Eight layers of NWPP in a 10 minute mask
About 10mins to make - 8 layers of NWPP
That's 304 gsm of SBPP.
The manufacturer said this fabric was 38 gsm per sheet, an I've put in 8 layers so that 304 gsm for all together. I weighed ten sheets on a kitchen scale, took the size measurement of a sheet then calculated that each sheet was 42 gsm. That's just the shipment I got. A second batch from the same manufacturer that had colored sheets weighed 38 gsm per sheet.
This is a magical washable fabric for filtration. Probably best not to iron it to
make it flat though. Or if you do, make sure the iron is on a cooler setting. The optional cotton layer can be ironed flat on its own of course. With that layer, this one is nine layers, but the spunbond stuff is where the bulk of the filtration is coming from, so you should think about dropping the cotton later unless you need a patten. If you keep the cotton outer, consider the lowest TPI cotton you can use in order to not negatively affect breathability too much.
The pattern is the RagMask with modifications. I used to call mine RagMask Max but many of the modifications I made previously I've just dropped. Now I have something that's closer to the original just a different order of events to the original.
Filtration calculations
(these figures from the MakerMask tests)
Eight sheets of the 38gsm stuff is about 79% filtration effectiveness (at 300nm particle size, 28 liters per minute). Add about 5% for the 180 TPI cotton later and this is in the low 80's for percentage.
Aaron Collins tested one like this - 84.9%
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