SIST EN 927-3:2019

SLOVENSKI STANDARD
SIST EN 927-3:2019
01-november-2019
Nadomešča:
SIST EN 927-3:2012
Barve in laki - Premazi in premazni sistemi za zaščito lesa za zunanjo uporabo - 3.
del: Preskus s staranjem v naravnih razmerah
Paints and varnishes - Coating materials and coating systems for exterior wood - Part 3:
Natural weathering test
Beschichtungsstoffe - Beschichtungsstoffe und Beschichtungssysteme für Holz im
Außenbereich - Teil 3: Freibewitterung
Peintures et vernis - Produits de peinture et systèmes de peinture pour bois en extérieur
- Partie 3 : Essais de vieillissement naturel
Ta slovenski standard je istoveten z: EN 927-3:2019
ICS:
71.100.50 Kemikalije za zaščito lesa Wood-protecting chemicals
87.040 Barve in laki Paints and varnishes
SIST EN 927-3:2019 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 927-3:2019

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SIST EN 927-3:2019


EN 927-3
EUROPEAN STANDARD

NORME EUROPÉENNE

September 2019
EUROPÄISCHE NORM
ICS 87.040
English Version

Paints and varnishes - Coating materials and coating
systems for exterior wood - Part 3: Natural weathering
test
Peintures et vernis - Produits de peinture et systèmes Beschichtungsstoffe - Beschichtungsstoffe und
de peinture pour le bois en extérieur - Partie 3 : Essai Beschichtungssysteme für Holz im Außenbereich - Teil
de vieillissement naturel 3: Freibewitterung
This European Standard was approved by CEN on 21 July 2019.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.





EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2019 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 927-3:2019 E
worldwide for CEN national Members.

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EN 927-3:2019 (E)
Contents Page
European foreword . 3
1 Scope . 4
2 Normative references . 4
3 Terms and definitions . 5
4 Principle . 5
5 Apparatus and materials . 6
6 Coating sampling . 6
7 Test panel selection . 6
7.1 Wood reference species . 6
7.2 Preparation and selection of wood panels . 7
7.3 Preparation of coated panels . 8
8 Procedure. 10
8.1 General . 10
8.2 Examination before exposure . 10
8.3 Exposure . 10
8.4 Examination after exposure . 10
9 Precision data . 11
10 Expression of results and test report . 11
Annex A (normative) Details of test methods . 12
Annex B (normative) Assessment requirements for panels of test coatings and WRM . 15
Annex C (informative) Example format for a test report . 16
Annex D (informative) Optional tests including variations to standard weathering test
procedure to obtain additional information on coating performance . 19
Annex E (informative) Explanatory notes . 22
Annex F (informative) Precision data . 23
Annex G (normative) Guidance on typical properties for some common wood species . 25
Annex H (informative) Determination of adhesive strength of tape on test surface . 29
Annex I (informative) Thermal or chemical modification to protect the wood . 30
Bibliography . 32

