it doesn't have to be replaced and the whole thing is washable (germs are killed around 175 degrees, I believe.)

Bravo to you for this project!

Works great. You can use light weight fleece or interfacing. I've made all the masks my family and friends wear and the ones I've donated this way.

My family, friends and neighbors yes. In my county we have a huge effort supplying masks to hospitals and other first responders. I'm in the group making and donating them to essential workers. I'm a retired teacher turned seamstress, this has been a great way to stay busy, feel a little bit useful and resist letting this damn virus hold me in fear.

with good instructions today (if you get the hard copy paper, you can cut out the pattern). They use fabric ties; although they said you can use elastic, they warn that elastic cannot be bleached, so may be harder to clean).

https://www.nytimes.com/article/how-to-make-face-mask-coronavirus.html?searchResultPosition=1

but I'm not sure if that's a washable material.

So my masks will now be three layers. And washable.

Before the pleats -

cut them in the shape of the masks to slip in and act as filters. Take it out and wash the mask, change the filter.