Understanding ISO and IULTCS leather test methods

First published: September 2026

Leather remains one of the most versatile materials across fashion, footwear, automotive, and interior design industries. However, ensuring that leather products meet stringent quality and safety requirements demands rigorous testing against internationally recognised standards. ISO leather testing and IULTCS test methods form the backbone of global leather quality assurance, providing brands and manufacturers with a unified framework for evaluating everything from chemical composition to physical durability and colourfastness.

The article provides an overview of ISO and IULTCS leather test methods to help leather brands and manufacturers navigate leather compliance testing.

If you need IULTCS/ISO leather testing, contact us here directly.

What is the IULTCS and how does it relate to ISO?

The International Union of Leather Technologists and Chemists Societies (IULTCS) is the globally recognised body responsible for developing test methods specifically designed for leather. Through its three specialist testing commissions, which are IUC (Chemical), IUP (Physical), and IUF (Fastness), the IULTCS creates and maintains methods that are explicitly relevant to leather manufacture and usage.

Following a formal agreement first established in 1990 and reaffirmed in 2005, ISO recognises the IULTCS as an International Standardising Body. ISO has assigned responsibility for developing leather test methods to the IULTCS, and the resulting documents are published as joint IULTCS-ISO standards. This means that when you encounter an ISO standard for leather, such as ISO 17075 for hexavalent chromium or ISO 3376 for tensile strength. It has been developed by the IULTCS commissions.

Additionally, the European Committee for Standardisation (CEN) has adopted many of these joint standards through its CEN/TC 289 Technical Committee "Leather", resulting in identical test methods published at international (ISO), European (EN), and IULTCS levels. This harmonised approach ensures that a single test result can satisfy multiple regulatory frameworks simultaneously, which offers a significant advantage for brands operating across global markets.

Categories of IULTCS/ISO leather test methods

The IULTCS organises its test methods into three principal categories, each addressing a distinct aspect of leather quality and performance.

Chemical test methods (IUC)

The IUC series focuses on the chemical composition and safety of leather. These methods are critical for verifying compliance with restricted substances legislation such as the EU REACH Regulation and CPSIA. Key chemical tests include:

• IUC 18 / ISO 17075
  Determination of hexavalent chromium content, a substance of significant concern in chrome-tanned leather.
• IUC 19 / ISO 17226
  Determination of formaldehyde content, measured via HPLC or colourimetric analysis.
• IUC 20 / ISO 17234
  Detection of certain azo colourants that may release carcinogenic aromatic amines
• IUC 25 / ISO 17070
  Determination of chlorophenol content, including pentachlorophenol (PCP)
• IUC 27 / ISO 17072
  Chemical determination of extractable and total metal content
• IUC 36 / ISO 20137
  Guidelines for testing critical chemicals in leather

These tests are essential for any brand placing leather products on regulated markets, particularly in the European Union, North America, and China.

Physical and mechanical test methods (IUP)

The IUP series evaluates the physical performance and durability of leather, helping manufacturers ensure their materials can withstand the demands of their intended end use. Key physical tests include:

• IUP 6 / ISO 3376
  Measurement of tensile strength and percentage elongation
• IUP 8 / ISO 3377-1
  Measurement of tear load (single edge tear)
• IUP 8 / ISO 3377-2
  Measurement of tear load (double edge tear)
• IUP 9 / ISO 3379
  Distension and strength of grain by the ball burst test (lastometer)
• IUP 20 / ISO 5402
  Determination of flex resistance using the flexometer method
• IUP 36 / ISO 17235
  Measurement of leather softness.
• IUP 48 / ISO 17076
  Measurement of abrasion resistance using Taber or Martindale methods.

Physical testing is particularly important for footwear, automotive upholstery, and fashion leather, where performance under repeated mechanical stress is a defining quality factor.

Colourfastness and finish test methods (IUF)

The IUF series assesses how well leather retains its colour and surface finish when exposed to various agents encountered during manufacture and use. Key fastness tests include:

• IUF 401/402 / ISO 105-B01/B02
  Colourfastness to light (daylight and xenon lamp)
• IUF 421 / ISO 11642
  Colourfastness to water
• IUF 426 / ISO 11641
  Colourfastness to perspiration
• IUF 450 / ISO 11640
  Colourfastness to cycles of to-and-fro rubbing
• IUF 470 / ISO 11644
  Test for adhesion of finish

These methods are vital for preventing consumer complaints related to colour transfer, fading, or finish degradation, and are routinely specified by leading fashion and footwear brands in their supplier requirements.

Common ISO & IULTCS standards for leather testing

The table below lists some of the most widely used ISO and IULTCS test methods. Always check the latest version of the standard to see whether it has been superseded or updated, or simply contact us to enquire about your leather testing needs.

Not sure which IULTCS/ISO standard to use for testing your leather products? Contact us now, and we will be in touch with you shortly. 

When do you need to use ISO and IULTCS standards for leather testing?

• Regulatory compliance verification: When regulations such as the EU REACH Regulation, CPSIA in the U.S., GB standards in China, or other market-specific legislation restrict certain substances in leather (e.g., hexavalent chromium, formaldehyde, azo dyes), the ISO/IULTCS test methods are the prescribed testing standards used to measure whether those substances are present, and at what concentration. Laboratories worldwide use these standardised methods to ensure results are reproducible and internationally comparable.
• Brand and retailer quality specifications: Major brands and retailers typically maintain their own Restricted Substances Lists (RSLs) and performance specifications. These specifications reference ISO/IULTCS test methods as the agreed procedure for verifying that suppliers' leather meets the required benchmarks.
• Supply chain due diligence: When sourcing leather from global suppliers, buyers use ISO/IULTCS testing to verify incoming material quality, authenticate genuine leather, and manage risk before materials enter production.

How does Eurofins Softlines & Hardlines support leather compliance testing?

It is important to understand that ISO and IULTCS standards are test methods. They define the analytical procedures for measuring specific properties or substances in leather. They do not set pass/fail limits. 

Compliance is determined when a test result obtained through the correct ISO/IULTCS method is evaluated against the limit values set by the applicable regulation, such as EU REACH, or by a brand's own restricted substances list (RSL).

This is precisely why working with an experienced testing partner is essential. A knowledgeable laboratory will not only conduct the correct test methods but also advise on which regulations and limit values apply to your specific product and target market.

The Eurofins Softlines & Hardlines network offers comprehensive leather testing and verification services designed to help brands and manufacturers achieve full compliance with confidence.

With specialist expertise housed at our Eurofins | BLC Leather Technology Centre, we deliver a complete suite of services:

• Chemical testing of restricted substances lists (RSL) and manufacturing restricted substances lists (MRSL) against key regulations e.g. EU REACH and CPSIA or clients’ own requirements
• Performance testing of the leather, such as flexing and colourfastness
• PFAS testing
• Fault diagnosis
• Durability testing
• Supply chain mapping
• Vegan certification
• ZDHC MRSL conformance services

Contact us today to discuss your leather testing needs and safeguard your products, your supply chain, and your brand reputation. For more details, visit our Leather Testing Service page.