Document is the UK implementation of CEN/TS16498:2013.The UK participation in i
2、ts preparation was entrusted to TechnicalCommittee STI/28, Paint systems for non-metallic substrates.A list of organizations represented on this committee can beobtained on request to its secretary.This publication does not purport to include all the necessaryprovisions of a contract. Users are resp
3、onsible for its correctapplication. The British Standards Institution 2013. Published by BSI StandardsLimited 2013ISBN 978 0 580 78945 8ICS 87.040Compliance with a British Standard cannot confer immunity fromlegal obligations.This Published Document was published under the authority of theStandards
4、Policy and Strategy Committee on 30 November 2013.Amendments issued since publicationDate Text affectedPD CEN/TS 16498:2013TECHNICAL SPECIFICATION SPCIFICATION TECHNIQUE TECHNISCHE SPEZIFIKATION CEN/TS 16498 November 2013 ICS 87.040 English Version Paints and varnishes - Coating materials and coatin
5、g systems for exterior wood - Assessment of tannin staining Peintures et vernis - Produits de peinture et systmes de peinture pour le bois en extrieur - valuation des taches de tanin Beschichtungsstoffe - Beschichtungsstoffe und Beschichtungssysteme fr Holz im Auenbereich - Beurteilung von unerwnsch
6、ten Verfrbungen aufgrund von Holzinhaltsstoffen This Technical Specification (CEN/TS) was approved by CEN on 12 February 2013 for provisional application. The period of validity of this CEN/TS is limited initially to three years. After two years the members of CEN will be requested to submit their c
7、omments, particularly on the question whether the CEN/TS can be converted into a European Standard. CEN members are required to announce the existence of this CEN/TS in the same way as for an EN and to make the CEN/TS available promptly at national level in an appropriate form. It is permissible to
8、keep conflicting national standards in force (in parallel to the CEN/TS) until the final decision about the possible conversion of the CEN/TS into an EN is reached. CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland
9、, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION
10、COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels 2013 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. CEN/TS 16498:2013: EPD CEN/TS 16498:2013CEN/TS 16498:2
11、013 (E) 2 Contents Page Foreword 3 Introduction .4 1 Scope 5 2 Normative references 5 3 Terms and definitions .5 4 Apparatus and materials .5 5 Procedure .6 5.1 Preparation of wood extract .6 5.2 Wood panels, extract application and sealing 7 5.3 Coating application8 5.4 Colour measurements after co
12、ating application 8 5.5 Cyclic climate exposure 9 5.6 Colour measurements after cyclic climate exposure 9 5.7 Calculation and assessment of colour differences 9 6 Test report . 10 Bibliography . 11 PD CEN/TS 16498:2013CEN/TS 16498:2013 (E) 3 Foreword This document (CEN/TS 16498:2013) has been prepar
13、ed by Technical Committee CEN/TC 139 “Paints and varnishes”, the secretariat of which is held by DIN. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN and/or CENELEC shall not be held responsible for identifying any or all such
14、 patent rights. According to the CEN-CENELEC Internal Regulations, the national standards organizations of the following countries are bound to announce this Technical Specification: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of M
15、acedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom. PD CEN/TS 16498:2013CEN/TS 16498:2013 (E) 4 Introduction Coatings
16、on exterior wood surfaces have both decorative and protective functions. A valued function of the coating system is to protect against discoloration caused by the presence of wood extractives in the coating migrating from the wood material. Bleeding of extractives can occur at different stages, incl
17、uding shortly after coating application and at a later stages in use, when driving forces like fluctuating humidity are present. PD CEN/TS 16498:2013CEN/TS 16498:2013 (E) 5 1 Scope This Technical Specification specifies a test method for assessing the discoloration of coatings on wood by tannin stai
18、ning due to wood extractives. The method uses an extract from Merbau wood as an indicator. Bleeding of wood extractives is assessed at two specified stages firstly after coating application and secondly after cyclic climate exposure. A qualification of colour differences that can be attributed to th
