Testing Microbial Resistance of Miscellaneous Materials
In addition to those tests listed below we also able carry out a range of less commonly used methods and ASTM methods. If the testing you require is not listed please contact us as we are usually able to adapt test methodology to any material or situation.
| Biodeterioration of Plastics | ISO 846: 1997 |
| Fungal Resistance: General | MIL-STD-810E |
| Fungal Resistance: Electrical and Electronic Equipment | BS 2011-2.1J |
Biodeterioration of Plastics: EBS EN ISO 846: 1997
Scope and Field of Application
The test methods described in this standard are designed for determining the deterioration of plastics due to the action of fungi, bacteria and soil organisms (but are not intended for the determination of biodegradability of plastics).
The tests are applicable to all plastic articles that have an even surface and thus can be easily cleaned. The exceptions are porous materials, such as plastic foams.
There are no pass/fail criteria. This is a matter of agreement between the parties concerned.
The actual standard is a copy-right protected document and we are not able to provide you with a copy. If required however, you can easily obtain one from the British Standards Institution.
Summary of Method
The tests involve exposing test specimens of plastic to the action of selected test strains of fungi and bacteria (or in the case of the soil burial-test, to microbially active soil) for specified or agreed periods of time under specified conditions of temperature and humidity.
At the end of the exposure, the test specimens are assessed by visual examination and/ or any change in mass or other physical properties is determined. The results are compared with untreated or sterile specimens kept under the same conditions.
For visual assessment of fungal growth the standard defines a six-point scale ranging from 0 (no growth) to 5 (heavy growth covering the entire test surface). Bacterial growth is visually assessed as growth or no-growth. The fungal and bacterial tests are terminated if growth is visible at 4-weeks. If the results are not positive the test period is extended. In the case of the fungal test, specimens are transferred to fresh agar and re-inoculated at 4-week intervals.
Sample Requirements
For each test we require a minimum of 15 samples, 30mm to 60mm square, with a maximum thickness of 2mm.
Fungal Resistance – General: MIL-STD-810
Scope and Field of Application
This test method is designed to assess the extent to which the test item will support fungal growth or how the fungal growth may affect performance or use of the test item. Although originally developed for U.S. military equipment, this is a useful general method for determining the fungal resistance of a wide variety of materials.
There are no pass/fail criteria defined in the standard. This is a matter of agreement between the parties concerned.
The actual standard is a copyright protected document and we are not able to provide you with a copy. If required however, you can easily obtain one from the American National Standards Institute.
Summary of Method
The standard describes the preparation of a fungal spore suspension. Cotton strips, dipped in a specified salts solution and allowed to dry are used as controls. Following conditioning, test items and controls are inoculated by spraying the spore suspension onto the test surface(s). Incubation is carried out in fungal test cabinets operating at 30°C for 20 hours and at 25°C for 4 hours in each 24 hour period. RH is maintained at 95%.
After 7 days the control strips are checked for satisfactory fungal growth. Incubation is continued for a minimum of 28 days but can be continued for up to 84 days if required.
Following incubation, test items and controls are assessed. For assessment the standard defines a five-point scale ranging from 0 (no growth) to 4 (severe growth).
Sample Requirements
The standard does not specify the number of replicates to be tested. We would recommend that where possible a minimum of 2 replicates should be provided for each test sample.
Fungal Resistance Testing – Electrical and Electronic Equipment: BS 2011: Part 2.1J: 1989
Scope and Field of Application
This standard was originally developed as an IEC standard and hence is intended primarily for testing electrical and electronic equipment for fungal resistance.
There are no pass/fail criteria defined in the standard. This is a matter of agreement between the parties concerned.
The actual standard is a copyright protected document and we are not able to provide you with a copy. If required however, you can easily obtain one from the British Standards Institution.
Summary of Method
This standard describes two variants of the test. Variant 1 specifies direct inoculation of the assembled specimens with mould spores whereas variant 2 specifies the pre-conditioning of the test specimens with nutrients which support mould growth.
The preparation of a mixed spore suspension is described. Cotton strips, dipped in a specified salts solution and allowed to drain, are used as controls. Test specimens and controls are inoculated by spraying the spore suspension onto the test surface(s). Incubation is carried out in fungal test cabinets operating at 28°C to 30°C and an RH of greater than 90%.
After 7 days the control strips are checked for satisfactory fungal growth. For variant 1, incubation is continued for 28 days or 84 days. For variant 2, incubation is continued for 28 days. (N.B. negative control specimens are required for variant 1: 84 days and variant 2).
Following incubation, test items and controls are assessed for the extent of growth. For assessment the standard defines a four-point scale ranging from 0 (no growth at a magnification of x 50) to 3 (growth plainly visible to naked eye and on more than 25% of test surface).
Sample Requirements
The standard does not specify the number of replicates to be tested. We would recommend that where possible a minimum of 2 replicates should be provided for each test sample (4 where negative controls are required).
- Back to
- Microbiology
- Laboratory Services
