A 2013 study (PDF) by Cambridge University, which studied how aerosolized bacteria and viruses passed through DIY mask materials inserted into a testing device, indicates that only vacuum cleaner bags came close to matching surgical masks’ ability to block one type of virus; among cloth masks, tea towels blocked the highest percentage of the virus. In Thailand, muslin cloth is the most recommended material from which to make masks.
Vacuum cleaner bag material. I have not been able to locate any sources for that online. If you do, please let me know and I will update this page. Many thanks!