So you've watched Helen Cody's video guide and made your own cloth mask. Or you've taken delivery of a bespoke handcrafted one you ordered online. What now? When do you wear it? Is it okay to pull it down under your chin to eat, vape or chat? How often should you wash it? And will it actually keep you safe from Covid-19?
First, then, do masks actually work?
The scientific thinking has begun to shift since evidence emerged that coronavirus can be spread by presymptomatic and asymptomatic people – those who haven't yet started feeling sick, or who may never show symptoms. The Government is now advising people to wear face coverings on public transport and in crowded indoor places, while keeping up with handwashing and social distancing.
Since Friday the position of the Health Protection Surveillance Centre has been that "although there is no definite proof of benefit, many experts… believe that if everyone wears masks when they are within two metres of other people this can reduce the risk that an infected person… will spread the infection to other people."
This is a long-winded way of saying you wear a mask to protect me; I wear one to protect you. And we all need to get on board for them to really work.
If at least 60 per cent of us wore masks that were just 60 per cent effective in blocking viral transmission, we could stop the coronavirus epidemic
It has the potential to be incredibly effective: a recent review of research suggests that if at least 60 per cent of us wore masks that were just 60 per cent effective in blocking viral transmission, we could stop the coronavirus epidemic.
Respirator masks – known in Europe as FFP2 masks and in the United States as N95 masks – and surgical masks are the most effective at stopping the spread of coronavirus. But respirator masks are rare, expensive and recommended only for healthcare workers. A recent Nature study found that surgical masks, which are made of melt-blown polypropylene-fibre fabric, blocked 99 per cent of the respiratory droplets expelled by sick people when they were correctly fitted. But they can't be reused and need to be disposed of properly after use. A study in the Lancet by researchers at the University of Hong Kong found that "a detectable level of infectious virus could still be present on the outer layer of a surgical mask on day seven". This makes them impractical for use outside a healthcare setting.
So can cloth masks keep you safe from coronavirus?
Again, the point isn't actually for them to keep you safe. It's to keep others safe from you. In turn, others wearing them keeps you safe.
A 2013 study found surgical masks are three times more effective than home-made cloth ones, but cloth ones are still useful, because they help you keep your droplets to yourself. Cloth masks serve another purpose, too: some experts believe they can act as a visual signal and a reminder of the importance of social distancing, and destigmatise mask wearing for those who really need them.
Which fabric is best?
There's no official word on this from the HPSC or, in the US, the Centers for Disease Control and Prevention. Diameter, permeability and thread count all play a part in determining how effective a mask is.
Tightly woven fabrics like cotton are among the best barriers. This isn’t scientifically validated, but a useful test is to hold the fabric up to the light: if you can see the individual fibres, it may be too thin to stop your infected droplets escaping.
A recent study at the University of Chicago suggested that the key is to layer up, using cotton and a second type of fabric. It found that single-layer masks were between five and 80 per cent effective at filtering small particles, but using two layers – cotton and silk; cotton and chiffon; cotton and flannel – increased the effectiveness to more than 80 per cent.
Better again was to create a sandwich consisting of one layer of the more tightly woven cotton plus two layers of silk, or two layers of chiffon, or one layer of flannel. But the fit is the most important thing. The mask shouldn’t let air in or out around the edges. Wool scarves wound around your face are among the least effective types of face coverings.
Carry the unused face covering in a clean, sealable waterproof bag, bring a second ziplock bag to carry the used mask, and make sure you don't mix them up
Do I need to wash it?
The HPSC advises that cloth face coverings be "stored safely and laundered regularly to ensure that they are clean". So wash it every evening, on a 60-degree cycle, once you've returned home.
Do you need to put kitchen paper or a coffee filter inside the mask to make it more effective?
A number of online guides to making your own mask suggest this is a good idea, but a large-scale review by scientists suggests it may not be necessary for cloth masks. A layer of paper towel or coffee filter "could increase filter effectiveness for PPE, but does not appear to be necessary for blocking droplet emission".
Should you wear it when leaving the house?
You shouldn't need to wear your mask just for walking outside or driving alone in your car. The HPSC suggests you carry the unused face covering in a clean, sealable waterproof bag, such as a ziplock bag, and put it on before going into a public place, like a supermarket or pharmacy, or on public transport. Bring a second ziplock bag to carry the used mask, and make sure you don't mix them up.
So when exactly should you put it on?
Wear it when you're inside a place "where a distance of two metres cannot be maintained, to reduce the risk of discomfort and skin irritation", the HPSC advises. This means you should put it on and make sure it's covering your nose and mouth before you enter a supermarket or hardware store, or go on public transport, for example.
Don't do the face-mask chin tuck if you want to chat with someone. Earlier studies assumed droplets were spread mainly through coughing, but more recent evidence suggests talking can also transmit the virus
Once it’s on, don’t fiddle with it. If it gets wet or dirty, take it off and replace it with another one. Don’t touch your eyes, nose or mouth when taking it off. Wash your hands as soon as you can after taking it off and storing it in your ziplock bag.
When should you take it off?
If you've been shopping and are going straight home, take off the face mask once you get back to the car, and store it carefully in the correct resealable bag. Disinfect your hands after removing it. Children under 13 shouldn't wear them at all.
When should you not take it off?
Don't do the face-mask chin tuck if you want to chat with someone. Earlier studies assumed droplets were spread mainly through coughing, but more recent evidence suggests talking can also transmit the virus. Don't remove your mask to eat or vape either. "If you need to uncover your nose or mouth, remove the face covering and place in the bag for used face coverings," the HPSC warns.
And if you do take it off, don’t put it on a table where you, or someone else, will be eating or drinking later.