ISO 3262-4:2023

Overview

ISO 3262-4:2023 specifies requirements and test methods for whiting (chalk) as an extender (filler). This second edition updates the original 1998 standard and defines compositional limits, laboratory test procedures and sampling rules to assess the quality of natural calcium carbonate derived from chalk used in pigment and filler applications.

Key topics and requirements

• Scope: Defines whiting (natural calcium carbonate from Cretaceous chalk) and limits use of the term “whiting” to this material.
• Essential compositional limits (Table 1):
  • CaCO3 content: min. 98% (Quality A) or 95% (Quality B) - method reference ISO 3262-1.
  • Volatile matter (105 °C): max 0.4% - ISO 787-2.
  • Loss on ignition: max 46% - ISO 3262-1.
  • Water-soluble matter: max 0.5% - ISO 787-3 or ISO 787-8 (to be agreed between parties).
  • pH of aqueous suspension: 8.0 to 9.5 - ISO 787-9.
  • Insoluble matter in hydrochloric acid: max 2% (Quality A) or 5% (Quality B) - test method given in Clause 6.
• Optional requirements (Table 2) (to be agreed between parties):
  • Sieve residue (45 µm) - ISO 787-7.
  • Particle size distribution by laser diffraction - ISO 8130-13.
  • Colour / whiteness - ISO 3262-1.
  • Resistivity of aqueous extract - ISO 787-14.
• Sampling: Representative sampling per ISO 15528.
• Detailed test procedure: Clause 6 describes the method for determining hydrochloric-acid-insoluble matter (reagents, apparatus, boiling with ~25% HCl, filtration on 0.8 µm membrane, drying at 105 ±2 °C, weighing and calculation using (m2 − m1)/m0 × 100).

Applications and practical value

• Ensures consistent quality control of whiting used as an extender/filler in pigment, coating and related industries.
• Provides harmonized test methods and acceptance criteria to reduce disputes between suppliers and buyers.
• Useful for laboratory analysts, QC managers and procurement teams who need to verify conformity of whiting consignments against an international specification.

Who should use this standard

• Manufacturers and suppliers of whiting (chalk) and other calcium carbonate fillers.
• Quality control and analytical laboratories testing extenders and pigments.
• Paints, coatings and powder-coating raw‑material purchasers and specifiers seeking standard test methods and acceptance criteria.

Related standards

• ISO 3262-1 (introductory and general test methods)
• ISO 787 series (general test methods for pigments and extenders)
• ISO 8130-13 (particle size by laser diffraction)
• ISO 15528 (sampling for paints, varnishes and raw materials)
• ISO 3696 (laboratory water quality)
• ISO 18451-1 (terminology for pigments, colorants and extenders)

Keywords: ISO 3262-4:2023, whiting, chalk, extenders, calcium carbonate, test methods, pigments, fillers, quality control.