Measure out a rectangle that is 23cm x 16.5cm on a piece of paper. For men or adults with a larger face, make the rectangle 27cm x 19cm. (For a medium sized mask, adjust the measurements to something in between.) Cut it out.
For the smaller sized mask, mark off 4.5cm from each of the corners. (For the larger size, mark off 5cm from each corner.) Draw a line diagonally across the corners from one mark to the other. Cut off the corners along the line drawn. You should now have a pattern that looks like an oblong octagon.
Cut out the fabric
Trace the pattern onto both pieces of fabric (the lining and the outer fabric).
Cut out both pieces of fabric using the tracing to guide you.
Sew the layers together
Place the 2 layers of fabric together with the right sides of the fabric facing each other. Sew around all of the edges, leaving a small opening on either the top or bottom edge (one of the long edges). The opening will be used to flip the fabric right side out.
Flip the fabric right-side-out
Using the opening left in the last step, pull some of the fabric through the opening to pull the fabric right side out. The seam will now be hidden inside and the right side of the fabric will now be showing.
Use either your fingers or a pencil or stick to press out the seams and corners.
Sew across the top and bottom edges
Sew across the bottom and top edges, close to the edge of the fabric. This will also close up the opening you used to flip the mask right side out.
Sew down the folds
With the lining fabric up, fold down the top and bottom sections at the point where the corners are. You will now have the outer fabric showing. Press the fold with an iron to help hold it in place.
Sew a seam along the fold near the edge. (If you sew further from the edge, your mask will end up being slightly shorter. You can adjust the mask, as needed, by keeping that in mind.)
Prepare the elastic for the ear loops
Cut two pieces of cording to be used as earloops. I like to use silicone cord locks to make adjustable straps. If using cord stops, make each cord around 23cm (9in) long. If not using cord stops, the ear loops should be shorter (around 7 inches or 18cm, dependent upon the person who will be wearing it).
Form the mask
To form the mask, fold back each of the 4 corners.
Fold down one of the corners, forming a v-shape, with the edge parallel to the side. To fold down each corner, fold the fabric down at the halfway point along the diagonal. Make sure the upper part of the diagonal edge lines up parallel to the side edge of the mask. You should end up with an N-shape fold with the center section showing a right triangle shape of the outer fabric. Line up the point with the folded edge of the mask.
Tuck the elastic under this center section before sewing along the edges of the "N" and along the side edge.
Sew along each of the edges and down the side.
Repeat on the bottom with the other end of the elastic tucked underneath.
Repeat on the other side with the other piece of elastic.
If using the cord stops, thread the cording on either side through the cord stop.
The mask is now finished.
You can fold the mask and store it folded. When opened, it will open out into a 3d shape.
For a 3 layer mask, cut out 3 layers of the same pattern. Layer the fabric you want to be in the middle over the lining fabric before sewing them together. (The right sides of the lining fabric and outer fabric should still be together. Then continue with the rest of the tutorial.)I use a cotton cloth to keep the mask more breathable. (I also personally don't feel comfortable breathing in the plastics and chemicals used in many synthetic fabrics.) That said, the WHO recommends using cotton, or another absorbent fabric, for the lining fabric. They then recommend using a non-woven middle fabric like polypropylene. They also recommend an outer layer of non-absorbant fabric like polyester.
Recipe printed from Oh, The Things We'll Make! Blog. https://thethingswellmake.com/diy-comfortable-breathable-face-masks/