How did we get here?
… or why we chose 100% cotton for our 3D Face Coverings?
After weeks of designing, revising and constructing many, many face coverings for my family, I feel confident we have agreed on a style that suits everyone. We have a couple of children in our family on the autism spectrum, which meant comfort and wearability was paramount when I was working on face coverings for them. The 3D Cotton Face Covering is breathable, comfortable to wear, fits very well on a variety of shapes and sizes, and is flexible enough to suit your needs and comfort level.
Mechanical filtration is simply the fabric physically catching the particles. This type of filter stops particles because of the small size of their pores. In fabrics such as cotton, high thread count works best. Basically, the smaller the pores in the fabric, the fewer particles can escape.
Thread count is measured as threads per inch or TPI. If a material is 100 threads per inch across the warp (vertically) and 100 threads per inch across the weft (horizontally), that fabric is 200 threads per inch, or 200 TPI.
Why Use 100% Cotton?
Recent studies show that well fitting, two-layer 100% cotton masks are between 69% and 79% effective in filtering organisms that are similar in size to flu viruses. Linen has 60-61% effectiveness. By comparison, an N95 respirator filters out at least 95% of particles as small as 0.3 microns, and a typical surgical mask has an efficiency of between 60% and 80%.
A few reasons cotton works well:
- Because COVID-19 lives longer on plastics than on cotton fibres, fabrics with polyester, spandex and other man-made materials may retain viruses longer than cotton fabrics.
- Cotton can be preshrunk to tighten the fibres, providing better filtering.
- It can be washed (and dried) in high heat with less damage to the fibres, unlike man-made fibres such as polyester and nylon.
- Cotton is easier than many fabrics to breathe through. If breathing is uncomfortable, we won’t want to wear the mask. Some high filtering fabrics are virtually unwearable.
- High quality quilting cotton is the best for face masks, as it is about 200 TPI or higher after washing.
How Long Do Viruses Live on Cotton?
Some studies show that COVID-19 may only last about 1 day on (dry) 100% cotton, and about 3 days on polyester fibres. However, viruses like COVID-19 will live longer on a mask or other face covering. See links at the bottom of this page.
COVID-19 will live longer on the inside and outside of a surgical mask. We are not certain at this point exactly how long it could remain active on cotton masks, but we must presume it could be as long as 7 days. “Strikingly, a detectable level of infectious virus could still be present on the outer layer of a surgical mask on day 7” — Study published in The Lancet (see below)
Also important to note is that if your cotton mask is stored in plastic after wearing, it will remain damp. This will increase the time it takes for the virus to die off. It is best to store masks in a pillow case, paper bag or net laundry bag.
Our Final Fabric Decision
Our final decision on fabric was 100% premium quilting cotton. If we pre-wash in warm to hot water and dry in a hot dryer, we can get our fabric to about 120-200 threads per inch (TPI). We do also have an option to order masks with an inner filter made of silk organza. See more about silk and it’s properties here.
Three Layer Face Masks
Word Health Organization Guidelines (June 5, 2020)
The new WHO guidance recommends that the general public wear cloth masks made from at least three layers of different fabrics “on public transport, in shops, or in other confined or crowded environments.” These are sometimes called ‘hybrid masks’. Hybrid masks have both mechanical and electrostatic filtration.
Mechanical vs Electrostatic Filtration Explained
Mechanical filtration is simply the fabric physically catching the particles. This type of filter stops particles because of the small size of their pores. Generally with fabrics such as cotton, high thread count works best. The smaller the holes, the fewer particles can escape. Electrostatic-based filtration is a little different. Think of a static material such as polyester. These filters are electrostatically charged, and thus attract and capture charged particles. An electrostatic filter keeps the aerosols on either side of the static environment. See ACS Publication below.
Silk Filter Material
N95 respirators are made from polypropylene fabric, which is also a good electrostatic filter material for cotton masks. Other fabrics in use as third layer filters are polyester and silk. All of these above mentioned fabrics provide electrostatic-based filtration in addition to the mechanical filtration provided by the cotton mask. Because both polyester and polypropylene can be difficult to breathe through, we have been using one layer of silk organza between the inner and outer layer of cotton. This extra silk organza filter layer is optional, and is available as an upgrade in our face coverings.
Please see more about the filtration properties of silk here:
Properties of Silk
Please continue to social distance. Even an effective and well fitting mask will not completely eliminate the spread of COVID 19, or any other virus.
For further reading:
- Laboratory Based Study Examining the Filtration Properties of Silk
- New York Times: What is the Best Material for a Mask? (has helpful info on filters as well)
- The Lancet: Stability of SARS-CoV-2 in Different Environmental Conditions
- CBC – Canada’s top public health doctor now recommends 3-layer non-medical masks
- ACS Publications: Aerosol Filtration Efficiency of Common Fabrics Used in Respiratory Cloth Masks
- Global News: WHO Recommends Wearing Masks in Public (& Guidlines)
See face covering use and care here:
Use & Care
Info on eyeglasses & fogging here:
Eyeglasses & Masks