High filtration cotton/satin mask with cut up IKEA placemat as stiffener.

Design & Materials

This is the RagMask Max design with further modifications. Size is XL.
  • One layer of 750 thread count cotton for the outer layer. This is where most of the filtration comes from (refer Konda et al, May 2020). I've used 750-tc in previous masks.
  • One layer of cheap satin from cut up sheets (from Amazon - Viceroy brand). As just about every mask I've made since March.
  • 12cm section of nose wire (I use "soft-twist-plant-ties" but the store that stocked them has discontinued it)
  • Plus a piece cut out of a IKEA "SNOBBIG" placemat- https://www.ikea.com/gb/en/p/snobbig-place-mat-light-grey-40343770/  <--- this is the new modification to previous constructions.
Notes:

1. Filtration estimate - 95% for droplet and "droplet nuclei", per Konda et al - https://pubs.acs.org/doi/pdf/10.1021/acsnano.0c03252.  See also my own calcs on fabrics - 

2. Important particle sizes (droplet and droplet nuclei) from Jie Zhou et al (March 2020) - https://www.pnas.org/content/115/10/E2386

Step by step

(also see "RagMask Max" guide and video, linked above) 

Top hem sewn, with nose wire in situ. You're lookin at the inside of the mask, 
and future sew lines have been drawn on:


NEW - "lanes" drawn for the strip of placemat to be inserted into before being sewn in (in such a way as they can't be removed after that moment) :



Sewn along those lines and a V section cut out:



That strip cut in half, and "castellated" :



Inserted, but not quite pushed "home" yet:



Placemat stiffeners pushed home, mask folded, 
central vertical seam sewing about to happen:



Central vertical seam sewn, excess fabric cut off. 
The cut up placemat no longer removable - I've sewn through those castellations. 
Not that I would have known the sewing machine didn't strain at all:
 


Look, you can just about see the ends of the placemat sticking out beyond the sew line:



Bias tape sewn done that central vertical seam. Unlike previous masks, I have not 
added a stiffener to this central vertical seam. The mask is still inside out:



Mask from a couple of one month ago shown on the left (slightly smaller), 
new one of the right for comparison:



The breathability was better with the new one, so I decided to retire the old one, and reuse it's straps. Cut off and reattached to the new mask (the fabric for that is 180-thread poly-cotton which is cheaper).



Nearly finished, one more line. This time TROUGH the fabric and the placemat.
The mask was popped to its final position (other sew lines were made inside out).


Here's a closeup of the placemat, and previous stiffeners 
I've used - a solid plastic placemat, and zip-ties.


And something I did earlier, but forgot to take a picture of was the sewing of bias tape on the bottom edge before adding the straps.



Conclusion

This new IKEA placemat (and anything like it) is so good, I am not going to use anything else for masks I make from now on. This is a cheap item and there's lots of availability. Even if the anti-mask community buys them all up and burns them, there will be alternatives. You can maybe make 20 masks from one placemat.  

The reason it is good is that you can breathe through it. There's no need to make thin strips from it as previous solid placemats I have used. 

This entire mask sewing took 20 mins, so it is quick, too.

You would make masks like this for people in high exposure situations with no access to commercial N95 or FFP2 masks. With the straps instead of ear-elastic, I'll say these are "all day" masks. You can talk in them, they fit well around the nose. If you sneeze, it catches all of it whereas ear-elastic ones don't. You would hand-wash them each night and air them if it is warm (or sunny) enough (not for humid climates). You could even machine wash them at 40 °C, but you should use a laundry (bra) bag and when the machine isn't crammed full. Best to have two, I guess and rotate them. 

On breathability?

This mask is less breathable than N95 and most other masks that are held away from your nostrils and lips. More breathable than multi-layer fabric masks that are touching your nostrils and lips. I own one of these - https://www.4dflexisport.com/collections/face-masks/products/single-reusable-facemask-respiratory-face-covering-rfc-by-4dflexisport - too, and it the mask I have just made is far less breathable than that. But again, for economies with citizen sewing machines and access to 600-tc (or above) cotton, this is a decent contingency mask for high-exposure workers. If you drop to 400-tc, you'll need to add more satin layer (per my calcs above).


More on that IKEA "SNOBBIG" placemat


Looks opaque ...


But is not -



Without any fabric involved at all and with your mouth open to one square inch 
(6.45 ㎠, 1.1" diameter, 2.8 cm diameter), covered by this placemat alone, you 
get the same air resistance ("pressure increase") as you get from just breathing 
through your nostrils with nothing covering them.  People who breath through 
their mouths in regular life (ill advised) are doing so because they think they 
need more air than their nostrils can supply.

Your intention with a mask is to breath through your nostrils alone, so you need the 
max surface area of your chosen materials. Aside from the cotton/satin,  this placemat cut 
up and sewn into the mask can also decrease the surface area in subtle ways. 
SNOBBIG material only partially blocks air (in and out). In that regard it 
is a clear improvement over previous materials I have used for stiffeners.

Update: Aug 10th

The vertical seam got crushed in the washing machine. It has lost strength and the sides pull into 
your nostrils/lips as you breath in now. SNOBBIG can't be put in the washing machine :(






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