With my blessing, the marvellous Mrs Sciencebase took one of my gig shirts and cut it into pieces, found a PPE mask template online folded and stitched, embedded a layer of silk and created a pocket for an additional filter. I can’t feel my breath through this when breathing hard so I assume it would work to reduce outflow of any viral-laden particles should I ever go out in public again.
Incidentally, it’s a good idea to make your mask with two different types of fabric, a tightly-woven cotton layer will catch most wannabe aerosol droplets from nose or mouth and they will be soaked up into the fabric. A synthetic, chiffon, or silk layer will act as an electrostatic and additional physical barrier to any smaller particles or droplets that might otherwise sneak through. Of course, any mask is only as useful as you are hygienic in your use of it, you must put it in place and leave it there for the duration of your time in relative close proximity to other people. You must also remember to wash your hands frequently and certainly before and after mask use.
Despite the claims from governments about it being safe to reduce social distancing, ending lockdown for the sake of the economy, re-opening non-essential shops, and getting people back to school and back to work, the virus has not changed, it has not suddenly gone away. The whole pandemic started with one infected person. It could cascade again and while we may have a better insight into how to control it with track and trace, social distancing, and homemade PPE, there are still huge risks to it taking many more lives in the months and years to come. Don’t risk it. Stay safe, stay well.