ISO 3262-3:2023

Overview - ISO 3262-3:2023 (Blanc fixe, extenders)

ISO 3262-3:2023 is the international standard that specifies requirements and test methods for blanc fixe, a synthetic (precipitated) barium sulfate (BaSO4) used as an extender in paints, coatings, plastics, ceramics and other formulations. The document defines essential quality criteria, sampling rules and two approved analytical routes for determining BaSO4 content: a gravimetric procedure and X‑ray fluorescence (XRF).

Key topics and technical requirements

• Material definition: Blanc fixe is defined as synthetic barium sulfate produced by precipitation.
• Essential requirements (selected):
  • BaSO4 content (min.): 95% mass fraction (determined gravimetrically or by XRF)
  • Residue on 45 µm sieve (max.): 0.2% mass fraction (ISO 787-7)
  • Matter volatile at 105 °C (max.): 0.5% (ISO 787-2)
  • Loss on ignition (max.): 3% (ISO 3262-1)
  • Matter soluble in water (max.): 0.5% (ISO 787-3)
  • pH of aqueous suspension: 6 to 10 (ISO 787-9)
• BaSO4 test methods:
  • Gravimetric method: simplified in this edition; includes fusion, extraction and precipitate ignition. Ammonium carbamate solution is specified for washing in place of the previous sodium carbonate solution. The gravimetric result may include strontium sulfate unless subtracted via additional analysis (e.g., ICP‑OES).
  • XRF (wavelength-dispersive): added as an alternative to gravimetry; barium is determined in a borax melt and calculated as BaSO4.
• Sampling and general methods: Sampling per ISO 15528; general pigment/extender tests referenced from the ISO 787 series and ISO 3262-1.
• Conditional/negotiable requirements: particle size distribution, colour/lightness, oil absorption and resistivity are to be agreed between supplier and purchaser.

Practical applications and users

ISO 3262-3:2023 is used for:

• Quality control laboratories verifying blanc fixe batches for BaSO4 content, fineness and purity.
• Extender and pigment manufacturers to certify product conformity and publish technical data.
• Paint, coatings, plastics and paper formulators specifying extenders for optical, rheological and cost-performance reasons.
• Procurement and compliance teams to define purchase specifications and acceptance tests. The standard supports consistent product performance, interchangeability and regulatory/commercial specification.

Related standards

• ISO 3262-1 (general test methods for extenders)
• ISO 787 series (general methods of test for pigments and extenders)
• ISO 15528 (sampling)
• ISO 3696 (lab water)
• ISO 12677 (XRF fusion method)
• ISO 18451-1 (terminology)

Keywords: ISO 3262-3:2023, blanc fixe, extenders, barium sulfate, BaSO4, gravimetric method, XRF, pigment testing, quality control.