Antifungal Activity, Assessment on Textile Materials: Mildew and Rot Resistance of Textile Materials
The AATCC Test Method 30 Test III is a qualitative test that employs a high concentration of the Aspergillus niger (ATCC #6275) fungal species, to determine the resistance of textile materials to fungal growth.
Background on the AATCC Test Method 30 Test III
A. niger can grow on textile materials without causing detrimental strength loss in a laboratory experiment. However, A. niger growth on textiles can cause undesirable and unsightly effects such as bad odor and discoloration.
The AATCC Test Method 30 was first released in 1946 as an official method to test the efficacy of fungicides treated on textile materials.
The current standard (AATCC Test Method 30) is the ninth version of this test method. We often are asked for a Method 30 free download. Unfortunately, due to copyright laws, we cannot provide copies of the actual test method. However, the method can be downloaded directly from AATCC for a relatively low cost.
Previous versions of this test method are listed below:
Examples of textiles tested using the AATCC Test Method 30 Part III include but are not limited to, polyester, cotton, rayon, nylon, silk, wool, linen, acrylic, spandex, viscose, etc.
Other materials such as polymers, paint, adhesives, cardboard, foams, and drywall may also be tested using the AATCC Test Method 30 Part III.
If the test sample is thick or non-porous, the A. niger spores will not have access to the nutrients on the agar plate. This may lead to a lack of fungal growth on the test sample causing inaccurate results.
AATCC Test Method 30 Test III Testing
Test samples are placed on an agar medium that is either carbon-rich or carbon-free (no readily available energy source) but contains the basic mineral salts required for fungi to grow. On the carbon-free medium, the fungi will grow on the sample and not on the surrounding agar surface.
After being placed on the carbon-rich or carbon-free medium, the test sample is inoculated with a concentrated spore suspension (inoculum) that contains A. niger.
A. niger was chosen by AATCC based on its capability of growing on textile products.
Test plates are incubated at 28 ̊C for 14 days when a carbon-free medium is used and 7 days when a carbon-rich medium is used to allow fungal growth to develop.
The samples are examined under a dissecting stereomicroscope at 40x magnification.
The description of the rating system is as follows:
If a carbon-rich medium was used, report the size of the growth-free zone (in mm) if present. For both mediums (carbon-rich and carbon-free) report the extent of the fungal growth on top of the specimens:
No growth
Microscopic growth (visible only under the microscope)
Macroscopic growth (visible to the eye)
The method does not outline pass/fail criteria.
Untreated fabric tested using the AATCC Method 30
The untreated cotton fabric sample supports heavy amounts of macroscopic A. niger growth. The cotton sample, treated with an antimicrobial agent, remains free of fungal growth (no growth) after 7 days of incubation, as per the test specifications.
Size of Test Specimens
The desired test specimen size is a 3.8 cm (1.5 inch) diameter circle. Before submitting samples for the first time, contact your chosen test lab for more information and guidance.
Strengths and Weaknesses of the Test Method
AATCC Test Method 30 Test III Strengths:
The test has a one or two-week incubation period, allowing for quick results especially in comparison to other fungal tests such as the ASTM G21, which has a 28 day incubation period.
Flexibility in testing with either a carbon-rich or free medium.
Since all the requirements for growth are present (minerals, temperature, humidity, high concentration of spores) except for a readily available energy source, the test specimen’s true capability of resisting fungal attack is evaluated.
AATCC Test Method 30 Test III Weaknesses:
The stringency of the carbon-rich medium version might overwhelm milder antifungal agents due to the high concentration of spores and the high nutrient content of the agar plate.
This method only evaluates the antifungal properties of one fungus.
Thick, non-porous, or hydrophobic samples will prevent the A. niger spores from accessing the nutrients on the agar plate, potentially causing inaccurate results.
The scoring guidelines are well defined; however, there is no stipulation to include the amount of growth on the sample. For instance, for some manufacturers of certain products, a trace amount of macroscopic growth may be acceptable compared to a test sample that is completely covered in fungal growth. It is important to have open communication with the laboratory that is testing the samples to ensure the desired information is captured. Better yet, a photo is worth a thousand words.
