Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
D6075-13 – Standard Test Method Technical Guide
ASTM D6075-13 (Reapproved 2020) establishes a standardized test method for evaluating the cracking resistance of leather when subjected to bending or folding. This method is essential for assessing the durability of leather used in applications ranging from heavy industrial products to light consumer goods. The test focuses on the grain or finish surface and is conducted on a pass/fail basis. It does not apply to wet blue leather.
📐 Specimen Preparation and Conditioning
Specimens are conditioned according to Practice D1610 to ensure consistent moisture content, which significantly affects cracking behavior. Thickness is measured per Test Method D1813 to ensure uniformity. The test covers both heavy leathers (e.g., harness, belt, strap, bag, case) and light leathers (e.g., shoe upper, upholstery, garment, glove), each requiring specific bending procedures. Proper conditioning is critical for reproducible results.
🛠️ Tip: Condition specimens at standard temperature and humidity (23±2°C, 50±5% RH) as per D1610 to minimize variability. This ensures that results are comparable across different test batches.
⚙️ Bending Procedures for Heavy and Light Leathers
Three bending procedures are defined. For heavy leathers, Procedure A involves bending the specimen around a mandrel using a clamp or vise, with a metal bar (thickness equal to mandrel diameter) placed between flesh surfaces. Procedure B is performed by hand, bending around a mandrel and holding flesh surfaces together. For light leathers, Procedure C requires cooling the specimen to a low temperature and performing a sharp double-fold (crosswise) bend while the specimen remains in the cold chamber. The grain or finish surface is always on the outside of the bend.
| 🟦 Procedure | 📏 Leather Type | 🔧 Bending Method | 🎯 Key Conditions |
|---|---|---|---|
| A | Heavy (e.g., belt, strap) | Mandrel with clamp/vise and metal bar | Mechanical force applied |
| B | Heavy | Hand bending around mandrel | Flesh surfaces held together |
| C | Light (e.g., upper, garment) | Sharp double-fold after cooling | Cold chamber for low temperature |
📊 Evaluation and Significance of Cracking Resistance
After bending, the specimen is examined for cracks or ruptures in the bend area. The test identifies finish cracking (ruptures in the finish layer) or grain cracking (ruptures of the grain enamel), which may extend deeper into the leather cross section. This method replicates conditions like bending around buckle frames or folding over seams, providing a pass/fail assessment of the leather’s resistance to cracking. The results help manufacturers determine the suitability of leather for specific end uses.
⚠️ Warning: When using Procedure C, ensure the cold chamber maintains the specified low temperature to achieve the required brittleness. Avoid excessive handling of the cooled specimen to prevent unintended cracking before the bend is completed.
❓ Frequently Asked Questions
🔍 What is the purpose of ASTM D6075-13?
This standard determines the cracking resistance of leather when bent or folded, helping manufacturers ensure durability in applications like buckles, seams, and welts. It provides a pass/fail assessment based on visual inspection after bending.
💡 How is the test evaluated?
The test is evaluated by examining the grain or finish surface for any cracks or ruptures after the bending procedure. The presence of cracks indicates failure, while their absence indicates passing resistance to cracking.
⚡ What is the difference between finish cracking and grain cracking?
Finish cracking refers to ruptures in the finish layer, potentially exposing the crust leather. Grain cracking involves ruptures of the grain enamel and can extend deeper into the leather cross section, indicating more severe damage.
📌 Which procedure is used for light leathers?
For light leathers, such as shoe upper or garment leather, Procedure C is used, which involves cooling the specimen and performing a sharp double-fold bend in a cold chamber.