1065 gsm of spunbond NWPP in a washable mask

 Start with the 16 of this blog entry, and create an insert of 12 layers:

Verdict: still breathable, but much less so than the 16 layer one on its own

The insert's pink template was made freehand. 

As a consequence it is a little short in the throat area,

which you can see in the last photo.

For reference, the mask I just made is more breathable than 

an FFP3 mask I've had for a couple of years: