The ASTM G21 test method qualitatively evaluates the ability of polymeric test material to support the growth of a mixture of five fungi. These polymeric test materials may be in the form of molded and fabricated articles, tubes, rods, sheets and film materials. The ASTM G21 test is applied for assessing the antifungal activity in paints and analyzing fungus mold resistance of construction materials made of or partly made of synthetic polymer plastics. The fungal cultures being cellulolytic, the test method can be extended to evaluate mold resistance of paperboard and wallboard. The ASTM G21 test method determines whether synthetic polymeric materials have established resistance to microbial / fungal invasion under various conditions such as varying temperatures and humid environments.
This test challenges materials with a wide variety of fungal species, ranging from common environmental fungi to agricultural pathogens and even antibacterial compound producing fungi, all of which have different growth requirements and enzymatic properties.
- In this ASTM G 21 method, freshly prepared spore suspensions of selected Fungi are separately washed in mineral salt solution.
- Fungi recommended are:
- Individual spore suspension at a concentration of 10^6 spores/ml are pooled together using equal volumes of all five fungi.
- Test samples are placed into Petri dishes filled with minimal salts agar. Test is setup in triplicate.
- Test samples are inoculated with this pooled spore preparation directly. This step is repeated for the positive control (fungal growth control) and negative control (agar only).
- All Petri dishes are sealed to maintain sufficient humidity and incubated for up to 28 days.
- Photographs are taken of each sample at regular intervals. Samples are given a performance score based on fungal growth after 28 days.
The sample requirements are - 3 test pieces, 2" x 2" with each piece labeled or in a bag that is labeled. An untreated control sample is also required and is considered an additional test sample.
TAT: 4- 5 weeks.
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