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EN 927-3:2019 (E)
European foreword
This document (EN 927-3:2019) has been prepared by Technical Committee CEN/TC 139 “Paints and
varnishes”, the secretariat of which is held by DIN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by March 2020, and conflicting national standards shall
be withdrawn at the latest by March 2020.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN 927-3:2012.
The main technical changes in comparison with the previous edition are:
a) the provision for using alternative wood species has been updated;
b) the Internal Comparison Product (ICP) has been replaced by a nominated reference material as
Weathering Reference Material (WRM);
c) mould growth assessment has been extended to visual disfigurement by microorganisms;
d) former Annex A was deleted;
e) new Annex G for typical properties for common wood species was added;
f) new Annex H for adhesive tape testing was added;
g) new Annex I for thermal/chemical modification of wood was added;
h) standard editorially revised.
According to the CEN-CENELEC Internal Regulations, the national standards organisations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the
United Kingdom.
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1 Scope
This document specifies a natural weathering test for exterior wood coating systems mainly intended
for decoration and protection of planed and sawn wood.
The test provides a means of evaluating the performance of a wood coating system during outdoor
exposure. It forms the basis for the performance specification in accordance with EN 927-2. It also
facilitates the comparison of coating systems performance on different substrates including the wood
species, or other wood modifications.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
EN 927-2, Paints and varnishes — Coating materials and coating systems for exterior wood — Part 2:
Performance specification
EN 16492, Paints and varnishes — Evaluation of the surface disfigurement caused by fungi and algae on
coatings
EN ISO 1513, Paints and varnishes — Examination and preparation of test samples (ISO 1513)
EN ISO 2409, Paints and varnishes — Cross-cut test (ISO 2409)
EN ISO 2808:2007, Paints and varnishes — Determination of film thickness (ISO 2808:2007)
EN ISO 2810, Paints and varnishes — Natural weathering of coatings — Exposure and assessment (ISO
2810)
EN ISO 2813, Paints and varnishes — Determination of gloss value at 20°, 60° and 85° (ISO 2813)
EN ISO 4628-1:2016, Paints and varnishes — Evaluation of degradation of coatings — Designation of
quantity and size of defects, and of intensity of uniform changes in appearance — Part 1: General
introduction and designation system (ISO 4628-1:2016)
EN ISO 4628-2, Paints and varnishes — Evaluation of degradation of coatings — Designation of quantity
and size of defects, and of intensity of uniform changes in appearance — Part 2: Assessment of degree of
blistering (ISO 4628-2)
EN ISO 4628-4, Paints and varnishes — Evaluation of degradation of coatings — Designation of quantity
and size of defects, and of intensity of uniform changes in appearance — Part 4: Assessment of degree of
cracking (ISO 4628-4)
EN ISO 4628-5, Paints and varnishes — Evaluation of degradation of coatings — Designation of quantity
and size of defects, and of intensity of uniform changes in appearance — Part 5: Assessment of degree of
flaking (ISO 4628-5)
EN ISO 4628-6, Paints and varnishes — Evaluation of degradation of coatings — Designation of quantity
and size of defects, and of intensity of uniform changes in appearance — Part 6: Assessment of degree of
chalking by tape method (ISO 4628-6)
EN ISO 15528, Paints, varnishes and raw materials for paints and varnishes — Sampling (ISO 15528)
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EN ISO 11664-4, Colorimetry — Part 4: CIE 1976 L*a*b* Colour space (ISO 11664-4)
ISO 554, Standard atmospheres for conditioning and/or testing — Specifications
ISO 18314-1, Analytical colorimetry — Part 1: Practical colour measurement
3 Terms and definitions
For the purposes of this document, the following term and definition applies.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at https://www.iso.org/obp
3.1
Weathering Reference Material
WRM
coating material of known aging performance
4 Principle
The resistance to natural weathering of the coating system under test, applied to a specified wood
substrate, is assessed. Durability is evaluated by determining the changes in decorative and protective
properties of coatings after 12 months of exposure.
The reference test substrate is Pinus sylvestris (European redwood or Scots pine, subsequently referred
to as pine) in order to obtain comparative results more rapidly. The sapwood, which is usually present
in joinery timber, was chosen as the substrate reference instead of heartwood, because paint failure is
more evident on the former. However heartwood and other grain orientations may be used as
alternatives.
Differences in nature and quality of wood, and in the weather and site conditions, are recognized and
1)
allowed for in the method by comparing the test system with a nominated WRM . The WRM is subject
to agreement by the customer and test institution and could be a nominated commercial product.
The standard test substrate is pine sapwood. Performance on substrates additional to pine can be
carried out using the same test method principles on a nominated substrate (or substrates), e.g.
alternative wood species, wood pre-treatments, and wood modifications. The results can be assessed by
the criteria of EN 927-2 and subject to meeting them, conformity claimed for the tested
substrate/coating combination.
Optional tests are described in Annex D. They can provide valuable additional information. However to
facilitate comparisons the standard requires that pine panels are included as part of each exposure
series. An alternative version of the test panel has a machined water-trap. This can accelerate some
types of failure.

