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D2813-03 – Standard Test Method Technical Guide
📝 Scope and Significance of ASTM D2813-03
This standard practice covers the sampling of finished leather and fabricated leather items for physical and chemical tests. The primary goal is to group products into homogenous lots that are randomly sampled in a manner that provides a representative sample of the entire lot. Based on the test results from this sample, the lot may be accepted or rejected in its entirety against applicable specification requirements.
⚠️ Natural Variability: Leather is a natural product and is subject to extensive variability. Physical and chemical properties differ considerably depending on the specific location on the hide, side, or skin. Proper random sampling from a predefined location and orientation, as defined by this practice, is essential to minimize test bias and variability.
📋 Lot Definition and Sampling Procedure
Defining a Lot or Batch
According to the standard, a lot (or batch) consists of units of products from a single type, grade, class, size, and composition, manufactured under essentially the same conditions. A unit is a piece of leather in the form it is purchased, such as a hide, skin, or a fabricated article like a shoe counter or gasket. Leather in formed lots must adhere to specific composition criteria:
| 🟦 Composition Criteria | 📋 Requirement per D2813-03 |
|---|---|
| Product Similarity | Units of similar size and type |
| Raw Materials | Tanning and finishing material from the same producer (functionally equivalent) |
| Manufacturing Method | A single product method |
| Production Timeline | Sequential production batches |
Selecting Samples from the Lot
Prior to sampling, the product must be properly identified as a lot. Units must be selected from various locations scattered throughout the lot, not just from a single portion (e.g., a single carton or layer). Samples must be taken without regard to quality.
The number of samples taken depends on the required reliability of the test results, the expected deviation of the properties, and the inherent error of the testing procedure. The number of samples taken is typically at the discretion of the user and should be explicitly recorded on the test report.
💡 Key Consideration: The standard requires that the number of samples taken for testing be recorded on the test report. This ensures traceability and allows for proper evaluation of the confidence level of the resulting test data.
🌡️ Conditioning Requirements for Physical Tests
Physical tests of leather and leather products must be performed under standard atmospheric conditions to ensure repeatability and reproducibility. Unless otherwise specified in the applicable test method, specification, or procurement document, conditioning must follow Practice D1610.
| 🟦 Environmental Parameter | 📋 Specified Value |
|---|---|
| Temperature | 23 ± 1 °C (73.4 ± 2 °F) |
| Relative Humidity | 50 ± 4 % |
| Governing Standard | Practice D1610 |
✅ Compliance Note: Adherence to these conditioning parameters is critical for achieving valid and comparable physical test results. The moisture content of leather, which directly impacts its mechanical properties, is directly influenced by the ambient temperature and humidity.
❓ Frequently Asked Questions
🔍 What constitutes a lot or batch under D2813-03?
A lot is defined as units of a single type, grade, class, size, and composition manufactured under essentially the same conditions. It must consist of similar sizes, functionally equivalent materials, a single product method, and sequential production batches.
💡 How should sampling units be selected from a lot?
Units must be selected from locations scattered throughout the lot, not from the same portion (e.g., a single carton or layer). Selection should be random and performed without regard to perceived quality to ensure the sample is entirely representative of the lot.
⚡ What defines a “unit” in this standard?
A unit is a piece of leather in the form in which it is purchased. This can be a single hide, skin, or any part thereof, or a fabricated leather article such as a shoe counter, gasket, or pair of shoes.
📌 What are the standard conditioning requirements for physical testing?
Unless otherwise specified, physical tests must be performed at a temperature of 23 ± 1 °C (73.4 ± 2 °F) and a relative humidity of 50 ± 4 %, as defined in ASTM Practice D1610.