Overview
ISO 2821:1974 - Leather - Raw hides of cattle and horses - Preservation by stack salting describes an internationally agreed method for preserving raw cattle and horse hides by stack salting. The standard excludes buffalo hides (buvalids) and explains the nature and origin of common preservation defects (microbial and chemical). It gives practical rules for preparing, salting, stacking and storing hides using a homogeneous mixture of salt (sodium chloride) and approved chemical products.
Key Topics and Requirements
- Scope: Applies to raw hides of cattle and horses; excludes buffalo hides.
- Defect types: Distinguishes microbial defects (red/violet stains, heating, putrefaction) from chemical defects (pitting on flesh or grain, round stains) and recommends measures to avoid each.
- Salt quality: Salt must be of good quality with ≥ 98% NaCl (dry basis) and free of harmful impurities.
- Additives: Use recognised antiseptics (example: naphthalene) and alkaline reagents (example: sodium carbonate) to prevent microbial growth and neutralise reactive ions that cause chemical damage. The standard explains that adding sodium carbonate converts reactive ions to insoluble carbonates, reducing harmful chemical reactions.
- Mixing and dosage: Salt must be mixed homogeneously with chemical products before use. Recommended minimum salt quantity is 40% of the mass of the hides to achieve adequate dehydration. Example mixtures given in the standard (for guidance) include:
- 100 kg salt + 2 kg naphthalene + 2–3 kg sodium carbonate
- 100 kg salt + 1 kg naphthalene + 1 kg boric acid
- Handling and timing: Wash hides appropriately, then salt within 5 hours of flaying (depending on ambient temperature). Prefer stacking with flesh side up (light hides may be flesh-to-flesh).
- Stacking and storage: Limit stack height to 1.5 m; keep the last salted hide in the stack for at least 15 days. Store in cool (~+10 °C), dim, low-ventilation premises with higher relative humidity for longer storage. Do not use recovered salt.
Applications and Users
Practical for tanneries, hide collectors, leather processors, logistics/quality managers, chemical suppliers and auditors. Use ISO 2821:1974 to:
- Prevent microbial spoilage and chemical staining during hide preservation and transit
- Standardise salting practices across collection and processing sites
- Guide procurement of preservation salt and additives
- Improve hide quality for downstream leather manufacture
Related Standards
- ISO 2820 - Leather - Raw hide presentation (referenced for presentation requirements)
- ISO 2822 - Leather - Vocabulary and defects of raw bovine and equine hides (related terminology and defect descriptions)
Keywords: ISO 2821:1974, leather preservation, raw hides, stack salting, sodium chloride, naphthalene, sodium carbonate, hide storage, tannery quality.
