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ASTM D3273
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ASTM D3273: 2021 – Standard Test Method for Resistance to Growth of Mold on the Surface of Interior Coatings in an Environmental Chamber
- Aspergillus niger (ATCC 6275)
- Penicillium species.
- Greenhouse soil is hydrated and equilibrated at ~32°C for 24 hours before fungal inoculation.
- Fungal suspensions of Aureobasidium pullulans, Aspergillus niger, and Penicillium are inoculated and sporulated in the soil for two weeks.
- Panels are exposed to the mold-rich chamber for 4 weeks and assessed weekly on a 0–10 mold growth scale.
- Minimizes mold-related health risks by validating material performance.
- Boosts consumer confidence and competitiveness by proving product reliability.
Results are evaluated using a 0–10 scale, assessing mold growth on panels weekly over 4 weeks.
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Abstract
The ASTM D3273 method is one of the key testing standards that was formulated with the sole purpose of testing the resistance of interior coatings to mold growth. It tests the performance of different types of interior coatings by subjecting them to controlled environmental conditions that favor the rapid growth of mold in close simulation of practical usage conditions over an accelerated period.
Interior coatings, including paints, are exposed to environments that encourage the development of mold where moisture content is usually high and ventilation is poor. ASTM D 3273 test method specifies the comparative resistance of coatings over a period of 4 weeks, employing specific temperatures and humidity that favor the growth of mold on test panels.
ASTM D3273 test conditions & requirements
- Relative humidity: A relative humidity of >93% shall be maintained in the chamber to promote mold growth.
- Temperature: The chamber temperature must be maintained at 32.5 ± 1°C (90 ± 2°F).
- Test panels: Test panels must be made up of the specified substrates such as softwood sapwood or gypsum board. Two coats of test product must be applied to the test panel. The panel is hung vertically with sufficient space in between for free airflow. The panels must not come in touch with each other or the chamber walls.
- Mandatory test strains: The mold cultures used for this test include Aureobasidium pullulans (ATCC 9348), Aspergillus niger (ATCC 6275), and Penicillium species.
- Incubation period: 4 weeks
ASTM D3273 test method
- Preparation of the environmental chamber
Greenhouse soil is placed in a tray within the chamber, and water is added to the tank to reach the required depth. The chamber is equilibrated, including the soil content and water content, for about 24 hours at approximately 32°C prior to inoculating the soil. - Inoculating the mold
Fungal suspensions of Aureobasidium pullulans, Aspergillus niger, and Penicillium are prepared and evenly spread over the surface of the greenhouse soil. The fungi are allowed to sporulate for two weeks before testing. - Sample preparation and exposure
Treated and untreated test panels are prepared with the required coating. The panels are then hung vertically in the chamber above the soil tray, with enough spacing for airflow. The test panels are left in the mold-rich environment for a continuous period of 4 weeks. - Monitoring and mold growth evaluation
Panels are assessed for mold growth on a weekly basis for 4 weeks. A rating scale of 0 to 10 will be used to assess the degree of growth in both treated and untreated samples.
Result interpretation
Rating | Defacement % |
10 | No defacement |
9 | 1-10 % defacement |
8 | 11-20 % defacement |
7 | 21-30 % defacement |
6 | 31-40 % defacement |
5 | 41-50 % defacement |
4 | 51-60 % defacement |
3 | 61-70 % defacement |
2 | 71-80 % defacement |
1 | 81-90 % defacement |
0 | 91-100 % defacement |
Factors affecting the ASTM D3273 test method
Environmental conditions
Mold growth can be sensitive to even slight changes in the humidity and temperature. Maintaining a constant environment is essential to obtain reproducible and accurate results.
Substrate material
The type of substrate used can influence the growth of mold. Organisms readily colonize substrates of wood compared to inert materials such as glass.
Coating thickness
Product performance also depends on the method of application of the coating. Uneven or incorrect application of the coating can provide misleading test results.
Controlling these variables is, therefore, necessary to ensure that the test gives a reliable measure of a coating’s resistance to mold growth.
Compliance and industry standards for ASTM D3273 testing
The test method is widely applied to assess the mold resistance of interior coatings. Several regulatory agencies and certification programs refer to this standard for ensuring that coatings used in moisture-prone and mold-growth environments meet desired quality and durability requirements. Compliance with this standard can support manufacturers meeting industry expectations for product performance and safety.
Importance of ASTM D3273 test
Besides aesthetic issues, mold growth can cause structural damage and health issues. Hence, it is essential for coatings used in high-humid areas to demonstrate resistance to fungal defacement. By performing this test manufacturers can verify the efficiency in protecting the coating against defacement thus maintaining its durability and aesthetic appeal.
Furthermore, the test can be used to compare their formulations and determine which best prevents mold growth. It also helps them enhance the performance of their product thereby improving the marketability. It serves as a crucial step in product development, ensuring compliance with industry standards and meeting consumer expectations for durability and quality in mold-resistant coatings.
Strengths of ASTM D3273 Test
1.Highly controlled conditions:
2. Comprehensive fungal exposure
3. Reliable testing methodology
4. Practical application
Advantages of ASTM D3273 testing for interior coatings
Accelerated results
Comparative analysis
Industry recognition
Conclusion: The role of ASTM D3273 in ensuring mold-resistant coatings
Testing the resistance of antifungal-treated plastics is paramount to manufacturers to validate their product claims. These test reports are required to meet regulatory compliance, which is in turn necessary for market approval. Compliance supports easy market entry and also increases the confidence of consumers in these products. Thus, testing for mold resistance is beneficial to manufacturers and businesses alike.
At Microbe Investigations Switzerland (MIS), we focus on delivering customized and analytical solutions aimed at improving the quality of antifungal coating materials. Leveraging our vast experience in antifungal testing, our team performs ASTM D3273 testing with the highest level of accuracy. We also offer ASTM G21 testing for polymeric materials.
Need a quote for ASTM D3273 or have specific questions? Contact our experts today to discuss your requirements.
Frequently Asked Questions
DR. Martinoz Scholtz
The fungal strains used are Aureobasidium pullulans, Aspergillus niger and Penicillium species.
Yes, this standard is specifically designed to assess the resistance of interior coatings to mold growth.
The test requires a temperature of 32.5°C and a relative humidity of >93%.
The test method does not apply to exterior coatings and results may not reflect long-term performance in all real-world conditions.
Mold growth is visually assessed and rated on a scale from 0 to 10, with 0 indicating complete defacement and 10 indicating no growth.
ASTM D3274 is for visual assessment of defacement of exterior coatings, while ASTM D 3273 test method evaluates mold growth in controlled environmental conditions.
ASTM D3273 is the standard method for interior coatings to check their resistance against mold.
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