- Swiss testing laboratory
ASTM G21
Hassle-free testing experience
Need to get a product tested? No worries! To and fro logistics are on us; we collect your products, test them and, deliver them back to you.
Related tests for you
Quick understanding of the test
ASTM G21 - Fungal Resistance Test
- Aspergillus brasiliensis
- Talaromyces pinophilus
- Chaetomium globosum
- Trichoderma virens
- Aureobasidium pullulans
- Test specimens and controls are placed on nutrient-salt agar and are inoculated with spore suspension.
- Samples are incubated at specified temperatures for up to 28 days.
- Specimens are rated on a 0โ4 scale based on fungal coverage.
- Helps manufacturers to improve material formulations for better antifungal efficacy.
- Assists in meeting industry and safety standards for antifungal properties.
Turnaround Time
Passing criteria
Do you have a product that needs testing?
Overview of ASTM G21 fungal resistance test
ASTM G21 is an international standard that describes the test method for determining the resistance of plastics and polymers to fungal growth. In general, synthetic polymers are resistant to the growth of fungi as they do not provide the nutrients required for their growth. However, the addition of certain substances such as plasticizers, lubricants, stabilizers, cellulose and colorants during the processing can promote fungal growth. Therefore, products that claim to be antifungal must be thoroughly tested to ensure their efficacy.
Why test for fungal resistance?
The growth of fungi on plastics enhances the rate at which they deteriorate, affecting the strength and performance of the material. This is a major concern for plastic products used in areas exposed to moisture and organic load that can stimulate the growth of fungi. Antifungal testing helps identify susceptible materials and allows manufacturers to improve their formulations, ensuring long-lasting products.
Products to be tested with ASTM G21
The ASTM G21 test is used to determine the resistance of synthetic polymeric materials against fungal growth. The ASTM G21 test is applicable for molded and fabricated products, tubes, rods, sheet, and film material.
ASTM G21 test requirements
Test specimens
The test requires specific specimens to be tested for fungal resistance:
- Standard specimens
Typically, specimens with dimensions of 50mmร50 mm are selected.
- Rod or tube specimens
Specimens with a minimum size of 76 mm are used.
- Film-forming materials
Films with dimensions of 50mmร25 mm (2 inchesร1 inches) are selected.
- Differing surfaces
If a specimen has different surfaces, three specimens are tested each with different surface orientations (face up and face down).
Test organisms
Test organisms include Aspergillus brasiliensis, Aureobasidium pullulans, Chaetomium globosum, Trichoderma virens and Penicillium funiculosum. These fungal strains are chosen due to their presence in various environments and their ability to grow on a wide range of materials, including materials containing plasticizers, cellulose, lubricants, stabilizers, and colorants as food sources.
ASTM G21 test methodology
1. Preparation and inoculation
- The test specimens are placed on the solidified surface of nutrient-salts agar and inoculated with a spore suspension. This setup mimics real-world conditions where fungi encounter the materials in a nutrient-rich environment.
- Untreated control samples are also inoculated and incubated alongside the test specimens to provide a baseline for comparison.
2. Incubation
- The inoculated samples are then sealed and incubated at a temperature range of 28ยฐC to 30ยฐC, and under conditions of 90% relative humidity.
- The standard incubation period is 28 days but the test may be terminated earlier if the test specimens show considerable mycelial growth, usually indicated by a growth rating of two or more.
3. Evaluation and rating
| Rating Scale | Description |
| 0 | No growth on the specimen |
| 1 | Traces of growth on the specimen (less than 10 %) |
| 2 | Light growth (10 to 30 %) |
| 3 | Medium growth (30 to 60 %) |
| 4 | Specimens completely covered with growth (60 %) |
Importance of ASTM G21 fungal resistance test
Ensuring material longevity and durability
Enhancing safety and hygiene
Several industrial sectors including healthcare and food packaging, can be negatively affected by fungal presence. Fungal growths on medical devices, packaging material or any surface that comes into contact with foods lead to contamination and spread of infections. This test makes sure that the materials used for these vital applications will not support the growth of fungi hence increasing safety and sanitation. This is particularly important in sterile environments where even minimal fungal contamination can have severe consequences.
Supporting innovation and development
This standard is a good tool for research and development in material science. Understanding how different additives and formulations affect fungal resistance can help researchers develop new materials with unique, improved properties. This test provides key information necessary for the formulation of new plastics and polymers that have higher resistance to fungal degradation while at the same time being durable, biodegradable, and sustainable.
Versatility in application
Enhancing consumer confidence
Supporting sustainable practices
The test contributes to sustainability by encouraging the use of strong and fungus-resistant products that help to avoid their rapid deterioration by fungi thus reducing regular replacements. This serves to reduce waste and conserve the available resources to the maximum possible extent.
Real-world applicability
Strengths of ASTM G21 test method
At Microbe Investigations (MIS), we test the efficacy of antifungal plastic finishes using the ASTM G21 test and other standard test methods like AATCC-30. With a team of experienced microbiologists and advanced technological capabilities, MIS provides a comprehensive suite of quality antiviral, antibacterial and antifungal testing services worldwide.
Contact our experts here to learn about the pricing, turnaround times and other related queries.
Frequently Asked Questions
DR. Martinoz Scholtz
Meet the best of the blend of
R&D, Efficacy Testing,
Innovation and Passionate
Experts at MIS.
Explore More
In the cosmetics industry, safety
Evidently, with the expanding cosmetics
In the competitive world of