19、ree different causes, bleeding of extractives, low opacity of the coating film or general yellowing in climate exposure, is included. This document does not specify acceptance values for colour differences that can be tolerated and it is not applicable to staining caused by knots for which there is
20、a different test method (e. g. CEN/TS 16359). 2 Normative references The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition o
21、f the referenced document (including any amendments) applies. EN 927-5, Paints and varnishes - Coating materials and coating systems for exterior wood - Part 5: Assessment of the liquid water permeability ISO 554, Standard atmospheres for conditioning and/or testing Specifications ISO 3131, Wood Det
22、ermination of density for physical and mechanical tests ISO 7724-2, Paints and varnishes Colorimetry Part 2: Colour measurement 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 tannin staining appearance of discoloration on coated surfaces cau
23、sed by wood extractives in the substrate 3.2 knot staining appearance of discoloration on coated surfaces caused by wood extractives in knots 3.3 wood extractives low-molecular weight wood components soluble in organic solvents or water 4 Apparatus and materials 4.1 1 l measuring cylinder. 4.2 Balan
24、ce, with an accuracy of 0,01 g. 4.3 CIELAB Spectrophotometer, with d/8 geometry, D65 light source and 10 standard observer. 4.4 Chips of Merbau wood (Intsia sp.), produced by drilling. 4.5 1 l round bottom flask with a water cooled condenser. PD CEN/TS 16498:2013CEN/TS 16498:2013 (E) 6 4.6 Round bot
25、tom heater. 4.7 Coating applicator, with a 60 m gap and 40 mm to 100 mm width. 4.8 Equipment for coating application. 4.9 Black/white contrast cards. 4.10 Climate chamber to maintain (20 2) C and (65 5) % relative humidity. 4.11 Climate chamber to maintain (60 2) C and (100 5) % relative humidity. 4
26、.12 Climate chamber to maintain (23 2) C and (50 5) % relative humidity. 5 Procedure 5.1 Preparation of wood extract For each test a fresh wood extract solution with defined concentration is produced using the following procedure: weigh approximately 30 g of Merbau wood (Intsia sp.) wood chips in a
27、1 l round bottom flask equipped with a water cooled condenser (see Figure 1); add approximately 500 g deionised water; heat this mixture 8 h at 100 C to boiling and let cool down 16 h. Repeat this cycle 3 times in total; cool the solution to room-temperature and filter; on a sample of the solution m
28、easure the solid content in % (by mass) by evaporation; concentrate the solution by evaporation and dilution with water to a remaining solution of 3 % solid content. The solution may be applied for a period of 1 month provided it is kept cool. The extraction apparatus is shown in Figure 1. PD CEN/TS
29、 16498:2013CEN/TS 16498:2013 (E) 7 Key 1 water out 2 water in 3 clamp 4 condenser 5 Merbau wood with deionised water 6 heat source Figure 1 Extraction model NOTE Merbau wood is a commercially used wood species that is known to have a very high amount of extractives compared to other wood species. 5.
30、2 Wood panels, extract application and sealing Boards of Beech wood (Fagus sylvatica) are selected with normal growth rate (i. e. 2 annual rings to 6 annual rings per 10 mm) and straight grain. From these boards panels with the dimensions 150 mm 74 mm 20 mm free from knots and cracks are produced, s
31、o that the inclination of the growth rings to the test surface is 60 to 90. The panels shall be planed to a smooth and uniform finish. In order to avoid an aged wood surface, the panels should be hand sanded (mesh 150) immediately before application of the Merbau wood extract. The wood shall be cond
32、itioned at (20 2) C and a relative humidity of (65 5) % (in accordance with ISO 554) until equilibrium has been reached, i. e. normally minimum for one month and maximally for 6 months. After conditioning, wood density is determined according to ISO 3131. Apply a layer of the Merbau wood extract usi
33、ng a coating applicator with a gap size of 60 m on 6 Beech wood panels across the grain (see Figure 2) and let the solution dry for min. 8 h at (20 2) C (65 5) % relative humidity. Repeat the application after drying. Seal all sides except the test face of the panels with a sealer according to EN 92
34、7-5. PD CEN/TS 16498:2013CEN/TS 16498:2013 (E) 8 Key 1 stained surface (S) 2 reference (R) 3 extract Figure 2 Drawing of sample with wood extract applied on a part of the test surface (regions for colour measurements) 5.3 Coating application Apply the coating system to the front side of 6 panels usi
