Overview - ISO 473:2019 (Lithopone pigments, testing and requirements)
ISO 473:2019 specifies the general requirements, marking and sampling, and the test methods for three types of lithopone pigments (approx. 20 %, 30 % and 60 % zinc sulphide (ZnS) content). The standard sets composition limits, physical requirements and analytical procedures used by manufacturers, quality-control laboratories and purchasers to verify pigment conformity for paints, coatings and related applications.
Key topics and technical requirements
- Types defined: Lithopone 20 %, Lithopone 30 %, Lithopone 60 % (calcined co‑precipitates of ZnS and barium sulfate, BaSO4).
- Marking & labelling: Pigments must be labelled to indicate their nominal ZnS content (20/30/60 %).
- Composition and tolerances (selected):
- Total zinc (as ZnS): Lithopone 20 % ≥ 18 %; Lithopone 30 % ≥ 28 %; Lithopone 60 % ≥ 58 %.
- Zinc oxide (ZnO): ≤ 1 % (mass fraction).
- Sum of total zinc (as ZnS) + BaSO4: ≥ 99 %.
- Matter volatile at 105 °C: ≤ 0.5 % (ISO 787-2).
- Matter soluble in water: ≤ 0.5 % (ISO 787-3).
- Residue on 63 µm sieve: ≤ 0.1 % (ISO 787-7).
- Colour, alkalinity, oil absorption, lightening power, hiding power: to be agreed between parties (some referenced to ISO 787 series).
- Sampling: Representative sampling required per ISO 15528.
- Analytical methods:
- Method A: Potassium hexacyanoferrate(II) titration (classical method) for total zinc and weight determination of BaSO4 - to be used in disputes.
- Method B: Sodium EDTA direct titration for total zinc - introduced as a time‑saving, easier alternative with proven accuracy.
- Test report: Clause 9 specifies required reporting details for results and test conditions.
Applications and who uses ISO 473
- Pigment manufacturers: product specification, production control and conformity certification.
- Paints & coatings formulators: raw material selection to meet hiding power, opacity and cost targets.
- Quality control laboratories: routine testing of lithopone batches (total zinc, BaSO4, volatile matter, sieve residue, solubles).
- Procurement and compliance teams: verifying supplier declarations and ensuring materials meet contractual or regulatory compositions.
- Regulatory bodies and testing labs: transport, safety and clearance assessments that require standardized composition data.
Related standards
Relevant normative references cited in ISO 473 include:
Keywords: ISO 473, lithopone pigments, ZnS, barium sulfate, testing methods, EDTA titration, potassium ferrocyanide titration, pigments standard, sampling, paint raw materials.