Six layers of satin - should be 93% (ish) protection

1. Take a single piece of 85cm x 33cm satin. No cotton needed.

2. fold it in half, sew it minimally to make that feel like a double thick 42.4cm x 33cm piece.

3. fold again to make six-thick 21x 33cm. 

4. sew back and forth to make 15mm rows.

5. do the bulk of the operations on it - nose wire, stencil etc, sew, snip, edges. 

6. Skip the stiffeners and retainers steps.

Verdict - breathable enough for a high filtration mask. This was 15
mins sewing time (no including making lengths of strap from sheets too).

Reminder on design features: 

1. washable/dryable
2. high filtration (good self-protection as well as protection for others)
3. breathable

Turns out that six months of work designing and sewing in "stiffeners" to boost breathability of varieties incorporating high-thread count (400+) cotton wasn't needed: satin on its own will do it if six layers thick AND you stitch the layers togethers to make some minimal stiffness.

Here's the offcuts from the finished mask:

Filtration effectiveness figures

Previously shared figures for this material apply.
A chart from there, note the green line near the top:

My percentages are kitchen-sink determined with a friend in Vermont who had the machinery to test. 

Update: Aaron Collins tests - Jan 10th, 2021

With a test particle size of 63nm (smaller than the viron itself), the 6-layer mask is 66% protective after the first wash & dry (55% before that). When Aaron did a second test with the edges pressed onto his face, the filtration was the same. Meaning for him at least the mask as supplied was a good fit. Look at the graph above. With Aaron's datapoint:

Our six layers of satin is now dotted blue - 0.063 µm the leftmost datapoint. 
It's no secret that cloth masks increasingly lose filtration effectiveness below 1 µm particle size.

All of Aaron's tests are on his Youtube channel

Konda et al (study)

Satin in multilayer configuration was also tested in Konda et al 2020. Only two layers though, and you'd have use some formulas to work out what protection you'd get with six layers. The result of that formula for six layers of satin (per Konda's results) would be near enough 100% protection for the important particle sizes. There are criticisms of Konda's methods online as yielding results that are too high, so I going to discount that the 100% possibility and use my Vermont friends more conservative 93% (ish) figures.

Me talking about the mask in use (4.5 mins)

Me making an identical one (18 min):

Me doing some home-improvement work to see how dusty I could get (1.5 mins):

Of course, whoever on earth want to test one more professionally, get in touch and I'll mail one for free:

See also Prof. Jose-Luis Jimenez's 2020_COVID-19_Aerosol_Transmission_Estimator s/sheet 
for general data, but two sections in particular for other percentages: 
1. Mask efficiencies in reducing virus emission (as they come out the nose and mouth of an infected person)
2. Mask efficiencies in reducing virus inhalation by a susceptible person (for virus already in aerosol particles floating in the air)  

See also which I put together with friends in many countries.

  1. I'm told off in social media for saying "satin" as some people might that thank includes silk or sateen (cotton). I'm on about the pure polyester variant with NO lycra/spandex. Also that is cheap satin that'd be used in bedding rather than garments or fashion.

  2. Konda et al's study has been criticized for having too optimistic protection percentages.


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