Federal Standard 191A constitutes a series of laboratory standards designed for the United States Military and Federal Government for the testing of textile materials against the standards set forth by Military and Federal specifications. Method 5760, titled “Mildew Resistance of Textile Materials; Mixed Culture Method,” is specifically designed to test the mildew resistance of textile materials (i.e. cloth, yarn, thread, tape, and cordage) against a pooled suspension of fungal spores.
Similar tests to Method 5760 include ASTM G21 and AATCC 30. The general concept of the test is to see if the fungal spores can break down the textile materials to use as a carbon source for growth since the agar medium supplies all the remaining nutrients for growth.
Summary of FED. STD. 191A Method 5760 – Mildew Resistance of Textile Materials
- Fungi are grown on solid medium and a spore suspension is prepared with the following fungal genera (requisite species listed in the official method):
- A mixed spore suspension is created per method specifications.
- The test sample is placed on method specified solidified agar medium.
- Test sample is inoculated with with spore suspension via pipet.
- Test sample is incubated under high humidity for 14 to 21 days.
- After incubation, test sample is evaluated for growth or no growth.
Strengths of the FED. STD. 191A Method 5760
- This test challenges materials with a wide variety of fungal species, all of which have different growth requirements and enzymatic properties.
- The method and parameters are designed so that every condition for growth is present (i.e., salts, minerals, water and a humid environment) other than a sufficient carbon and/or sugar source, thus testing a materials true ability to withstand fungal attack. The initial spore concentration is relatively high, thus providing a critical challenge to textile materials.
- Scoring of the test is simple, either growth is observed or it is not present.
Weaknesses of the FED. STD. 191A Method 5760
- The method compares growth under static temperature and humidity parameters, whereas real product usage may be better represented by a range of temperatures and humidity in some instances.
- The method does not account for real-world conditions due to human activities, such as regular cleaning of the surface.
- The test offers little information about the product’s long-term performance.