Aaron's video test of my three masks - shortest clip

Third set of particle tests I have participated in (Jan 2021) [6th], [5th], [4th], [2nd], [1st]

Citizen Scientist, Aaron Collins (@masknerd on Twitter) tested three more washable masks of mine. 

• Four layers of spunbond polypropylene (38 gsm Smart-fab), with one outer layer of 180 TPI of poly-cotton
• Same, but with eight layers of the spunbond polypropylene (SBPP)
• Same, but with twelve layers of the SBPP Aaron’s two hour livestream: https://www.youtube.com/watch?v=73JWxBXqIR0

What follows is just my masks from the middle of his live stream. Results:

Four layers SBPP (152 gsm) + one of 180 TPI polycotton

Filtration Efficiency:             73.0% Time to Max Breath @ 0.25" H20:    2.23 Pressure Drop:                      0.13 Quality Factor:                  10.2

Eight layers SBPP (304 gsm) + one of 180 TPI polycotton

Filtration Efficiency:             84.9% Time to Max Breath @ 0.25" H20:    3.02 Pressure Drop:                     0.17 Quality Factor:                  10.9

Twelve layers SBPP (456 gsm) + one of 180 TPI polycotton

Filtration Efficiency:             85.7% Time to Max Breath @ 0.25" H20:    3.84 Pressure Drop:                      0.22 Quality Factor:                8.7

Aaron talks of early fabrication studies, some differences between melt blown and spunbond PP,

breathability, pressure drop, a few cents per mask cost, suitability for the developing world.

One key thing Aaron says:

“we should not have wasted our time with cotton” Previously, Aaron had tested a mask made from six layers of satin (polyester) in the same design as here. He tested that one and it came in at 55% filtration effectiveness. A couple of weeks later he had washed it and dried it and tested it again at 65% filtration effectiveness. Many fabrics will be better after one wash. Aaron's spreadsheet: https://docs.google.com/spreadsheets/d/1M0mdNLpTWEGcluK6hh5LjjcFixwmOG853Ff45d3O-L0/edit#gid=1976839763 All of mine are in there as "Rag Mask". You should assume you'd get the same filtration effectiveness for any 3D-style pattern made with the same gsm of SBPP that is a good fit.