35、ng the method specified by the manufacturer to give a wet film thickness corresponding to the mean value (20 %) of the manufacturers recommended spreading rate. Record the quantity of coating applied. The values should be stated preferably in gram per square metre, but may also be expressed as wet f
36、ilm thickness, in micrometres. Apply the same coating system on a black/white contrast card. For spray applied coating systems fix the contrast card on a wood panel and use the same application method as on the Beech wood panels. Brush applied systems shall by applied on the contrast card using a fi
37、lm applicator. After coating application, condition the panels and contrast cards for 7 days in the controlled environment at (20 2) C and a relative humidity of (65 5) % in accordance with ISO 554. 5.4 Colour measurements after coating application After conditioning the panels for 7 days in the con
38、trolled environment, colour is measured on each panel at six spots in the region S (surface over wood extract) and on six spots in the region R (surface without wood extract) according to Figure 2. It is recommended to fix the position of the spots for measurement by using a template. After conditio
39、ning the black/white contrast cards for 7 days in the controlled environment, colour is measured on four spots on the coated white substrate and on four spots on the coated black substrate. The colour shall be measured in CIELAB colour coordinates with an apparatus with illuminant D65/10 standard ob
40、server as specified in ISO 7724-2. Specular gloss may be included or excluded, but the selected principle should be stated. PD CEN/TS 16498:2013CEN/TS 16498:2013 (E) 9 5.5 Cyclic climate exposure The coated Beech wood panels are subjected to cyclic climate exposure consisting of 8 cycles of 24 h at
41、(60 2) C and (100 5) % relative humidity and 24 h at (23 2) C and (50 5) % relative humidity. Over the weekends panels are stored at (23 2) C and (50 5) % relative humidity. 5.6 Colour measurements after cyclic climate exposure After cyclic climate exposure, colour is measured on each panel at six s
42、pots in the region S (surface over wood extract) and on 6 spots in the region R (surface without wood extract) according to Figure 2. It is recommended to measure in the same positions as before climate exposure by using a template. Colour measurements are carried out according to the CIELAB-System
43、with d/8 geometry, D65 light source and 10 standard observer. 5.7 Calculation and assessment of colour differences From the CIELAB colour data measured before and after cyclic climate exposure colour differences are calculated as E*, L* and b*. Table 1 describes the colour differences that shall be
44、calculated by subtracting the standard values from the values in the end condition or on the stained area. Results are stated as mean values and standard deviations and marked with indices as described in Table 1. These colour differences are used to assess bleeding of extracts according to Table 2.
45、 To qualify if bleeding is present after coating application (phase 1) the difference in brightness (L*P0) on the samples shall be lower than the difference in brightness on the black/white contrast card (L*D), both differences in brightness shall be negative values (because of the calculation defin
46、ed in Table 1) and changes on the blue-yellow scale (b*P0) shall result in positive values. If these conditions are not fulfilled, measured colour differences shall be attributed to low opacity of the coating film and not to bleeding of extractives. After cyclic climate exposure bleeding is present
47、when the total colour difference on the stained surface (S) is larger than on the reference surface (R), the difference in brightness on the stained surface (S) is lower than on the reference surface (R) (both values shall be negative) and the difference on the blue-yellow scale (b*) on the stained
48、surface (S) is larger than on the reference surface (R). If these conditions are not fulfilled, measured colour differences shall be attributed to general yellowing of the coating film and not to bleeding of extractives in cyclic climate exposure. Colour differences on the sample measured after coat
49、ing application (phase 1) and after cyclic climate exposure (phase 2) may be used to quantify bleeding of extractives if the conditions above are fulfilled. NOTE Colour differences on the red-green scale (a*) are not relevant for bleeding of wood extractives. Table 1 Assessment of colour measurements in phases of extract bleeding; colour differences; end condition minus standard (regions R and S according to Figure 2) Phase Colour difference CIELAB colour data Index End condition Sta
