How to make a reusable and (relatively) safe mask.
This is an evolving document, I’m updating it with more tips and designs as I go along. If you’d like to make a suggestion or ask a question, please leave a comment.
I’ve made close to 900 masks, and designed and redesigned masks for better general fit, comfort, and safety. Here is what I do now, along with one of my own designs.
A note up front, this isn’t going to cover the basics of sewing. This article assumes that you have some grounding in making sewn products and the equipment to do so. Ok, back to the masks.
What makes a good mask of any type — disposable, reusable, handmade, certified respirator, etc., is this: materials and fit. Both factors are vital for safety and efficacy. The best filter in the world won’t do a thing if it’s not covering your nose and mouth, and the most comfortable and sealing mask is insufficient if it lets droplets through. When professionals are getting ready to do a shift in the Covid-19 ward, they generally don a fit-tested mask made of an N95 or equivalent material to keep their respiratory T (eyes-nose-mouth) protected from the virus, and to keep from spreading anything they might have without knowing it. (A fit test is a scent test that lets you judge how well your mask is sealing, more on that later)
Materials
I use a three layer design:
- A thin inner cotton layer.
- A middle layer of electrostatic polypropylene fabric, non-woven, 40-80gsm.
- An outer layer of stiffer quilter’s cotton.
Plus:
- Nose wire
- Attachment
Let’s take the function of each of the layers and parts one by one.
The Inner
The cotton inner is there for comfort and catching the moisture leaving your mouth. It should be thin, nice against your skin, and somewhat absorbent, without getting clingy. Some people have tried to use silk here, but in my experience it’s an awful fabric to have next to your respiratory bits — your nose and mouth — for any considerable length of time. Cotton is both cheap and pleasant. This layer doesn’t need to be thick, it’s not doing much more than catching large droplets leaving your mouth. It’s there to make you not hate wearing a mask.
The Filter Layer
The middle layer of blown or non-woven (these mean the same thing) polypropylene fabric is pretty much where the magic happens and why this cloth mask isn’t strictly speaking a cloth mask. Electrostatically charged non-woven PPL is what both surgical masks and the coveted N95-grade masks are made of, along with other materials. You can often buy this kind of polypropylene in rolls or bolts from wholesalers, but it will probably take a bit of research. You can often find it on Amazon as well, in smaller and more expensive batches. We’ve used Amazon to find vendors, then went and bought bolts directly from them.
The weight of polypropylene melt-blown fabric is measured in GSM, or grams per square meter. The GSM weight of the PPL in a surgical mask is usually around 20–25 from what I’ve been able to gather in my research. In my own masks I use between 40–80 gsm, since these babies are meant to be reused. The heavier weight sacrifices some breathability — I wouldn’t run in these masks as an asthmatic. Walking, shopping, talking, etc., has always been fine, and I’m a person with chronically weak lungs. I’ve even monitored my blood O2 in my masks, while inducing trouble breathing from quickly climbing stairs. If I really push it I can get myself borderline, but it took work, and longstanding lung problems. There is no reason to worry about polypropylene limiting air intake in a mask for anyone with nominally normal lung function.
I wish I could link you to the perfect vendor for buying your PPL, but this process has been very unstable, and it will take research. I’ve bought three bolts, the last one 25 meters from a German company, because I was tired of hunting the internet for suppliers. I’d start with Amazon, but not buy through them. You might also have a hard time figuring out if your PPL is electrostatically charged, we have. All I can say is talk to your vendors.
The Outer
The outer layer of the mask should be a stiff cotton that can help the mask keep its form. Most of the time when people feel like a mask isn’t breathable or pleasant to wear, it’s because it’s too close to their face or doesn’t have enough interior room in the mask to go through the mechanics of breathing comfortably. It’s not fun to have something right against your face, and the design and material should both hold the mask away from your mouth and nose, top of your nose notwithstanding. The outer is also cosmetic, and cosmetics don’t get enough attention. Masks should be comfortable and safe, but they also should be cool and fun. If you like your mask, you’re much more likely to remember it, wear it, have some loyalty to the concept of masking. I find a lot of fun patterns in quilters cottons, but also use fabric paint to make things special for the people who wear my masks.
The Nose Wire
Use coffee bag closures for reusable masks. I tried a lot of different things — learn from my failures. They are the best. You can buy them, or scavenge them from coffee and tea bags. They just last, and they have the best seal of anything I’ve tried. You will probably have to cut them down to size, but regular scissors work fine. The wires used in surgical masks and N95 type masks often start to fatigue within a few uses. By the time your adhesive stick and sew two-wires-in-plastic nose piece is fatiguing, you should have let go of that mask a while back.
Attachment
How a mask attaches to your face is a personal thing. Masks can go behind the ears or behind the head, and they can be tied or elastic. Behind the head is often slightly better for fit, and also it’s wear most people land for any long term wear. But behind the ear is fast and easy. I keep a stash of both, and give both out for people to pick their preference.
When shopping for behind-the ear-elastic, look for soft and round. You want is about as thin as the picture, thinner can cut into the skin or be too weak to hold on the mask, and thick can irritate the skin behind the ear. To make the mask adjustable, I fish the elastic through a bead using a wire or thread, and then use yarn to keep the bead in place. It’s easy to slide the bead around, and this lets the mask wearer adjust the size of the look behind their ears for comfort and fit.
I’d love to embed a video on how to do this, but since Medium hasn’t worked out how to embed video properly in its many years of existence, here’s a link to a flickr video where I demonstrate making an adjustable elastic ear loop for a mask.
