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ISO 28499-2:2009 – Buffalo Hides and Calf Skins – Grading by Mass and Size
Standardized methods for classifying raw buffalo hides based on weight and surface area
1. Introduction to ISO 28499-2 and Hide Grading Principles
ISO 28499-2:2009 establishes standardized procedures for grading raw buffalo hides and buffalo calf skins on the basis of mass and physical size. This standard complements Part 1 (defect description) and Part 3 (defect-based grading), forming an integrated quality assessment system for the international leather trade. The standard applies to water-buffalo hides and calf skins in four preservation states: raw, wet-salted, dry-salted, and dried.
Grading by mass and size is the first step in hide valuation. A hide’s weight category directly influences its application — lightweight calf skins are preferred for garment leather, while heavy hides are used for industrial belting and shoe soles.
2. Trimming Requirements Before Classification
Consistent trimming is essential for accurate classification. ISO 28499-2 specifies precise trimming procedures for both hides and calf skins:
| Component | Buffalo Hides | Buffalo Calf Skins |
|---|---|---|
| Fore shanks | Knee-trimmed | Trimmed short |
| Hind shanks | Trimmed square at hock | Trimmed short |
| Tail | Tailbone removed | Tailbone removed |
| Head | Mask, ears, lips removed (cheeks retained) | Cut off behind ears, no cheeks |
| Brisket | Fairly shaped | — |
| Horns | Removed | — |
Improper trimming is a common source of grading disputes. A hide with excessive head or shank material will be incorrectly assigned to a higher mass category, leading to unfair pricing. Buyers and sellers must agree on a consistent trimming standard — ISO 28499-2 references ISO 2820 for detailed trimming specifications.
3. Mass Determination Procedures
The standard prescribes different weighing procedures depending on the preservation state of the hide:
3.1 Raw Hides
Raw buffalo hides are weighed to the nearest 0.5 kg and calf skins to the nearest 0.1 kg, with allowances made for dung and residual flesh.
3.2 Wet-Salted Hides
Each hide is opened, shaken vigorously by hitting against the ground or a support (300-400 mm high), and brushed to remove leftover salt before weighing. Wet-salted hides are weighed to 0.5 kg precision and calf skins to 0.1 kg.
3.3 Dry-Salted and Dried Hides
These are simply shaken to remove extraneous matter and weighed to 0.1 kg precision. The lower moisture content results in tighter weight ranges compared to wet-salted hides.
| Category | Calf Skins | Light Hides | Medium Hides | Heavy Hides | Extra-Heavy |
|---|---|---|---|---|---|
| Raw (kg) | Up to 13.0 | 13.5-22.0 | 22.5-30.0 | 30.5-36.0 | Above 36.0 |
| Wet-salted (kg) | Up to 11.0 | 11.5-18.0 | 18.5-25.0 | 25.5-30.5 | Above 30.5 |
| Dry-salted (kg) | Up to 7.0 | 7.5-12.0 | 12.5-16.5 | 17.0-20.0 | Above 20.0 |
| Dried (kg) | Up to 4.5 | 4.4-7.2 | 7.3-10.0 | 10.0-12.0 | Above 12.0 |
The mass-based grading table enables straightforward conversion between preservation states. A hide that classifies as “medium” in the raw state (25 kg) will also classify as “medium” when wet-salted (approximately 21 kg), assuming normal salt and moisture content. This consistency is essential for contract specifications.
4. Size-Based Grading and Engineering Applications
Size grading uses surface area (dm²) as the metric. The standard defines five categories: calf skins (up to 150 dm²), light hides (151-180 dm²), medium hides (181-250 dm²), heavy hides (251-300 dm²), and extra-heavy hides (above 301 dm²).
For engineers designing leather processing equipment, these size categories directly inform equipment specifications — drum capacities, fleshing machine widths, and splitting machine apertures must accommodate the largest hides in each category. A tannery processing primarily heavy and extra-heavy hides requires larger drums and wider machines than one handling calf skins.
Area measurement is particularly sensitive to stretching. Hides that have been over-stretched during flaying or curing will show artificially large area values, potentially shifting them into a higher size category. This must be accounted for when establishing acceptance criteria for incoming raw materials.
5. Frequently Asked Questions
Q1: Why are the mass ranges different for raw, wet-salted, dry-salted, and dried hides?
A: The preservation method significantly affects moisture content. Wet-salting retains considerable moisture, dry-salting removes more water, and drying removes the most. The different ranges account for these weight differences so that a hide maintains consistent grade classification regardless of preservation state.
A: The preservation method significantly affects moisture content. Wet-salting retains considerable moisture, dry-salting removes more water, and drying removes the most. The different ranges account for these weight differences so that a hide maintains consistent grade classification regardless of preservation state.
Q2: Can a hide be graded by both mass and size?
A: Yes, the standard provides independent grading systems for both metrics. In practice, mass grading is more common for commercial transactions, while size grading is important for determining suitability for specific leather products.
A: Yes, the standard provides independent grading systems for both metrics. In practice, mass grading is more common for commercial transactions, while size grading is important for determining suitability for specific leather products.
Q3: How does trimming affect grade classification?
A: Trimming directly impacts both mass and size. Consistent trimming per ISO 2820 is essential to ensure that hides are not unfairly penalized or advantaged. Over-trimming reduces usable area; under-trimming inflates mass.
A: Trimming directly impacts both mass and size. Consistent trimming per ISO 2820 is essential to ensure that hides are not unfairly penalized or advantaged. Over-trimming reduces usable area; under-trimming inflates mass.
