High filtration cloth mask with ribs sewn in to force cupping that aids breathabiity

Mid 2021 update:  High thread count cotton and/or multi-layer polyester satin isn't a good choice for high filtration masks. They're not breathable enough at mid filtration performance. And additional layering to get to hight filtration still only decreases breathability further. With that they get hot and uncomfortable as well as giving your chest muscles a good workout.

Mask design is RagMask Max with modification (detailed below). 

For this mask, I made a choice of 750 thread count (750-tc) cotton and satin 

(one layer of each). Konda et al 2020 picked 600-tc cotton. I have

  drilled into the filtration figures from the fabric in their study before. 

The finished mask discussed:

Pics that from the construction up to the video, showing the new experiment 

- cutting a rectangle of the plastic placemat into a "comb" of sorts:

Each "prong" of the comb goes to an alternate side of the mask 

(between the cotton and satin layer):

Sew:

Sewn:

Trimmed:

Add bias tape:

Pop the mask from inside-out to "right way" for wearing:

Update (July 3rd 2020): simplification to the stiffener/ribs

Update2 (July 5th): further simplification 
- swim-lanes sewn first and zip ties used as ribs

See separate blog entry

https://fu-cv.blogspot.com/2020/07/masktech-sewing-swim-lanes-for-ribs.html