Homemade Face Mask with Waterproof Barrier

April 15, 2020

For a homemade face mask to really work, it needs to stop the water droplets formed by sneezing or coughing. Thus, a waterproof barrier is everything. But, it also has to be breathable, secure, and comfortable.

To that end, here’s a simple design created by the founder of Skratch Labs Dr. Allen Lim, ER Physician Dr. Shannon Sovndal, and pattern maker Jennie Yu. We hope this helps.

That said, this design is just one option. The simple goal is to place a waterproof layer over any existing fabric face covering. 

Big thanks to Tim Love @MitEvol for the illustrations, and Kirk Warner + Pocket Outdoor Media for the video.

The Story Behind a Waterproof Face Mask:

by Allen Lim, PhD

When the Center for Disease Control (CDC) recommended that all Americans begin wearing face coverings, like many, I was confused about what to use. Amidst this confusion, I sought advice from one of my best friends, Dr. Shannon Sovndal – an ER Physician on the frontline of the COVID-19 pandemic and the medical director of the Boulder Fire Department and Boulder Police Department. We started talking about all of the various medical masks out there and what the public actually needed so that they could better protect themselves and others.

What I learned from Dr. Sovndal is that COVID-19, as far as we know, is a droplet borne virus. This means that we want to prevent viral laden water droplets from getting into our eyes, nose, or mouth. This can occur when someone nearby who is infected (and potentially asymptomatic) sneezes or coughs or when we touch our face with contaminated hands that have touched surfaces with the virus.

Since droplets from a sneeze or cough can travel quite a distance, we need to keep our physical distance. And since droplets can contaminate a wide range of surfaces and survive anywhere from 1 to 3 days, we need to wash our hands and also do our best not to touch our face.

A face covering is meant to catch droplets when we cough or sneeze so that we can protect others from ourselves by keeping those droplets off of other people, surfaces, and our own hands (which may then touch and contaminate things we touch). A face covering is also meant to catch droplets that are projected by someone else who might have sneezed or coughed. A surgical mask accomplishes this because it has a waterproof outer layer. But unlike an n95 mask, that forms an air-tight seal around the face and that also filters out airborne germs, a surgical mask allows air to flow freely along its edges. A surgical mask is a barrier, not a filter.

Ignorant of these simple distinctions, when I first went to Dr. Sovndal for advice, my science mind had all sorts of ideas for filtration systems, chemical barriers, and elaborate ways to make what I thought was a safe mask. But, as a pragmatic practitioner seeing COVID-19 patients each day, Dr. Sovndal’s advice was simple - “Cover your face with something that is waterproof like Gortex.”

As he explained to me, the hope or need is not to get to the level of protection provided by an n95 mask, but to at least strive to get to the protection of a surgical mask. Unfortunately, making something with a waterproof layer that is also breathable, secure for a wide range of people, comfortable to wear for a long period of time, and easy to make with common materials wasn’t initially intuitive.

To solve this problem for myself and my team at Skratch Labs, I started tinkering with the help of pattern designer, Jennie Yu. Out of the gate, we came up with a number of designs, but they all required some experience to make and components that weren’t easily available. In observing what others in our community were actually doing, we saw a lot of people simply using neck gaiters, like “Pandanas” or “Buffs” pulled over their face. It occurred to us that the simplest solution was improving on existing neck gaiters by making them waterproof. Essentially, all we needed to do was take a piece of waterproof material from a rain jacket, plastic shower curtain, or waterproof packaging and sew or staple it to a neck gaiter. It wouldn’t look like a conventional medical mask and it wouldn’t be fancy, but it would solve all of the problems we were challenged with.

While not totally necessary, we took Dr. Sovndal’s advice and sourced some Gortex material with the help of companies like 37.5 Technology, 7-Mesh, Panache, and Arcteryx. We then sewed an 8 x 6-inch piece of that waterproof material to the top of an existing neck gaiter from Pandana. The result was a modified neck gaiter that you could pull over your face, with the waterproof material placed over the nose and mouth. We showed our design to Dr. Sovndal and he was so happy with how it worked that he approved the design for use by our local Emergency Medical Services. Dr. Sovndal then found us hundreds of neck gaiters initially earmarked for our Medical Evacuation Teams and with a community of local sewers that included Jennie Yu, Meghan Newlin, Adin Baird, Jane Saltzman, and Kelsey Phinney we modified those gaiters with a Gortex layer.

It was nice to help out locally. But, realizing that we aren’t a face mask manufacturer and can’t do this for everyone, we decided to share this simple why and how video along with printable instructions for anyone interested. If anything, just knowing that adding something waterproof over any homemade cloth mask was an epiphany for us. While it has made us feel a little more secure, we also know that this doesn’t change any of the other advice that we’ve been asked to follow, like washing our hands, staying home, and keeping our distance. Ultimately, we just hope that by sharing, we help make things a little better.

For more information and references please see the CDC and www.drsovndal.com/covid.

Additional Studies
A Cluster Randomised Trial Of Cloth Masks Compared with Medical Masks in Healthcare Workers

Raina MacIntyre-Holly Seale-Tham Dung-Nguyen Hien-Phan Nga-Abrar Chughtai-Bayzidur Rahman-Dominic Dwyer-Quanyi Wang - https://bmjopen.bmj.com/content/5/4/e006577

Surgical Mask vs N95 Respirator for Preventing Influenza Among Health Care Workers A Randomized Trial

Loeb, M., Dafoe, N., Mahony, J., John, M., Sarabia, A., Glavin, V., et al. (2009). Surgical Mask vs N95 Respirator for Preventing Influenza Among Health Care Workers: A Randomized Trial. Jama, 302(17), 1865–1871.

Medical Masks

Desai AN, Mehrotra P. Medical Masks. JAMA. Published online March 04, 2020. doi:10.1001/jama.2020.2331

N95 Respirators vs Medical Masks for Preventing Influenza Among Health Care Personnel A Randomized Clinical Trial

Radonovich LJ, Simberkoff MS, Bessesen MT, et al. N95 Respirators vs Medical Masks for Preventing Influenza Among Health Care Personnel: A Randomized Clinical Trial. JAMA. 2019;322(9):824–833. doi:10.1001/jama.2019.11645

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