1) Previous versions of EN 927-3 have used a tightly specified semi-transparent wood stain as the WRM and
known as the Internal Comparison Product (ICP). It has proved increasing difficult to source the raw materials for
the ICP and legislation has made some materials unavailable. The ICP was primarily used to assess the severity of
the climatic exposure at the weathering site but proved to be relatively insensitive to location. Interpretation of
this revised Standard places more emphasis on the absolute test result but allows manufacturers and research
organisations to make comparison with tried and tested compositions.
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5 Apparatus and materials
5.1 Exposure racks, inclined at an angle of 45° to the horizontal, on which the specimens are facing
towards the equator in accordance with EN ISO 2810.
5.2 Glossmeter, for the measurement of specular gloss in accordance with EN ISO 2813, at 60°
geometry.
5.3 Tristimulus colourimeter or spectrophotometer, for the measurement of colour and
calculation of colour difference in CIELAB colour coordinates in accordance with EN ISO 11664-4.
5.4 Tape and cutting tool, for the assessment of adhesion in accordance with EN ISO 2409.
5.5 Microscope, with a magnification of × 10 for the assessment of surface defects.
5.6 Microscope, for measurement of film thickness in accordance with ISO 2808:2007, method 6A.
5.7 Self-adhesive, transparent tape, in accordance with EN ISO 4628-6 for the assessment of
chalking.
5.8 Climate chamber.
6 Coating sampling
Take a representative sample of the product tested or of each product in the case of a multi-coat system,
as described in EN ISO 15528.
Examine and prepare each sample for testing as described in EN ISO 1513.
7 Test panel selection
7.1 Wood reference species
The reference test panel shall be pine that has been selected to be free from knots, cracks and resinous
streaks and to be straight-grained and of normal growth rate (i.e. 3 to 8 annual rings per 10 mm). The
inclination of the growth rings to the face shall be 5° to 45° (see Figure 1).
The wood shall be free from blue stain and evidence of surface or bulk fungal infection. Abnormal
porosity (caused by bacterial attack) shall be avoided (see Annex A, A.10).
The wood shall be conditioned at (20 ± 2) °C and a relative humidity of (65 ± 5) % to an equilibrium
moisture content of (13 ± 2) %.
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a)

b)

c)

