ISO 4625-3:2026

Overview

ISO 4625-3:2026 sets out the cup method (without a ball) for determining the softening point of resins, including rosins, commonly used as binders in paints and varnishes. This international standard, developed by ISO Technical Committee 35 (Paints and Varnishes), allows users to obtain results that can be comparable-under user-defined conditions-to those from other standardized softening point methods, such as those detailed in ISO 4625-1 and ISO 4625-2.

Understanding the softening point of resin binders is essential in quality control, formulation, and product evaluation processes within the paints and coatings industry. The method described in ISO 4625-3 is particularly valued for its efficiency, reproducibility, and suitability for European industry practices.

Key Topics

• Softening Point Determination: The standard specifies how to measure the temperature at which a sample of resin softens and flows a specified distance (19 mm) under controlled heating, using a cup without a ball.
• Apparatus and Calibration:
  • Describes equipment required, including temperature-controlled measuring cells and sample cup assemblies.
  • Outlines procedures for calibration using a primary reference material (e.g., benzoic acid) and secondary standards.
• Sample Preparation and Testing:
  • Provides procedures for preparing and filling sample cups, ensuring homogeneity and the absence of air bubbles.
  • Details the protocol for conducting the test, including temperature ramp settings and sample handling.
• Results and Reporting:
  • Explains how to calculate and report the mean softening point, including test parameters such as heating rate and any deviations from the standard method.
  • Specifies mandatory elements for the test report to support traceability and reproducibility.
• Precision Data:
  • Based on interlaboratory comparisons, repeatability and reproducibility limits are provided for low and high softening point resins.

Applications

ISO 4625-3:2026 is especially relevant for:

• Paints and varnishes manufacturers: Ensuring product consistency and meeting industry specifications for binder resins.
• Formulators of coating systems: Comparing resin properties for optimal performance in end-use environments.
• Quality control laboratories: Standardizing routine testing to monitor production batches or incoming raw materials.
• Research and development: Evaluating new resin types or formulations against established benchmarks.
• Resin suppliers: Demonstrating compliance with international standards when marketing products globally.

By adopting the cup method (without a ball), organizations benefit from a less time-consuming, user-friendly procedure that uses widely accessible laboratory equipment. This method is also more cost-effective than traditional ring-and-ball setups, while offering reliability across a broad range of resin types.

Related Standards

Organizations implementing ISO 4625-3:2026 should also consider the following related standards to ensure comprehensive quality and compatibility in softening point measurements:

• ISO 4625-1: Binders for paints and varnishes - Determination of softening point - Part 1: Ring-and-ball method
• ISO 4625-2: Binders for paints and varnishes - Determination of softening point - Part 2: Cup-and-ball method
• ISO 4618: Paints and varnishes - Vocabulary (for terminology and definitions related to coating materials)

These standards together establish a harmonized framework for evaluating softening points, vital for materials selection and quality assurance in the coatings industry.

Keywords: ISO 4625-3:2026, softening point, cup method, resins, paint binders, varnishes, quality control, calibration, interlaboratory comparison, standardization, coatings industry.