ISO 18919:1999

Overview

ISO 18919:1999 - Imaging materials - Thermally processed silver microfilm - Specifications for stability defines stability and performance requirements for thermally processed silver (TPS) microfilm intended for record storage. The standard covers microfilms with a poly(ethylene terephthalate) (PET) safety polyester base and image-forming metallic silver produced from silver behenate salts dispersed in a non-gelatinous binder and developed by heat. It applies to TPS microfilms with ultrasonic or dielectric (induction) splices and sets criteria for image stability, mechanical properties and ageing behavior. Films with adhesive-tape splices, lacquered films, colour products, TPS papers or conventionally wet-processed silver‑gelatin films are excluded.

Key topics and requirements

• Scope and definitions: Terminology for life expectancy (LE), archival storage conditions and TPS film construction.
• Base material: Requirement for PET safety film base and limits on residual free acid - the polyester base must not exceed the equivalent of 1.0 ml of 0.1 mol/L NaOH per gram of film; change after accelerated ageing is limited.
• Mechanical properties: Tensile property testing and limits for loss of tensile strength after accelerated ageing; tests follow referenced methods such as ISO 527-3.
• Image stability:
  • Classification criteria (e.g., LE‑100 designation requires passing both reader exposure and dark-ageing tests).
  • Microfilm‑reader test: Status A blue diffuse transmission density patches are exposed in a reader; after 1 hour at 70 °C the low‑density patch must not increase by more than 0.4 density units.
  • Accelerated image stability tests and dark-ageing procedures are specified.
• Layer integrity and handling:
  • Tape-stripping and humidity-cycling adhesion tests (no removal, separation or cracking that impairs use).
  • Binder brittleness limits and blocking (sticking) tests.
• Test methods and safety: Detailed laboratory methods, handling hazards and normative references for measurement standards (e.g., ISO 5-2, ISO 5-3).

Applications and who uses it

• Archival repositories, libraries and records management teams specifying long-term microfilm records.
• Microfilming service providers and manufacturers of TPS microfilm products ensuring stability, durability and LE ratings.
• Quality assurance and test laboratories performing compliance tests (image stability, tensile, adhesion, accelerated ageing).
• Institutions planning microfilm storage conditions and life-expectancy assessments for legal, historical or regulatory records.

Related standards

• ISO 10602 (processed silver‑gelatin film stability)
• ISO 543 (safety photographic film)
• ISO 5-2 / ISO 5-3 (density measurement methods)
• ISO 527-3 (tensile testing for films)
• ISO 8225, ISO 9718 (related film-type stability standards)

Keywords: ISO 18919:1999, thermally processed silver microfilm, TPS microfilm, silver behenate, polyester (PET) base, microfilm stability, LE‑100, accelerated ageing, image stability, archival microfilm.