d)
Key
a) Example of a panel with no heartwood (if present) closer than 10 mm to the
test surface fulfilling the requirement for growth ring orientation (5° to
45°) at the front side.
b) This panel does not meet the specification because the heartwood is too close
to the front side.
c) This panel does not meet the specification because the growth ring
orientation is not within the 5° to 45° band. The growth rings incline −10°
at the left of the panel and 30° at the right. Consequently a part of the
surface contains tangentially cut wood surface (growth ring inclination
0°), with considerable risk of crack formation.
d) This panel does not meet the specification because the growth ring
orientation is not within the 5° to 45° band. The growth rings incline 45°
at the left of the panel and 70° at the right.
NOTE The top side of panels is the exposed side; the bottom is the rear face.
Figure 1 — Cross section of panels
7.2 Preparation and selection of wood panels
7.2.1 Reference (standard) test panels
The panels shall be cut from boards planed all round and shall be nominally
(375 ± 2) mm × (78 ± 3) mm and (20 ± 2) mm thick. For details of panel preparation see Figure 2. The
panels shall be planed to a smooth and uniform finish. In order to avoid aged wood surface, the panels
shall be hand sanded (mesh 150) immediately before coating. Rounding of edges is not permitted.
The panels shall be selected to give a sapwood test surface on the convex side of the growth rings, with
any heartwood confined to a zone no closer than 10 mm from the front side. Heartwood shall be
checked with the reagent described in A.11, at both ends of each panel.
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Any panels showing surface splitting shall be rejected. Where the presence of some minor defects in the
test area is unavoidable, their position should be noted and their influence excluded during assessment
of coating performance.
7.2.2 Alternative test panels
Alternative substrates including other wood species than pine, modified or impregnated wood may be
tested according to the requirements of the test specifier (customer). Preparation of the panels should
follow the procedure for sizing, planning and sanding as in 7.2.1. However the requirements for
heartwood to sapwood ratio and grain orientation may be different. These should be agreed with the
user by the testing organization (if different) and the information recorded on the test report. Some
guidance on typical properties for some common wood species is given in Annex G.
7.3 Preparation of coated panels
7.3.1 Wood conditioning
Prior to coating, condition the panels at (20 ± 2) °C and a relative humidity of (65 ± 5) % according to
ISO 554 until constant mass. Keep the panels under the same conditions during drying of the coating
system and during subsequent storage of test panels before exposure. Panels may be transferred for
brief periods to other ambient conditions where this is required for the conduct of specific operations
or assessments.
7.3.2 Preparation of panels for the test coating
For each coating system, select four panels on a random basis from the available supply for each species
to be tested including the reference. Three panels shall be used for exposure and the fourth shall be for
unexposed reference.
Apply the coating system to the front and side faces of each panel. The front side of the panel is the side
facing the bark of the tree. The back of the panel and end-grains shall be left uncoated.
Apply the coating system using the method specified by the manufacturer to give a spreading rate
corresponding to the mean value (± 20 %) of the manufacturer's recommended spreading rate.
Record the quantity of coating applied to each test panel and subsequently calculate a mean value for
2 2
the four panels. The values should be stated preferably in l/m or g/m , but may also be expressed as
wet film thickness (in micrometres).
7.3.3 Preparation of panels for the Weathering Reference Material (WRM)
Prepare four panels by applying the WRM to the front and side faces of each panel. The back of the
panel and end-grains shall be left uncoated. Apply the WRM by applying the coating system according to
the manufacturer’s instructions and allowing for the necessary number of coats and the drying period
between coats. The dry film thickness shall be recorded in μm on pine.
One set of WRM panels exposed at the same time may serve as the comparison for one or more test
coatings on the reference substrate. The WRM should also be used on each alternative substrate tested
as the comparison for one or more test coatings.
7.3.4 Sealing and ageing
When all the coatings have dried, seal thoroughly the ends of the panels with at least two coats of a
flexible, moisture-impermeable white paint, for example, but not limited to, a long-oil alkyd type, and
capable of withstanding 2 years of natural exposure without breakdown. The ‘sealer’ may be applied by
brushing or dipping. The sealer shall be applied to the bands marked “a” and “c” at the ends of the panel
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shown in Figure 2. It is important that the sealer is applied all round, i.e. that front, sides, end grains and
rear face of the bands are coated.
After sealing, age the panels for approximately 7 days in the controlled environment at (20 ± 2) °C and a
relative humidity of (65 ± 5) %, before carrying out initial panel examinations.
Exposure shall start at the latest 28 days after completion of sealing.
Dimensions in millimetres

