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D2816-18 – Standard Test Method Technical Guide
🔬 Scope and Summary of Test Method
ASTM D2816-18 defines a sequential procedure for verifying that a cashmere sample’s coarse-hair content does not exceed a predefined maximum value. This standard is essential for determining compliance with quality specifications, most notably the now-withdrawn Specification D2817. The test method is strictly limited to cashmere in the forms of roving, yarn, or fabric, and is only applicable when the expected coarse-hair content is 5.0 mass percent or less. For higher percentages, Test Methods D629 must be employed.
The core procedure involves the microscopic examination of at least 1,000 individual cashmere fiber segments of a fixed length. Each segment is classified as either fine cashmere down or cashmere coarse-hair based on its measured width. The percentage of coarse-hair segments by count is directly equivalent to the percentage of coarse-hair by total length in the sample.
⚠️ Applicability Limitation: Do not use this method for samples expected to have a cashmere coarse-hair content greater than 5.0 mass percent. Quantitative analysis of blends and higher coarse-hair contents is covered under Test Methods D629.
⚙️ Sequential Analysis Plan and Decision Table
The sequential test plan provides statistical efficiency. As fiber segments are counted and categorized, the cumulative number of cashmere coarse-hair fibers is continuously compared against the acceptance and rejection numbers in Table 1 of the standard. This table is built upon specified levels of confidence protecting both the producer and the consumer.
Testing proceeds until a clear decision is reached: Accept the lot if the total coarse hairs fall at or below the acceptance number, Reject the lot if they meet or exceed the rejection number, or Continue testing if the count lies between the two thresholds.
| 🟦 Total Fibers Examined (n) | 🎯 Accept Lot if Coarse Hairs ≤ | ⚡ Reject Lot if Coarse Hairs ≥ |
|---|---|---|
| 1,000 | 37 | 63 |
| 1,200 | 46 | 74 |
| 1,400 | 55 | 85 |
| 1,600 | 64 | 96 |
| 2,000 | 82 | 118 |
📏 Terminology and Significance of Results
Key terminology is aligned with ASTM D4845 (Terminology Relating to Wool) and D123 (Terminology Relating to Textiles). The test is significant for its role in maintaining the integrity of cashmere products by objectively measuring the coarse-hair content, which directly impacts softness and perceived quality. The precise microscopic procedure (detailed in Sections 7.1 and 7.2 of the standard) uses a microprojection method consistent with Test Method D2130 for fiber width classification.
💡 Statistical Efficiency: The sequential design of this test method minimizes the required sample size while maintaining high statistical confidence, making it a highly efficient tool for routine quality control and compliance verification in the cashmere industry.
❓ Frequently Asked Questions
🔍 What is the primary purpose of ASTM D2816-18?
To determine, via a sequential sampling plan, whether a cashmere sample conforms to a specified maximum allowable coarse-hair content, thus ensuring the quality standard of the final fiber product per Specification D2817.
💡 What specific forms of cashmere can be tested using this method?
The standard explicitly applies to cashmere in the form of roving, yarn, or fabric. It also applies to blends with other fibers, provided the expected coarse-hair content is 5.0 mass percent or less.
⚡ How are fibers classified as cashmere down vs. coarse-hair?
Fibers are classified through microscopic examination using a microprojection method. Fixed-length fiber segments are measured for fiber width; those exceeding the width threshold for fine down fibers are classified as coarse-hair (kemp).
📌 What happens if the coarse-hair count falls within the “continue testing” zone?
If the cumulative count of coarse hairs falls between the acceptance number and the rejection number for the current sample size, testing simply continues with additional fibers until the count clearly passes one of the thresholds, allowing a definitive accept or reject decision.