One of the most important strategies in place to stop the spread of SARS-CoV-2 is the wearing of a face mask covering. However, not all masks are the same, and there are only certain types and fabrics that are actually successfully in preventing the penetration of tiny droplets from sneezes and coughs that carry and transmit the Covid-19 virus.
CDC Recommendation
It is currently recommended by the CDC to wear a face mask in public in places where it is difficult to maintain social distancing such as in grocery outlets and the pharmacy. It is especially important to wear a mask in areas that are still registering significant levels of community-based transmission. Advice from the CDC goes on to say that the wearing of a simple cloth mask will help slow down the spread of the virus and will ensure that people who are asymptomatic will not spread the virus to others unknowingly. As a voluntary measure you may like to make a simple cloth face covering scarf out of common materials or household items you have to hand.
Face masks should not be used on infants under the age of 2, nor should they be used on those who suffer from breathing difficulties, who are incapacitated, who cannot remove their mask themselves, or on the unconscious.
Recommendations from the CDC are saying that N95 and surgical masks should be prioritized for frontline workers and medical personnel, meaning that if you need or want a mask, you should either purchase one or make a cloth one at home.
Silk, Chiffon and Cotton are the Best Materials for Making Face Covering at Home
If you are considering a cloth mask at home, you will be interested to learn which materials are the best for keeping other people’s germ out and you own germs in. In order to determine which materials work best, either on their own, or in combination with other, researchers carried out trials to establish the average number and size of particles in the air. Once this data was established, a fan was then used to blow aerosols across the different fabrics to see which materials were the most successful in blocking out particles.
Researchers from the U.S based University of Chicago and from the Argonne National Laboratory took and tested under laboratory conditions a variety of the most commonly found materials, investigating their electrostatic and mechanical filtration properties. Results of the study by the team that the best results for filtering particles were found when multiple layers of mixed fabrics were used; improper fitting of the mask however can run everything.
“We carried out these studies using several of the most common fabrics including chiffon, silk, flannel, cotton, and various synthetics, as well as their combinations,” the research team explains in their paper. “Overall, we found that using a combination of different fabrics that are commonly available in cloth face coverings provides the potential to significantly protect against aerosol particle transmission.” (Konda et al. ACS Nano 2020).
Our scarves are made from the best material to use for making a comfortable home made face covering. Available to purchase now! See our NEW Cherry Blossom scarf made from habutai silk link here at https://encausticstudios.com/product/cherry-blossom-silk-scarf-long-16-x-72/
Only Use the Best-Tested Fabrics
The winners in the testing of homemade face masks were cotton sheets that were tightly woven, used in combination with 2 layers of spandex-polyester chiffon, a sheer fabric that is commonly used in dressing and evening gowns. This particular combination of materials blocked between 80 and 99% of the droplets, the results varying depending on the size of the droplets. We have a beautiful blue chiffon scarf available for you to buy now at link https://encausticstudios.com/product/blue-medulli-long-scarf/ to use as a face covering scarf.
Similar results were found by the team when they used a cotton quilt with polyester batting, or substituted flannel or natural silk for chiffon. However, they warned that the mask must fit snuggly, and even a very small gap between the mask and face can reduce the efficiency of the filtering by up to half, if not more.
Examine the Science
To sample the number of aerosols present in the air, the team used an aerosol mixing chamber. They then went on to pass the particles through each of the fabrics they tested (which were secured tightly on to the end of a PVC tube) and sampled air that made it all the way through the material. The y carried out tests for a large range of particle size, from 10 nanometres to 10 micrometres. To give you some perspective here, a human hair averages a diameter of 50 micrometres, and in every micrometre there are 1000 nanometres. Particles of coronavirus are somewhere between eighty and one hundred and one hundred and twenty nanometers in diameter.
What this means is the particles that were tested were tiny, and there is still debate on if or not these tiny aerosolized particles can actually cause an infection, but if you are getting the smaller particles then you are definitely getting the larger ones. So, if you make sure that the mask you make filters out the smallest of particles, then it’s a good indication that it is also blocking out the larger ones.
The team also found that hybrid particles such as those that layer multiple types of materials were also good at filtering out the majority of particles. For example, a hybrid made up of cotton and silk, or cotton and flannel or cotton and chiffon has a filtration efficiency of more than 80% (for particles ninety percent (for particles greater than 300 nanometres)” The researchers speculared that the better performance of hybrid materials is likely to be due to the combined effect of electrostatic and mechanical-based filtration.
Mechanical filtration is the process by which the fabric catches the particles- the team observed that with materials such as cotton, a higher thread count worked better. Logically, the smaller the holes in the materials, the less large particles are capable of escaping.
The process of electrostatic-based filtration works a little differently. Imagine a material that is really static-y like polyester. Instead of being able to zap a friend with the static electricity you were able to save up, the filter works to keep the aerosols kept inside the static environment.
But as we said before, and cannot stress enough, none of this matters if you fail to wear your mask correctly. In the 2nd part of the experiment carried out by the team, small holes were poked into the tested fabrics, the results being pretty ugly. “Our studies also show that gaps caused by the ill-fitting of your mask can result in a decrease of filtration efficient of over 60%. So, regardless of the material that you choose for your mask, ensure that you wear it correctly.
If you are interested in the process of making a mask out of a hybrid material, there are plenty of tutorials you can check out online. If you need a simpler way to make a mask, from simple fabrics that you have at home, follow this CDC link for advice.
Sources:
Supratik Guha et al, “Aerosol Filtration Efficiency of Common Fabrics Used in Respiratory Cloth Masks,” ACS Nano, April 24, 2020.
CDC: https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/diy-cloth-face-coverings.html
