ISO 9689:2025

Overview

ISO 9689:2025 - "Raw optical glass - Resistance to attack by aqueous alkaline phosphate-containing detergent solutions at 50 °C - Testing and classification" - defines a standardized laboratory method to assess and classify the phosphate resistance of raw optical glasses. The test exposes polished glass samples to an aqueous alkaline phosphate-containing detergent solution (tripolyphosphate-based) at 50 °C, measures material loss by weight, and converts that result into a phosphate resistance classification (PR). This standard is intended for samples of raw optical glass used in optical components and production quality control.

Key topics and technical requirements

• Test principle: Immerse polished glass samples in a 0.01 mol/L tripolyphosphate solution at 50 °C, determine mass loss after specified exposure times and compute the time to remove a 0.1 µm surface layer to derive the PR classification.
• Test solution & chemistry: Preparation involves purified pentasodium triphosphate (tripolyphosphate) and dilution to produce a test solution with pH 10.0 ± 0.1 (at 20 °C).
• Sample preparation:
  • Nominal size: (30 ± 1) mm × (30 ± 1) mm × (2.5 ± 0.5) mm after polishing.
  • Lapping and polishing requirements (cerium oxide < 2 µm grit) to meet surface grade P1 per ISO 10110‑8 and remove sub‑surface damage.
  • Cleaning by ultrasonic bath with isopropyl alcohol and desiccator storage prior to testing.
• Apparatus & controls:
  • Thermostatically controlled bath at 50.0 ± 0.2 °C.
  • Specified test vessel and stirrer configuration (stirrer ~15 mm above vessel bottom).
  • Analytical balance with accuracy of ±0.1 mg and surface area measurement to 2% uncertainty.
• Procedure & results:
  • Weigh samples before and after exposure; calculate material loss and derive the duration to remove 0.1 µm.
  • Classification and designation into phosphate resistance (PR) classes are provided by the method.
• Quality requirements: Use reagents of analytical grade and follow specified cleaning, handling and measurement tolerances.

Applications and users

ISO 9689:2025 is used for:

• Quality control and acceptance testing of raw optical glass for lenses, prisms, and precision optics.
• Material selection and R&D for optical glass manufacturers and suppliers.
• Independent test laboratories performing standardized corrosion/resistance testing.
• Design and procurement teams who require documented phosphate resistance (PR) classifications for components exposed to alkaline phosphate detergents.

Keywords: ISO 9689:2025, raw optical glass, phosphate resistance, aqueous alkaline phosphate-containing detergent, optical glass testing, tripolyphosphate, PR classification.

Related standards

• ISO 10110-8 - surface texture requirements for optical elements
• ISO 3696 - water for analytical laboratory use
• ISO 3585 - borosilicate glass 3.3 properties
• ISO 2768-1 - general tolerances (dimensions)

For implementation and laboratory practice, refer to the full ISO 9689:2025 text for complete procedural details, apparatus drawings and annexes.