ISO 20433:2024

Overview

ISO 20433:2024 (IULTCS/IUF 452:2024) defines a standardized method to determine colour transfer from coloured leather to other surfaces by rubbing (crocking). The method requires two separate assessments: one with a dry rubbing cloth and one with a wet rubbing cloth. It is applicable to all types of coloured leather and can be used before and/or after surface after-treatments and finishes.

This standard supports reliable quality control, comparative testing and verification of leather finishes to limit staining of adjacent materials in end-use applications.

Key Topics

• Principle: A conditioned rubbing cloth fixed to a cylindrical finger moves back and forth across a leather test piece under controlled force and stroke length. Colour transferred to the cloth is assessed.
• Apparatus: The test device uses a rubbing finger (16 mm diameter) executing a linear reciprocating motion over a 100 mm track and applying a downward force of 9 N. Commercial examples (informative) include crockmeters such as the AATCC Crockmeter.
• Rubbing cloth: White cotton cloths (desized, bleached, ~50 mm × 50 mm) conforming to ISO 105-F09 are specified for consistency.
• Procedure: Two test pieces (minimum 140 mm × 50 mm each) are conditioned per ISO 2419 and tested separately for dry and wet crocking. The wet cloth is prepared to a defined water pick-up before testing.
• Evaluation: Staining on the rubbing cloth is assessed visually using the grey scale for assessing staining (ISO 105-A03) or instrumentally with a spectrophotometer/colorimeter per ISO 105-A04 when staining is even.
• Test report: Must reference ISO 20433:2024 and include leather description, evaluation method, numerical grey-scale ratings for dry and wet tests, deviations, unusual observations and test date.

Applications

ISO 20433:2024 is practical for:

• Leather manufacturers validating dye fixation and surface finishes.
• Quality control in tanneries and finishing plants to prevent unwanted staining of lining fabrics, garments or furniture textiles.
• Product development for automotive, upholstery, footwear and leather goods where crocking performance affects consumer acceptance.
• Comparative evaluation when changing dyes, finishing processes or after-treatments.

Benefits include consistent test conditions, repeatable results and clear reporting requirements to support supply‑chain quality decisions.

Related Standards

• ISO 7906 - General principles for leather colour fastness testing
• ISO 2418 / ISO 2419 - Specimen preparation and conditioning
• ISO 105-A03 / ISO 105-A04 - Grey scale and instrumental staining assessment
• ISO 105-F09 - Specification for cotton rubbing cloth
• ISO 105-X12, ISO 11640, AATCC TM8 - Additional colour fastness and crocking references

For implementation, follow the clauses on apparatus, specimen preparation, procedure, evaluation and reporting as specified in ISO 20433:2024 to ensure accurate and comparable crocking results.