ISO 18941:2020

Overview

ISO 18941:2020 - Imaging materials - Colour reflection prints - Test method for ozone gas fading stability - specifies a laboratory test method for assessing how colour reflection prints (both digital inkjet hardcopy and traditional analogue photographic prints) respond to controlled ozone exposure. The standard describes equipment, procedures and measurement methods to generate a known ozone exposure and quantify the resulting colour change. It uses elevated ozone levels for accelerated testing and warns that the method is suitable only when ozone is the principal gas-fading mechanism.

Key topics and technical requirements

• Scope and applicability: Applies to digitally printed hardcopy images and continuous-tone photographic colour prints; not appropriate if gas fading is driven by other pollutants.
• Apparatus and components: Defines requirements for an ozone test device, ozonized-air source, ozone concentration control, ozone concentration measurement, gas-flow control and a test-piece carrier.
• Test procedure: Specifies sample preparation (target selection, replicates, reference samples), chamber operation modes (open-loop vs closed-loop), and the procedural steps for controlled ozone exposure and post-exposure measurement.
• Environment and control: Details holding and measurement conditions including relative humidity control, temperature, agitation/air flow (volume turnover), and operational uniformity/operational fluctuations.
• Measurement and reporting: Requires quantitative measurement of colour change and defined reporting elements for reproducibility and comparison.
• Reciprocity and interpretation: Emphasizes reciprocity considerations - accelerated ozone levels may not scale linearly to ambient conditions. Factors such as diffusion-controlled reactions, reactant ratios (ozone vs colourant), humidity, pH and airflow can alter reaction rates and the validity of longevity predictions.

Practical applications and who uses it

ISO 18941 is used by:

• Imaging-material manufacturers (inkjet media, photographic paper) for product development and quality control.
• Independent testing laboratories for standardized accelerated ageing reports.
• Print service providers and photographers evaluating print permanence under polluted-air/display conditions.
• Museum, archival and conservation professionals assessing display vulnerability of unprotected prints.
• R&D teams studying fading mechanisms and improving ozone resistance.

Benefits include consistent, reproducible ozone-fading data to compare materials, guide product improvements, and inform storage/display recommendations.

Related standards

• ISO 18913 - Imaging materials - Permanence - Vocabulary
• ISO 5-3 / ISO 5-4 - Density measurement conditions for photography and graphic technology
• ISO 13655 - Spectral measurement and colorimetric computation for graphic arts images
• ISO 1431-3 - Methods for determining ozone concentration in test chambers

Keywords: ISO 18941, ozone gas fading, imaging materials, colour reflection prints, test method, accelerated aging, image permanence, photographic prints, inkjet fading, ozone exposure.