ISO 5431:2022

Overview - ISO 5431:2022 (Leather - Wet blue goat skins - Specification)

ISO 5431:2022 defines requirements, sampling and test methods for wet blue goat skins tanned without hair using basic chromium sulfate as the primary tanning agent. The third edition (2022) updates chemical requirements and adds tests such as determination of matter soluble in dichloromethane and chromic oxide content. This standard ensures consistent quality, safety and traceability for wet blue goat leather in commerce and manufacturing.

Key topics and technical requirements

• Raw material & tanning
  • Wet blue goat skins processed from cured or fresh goat skins.
  • Tanning with basic chromium sulfate; visual bluish penetration of the cut cross-section.
  • Tanning pH: 3.0 or above.
• Physical and appearance
  • Grain side free from hair (including short/fine hair); well fleshed; tight grain preferred.
  • At least 95% of skins in a lot should be free from chromium-salt stains; stained area per piece ≤ 10%.
  • Free from creases, drum folds and iron-salt stains.
• Thermal and chemical limits
  • Shrinkage temperature ≥ 95 °C (ISO 3380).
  • Volatile matter > 50% of dry mass (or as agreed).
  • Matter soluble in dichloromethane < 2% of dry mass (or as agreed).
  • pH of water extract ≥ 3.2.
  • Chromic oxide ≥ 3.0% of dry mass (used to estimate rechroming to reach shrinkage targets).
• Fungicidal treatment
  • Fungicides recommended to inhibit mould and pigmentation; should be effective, safe and agreed between purchaser and supplier.
  • Preferably sufficient to preserve skins for up to 4 months under storage conditions.
• Sampling & testing
  • Sampling for routine or dispute cases (number of samples by lot size specified).
  • Test methods referenced: ISO 3380, ISO 4044, ISO 4045, ISO 4684, ISO 4048 and ASTM D4576 (fungicide effectiveness).
• Packaging & marking
  • Pack to preserve original wet condition; packages labeled with material, manufacturer, tanning date, number of skins and purchaser details.

Applications - who uses ISO 5431:2022

• Tannery quality managers and production teams controlling wet blue goat skin processing.
• Leather traders, exporters/importers and procurement teams specifying material quality.
• Leather product manufacturers (footwear, garments, accessories) relying on consistent wet blue inputs.
• Testing laboratories and conformity assessors performing chemical and physical tests.
• Regulatory and compliance officers monitoring chemical limits (chromium/chromic oxide, solvents).

Related standards

• ISO 3380 - shrinkage temperature
• ISO 4044, ISO 4045, ISO 4048 - sample preparation and chemical tests
• ISO 4684 - volatile matter
• ISO 2418 - sampling location
• ISO 5398-1 - chromic oxide determination
• ASTM D4576 - fungicide/mold resistance test

Keywords: ISO 5431:2022, wet blue goat skins, leather specification, chromium sulfate, shrinkage temperature, chromic oxide, fungicide, sampling, matter soluble in dichloromethane, volatile matter, pH of water extract.