🔩 Exposure of paint and varnish coatings to laboratory light sources (artificial accelerated weathering and irradiation) — general guidance, requirements for devices: irradiance uniformity, black-standard and black-panel thermometers, interpretation of results, PN-EN ISO 16474-1

Materials and NDT PN-EN ISO 16474-1

Overview

WHAT THE STANDARD COVERS. Scope from the PKN catalogue card of PN-EN ISO 16474-1:2014-02 (English version), in full (our translation): “This standard provides information and general guidance on the selection and operation of the methods of exposure described in detail in subsequent parts. It also describes general performance requirements for devices used for exposing paints and varnishes to laboratory light sources. Only producers of devices for artificial accelerated weathering and artificial accelerated irradiation need information about such requirements. This part of ISO 16474 also provides information on the interpretation of data from artificial accelerated weathering or artificial accelerated irradiation”. The word “only” in the sentence about device producers is on the card — the ISO text says that this information “is provided for producers” of devices, without narrowing. We read the text in the sample of ISO 16474-1:2013 (the same edition is introduced by PN-EN ISO 16474-1:2014-02) from the cover to 5.2.3; we do not have the rest of Clause 5 (humidity and wetting, other requirements), the clauses on specimens, conditions and the report, or the annexes (among others A — measurement of irradiance uniformity, B — factors that change the durability ranking, C — benchmark solar spectrum).

ACCORDING TO THE TEXT OF ISO 16474-1:2013 (foreword, introduction, Clauses 1–5.2.3). The standard was prepared by ISO/TC 35 “Paints and varnishes”, SC 9 “General test methods for paints and varnishes”. The first edition of ISO 16474-1 together with ISO 16474-2 replaced ISO 11341:2004, and together with ISO 16474-3 — ISO 11507:2007. The series has four parts: 1 — general guidance, 2 — xenon-arc lamps, 3 — fluorescent UV lamps, 4 — open-flame carbon-arc lamps. Introduction: coatings are exposed to solar radiation (also behind glass), heat and moisture; natural exposures are described in ISO 2810, while laboratory exposures accelerate degradation under better controlled conditions; no laboratory test is a total simulation of actual-use conditions, and the acceleration depends on the material and its formulation. Scope (1): information and general guidance on the selection and operation of the methods of exposure in the subsequent parts, general requirements for devices (information for device producers) and information on the interpretation of data. References (2): ISO 1513, 1514, 2808, 3270, 4618, 9370, 15528 and ISO 16474-2, -3 and -4. Terms (3): artificial accelerated irradiation (simulation of solar radiation behind window glass or of interior lighting with small changes in temperature and humidity — so-called fading or light-fastness tests), artificial accelerated weathering (cyclic and intensified conditions: radiation source, heat, moisture in the form of relative humidity, water spray, condensation or immersion), control material (similar composition and construction, exposed at the same time), file material (stored under stable conditions for comparison of the unexposed and exposed state), reference material of known performance and reference specimen. Principle (4.1): specimens are exposed under controlled conditions; the methods include requirements for measuring irradiance and radiant exposure in the plane of the specimen, the temperature of black and white sensors, the chamber air temperature and the relative humidity. Significance (4.2): results are representative of actual use only when a rank correlation has been established for the specific material and the type and mechanism of degradation are the same; it is invalid to assign to all materials a “general acceleration factor” (x hours or megajoules = y months or years), because factors depend on the material and formulation, on the variability of degradation, and those calculated from irradiance ratios ignore temperature, moisture and spectral differences; a factor for a specific formulation is valid only with a sufficient number of natural and laboratory exposures and statistical analysis. Factors that spoil correlation: a spectrum different from solar radiation, irradiance higher than in use, continuous exposure without dark periods, too high specimen temperatures, unrealistic temperature differences between light and dark specimens, frequent temperature cycling or thermal shock, unrealistic moisture, absence of biological agents, pollutants and acid precipitation. Use (4.3): results are best used to compare materials tested at the same time in the same device; at least one control material is strongly recommended (preferably two — of good and poor durability) and at least three replicates of each material; for destructive tests — a separate set for each exposure period; a reference material (e.g. blue wool) can be misleading if its composition differs from the test material; a “pass/fail” result after a specified time may be used only when the combined reproducibility of the cycle and the property measurement method has been established. Devices (5): irradiance, temperature, humidity and wetting; at every point of the exposure area the irradiance at least 70 % of the maximum (the measuring procedure for producers is given in Annex A); at 70–90 % of the maximum the specimens have to be repositioned periodically; random placement of replicates is good practice; lamp and filter replacement according to the device manufacturer; radiometer according to ISO 9370, placed so that it receives the same radiation as the specimen, calibrated in the emission region of the light source used with the same source–filter combination (for fluorescent UV lamps — with lamps of identical spectral distribution); the irradiance is reported in an agreed wavelength range (e.g. 300–400 nm, 300–800 nm or in a narrow band around 340 nm). Temperature (5.2): the temperature in the chamber is measured and controlled by a black surface sensor: black-standard thermometer (BST — stainless-steel plate 0,5–1,2 mm, typically about 70 mm × 40 mm, black coating reflecting not more than 10 % of radiation up to 2 500 nm, platinum sensor, PVDF base 5 mm; alternative designs permitted if they read within ± 1,0 °C and the time to steady state is within 10 %) or black-panel thermometer (BPT — metal plate about 150 mm × 70 mm × 1 mm, sensor at the centre of the exposed surface, back side open); in typical exposures BST reads 3–12 °C higher than BPT, and the difference should preferably be determined for each exposure condition; another sensor construction has to be described in the report.

