Overview
EN ISO 17233:2017 - "Leather - Physical and mechanical tests - Determination of cold crack temperature of surface coatings" specifies a standardized test method to determine the cold crack temperature of surface coatings applied to leather. Published by ISO and adopted as a CEN standard, this method applies to all easily flexed leathers with a surface coating and defines apparatus, sample preparation, procedure and reporting requirements for reproducible laboratory testing.
Key topics and technical requirements
- Purpose: Identify the temperature at which a leather surface coating develops cracks when folded at low temperature.
- Apparatus:
- Cooled chamber capable of maintaining +5 °C to −30 °C with temperature control ±2 °C; minimum internal dimensions: height 500 mm, width & depth 300 mm.
- Hinged sample holder designed to hold at least six test pieces without contact; can fix samples with countersunk bolts or adhesive tape.
- Press knife (cutting test pieces per ISO 2419); magnifier (4–6×); temperature measuring device readable to 1 °C; adhesive tape suitable down to −30 °C.
- Test pieces: Rectangular specimens (90 ± 1 mm × 10 ± 1 mm). For each temperature, six test pieces are used - three cut parallel and three perpendicular to the backbone (or equivalent if backbone unknown). When using bolts, test pieces require a 5.0 ± 0.5 mm diameter hole centered 6.0 ± 0.5 mm from each end; holes are not required if adhesive tape is used.
- Procedure summary: Condition samples in the cooled chamber, place in hinged holder with coating outwards, cool (typical sequence: +5 °C then 0, −5, −10, −15, −20, −25, −30 °C), snap the holder shut rapidly in the chamber, return to room temperature, and inspect the flexed arc for cracks with the magnifier. Continue until at least two of six specimens crack. If no crack at −30 °C, report as