I did a lot of research and made a couple of prototypes. This mask is easy to make, washable and effective. Unfortunately, I did not bookmark my research. I’ll try to find some of it and post later. The research showed the effectiveness of different materials at filtration down to 0.1 micron (smaller than corona), as well as real world effectiveness of DIY masks at preventing transmission of influenza and SARS, which are very similar to corona. The bottom line to the research went like this:
Anyway, I don’t have a pattern or anything, but if you can operate a sewing machine even in the most basic way (like me), then you can make it.
The basic concept is a 3 layer mask made up of the following:
Outside: reuseable shopping bag – the kind you find in every grocery store for 99 cents.
Middle: toilet tissue
Inside: cotton tshirt
The reuseable shopping bag is breathable and water-resistant. Its important for the outside layer to keep out death vapors, spittle and sneeze residue. Put the bag to your face and try breathing through it before cutting it up.
The cotton tshirt can be a cotton blend. One study suggested a cotton blend was slightly more effective at filtration than 100% cotton.
The toilet paper is your disposable filter medium.
Start by cutting the seams off the bag. Bag construction differs between bags, so use your best judgement. I found that the edge sides and bottoms are usually the right size. Cut a piece about the size of a sheet of paper. HEM ONE LONG EDGE. The hem should be wide enough to slide a wire into later.
Cut the tshirt sleeves and neck off and lay it out flat. Lay the hemmed bag piece over it so the waist hem from the tshirt lines up with the bag material hem. Use pins to hold them together and trim the tshirt a little larger than the bag.
Sew the 3 un-hemmed sides together and trim off the waste. The unsewn side will the top of the mask and will form a pocket for the disposable filter medium.
Hem the bottom of the mask.
Make two pleat folds lengthwise and put a few stitches to hold it toghether. No need for anything fancy here, its just to hold it together. I found that after the pleating, the pins don’t work great at holding it together.
Fold one of the sides over about 1" and stitch that through a few times. Then do the other side. These are the loops for the strings (and final stitching for the pleats).
Now you’re done with the mask. Next get a piece of wire for the nose bridge. A small unfolded paperclip is both perfect length and malleability . Use pliers to make a little fold at each end of the wire which keeps the wire from poking through. The little fold is also a place to sew it in place.
Push the wire into the hem of the bag material, center it and lock it in place with a couple of stitches at each end.
For the string, use anything. Even the bag seams you cut at the beginning. They make great strings (comfortable, easy to tie). Shoe strings work great. Elastic is the best because you don’t have to tie/untie. But anything that holds it tight to your face is good.
That’s it. :-)
Losing fingers since 1969