ASTM G21 Testing

Determining the resistance of synthetic polymeric materials to fungal growth.

What Is ASTM G21?

ASTM G21 is a qualitative test method used to determine the antifungal effectiveness of antimicrobial-treated polymer samples.

How Does ASTM G21 Work?

The test uses a mixture of common environmental fungi: Aspergillus brasiliensis, Penicillium funiculosum, Chaetomium globosum, Trichoderma virens, and Aureobasidium pullulans.

Test samples are placed on a non-nutritive agar plate and sprayed with a mixture of test organisms. They remain in contact with the fungal mixture for a 28-day period. During this time, the fungus and samples are kept at a temperature of 29°C and high humidity, providing optimal conditions for the fungus to grow.

Following the exposure time of fungus to the test material, the samples are examined to see if there is any fungal growth on the sample.

The Microban Standard: 0-4 Rating Scale

Test samples analysed under the ASTM G21 antifungal test method are rated on a scale of 0-4. The rating is determined by the presence of fungal growth on the sample, which is measured in percentages:

  • 0 – no fungal growth on sample
  • 1 – less than 10% growth covering sample
  • 2 – light growth, 10-30% growth covering sample
  • 3 – medium growth 30-60% growth covering sample
  • 4 – more than 60% growth covering sample

Find Out More

For more information on our ASTM G21 testing capabilities, contact a member of the Microban team today.