Adine Gericke, a textile specialist from Stellenbosch University's Department of Chemistry and Polymer Science, has developed a standardised test for use by the clothing and textile manufacturing industry to evaluate the effectiveness of textile fabrics and filter materials used in fabric face masks.
The test method is based on the World Health Organisation's (WHO) guidelines published on 29 March 2020 and relies on the latest evidence that the virus appears to largely exit through the mouth of an infected individual in micro-droplet form during talking, coughing or sneezing. It is therefore believed that fabric masks can play in important role in reducing the community transmission of the virus.
Adine, one of only a handful of textile specialists in South Africa, was directly involved in updating the Department of Trade, Industry and Competition's guidelines for fabric masks, published online on 29 April 2020. In South Africa, it is now compulsory to wear a face mask in public.
She says the effectiveness of fabric face masks can be greatly improved by the selection of an optimum combination of fabric layers: “Masks typically consist of two to three layers or fabrics, which could include a filter layer in the middle. Each layer contributes to the performance properties of the end product. Fabrics can be tested in single layers or in combinations according to the design of a specific mask."
But while a mask should act as a barrier, it must not block airflow: if a person cannot breathe normally while wearing the mask, this will lead to the mask being removed or frequently touched by the wearer, she warns.
Since the lockdown, she has been working around the clock to test a range of textiles and nonwoven materials for the industry: “Textiles are deceptive. One cannot just assume that one material will perform better than another only because it is, for example, thicker than another."
For home sewers, her advice is as follows:
- In order to stop micro-droplets, use two but preferably three layers of fabric;
- Try to include a “filter layer" in the middle (such as interfacing or any lightweight stiff fabric), as it will have a huge impact to increase barrier efficiency;
- The mask must be comfortable, especially if it is going to be used in the workplace. Some fabrics have good barrier efficiency, but might have very low air permeability. Test your design by wearing the mask for at least 30 minutes (a five minute test is not enough) to make sure your combination of fabrics does not restrict breathability, build up heat or cause irritation to the extent that you need to remove the mask;
- Lastly, experiment with different fabrics until you find the right combination.
She says it was hugely gratifying to do research with an immediate and practical benefit to society: “Most of the manufacturers I've worked with are committed to manufacturing face masks that are functional and made from locally-produced fabrics, and taking care to select the best fabrics for the masks."