Cut the arm of an old t-shirt to about 5 1/2 inches long. The arm will make multiple masks. I find that the middle and upper parts of a tapered arm are better for adults.
Cut the body of the t-shirt into long strings that are about 1 inch wide. This shirt was large enough that I was able to get two ties from each cut across.
Add the ties to both sides of the sleeve by running them through the inside. If you are going to add a filter, you will need to glue this shut across the bottom leaving room for the ties. Then just put your filter in from the top.
To wear, I like to make a bow at the top. Then put the top loop on the top of the head, pull the mask into place and tie the bottom tie behind the neck. I also like to turn the seam of the sleeve to the middle of the outside in order to tell the front from the back. Then just enjoy your new t-shirt face mask.