STATUS (PKN catalogue cards as of 02.10.2026). The card of PN-EN ISO 16474-1:2014-02 (English version, published 03-02-2014, 36 pages, price group R) has no “Withdrawn” header: Chemistry Sector, KT 175 Paints and Varnishes, ICS 87.040, “Introduces: EN ISO 16474-1:2013 [IDT], ISO 16474-1:2013 [IDT]”, “Replaces: PN-EN ISO 11341:2005 – Polish version, PN-EN ISO 11507:2008 – Polish version”, additional element PN-EN ISO 16474-1:2014-02/Ap1:2016-11E (we did not read the card of this amendment — we do not give its content). The PKN search engine (query “PN-EN ISO 16474-1”, 02.10.2026) shows only this one edition, in the English version. According to the EVS catalogue, ISO 16474-1:2013 is valid from 06.11.2013, and in the history of the standard it is preceded by ISO 11341:2004 and ISO 11507:2007.

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database, data up to 17.09.2026, read 02.10.2026). The number 16474-1 appears in 7 records of 7 laboratories: AB 128, AB 163, AB 240, AB 369, AB 910, AB 1424, AB 1552. In the current scopes on the PCA website (read 02.10.2026, issues from 17.12.2025 to 01.09.2026) four laboratories cite the 2014-02 edition (AB 163 also with amendment Ap1:2016-11), three — the designation alone without a date (AB 128, AB 369, AB 910). In every record Part 2 (xenon-arc lamps) or Part 3 (UV lamps) stands next to it, and in several also PN-EN ISO 4892 for plastics. The “Laboratories” tab (“PN-EN ISO 16474-1”) shows 6 laboratories — without AB 1424, whose field begins with PN-EN ISO 16474-3 — checked with a query of the tab on the labcoda.pl production server on 02.10.2026.

WHAT THE LABORATORIES TEST (PCA entries). “Resistance to a light source”, “Resistance to weathering and artificial radiation”, “Exposure to laboratory light sources — fluorescent UV lamps” (AB 1424), “Resistance to artificial weathering, method C, cycle 4” (AB 240); objects: paint systems and anticorrosive coatings, varnish coatings, plastics, metal products, materials for consumer products, building products.

WHERE A SEEMINGLY CORRECT RESULT IS EASY TO GET. During interpretation: converting hours in the device into years of use with one factor is invalid according to the standard (4.2.3); the result of one exposure can be transferred to another environment only with an established correlation (4.2.2). During comparison: materials are compared only when exposed together in the same device, with at least three replicates and a control material (4.3.1); a reference material of different composition can shorten or lengthen the exposure misleadingly (4.3.2). With the device: where the irradiance is 70–90 % of the maximum, specimens that are not repositioned receive a lower dose (5.1.4); a radiometer calibrated with a different lamp–filter combination measures wrongly (5.1.6.2). With temperature: BST and BPT differ by 3–12 °C under typical conditions — a set point of “65 °C” without the type of sensor does not define the conditions (5.2.3). With the edition and part: this part does not describe the exposure cycle — the conditions are in Part 2 or 3, and they decide the result.

WHAT WE DO NOT GIVE. We do not have the text from 5.2.4 onwards: requirements for humidity and wetting, specimen preparation, evaluation after exposure, the report, Annexes A–C or the content of amendment Ap1:2016 — so we give no values from those places; exposure cycles (times, irradiances, temperatures) are not in this part of the standard.

Method principle

Coating specimens are exposed in a device with a laboratory light source (xenon — Part 2, UV — Part 3, carbon arc — Part 4) under controlled irradiance, temperature (black-standard or black-panel thermometer) and humidity; the change in properties is evaluated in comparison with a control material exposed at the same time and with the file material — the results serve to compare materials, not to convert into years of use.

Applications

• Varnish coatings, paint systems and anticorrosive coatings — resistance to light and weathering in laboratory tests; 7 laboratories in PCA scopes
• Plastics and building products — together with PN-EN ISO 4892 and Parts 2–3 of the 16474 series
• Comparison of formulations and batches with a control material of known performance (4.3.1)

Key parameters

Standard

Standard number

PN-EN ISO 16474-1:2014-02 (wersja angielska; EN ISO 16474-1:2013 IDT, ISO 16474-1:2013 IDT)

Title (PL)

Farby i lakiery — Metody ekspozycji na laboratoryjne źródła światła — Część 1: Uwagi ogólne

Title (EN)

Paints and varnishes — Methods of exposure to laboratory light sources — Part 1: General guidance

Step-by-step procedure

1. Choice of method

   Choose Part 2, 3 or 4 and an exposure cycle suitable for the expected use of the coating; take into account the factors that spoil correlation (4.2.4). PN-EN ISO 16474-1:2014-02 current (PKN cards as of 02.10.2026).

2. Specimens

   At least three replicates of each material and of the control material; file material stored under stable conditions; for destructive tests a separate set for each period (4.3.1).

3. Device

   Check the irradiance uniformity (at least 70 % of the maximum); replace lamps and filters according to the manufacturer; radiometer according to ISO 9370; BST or BPT temperature sensor in the exposure area (5.1, 5.2).

4. Exposure

   According to the chosen part of the series; at an irradiance of 70–90 % of the maximum reposition specimens periodically; place replicates randomly (5.1.4).

5. Evaluation

   Compare the change in properties with the control material exposed at the same time; do not use a general acceleration factor; a “pass/fail” result only with established reproducibility (4.2.3, 4.3.3).

Required equipment and apparatus

Health and safety (OHS)

• The standard contains no safety warnings in the part we read; xenon and UV lamps emit radiation harmful to eyes and skin — rules for working at the device according to the manufacturer’s instructions
• TECHNICAL NOTE: the standard considers invalid a “general acceleration factor” converting hours in the device into years of use

Frequently asked questions