ISO 16474-4:2013

Overview

ISO 16474-4:2013 - Paints and varnishes: Methods of exposure to laboratory light sources - Part 4: Open‑flame carbon‑arc lamps specifies controlled laboratory procedures to reproduce the weathering effects caused by daylight or daylight filtered through window glass. The standard defines how to expose coated specimens to filtered open‑flame carbon‑arc radiation in the presence of moisture, with control of temperature, humidity and wetting, and how to measure the light exposure (irradiance and radiant exposure) for accelerated weathering tests.

Key topics and technical requirements

• Test principle: Exposure of specimens to glass‑filtered open‑flame carbon‑arc light combined with heat, humidity and/or water spray or condensation to simulate real‑world ageing.
• Light sources and filters: Use of open‑flame carbon‑arc lamps with different glass filters to simulate (a) direct daylight (Type 1), (b) window‑glass filtered daylight (Type 2) and (c) extended‑UV conditions (Type 3). The standard gives typical spectral distributions and examples of filters (informative only).
• Apparatus elements: Specification and guidance for laboratory light sources, test chambers, radiometers, black‑standard/black‑panel thermometers, wetting/humidity equipment, specimen holders and instruments to assess property changes.
• Exposure conditions: Controlled settings for temperature, relative humidity, spray/wetting cycles and light/dark timing. Measurement and reporting of irradiance and radiant exposure are required to quantify test severity.
• Procedure and reporting: Instructions for mounting specimens, exposure duration, measurement of radiant exposure, and items to include in the test report. Specimen preparation and post‑exposure evaluation are referenced to material‑specific standards.
• Intercomparison caution: Results from different apparatus should not be directly compared unless a statistical correlation is established.

Practical applications

• Accelerated weathering and durability testing of paints, varnishes and coating systems to predict performance under sunlight or behind window glass.
• Product development and formulation screening (R&D) to compare resistance to colour change, gloss loss, chalking and other ageing effects.
• Quality control and batch verification in manufacturing.
• Support for claims about outdoor or interior (behind glass) durability, lifetime prediction and comparative performance.

Who should use this standard

• Coatings manufacturers and formulators
• Independent testing laboratories and QA/QC teams
• Materials scientists and accelerated‑weathering researchers
• Specifiers, auditors and regulatory bodies assessing coating durability

Related standards

• ISO 16474‑1 (General guidance)
• ISO 4892‑4 (Open‑flame carbon‑arc exposures for plastics)
• ISO 4582, ISO 4618, ISO 9370 (normative references used for measurements and terminology)

Keywords: ISO 16474‑4:2013, open‑flame carbon‑arc lamps, paints and varnishes, laboratory light sources, accelerated weathering, radiant exposure, exposure methods, window‑glass filters.