Overview
EN ISO 20433:2024 - Leather: Tests for colour fastness - Colour fastness to crocking (ISO 20433:2024) defines a standardized laboratory method to measure the amount of colour transferred from coloured leather to other surfaces due to rubbing. Adopted by CEN in 2024 and replacing the 2012 edition, this method applies to all types of coloured leather and can be used before and/or after surface finishes or after‑treatments.
Keywords: EN ISO 20433:2024, colour fastness to crocking, leather crocking test, colour transfer, crockmeter.
Key Topics
- Scope and principle: Quantifies staining on a white cotton rubbing cloth produced by rubbing leather under controlled conditions (dry and wet).
- Test apparatus: A crocking device with a cylindrical rubbing finger (16 mm diameter) moving along a 100 mm ± 5 mm track, applying a 9 N downward force.
- Rubbing media:
- Dry rubbing cloth - white, desized, bleached cotton, ≈50 mm × 50 mm.
- Wet rubbing cloth - conditioned and wetted to ~100% water pick‑up (distilled water).
- Procedure: Each test uses a separate leather test piece (≥140 mm × 50 mm). The rubbing finger is moved reciprocally (10 turns at ~1 turn/s) against the leather; one test for dry, one for wet conditions.
- Evaluation:
- Visual assessment using the grey scale for staining (ISO 105‑A03) after backing the stained cloth with three layers of white cloth.
- Optional instrumental assessment (spectrophotometer/colorimeter) in accordance with ISO 105‑A04 when staining is even.
- Reporting requirements: Reference to ISO 20433:2024, leather type, evaluation method, numerical grey‑scale ratings for dry and wet crocking, deviations, observations and test date.
Applications
Who uses EN ISO 20433:2024:
- Leather manufacturers and tanneries - quality control of dyes and finishes.
- Footwear and leather goods producers - ensuring durability and consumer safety.
- Automotive and upholstery industries - assessing staining risk on adjacent materials.
- Independent testing laboratories and conformity assessors - standardized test reports for specifications and contracts.
Practical benefits include consistent measurement of crocking performance, comparison of treatments and finishes, and support for product specifications and claims.
Related Standards
- ISO 105‑A03 - Grey scale for assessing staining
- ISO 105‑A04 - Instrumental assessment of staining
- ISO 2418 - Position and preparation of leather specimens for testing
- ISO 2419 - Specimen conditioning
- ISO 7906 - General principles of testing for colour fastness
EN ISO 20433:2024 provides a clear, repeatable method for evaluating leather colour fastness to crocking, supporting product development, quality assurance and compliance across leather supply chains.
