ISO 787-3:2000

Overview

ISO 787-3:2000 specifies a laboratory hot extraction method for determining the percentage by mass of matter soluble in boiling water in pigments and extenders (fillers). The method is part of the ISO 787 series of general test methods for pigments and extenders and is intended for use where determination of water‑soluble components is required for quality control, specification compliance and formulation decisions. The standard requires duplicate determinations, dilution to a defined volume, filtration or centrifugation, evaporation of an aliquot and gravimetric measurement of the residue.

Key topics and technical requirements

• Scope: Quantitative determination of matter soluble in boiling water for pigment and extender samples.
• Reagent: Freshly bidistilled or demineralized water, pH 6–7 (unless otherwise agreed).
• Equipment: 250 ml single‑mark volumetric flask, colloidal filter (or agreed alternative), evaporation dish (glass/porcelain/platinium/silica), water bath, oven at (105 ± 2) °C, dessicator, balance to 1 mg, centrifuge if needed.
• Sample size: Typically 2–20 g - chosen to suit expected soluble content; same mass must be used across comparative tests.
• Procedure highlights:
  • Wet and disperse sample (use non‑ionic wetting agent or ethanol as required).
  • Add 200 ml boiling water and boil the suspension for 5 minutes (unless specified otherwise).
  • Cool, transfer solids and liquids to a 250 ml volumetric flask, dilute to the mark, mix and filter (or centrifuge).
  • Pipette 100 ml of clear filtrate, evaporate to dryness, dry residue at 105 °C and weigh to 1 mg precision.
• Calculation: Because 100 ml of a 250 ml dilution is analyzed, the mass of residue is multiplied by 2.5 and expressed as a percentage of the original test portion mass.
• Quality criteria: Perform duplicate tests; if results differ by more than 10% of the smaller value perform a third determination. Report the mean (or all values if repeatability is not achieved). Results are reported to one decimal place.
• Reporting: Include reference to ISO 787-3, product identification, test result, sample mass, type of water and filter, any wetting agent used, deviations from method, and test date.

Applications and users

• Who uses it: Paint and coatings manufacturers, pigment and extender producers, QC laboratories, formulation scientists, standards bodies and procurement/specification authors.
• Why it’s used: To assess water‑soluble impurities or components that influence dispersion, color stability, pH, conductivity of aqueous extracts, and overall performance in water‑based systems. Useful for incoming material inspection, supplier verification and regulatory/specification compliance.

Related standards

• ISO 787 series (general test methods for pigments and extenders) - e.g., ISO 787-8 (cold extraction method) and ISO 787-4 (acidity/alcalinity of aqueous extract).
• ISO 1042 (volumetric flasks) and ISO 15528 (sampling) are normative references cited by ISO 787-3.

Keywords: ISO 787-3:2000, pigments and extenders, matter soluble in water, hot extraction method, pigment testing, water‑soluble matter, laboratory test method, paint industry.