Overview
ISO/TR 18945:2018 is a Technical Report from ISO that documents a round‑robin study comparing image degradation observed in ISO 18930 accelerated weathering tests with actual outdoor exposure at nine sites. It covers the experimental framework, data analysis, and conclusions about how well accelerated laboratory simulations predict real‑world fading and colour shifts of pictorial colour reflection prints. The tested digital printing classes include aqueous inkjet, solvent inkjet, UV‑curable inkjet, digitally‑exposed silver halide, and thermal mass transfer. Correlations presented are illustrative for these classes and note that extension to other technologies (e.g., dye sublimation) requires verification.
Key Topics
- Test scope and methodology
- Round‑robin design comparing ISO 18930 accelerated tests with outdoor racks at nine geographic sites.
- Both outdoor weathering and laboratory accelerated weathering procedures are described.
- Acceleration and correlation metrics
- Acceleration factor (time ratio between outdoor and accelerated tests).
- Pearson correlation coefficient to quantify linear agreement between test methods.
- Fundamental drivers of degradation
- Importance of light, heat, and water; ultraviolet (295–400 nm) is especially damaging to polymers and colourants.
- Role of spectral power distribution (SPD) of test lamps; filtered xenon‑arc sources are highlighted as state‑of‑the‑art for simulating sunlight.
- Data analysis and variability
- Colour fade acceleration factors, colour shift analysis, replicability of results, and two‑year data evaluation.
- Cautions on site‑ and material‑specific variability (acceleration factors can vary substantially; one study noted ±50% variation by material at a location).
- Supporting material
- Informative annexes with SPD data, photographs of degradation, environmental condition datasets, and detailed comparisons (e.g., Annex G).
Applications
ISO/TR 18945:2018 is practical for:
- Material and ink manufacturers assessing print stability and comparing technologies.
- Testing laboratories developing accelerated weathering protocols and interpreting correlations to outdoor life.
- Print service providers, signage, and outdoor graphics producers estimating outdoor durability and warranty lifetimes.
- Conservators and photographic archivists wanting evidence‑based guidance on expected outdoor behaviour.
- R&D teams selecting substrates/coatings or validating new printing processes against outdoor performance.
Practical takeaways: use ISO 18930 accelerated tests to shorten evaluation time, but apply acceleration factors cautiously and validate correlations for each material class and exposure climate.
Related Standards
- ISO 18930 (accelerated and outdoor weathering test methods for print stability)
- ISO 4892‑1 (general guidance on laboratory weathering devices)
- ASTM G155 (xenon arc accelerated weathering)
These references help implement and interpret accelerated weathering in the context of ISO/TR 18945 findings.