Ties are deceptively simple. After trying and rejecting paracord, bias tape, thick yarn and sheets cut into strips, I found my absolute best material for tying a mask to your head all day long: jersey yarn, also known as T-shirt yarn. It’s got just the right amount of stretch to hold on your head without stretching out too much. You can also buy it in small or big rolls, depending on how many masks you want to make. I cut my ties to a length of 38cm/15 inches, and that gets around pretty much all human heads without too much to spare. I cut them, tie them in loose knots of four, and set them aside for later.
There is a third way, and potentially the best way, to attach your mask, and that’s with elastic bands around the head. This is also how most N95 style masks attach, and it’s the most worry free way of slapping a mask on your face, without having to make sure you have your knots right. But in a reusable mask it requires fitting spandex or latex straps for each individual head. This isn’t practical if you’re making masks for people beyond your own bubble, which is most of what I do. But it’s a possibility when you can fit the stretchy cloth to a head right in front of you.
Sewing Masks
Up front I must says that these masks are not something you can do without equipment, they are not hand-sewn and they are not quick and easy. I make my masks in batches, usually between 10–50, starting with cutting filters, inners, and outers. I sew the filter and outer layers together and then sew a bit stack of inners together and sew on their nose wires. I will often then batch up as many as 50 masks to sew inners and outers into the main body of the mask, coordinating them by color to minimize how often I have to rethread my machine. I will batch them up differently for sewing on the attachment, based on size and color.
Batching masks like this allows me to shave a little time off the process, but the time going into each mask is generally between 15–30 minutes. Sourcing materials, coordinating my work space, packaging and sending masks, they all take time and money. Between materials, equipment, and shipping, I have spent thousands of dollars/euros making and sending masks. But a lot of that was also testing and trial, a lot of those masks were failures, and I’ve abandoned and revised my methods along the way. So it won’t be as hard for you, but making these masks is always going to be a commitment.
Still, how often do you get to use crafting and design skills to save lives?
Picking a mask design is complicated, and there is no one mask that fits all faces. I currently work with three designs with three sizes, churning out nine styles of mask in total, though one design has two variations on the large design and another, the one I am sharing here, currently has no large. (I ran out of large people to test my masks, I hope to fix that situation soon.) The design below went through a lot of iterations, and draws on a lot of previous masks including various curved front masks and the University of Florida prototype 2 mask, which managed to pass some hospital fit tests.
Here are my best working mask designs at the moment:
You might notice I don’t include an explicit seam allowance. Because you end up sewing these in parts, and then sewing them in together, creating essentially two levels of seam allowance, I just go with “leave some room” and that works for me. But if you want to revise them, make them more explicit, useful or fit better, do as you like. They are CC0. I may have made them, but they are not mine, they are everyone’s. You can also halve this design if you want two distinct pieces for aesthetic reasons.
I have found this design, of the many dozens I have sewn, to have the best top fit, largely because the bottom fit supports the rest of the mask. The nose isn’t “holding up” the mask, per se — the darted chin design is. That means the forces on the nose can just do the job of sealing rather than being an anchor for the mask as well as sealing. If that’s too much detail and you don’t care, sew it, put it on, and feel around the mask while you blow out of it to figure out how and wear it leaks.
Fit(-ish) Testing
In the world of medical N95 or equivalent masks, you don’t just put one on and go to the Covid ward. Because faces are endlessly diverse, medical staff and other people needing to use proper PPE do a “fit test” before they use their masks for realsies. A fit test is a qualitative test, not a quantitative test. That means that instead of something, say, counting the particles that get around a given mask, the tester puts you in a hood, spritzes you with something smelly, and asks if you can tell it’s there.
I wouldn’t recommend my jenky home fit testing replace anything done by professionals, but I would call it better than nothing. My go-to fit tests are incense and soup. If, when you don your mask, you can’t smell the cooking, and you can’t smell smoke, it’s probably sealing ok for getting on a bus. To test actual wearing conditions (and my family have also done with with actual N95s before unavoidable travel) make sure that you can’t smell the target smell before you put on the mask, then move into the area with the scent, or light the incense. If that goes well, start moving your head around. Go side to side, up and down, try to mimic all your normal movements to see if the seal allows in the smells. If it doesn’t, that’s a good sign. If it does, you can try a different mask or check how you’re wearing the one you have. If there’s a problem you can’t get around and you’re very worried, there is no seal so bad that it can’t be fixed with enough medical tape.
Cleaning masks
The gentlest method of getting virus off your PPE is letting it sit for a few days while the virus falls apart on its own. There is no reason to sterilize a home use masks, just have a few in rotation. On the subject of active cleaning, there’s a lot of conflicting data out there, but I’d recommend quickly and gently with soap and water. Almost everything else has been shown to degrade the quality of masks, though every study I found was looking to sterilize masks, which is by definition tougher than you need if you’re rotating masks and letting them rest between uses. Cleaning masks shouldn’t be about killing the virus, just let time do that. Cleaning should be reserved for that time you sneezed inside your mask and it’s gross now. Time works, and keeps your filtration stronger for longer. Soap and water are just to make your masks smell less like your breath.
Do you have more questions or suggestions?
I will be adding to the document in the coming weeks, let me know what you’d like to know, or would suggest, in the comments.
Thanks to my Patrons on Patreon who support this work. If you’d like to see more, head over to my Patreon account.
