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D2020-92 – Standard Test Method Technical Guide
The ASTM D2020-92 (Reapproved 2003) standard provides standardized qualitative test methods for determining the resistance of paper and paperboard to mildew (fungus) attack. Specifically applicable to papers with a fungus-resistant treatment, it outlines two distinct procedures tailored to different environmental exposures.
🔬 Test Methods and Applications
Method A, the Direct Inoculation, Pure Culture, Nonsterile Specimen method, is the preferred technique for paper products stored in damp, warm atmospheres but out of contact with damp soil. Method B, the Soil Burial method, is recommended for evaluating papers in direct contact with damp soil for extended periods. Both methods offer a qualitative measure of fungus resistance and the permanency of protective treatments.
| 📏 Feature | 🟦 Method A (Direct Inoculation) | ⚡ Method B (Soil Burial) |
|---|---|---|
| Simulated Environment | Damp, warm atmosphere | Contact with damp soil |
| Primary Application | Preferred for treated papers in storage/use | Recommended for prolonged ground contact |
| Source of Attacking Organisms | Pure culture inoculum | Natural soil microbial flora |
| Specimen Condition | Nonsterile specimen | Not specified (simulates field conditions) |
⚙️ Required Apparatus and Environmental Conditions
Method A requires precise laboratory equipment. An autoclave capable of 15 psi (103 kPa) at 121°C (250°F) is required for sterilizing media. An oven is specified for dry-heat sterilization at 165°C. The incubator must be strictly maintained at 28 ± 1°C. Inoculating needles must use 22- or 24-gage Nichrome wire. Test organisms are grown in 18 by 150 mm rimless test tubes, and specimens are placed in 100 by 15 mm disposable Petri dishes. Water dilution blanks are prepared using 250-mL bottles scribed at the 99-mL level, containing approximately 13 mm of glass beads.
💡 Key Condition: The incubator temperature of 28 ± 1°C is critical for the proper growth of the inoculum and the incubation of the inoculated specimens. Water blanks must be prepared with a suitable wetting agent to ensure a homogenous spore suspension.
| 📐 Apparatus | 🎯 Specification |
|---|---|
| Autoclave | 15 psi (103 kPa) at 121°C (250°F) |
| Dry-Heat Oven | 165°C |
| Incubator | 28 ± 1°C |
| Inoculating Needle Wire | 22- or 24-gage Nichrome |
| Test Tubes | 18 by 150 mm (rimless, bacteriological) |
| Petri Dishes | 100 by 15 mm (disposable recommended) |
| Dilution Bottles | 250-mL, narrow-mouthed, scribed at 99-mL |
📊 Significance and Sampling Protocol
Paper products used or stored in damp warm atmospheres, or in contact with damp soil, are subject to attack by fungi and other microorganisms. These test methods evaluate the degree and permanency of protection provided by paper treatments. To ensure representative test results, sampling of the paper product must strictly follow Practice D 585, covering the sampling and acceptance of a single lot of paper, paperboard, or fiberboard. Terminology must align with Terminology D 1968 and the Dictionary of Paper.
⚠️ Safety Responsibility: This standard does not purport to address all of the safety problems associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
❓ Frequently Asked Questions
🔍 What is the main difference between the two test methods in ASTM D2020?
Method A (Direct Inoculation) is designed for products exposed to damp, warm air without soil contact, using a pure culture of fungus. Method B (Soil Burial) is designed for products in prolonged contact with damp soil, utilizing the complex microbial flora found in soil.
💡 Why are nonsterile specimens used in Method A?
The “Nonsterile Specimen” designation means the paper samples are not sterilized before testing. This simulates real-world conditions where the paper may harbor some natural background organisms, specifically measuring the incremental resistance against the introduced pure culture of mildew.
⚡ What is the role of glass beads and the scribed 99-mL level in the water blanks?
The approximately 13 mm layer of glass beads helps to mechanically break up clumps of fungal spores or mycelium during shaking, creating a uniform suspension. The 99-mL scribed mark on the 250-mL bottles provides a consistent dilution volume for the spore or mycelial concentration.
📌 How should the paper sample be obtained for testing?
The sample must be obtained in accordance with ASTM Practice D 585, which provides standard procedures for sampling and accepting a single lot of paper, paperboard, fiberboard, or a related product.