Overview
ISO 2846-2:2007 - Graphic technology - Colour and transparency of printing ink sets for four‑colour printing - Part 2: Coldset offset lithographic printing defines the colourimetric and transparency requirements for printing ink sets used in four‑colour coldset web offset processes. The standard specifies how inks should be tested (using a printability tester and a defined reference substrate) and describes the colour measurement and transparency test methods to ensure conformance. It excludes fluorescent inks and does not mandate specific pigments, allowing future pigment technologies while maintaining colorimetric aims.
Key topics and technical requirements
- Scope: Color and transparency expectations for CMYK inks when printed under specified laboratory conditions for coldset offset.
- Colorimetric targets: The standard provides CIELAB target values and tolerances for Yellow, Magenta, Cyan and Black (measured under specified conditions). These targets establish a repeatable colour aim for process inks.
- Transparency limits: Transparency is quantified by a regression‑based measurement value T; minimum thresholds are specified: Yellow T ≥ 0.1, Magenta T ≥ 0.2, Cyan T ≥ 0.3. Highly transparent inks (especially cyan) that give near‑zero or negative slopes are treated as meeting the specification.
- Ink film thickness range: Standard conformity is evaluated within a specified ink film thickness range of 0.7 µm to 1.3 µm.
- Test method & measurement:
- Prints are produced on a reference substrate (defined colour, grammage ~48.8 g/m², opacity >94%, roughness ~3.4 µm).
- Colour is measured spectrally according to ISO 13655 (0°:45° or 45°:0° geometry, CIE 1931 2° observer, illuminant D50) using white backing per ANSI/CGATS.5:2003.
- Transparency is assessed by overprinting primaries on a black substrate and calculating the slope of colour difference vs. film thickness.
- Test preparation: Samples are conditioned (e.g., 12 h setting) and measured after printing on a printability tester per ISO 2834‑1.
Practical applications and users
Who benefits:
- Ink manufacturers - certify that CMYK ink sets meet coldset colour/transparency aims.
- Newspaper and publication printers using coldset web offset - ensure predictable colour reproduction across suppliers.
- Color management and QA labs - perform verification testing and batch acceptance.
- Prepress and process control engineers - base separations and tone value targets on standardized ink aims.
Practical uses:
- Supplier qualification, incoming ink acceptance, process control, and cross‑vendor colour consistency for four‑colour coldset printing.
Related standards
Keywords: ISO 2846-2:2007, coldset offset lithographic printing, four‑colour printing, printing ink sets, colour and transparency, CIELAB, ink film thickness, reference substrate, printability tester.
