Overview
ISO 20701:2024 - Leather - Tests for colour fastness - Colour fastness to saliva specifies a laboratory method to assess whether colouring materials can migrate from leather to the mouth or mucous membranes. The test uses an artificial saliva solution and a short controlled exposure (37 ± 2 °C for 120 ± 5 minutes) to simulate oral contact and evaluates both staining of a filter paper and change in colour of the leather.
Keywords: ISO 20701:2024, colour fastness to saliva, leather testing, artificial saliva solution, colour fastness tests.
Key topics and technical requirements
- Scope: Applicable to all kinds of leather, independent of colouring procedure.
- Test principle: A strip of filter paper soaked in artificial saliva is placed on the leather wearing surface; the assembly is held at 37 ± 2 °C for 120 ± 5 min, then dried and assessed.
- Apparatus and materials: filter paper (cellulose type), adhesive tape or cling film for fixation, desiccator with water, oven at 37 °C, pH meter, spectrophotometer/colorimeter (optional).
- Artificial saliva composition (per litre; tolerances ±1%):
- Magnesium chloride (MgCl2·6H2O): 0.17 g
- Calcium chloride (CaCl2·2H2O): 0.15 g
- Dipotassium hydrogen phosphate (K2HPO4·3H2O): 0.76 g
- Potassium carbonate (K2CO3): 0.53 g
- Sodium chloride (NaCl): 0.33 g
- Potassium chloride (KCl): 0.75 g
- Adjust pH to 6.8 ± 0.1 with 1% HCl; solution stable ~2 weeks
- Evaluation: Visual assessment using grey scales - ISO 105‑A03 for staining and ISO 105‑A02 for change in colour - or instrumental assessment per ISO 105‑A04 / A05. Typical inter-person precision: ±0.5 grey-scale units.
- Reporting: Test report must reference ISO 20701:2024, describe leather type and surface tested, method of evaluation, numerical grey-scale ratings for staining and colour change, deviations, observations and test date.
Applications and users
ISO 20701:2024 is used by:
- Leather manufacturers and tanneries for quality control of dyed and finished leathers.
- Test laboratories performing conformity and fastness testing.
- Product designers and safety assessors evaluating leathers used in items that may contact the mouth or mucous membranes (e.g., some footwear components, gloves, children’s products).
- Compliance and procurement teams wanting documented evidence of low colour migration to saliva.
Practical benefits include verifying colour stability under simulated oral exposure, reducing consumer safety risks and supporting product claims about fastness.
Related standards
- ISO 7906 - General principles of testing for colour fastness (referenced)
- ISO 2418 - Position and preparation of leather specimens
- ISO 3696 - Water for analytical laboratory use
- ISO 105-A02 / A03 / A04 / A05 - Grey scales and instrumental assessment for colour fastness
Using ISO 20701:2024 helps ensure consistent, reproducible testing for saliva-related colour migration and supports product safety and quality assurance in the leather supply chain.