Overview
ISO 18929:2012 - "Imaging materials - Wet-processed silver‑gelatin type black‑and‑white photographic reflection prints - Specifications for dark storage" - defines how wet‑processed silver‑gelatin black‑and‑white photographic prints are evaluated for long‑term dark storage. The standard covers fibre‑base and resin‑coated (RC) silver‑gelatin prints, including prints treated with gold, selenium, sulfur or similar toners and prints processed in a thiosulfate monobath. It sets requirements, test methods and a life‑expectancy (LE) classification for archival storage performance.
Key topics and technical requirements
- Scope and exclusions
- Applies to wet‑processed black‑and‑white silver‑gelatin reflection prints (all weights).
- Excludes instant, stabilization‑processed, thermal, colour/dye‑based prints, PET support, displayed or laminated/mounted prints and monobaths that do not use thiosulfate.
- Physical stability tests
- Wedge brittleness (paper embrittlement evaluation).
- Tensile energy absorption (mechanical strength; see Annex C).
- Resin cracking for RC papers (environmental resistance; see Annex D).
- Image/process stability tests
- Residual thiosulfate concentration (processing by‑products that can promote degradation).
- Residual silver concentration (potential for image oxidation).
- Yellowing limit and methods for measuring discoloration (see Annex G and H).
- LE designation
- Predictive life‑expectancy classification (e.g., LE‑100 indicates ≥100 years under defined storage conditions).
- Test methods and safety
- Standardized procedures (see Clause 8) and normative references, including ISO 18907, ISO 18917, ISO 5‑3/5‑4 and TAPPI T494.
- Safety and hazard code guidance for handling chemicals used in testing.
Practical applications - who uses ISO 18929:2012
- Archives, libraries, museums and cultural heritage institutions - for selecting and qualifying prints and setting dark‑storage policies.
- Photographic laboratories and print manufacturers - for quality control, product specification and process optimization (fixing, washing, toning).
- Conservators and collection managers - to assess risk (residual chemicals, yellowing, resin cracking) and plan stabilization or rehousing.
- Procurement and standards teams - to specify LE ratings and compliance for long‑term image preservation.
Related standards
- ISO 18907 - wedge test for brittleness
- ISO 18917 - determination of residual thiosulfate
- ISO 5‑3 / ISO 5‑4 - density measurement conditions
- TAPPI T494 - tensile properties of paper
ISO 18929:2012 is a practical tool for evaluating the durability of silver‑gelatin black‑and‑white prints in dark storage and for making informed decisions about processing, conservation and long‑term archival management.