Overview
ISO 14088:2020 - Leather - Chemical tests - Quantitative analysis of tanning agents by filter method - specifies a reproducible laboratory procedure to determine the amount of tanning agents in leather products and tanning formulations. The standard covers both vegetable and synthetic tanning agents and defines sample preparation, reagents, apparatus (notably the Procter bell and vacuum filter system), filtration procedures and gravimetric calculations to express tanning content as dry substance.
Key topics and technical requirements
- Scope and principle
- Indirect gravimetric analysis by fixing tannins on low‑chromed hide powder and measuring retained/removed solids.
- Reagents
- Grade 3 distilled water (ISO 3696), hide powder with specified chromium/ moisture limits, gelatine solution and formic acid.
- Apparatus
- Procter bell (dimensions defined), vacuum filter system, cellulose acetate membrane filters (0.45 µm; 3 µm for pre‑filtration), analytical/technical balances, drying oven (102 ± 2 °C), desiccator.
- Sample preparation
- Homogenisation (milling if necessary), preparation of analytical solution for:
- Vegetable tanning agents (target ~4.00 ± 0.25 g/L tannin)
- Synthetic tanning agents (specified sample masses for powder/liquid)
- Filtration and determination steps
- Preparation/packing of Procter bell with hide powder, controlled siphoning to collect de‑tanned filtrate, checks for breakthrough using gelatine precipitation, measurement of:
- Non‑tanning (de‑tanned) solids
- Soluble substances (filtered through 0.45 µm membrane)
- Total solids (evaporation and oven drying to constant mass)
- Calculation and reporting
- Gravimetric calculations to express percentage of dry substances and reporting requirements. Annexes include hide powder blank value procedure and supplier examples.
Practical applications and users
- Quality control in tanneries and leather finishing operations to verify tanning levels.
- Independent leather testing laboratories for certification, conformity assessment and comparative product analysis.
- R&D teams developing vegetable or synthetic tannins, or optimizing formulations.
- Suppliers of tanning agents for product specification validation and technical data sheets.
- Regulatory bodies and procurement teams requiring standardized test evidence.
Related standards
- ISO 3696 - Water for analytical laboratory use (referenced for reagent quality).
- IULTCS/IUC 32 (equivalent designation in the leather test community).
Keywords: ISO 14088:2020, leather chemical tests, tanning agents, filter method, Procter bell, hide powder, quantitative analysis, vegetable tanning agents, synthetic tanning agents, cellulose acetate membrane, total solids, leather testing.
Open preview (PDF)Leather — Chemical tests — Quantitative analysis of tanning agents by filter method
