Aucklanders are back in alert level three, and should be wearing face coverings when out and about. The rest of the country is in level two, which means mandatory masks on public transport. We’ve all been here before, but if your mask game needs a refresh, epidemiologist and mask enthusiast Lucy Telfar Barnard is here to simplify the mind-boggling variety of fabrics, fits, layers and patterns on offer.

First published September 2, 2020

This isn’t about why you need to wear a mask – lots of people have covered that already. This is about what to look for if you’re buying or making your own. 

Firstly, a few points to keep in mind:

1. If you can’t make or buy the “ideal” combination described below, or you need to make do with some other fabric face covering, that’s OK. Just do what you can. Congratulate people for their ingenuity in covering their face well in novel and ingenious ways.

2. Whatever fabrics you choose, two layers is better than one, and three layers is better than two (so long as you can still breathe!)

3. Current evidence suggests that the best combination of fabrics is as follows:

• an outside layer made out of a hydrophobic (water-repelling) fabric that can hold an electrostatic charge. Your best options here are woven silk, woven polyester, or a blend of the two.
• a middle layer that provides a good filter. Your best option here is a “spun bond” (not a knit or a weave) polypropylene fabric.
• an inner layer made out of an absorbent (hydrophilic) fabric. Woven 100% cotton or woven 100% linen, or a blend of the two, is what you should be looking for here.

4. Fit is really important. It needs to fit all the way round. If the mask moves in and out when you breathe, that’s a good sign that the fit is good. If you can feel your breath leaking out down your neck, or out at your cheeks, or up into your eyes, see if you can adjust it to fit, or maybe find something that’s a better fit. NB: A nose wire really does help with fit. So can layering a section of pantihose over the top, around the head.

5. WHO advice is to avoid knit and stretch fabrics if you can – use woven fabrics instead. When fabric stretches, it opens up gaps between threads, where the virus can sneak through. Stretch fabrics also tend to lose their stretch over multiple washes – as they become looser, their filter properties decline.

6. Go for tight weaves. If you hold the fabric up to the light, can you see light between the threads? If so, that’s where the virus will get in or out.

7. You may be able to improve the efficiency of your mask by starching it (unscented is best for allergies).

Buying masks

If you’re buying a mask, look for the materials listed above. I’ve seen a lot of masks for sale made of cotton knit. If that’s the only fabric in them, I’d recommend spending your money elsewhere (see “don’t use” in next section). I’ve also seen masks for sale with raw silk or “natural linen” outer layers. They look lovely, and they’re probably quite breathable, but that loose weave means they’re not going to be doing such a good job of filtering the virus. If you’re reluctant to wear a mask you don’t like the look of, see if you can find something you also like the look of that’s made out of more suitable fabrics, or look for inner layers with better filter fabrics.

Fabric options

Outer layer: polyester is your budget option here, and for once the budget option is not a compromise. In fact, it’s a smidge more effective than silk, as it holds an electrostatic charge a bit better. If you can’t get either of those, polycotton would still be better than plain cotton. A lot of cheaper sheets and duvet covers are made out of polycotton. A single polycotton sheet from an op shop would make a lot of masks!

Middle layer: the ideal here is spun bond polypropylene. Spun bond polypropylene is sold as: “sew-in interfacing” at fabric stores; disposable painting overalls at hardware stores; frost cloth at gardening centres; and reusable shopping bags.

Other options are quilt batting, canvas or denim, but check these for breathability. I’ve been using “shop towels”, but they’re not widely available (I’d never heard of them before I started looking at US mask fabric tests) and I’m not sure how well they’ll hold up to being washed over and over. 

If you don’t have polypropylene, quilt batting, canvas, denim or shop towels, a middle layer of any fabric at all will still do more than just two layers. Again, do what you can. Some masks will have a pocket for a replaceable filter. If yours does, kitchen paper towels cut or folded to fit are an easily available option.

Inner layer: this is the layer that goes next to your face, so you’re going to want it to be comfortable. It also needs to be absorbent to capture the moisture from your breath. That makes cotton and/or linen your best choice here. Polycotton is an OK second choice (the cotton in it does the absorbing). 

Nose wire options: First choice is the resealable aluminium strip in the top of coffee bags, but you’d have to have some very “wired” (sorry not sorry) caffeine addicts in your household to have enough for the number of masks you’ll need. Other options are pipe cleaners (I use 30cm chenille-covered lengths bent into thirds), wire bread ties, florist wire and plant ties. Fold and twist the ends down with tweezers so they don’t poke through the fabric into your skin.

Don’t use: wool. Not even wool scarves. Yes, some smart people have made a very good technical wool fibre material for use as a filter in masks, which are great – use them with confidence. But they’re not the wool fabric in your clothes or fabric stores. Wool clothing, fabric or scarves are not a good filter for small viral particles.

Also take care with other knit fabrics: you may see lots of studies testing T-shirt fabric, and a lot of masks made out of cotton knit. The problem with the tests is that they’re testing the fabric as is, not stretched. Stretching knits opens up gaps between the fibres, which will allow the virus through. Knit might be OK if it’s thick or has a non-stretch backing, but it will likely lose its stretch and filter qualities over multiple washes. If T-shirt is what you have to use for a face covering or mask, go for the thickest T-shirt you can find, and please make sure you’ve got a good few layers over your face!

Patterns

Pleats? A central seam? Batwing? 3D? Origami? A cleverly cut sock? There are so many patterns around the internet, in fabric shops, and so on. Sewstine has a great (but 25-minute) YouTube blower test of some different patterns. Spoiler: only one passed, and even that needed some tape. Luckily, unlike her, we’re not looking for medical-grade PPE. 