Key
1, 2 and 3 exposure panels
R unexposed reference panel
a sealed end (may be used for numbering or marking of test panels)
b section for application of coating system
c sealed end
NOTE The figure is not to scale.
Figure 2 — Details of test panels
7.3.5 Thickness of the coating
Determine the dry film thickness of the WRM and the test coating(s) using the unexposed reference
panels. Examine three small chips of coated wood removed from each reference panel by microscopy in
accordance with EN ISO 2808:2007, method 6A. The three chips shall be removed at three different
places spaced evenly across the panel width. Make five measurements on each of the three chips and
calculate and record the mean value in micrometres.
The thickness is stated in micrometres and refers to the layer on (above) the wood surface. Coating
materials may penetrate the wood material to some extent, but this part is not included in the
determination.
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8 Procedure
8.1 General
Carry out all examinations in accordance with Annex A and Annex B.
8.2 Examination before exposure
Before exposure, carry out the following measurements on all the test panels and the WRM:
— mass of coating system applied (by weighing) (see 7.3.2);
— coating thickness (see 7.3.5);
— gloss;
— colour.
Assess the adhesion on the reference panel for the test coating and the WRM.
As wood is a natural material, unexpected defects can be detected in the coated panels just before
exposure, even though the wood material has been selected, inspected and prepared along the
guidelines of 7.1 and 7.2. If such panels as an exception are exposed, the type, size and position of
defects shall be noted, so as to avoid any influence on the assessment after exposure.
For further details, see Annex A and Annex B.
8.3 Exposure
Expose three of the four panels with their long edge horizontal and the 50 mm band to the left of the
exposed face, for a period of 12 months, using the exposure racks (5.1). Record the starting and ending
dates.
Store the reference panels indoors at a temperature of (20 ± 2) °C and a relative humidity of (65 ± 5) %.
8.4 Examination after exposure
8.4.1 Examination on the exposure racks
At the end of the 12 months exposure period, examine the panels on the exposure racks and record any
blistering. Remove the panels from the racks to the laboratory and condition for 7 days at a
temperature of (20 ± 2) °C and a relative humidity of (65 ± 5) %.
8.4.2 Laboratory examination of unwashed panels
Assess the panels for the following properties:
— flaking;
— cracking;
— visual disfigurement by microorganisms;
— chalking;
— general appearance.
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8.4.3 Laboratory examination of washed panels
After the first examinations (8.4.1 and 8.4.2), wash the panels by sponging with clean lukewarm water
to remove surface deposits and atmospheric pollutants, and allow to dry.
Examine the coating on the reference and exposed panels for gloss and colour.
Examine the coating on the exposed panels for visual disfigurement by microorganisms, adhesion and
general appearance.
9 Precision data
Further information for precision data is given in Annex F.
10 Expression of results and test report
The test report shall contain at least the following information:
a) all details necessary to identify the product tested, including name and address of the manufacturer
or supplier of the coating system tested, name or other identification marks of the coating system
tested, including the batch number, description of the coating system tested, method and date of
application, coating thickness and colour;
b) in the case of additional alternative substrates each substrate should be given a general description.
Where the alternative is a different wood species from the Pine reference then density, heartwood
sapwood ratio and grain orientation should be reported using the headings listed in Annex G. The
source of the wood should also be clearly stated in the test report.
c) reference to this part of EN 927 (i.e. EN 927-3);
d) name and address of the testing laboratory;
e) exposure site;
f) identification number of the test report;
g) name and address of the organization or the person who ordered the test;
h) method of sampling, date and person responsible for the sampling;
i) date of receipt of the coating system tested;
j) exposure period (start and finishing dates);
k) any deviations from the test methods specified;
l) test results (see 8.2, 8.4.2 and 8.4.3);
m) date of authorization of the test report;
n) type of cutting tool used for adhesion measurement (see A.9.2.1);
o) method of colour measurement, i.e. 45°:0° (specular component excluded) or di:8° (specular
component included); any deviations from the test methods specified.
An example for a suitable form is given in Annex C.
A copy of the test report together with data sheets should be stored to comply with quality assurance
requirements.
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Annex A
(normative)

Details of test methods
A.1 Gloss and change of gloss
Measure the specular gloss in accordance with EN ISO 2813 using a glossmeter at 60° incident light
angle. Determine the value for each area along the grain, i.e. with the light beam parallel to the grain.
Obtain three measurements on separate areas along the length of the panel. Rotate the glossmeter 180°
and obtain another three measurements on adjacent areas. Take the mean of the six measurements
obtained.
Calculate the change of gloss CG of each of the three exposed panels, and of the unexposed reference
panel. Calculate the mean of the gloss change of the three exposed panels. State the final result to one
decimal place.
A.2 Colour and colour change
Measure the colour in accordance with ISO 18314-1 using the measurement geometry 45/0 or d/8 with
specular component included (sci/spin). The geometry used shall be stated in the test report.
Determine the CIE 1976 colour coordinates (L*, a*, b*) for the standard illuminant D65 and standard
observer 10° for each panel as a mean of 6 single measurements.
*
Calculate the colour change ∆E of each of the three exposed panels and of the unexposed reference
ab
panel. Calculate the mean of the colour change of the three exposed panels. State the final result to one
decimal place.
A.3 Blistering
The assessment for quantity (density) and size is made on each exposed panel separately in accordance
with EN ISO 4628-2.
Calculate and record the mean value for quantity and size to one decimal place.
A.4 Flaking
Assessment for qu
...