ISO 787-1:1982

Overview

ISO 787-1:1982 - General methods of test for pigments and extenders - Part 1: Comparison of colour of pigments - establishes a standardized procedure for visually comparing the colour of a coloured pigment with an agreed reference sample. The standard accepts two procedures (hand method and automatic muller), with the automatic muller specified as the reference method. The binder is not fixed by the standard and must be agreed between parties; if none is specified, linseed oil conforming to ISO 150 is recommended.

Key topics and requirements

• Scope: Comparative colour assessment of pigments by preparing ground pigment pastes and applying opaque strips for visual comparison.
• Reference method: Automatic muller (preferred) - details include plate diameters, rotational frequency (70–120 r/min), pre-set revolutions (multiples of 25), and applied force up to about 1 kN.
• Alternative methods: Hand muller (70–75 mm diameter) or palette knife preparation are acceptable.
• Binder: Agreed between parties; default is linseed oil per ISO 150 when unspecified.
• Sampling: Representative sampling as described in ISO 842.
• Test portion and preparation:
  • Typical test portion mass: 0.1 to 1.0 g (adjusted for pigment oil absorption).
  • Pigment is mixed with binder, milled in stages (50-revolution stages), and finished with an additional 25 revolutions.
  • Spread pastes in opaque strips (≥25 mm wide, touching edges ≥40 mm long) on a suitable substrate for comparison.
• Viewing conditions: Compare in diffuse daylight or artificial daylight following ISO 3668; calorimeters may be used by agreement.
• Reporting: Test report must include pigment ID, reference to ISO 787-1, binder used, procedure chosen, procedural details, result (colour equal or different), deviations, and test date.

Applications and users

ISO 787-1:1982 is used by:

• Pigment manufacturers for batch acceptance and product specification.
• Paint and coatings formulators for colour matching and quality control.
• Independent testing laboratories and QC departments verifying supplier claims.
• R&D teams assessing pigment performance in formulated systems. The standard ensures consistent, repeatable visual colour comparisons for production control, supplier qualification, and dispute resolution between buyers and suppliers.

Related standards

• ISO 150 - Linseed oil specifications (recommended binder if unspecified)
• ISO 842 - Sampling of raw materials for paints and varnishes
• ISO 3668 - Visual comparison and viewing conditions for paint colours
• Other parts of the ISO 787 series cover additional pigment tests (e.g., oil absorption, tinting strength, lightfastness)

By standardizing apparatus, preparation, and reporting, ISO 787-1 helps professionals perform reliable pigment colour comparisons across laboratories and supply chains.