Overview
ISO 18910:2000 defines standardized methods to determine and express curl of imaging materials - specifically photographic film and paper (unprocessed and processed) in sheet, roll or strip formats. The standard specifies three measuring methods (A, B and C), the required conditioning and sampling practices, and how to report curl values. It is intended for laboratory and quality-control testing, not for monitoring curl during processing or drying.
Key topics and requirements
- Curl definition and notation
- Curl is a departure from flatness; direction is identified as L (lengthwise), T (transverse), D (diagonal) or C (cupping).
- Curl sign: “+” (emulsion-in) or “–” (emulsion-out).
- Three measurement methods
- Method A (vertical measurement): For sheets or rolls without cupping. Use square specimens (50×50 mm to 100×100 mm) or circular specimens (50–100 mm diameter). Curl is expressed as 1/R where R is radius in metres. Apparatus: curl-board template and a specimen clamp.
- Method B (horizontal edge measurement): For long roll film; measures cross-direction curl. Use standard widths (e.g., 8, 16, 35, 70, 105 mm) and specimen length ≥ 6× width. Measure edge height (H) with a depth/height gauge; small-curl approximation: 1/R ≈ 8H/W (W = film width).
- Method C (horizontal sheet/microfiche measurement): Place specimen concave-side up and measure corner heights; report mean of four corner distances. Useful for large sheets where gravity and stiffness affect curl.
- Sampling, handling and conditioning
- Samples must be representative and handled uniformly (use gloves/pincers; avoid breathing on specimens).
- Conditioning: recommended 23 °C ± 2 °C; suggested RHs 15%, 30%, 50%, 70%, 85% (preconditioning at 50% may be used). Typical equilibration: ~2 h for films, ~1 day for fibre-base papers, ~7 days for resin-coated papers.
- Reporting
- Include test method, specimen description, conditioning conditions, curl value, curl sign and direction, precision and specimen dimensions or roll position.
- Important notes
- Results from methods A, B and C are not directly comparable because of differences in specimen configuration, measurement orientation and gravity effects.
- Not intended for measurements during processing or drying.
Applications and users
ISO 18910 is used by:
- Photographic film and paper manufacturers for quality control and specification testing
- Photographic labs, conservation labs and archives assessing storage and handling risks
- Equipment designers (cameras, printers, film transport) to evaluate material feed and transport behavior
- Test laboratories preparing compliance and technical data sheets
Keywords: ISO 18910, curl determination, photographic film testing, photographic paper curl, curl measurement methods, 1/R curl, imaging materials testing.
Related standards
ISO 18910 replaces earlier ISO 4330 and belongs to the ISO 18900–18999 block covering imaging materials physical properties. Consult other ISO 189xx standards for related tests on dimensional change, stability and handling of photographic materials.
