ISO 26082-2:2012 – Leather Soiling Resistance: Tumbling Method

Introduction to ISO 26082-2 and the Tumbling Soiling Method

ISO 26082-2:2012 (IULTCS/IUP 53-2) specifies a tumbling method for determining the resistance of all forms of leather to visible soiling through repeated impact with soiled felt pads. This method complements the Martindale rubbing approach covered in Part 1, providing an alternative mechanical action that better simulates certain real-world soiling scenarios such as abrasion against contaminated surfaces in a random, impact-dominated manner. Published as a first edition in 2012, this standard was developed by the Physical Tests Commission of IULTCS in collaboration with CEN/TC 289. It addresses the need for a more aggressive soiling test method for leathers used in demanding environments such as industrial footwear, work gloves, and heavy-duty upholstery.

Apparatus and Reagent Specifications

The key distinction of the tumbling method lies in its specialized rotating cylinder apparatus and the synthetic sebum soiling composition. The tumbling machine operates at 24 +/- 2 r/min with automatic direction reversal every 10 minutes to ensure uniform soiling distribution across the specimen surface. At least four cylinders are required for simultaneous testing, each with internal dimensions of 300 mm length and 100 mm diameter. The cylinders are equipped with removable lids at both ends and annular specimen retaining collars with internal diameters of not less than 75 mm.

Test Procedure and End-Point Determination

The specimen is fixed at one end of the rotating cylinder while a standard fabric is fixed at the opposite end. Soiled felt pads measuring 30 mm x 30 mm x 15 mm are preconditioned with the synthetic sebum and colloidal graphite mixture for a minimum of 2 hours at 20 degrees C to ensure uniform penetration. As the cylinder rotates, the felt pads repeatedly impact both surfaces. The change in colour of the standard fabric serves as the end-point determinant for the soiling treatment, providing an objective measure of when sufficient contamination has been transferred.

Evaluation follows the same grey scale methodology as Part 1, using ISO 105-A02 for colour change assessment and ISO 105-A03/A04 for staining evaluation. The optional pretreatment procedure for simulating wear before soiling is also retained, allowing engineers to assess the durability of soiling resistance under realistic service conditions. End-point determination is critical because over-soiling can saturate the leather surface, masking differences between materials with genuinely different soiling resistance.

Engineering Design Insights for Test Optimization

From a test engineering perspective, several factors critically influence repeatability and reproducibility. The felt pad preconditioning time must be strictly controlled as incomplete penetration of the sebum mixture results in non-uniform soiling. The cylinder fill ratio directly affects the impact energy transferred to the specimen surface, and the number of tumbling cycles must be optimized for each leather type to reach the ideal soiling level without saturation. For quality control applications, including a reference leather of known soiling resistance in each test run enables normalization of batch-to-batch variability and improves comparability of results across different testing sessions.

Frequently Asked Questions