EN 927-3:2019

SLOVENSKI STANDARD
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
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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.

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

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.
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)
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
...