So which should you choose? Overall, fit and fabric choice is more important than pattern style. Lots of people have success with the 3D option, but my personal favourite is the University of Florida Prototype 2, sewn with standard fabrics since Halyard H600 isn’t machine washable (and I don’t have any anyway), and with additional seam allowance. Like Sewstine, I found it provided a good fit, for both my small round face and my husband’s larger, narrower face. It’s a little more fiddly to cut and sew than some other styles though, so if you’re not a confident sewer or you’re wanting to sew lots of them, you’ll likely find a more basic “Olson”-style central seam (see the Jesse Killion pattern if you want to try sizing to fit) or pleated style easier and faster to put together. If you’re even a little confident, do try a 3D style!

I invite you to submit any mask patterns you come across to the University of Otago Covid-19 mask pattern repository.

Comfort and breathability

You really don’t need to worry about hypoxia, but you do want to be as comfortable as you can be. You might initially be feeling a bit self-conscious about wearing your mask or face covering, so you don’t need physical discomfort on top of that. It’s better to have two layers of cotton if the ideal three layers are just too hot for you, especially if being more comfortable means you’re more likely to keep your mask on.

Ties or elastic? Behind the ears or behind the head?

As a wearer of glasses, I find elastic around the back of the head more comfortable than elastic behind the ears, but whatever works for you and gives you a good fit is good. Younger people who didn’t spend their School Cert study break teaching themselves how to French braid their own hair may also find it fiddly to tie ties behind their head. If you’re buying a mask with elastic (behind the head or behind the ears), check that you can adjust it to fit the size of your own head. My masks are too tight for my husband’s head; his masks fall off my head unless I put a knot in the elastic.

Can’t find elastic but want something stretchy rather than ties? I’m planning to try some experiments with horizontal strips cut from a pair of old pantyhose. It’s good and stretchy, and with some knots, or some strips knotted together, I should be able to get it to the right length. This is also a good place to use an old T-shirt – cut strips to use as ties!

Speaking of glasses…

I’ve tried multiple styles and even with a good wire and a good fit I’ve yet to find a mask that doesn’t leave me half-blind trying to read through a layer of fog. Things that can help include: putting a folded tissue under the nose wire; taping the top of your mask to your face with “micropore tape” (available from chemists); or washing your glasses with soapy water or shaving cream and letting them air dry. Failing that… strike up a (physically distanced) conversation with the nearest blur on your bus and ask them to let you know when you reach your stop?

Care and handling

Ideally, masks are washed in hot (60o°C) water, and dried with heat.

When I get home, I go straight to the bathroom. I take my mask off into the basin and wash my hands, then I wash my mask in the sink with hot water and hand-washing soap, and hang it on the towel rail to dry. When it’s dry, I iron it to recharge the outside layer. 

The hand-washing is mostly because I’m using silk and shop towels. If you’ve used polyester, polypropylene, interfacing, cotton, and/or linen, you can throw your mask(s) into the washing machine and then the clothes dryer. If you don’t have the chance to iron the mask before wearing, you can try rubbing it briskly on another fabric to create the static charge.

If you’re out and about so needing to wear more than one mask in a day (one on the way to work, one on the way home), it’s a good idea to have a plastic bag to keep your used mask in until you can get it home to wash (rather than, say, leaving it loose in your pocket or work bag). Remember to wash your hands before you put your mask on, and immediately after taking it off. And make sure your mask is completely dry before you reuse it.

A note on cost

I’ve tried to suggest budget options wherever possible. I spent half my childhood being raised on the DPB, so I know that “just $2 for some discount shop pipecleaners” is a couple of loaves of bread and doesn’t count the bus fare to get there, or where you’re meant to find a sewing machine, or the thread to put in it, or the mental energy to think about it when it takes all your energy just trying to get by.

If making or buying a mask isn’t an option for you right now, and you’re really keen to have an actual mask rather than making do with a well-layered-up cotton scarf or T-shirt, the lovely people at Masks for All New Zealand may be able to put you in touch with a local community organisation that’s making free masks for others, or you may be able to access some of the free masks the government has provided for broader distribution by community organisations including food banks, marae, Barnados, Pacific community churches, and aged care organisations.

That sock mask video…

I love this woman’s ingenuity. I don’t love the mask as demonstrated in the video. It’s a single layer of knit fabric. It’s not going to be preventing much viral transfer in or out. However, if you have two socks (sorry to all those who thought this would be a good use of all your odd socks), you could make something much more useful by cutting up both socks, then layering them with a filter layer sandwiched in between. A kitchen paper towel cut to the right size, or even a couple of sheets of toilet paper, will make a disposable filter that will make a real difference to the effectiveness of the “sock mask” option. Also make sure the socks are clean before you start cutting.

Advice for employers

If you’re thinking about buying masks to distribute to your staff, good on you! But please make sure those masks are at least two layers. You may be thinking, “but surely even one layer is better than nothing”? Sure, one layer is marginally better than nothing, but it’s not adequate. If distributing single-layer masks means your employees don’t seek out something that is adequate, that would be worse than nothing. 

If you’ve already distributed single-layer masks to your workers, and/or you don’t have the budget to do better, you can recommend similar things to the suggestions above for sock masks: if some of your staff don’t need them, they can donate them to those that do so they can wear two at once. Alternatively, a paper towel over the nose and mouth under the mask will definitely improve its filter qualities.

Masks for pets?

Despite the title, and to my great disappointment, Chan et al’s paper showing masks reduced Covid-19 transmission in hamsters did not in fact involve putting tiny masks on hamsters. Fortunately, while pets can catch Covid-19 from humans, for now the evidence says there’s not much likelihood you’ll catch Covid-19 off your pets. Since most of the benefit of wearing a mask is preventing spread to others, and pets aren’t likely to spread to others, you don’t need to put masks on your pets.