Researchers at Cambridge University tested a wide range of household materials for homemade masks. To measure effectiveness, they shot Bacillus atrophaeus bacteria (0.93-1.25 microns) and Bacteriophage MS virus (0.023 microns in size) at different household materials.
They measured what percentage the materials could capture and compared them to the more common surgical mask. Smartfilters.com compiled the graphs below:
The surgical mask performed best, capturing 97% of the 1-micron bacteria. Yet every single material filtered out at least 50% of particles. The top performers were the vacuum cleaner bag (95%), the dish cloth (“tea towel” in the UK! 83%), the cotton blend shirt fabric (74%), and the 100% cotton shirt (69%).
Homemade Masks vs. Viruses
The test above used bacteria that were 1 micron large, yet the coronavirus is just 0.1 microns – ten times smaller. Can homemade masks capture smaller virus particles? To answer this question, the scientists tested 0.02 micron Bacteriophage MS2 particles (5 times smaller than the coronavirus).
The homemade masks captured 7% fewer virus particles than the larger bacteria particles. However, all of the homemade materials managed to capture 50% of virus particles or more (with the exception of the scarf at 49%).