Friends, we are publishing our process for a better-than-nothing surgical mask - designed to be made in bulk in a small to medium sewing shop that usually makes garments...or, you know, doll clothes for organic woodland animals. It's currently estimated to take 3-4 person minutes per mask. This mask features an aluminum strip to create a better seal over the nose, and a pocket to hold a filter fabric. Our process uses a single needle machine, a merrow machine / serger, and a cover stitch machine with a folder - all common equipment in a shop that sews knit fabrics like t-shirts.
IMPORTANT: THIS MASK IS DEFINITELY NOT FDA APPROVED OR TESTED AT ALL! We have spoken with doctors who have confirmed that the pattern/fit is good, and that this is better than a bandana which is what some medical professionals are using and what the CDC is recommending doctors use as a last resort. However, WE ARE SEEKING ONGOING GUIDANCE AND ASSISTANCE SOURCING MATERIAL FOR THE OUTSIDE LAYER, LINING LAYER, AND REMOVABLE FILTER LAYER. PLEASE HELP US FIND ADVISORS WITH EXPERTISE. Meanwhile, we will make the best masks we can, and try to get them to medical workers, because we ❤️ America and we hear the need is urgent. We will keep this post updated with the best information we have.
Our current best guesses for materials are:
- Water resistant breathable outside (a tightly woven synthetic, or a water-resistant treated poly-cotton like this)
- Nonwoven stiff polypropylene lining (stiff enough to hold mask away from the face, very breathable, different color from outside) - such as weed control cloth like this or heavy sew-in interfacing
- Felt removable filter (seems like it must be better than nothing as a filter - please advise!)
We cut the lining cloth into strips 8” wide.
The outside fabric should be cut or torn into strips 9.5” wide. We ripped across the goods and got pieces about 56” long. We cut the 8” lining strips to a similar length.
Pictured here is a white cotton poplin which is closely woven yet breathable - BUT our latest understanding is, it’s better to use an outside fabric with more waterproof properties (although it still has to be breathable).
In our shop, it’s very easy to switch between cutting and sewing, so we can do the first steps with fabric in long strips, then easily chop the partially completed strips into smaller pieces to finish the masks. But if it’s more of a hassle for you to transition between cutting and sewing, then you could cut all the outside pieces 9.5”h x 7.5”w, and all the lining pieces 8”h x7.5”w.
On the merrow (industry jargon for a serger, the sewing machine that does a seam like on the side seam of a t-shirt), we finished one long edge on each lining strip and each outer strip.
We sewed the other long edges together on the merrow.
We flipped the outer layer around the merrow seam, and stitched “in the ditch” along the entire strip, creating a channel about 5/16” or ⅜” along the top edge.
Then we chopped these strips into pieces 7.5” long. In production, you can stack them up higher for this step, depending on your cutting equipment. With our trusty rotary cutter I would confidently cut 4 at once.
Now we have a stack of individual pieces to finish. On the single needle machine, we tacked the top channel closed 1.75” from each end. Note the magnetic guide to the right, positioned 1.75” from the needle.
We folded the outside layer over the lining layer on the bottom, and tacked in place at both corners. The bottom opening is meant to stay open - it's a pocket for a filter material.
For the pleats, we made a folding guide from poster board with dimensions as marked here. It’s 7.5” wide and 8” tall total, just like the mask pieces at this point.
It seems to be fastest to fold the pleats on one side by using the guide, then immediately tacking on the single needle ...
And to eyeball the pleats on the other side to match the first side, then tack the second set of pleats.
Here are some masks, ready to have their ties put on. The pleats aren’t super exact, but they’re good enough and the pleating process could be a real time sink if we let it. Each pleated edge is 4” plus or minus ¼”.
Like many sewing shops, I suspect, we have a big stash of accumulated pre-cut binding from old projects. I thought we would never use these, but I guess no one expects coronavirus. The knit bindings are perfect here because they’re soft and a little stretchy, but wovens will work fine too. If you look at real surgical masks with ties, they're usually made of the same nonwoven as the rest of the mask.
This is how we put the ties on: a cover stitch machine on the chain stitch setting, with a folder. This set-up looks exotic but it’s common in garment factories that sew knit items like t-shirts or tank tops. We tried to sew ties long enough that each one would be 15”, but it seems to me any length between 12” and 18” will work okay.
We put on the ties in bulk. From this point on, all the steps can be done by a non-sewing volunteer. We cut the masks apart, trimmed the loose threads and checked them for major sewing defects - in our case, mostly ties that were way too short.
For the nose pieces, we used aluminum flashing which is very cheap and plentiful at the hardware store. We used utility scissors to cut a strip 3.75” long and about 3/16” wide, then rounded the corners of the strip a little.
We snipped a little hole in the lining side of the top channel, and poked the nose piece into the channel.
This way, the wearer can bend the top edge to fit more closely over their nose. Don’t pre-bend it though, let the eventual wearers do their own.
Here’s a bunch of finished masks with filters. The filters are 5” square. This is a wool/rayon felt which I assume is better than nothing, but you can and should use the best filter available. A piece of HEPA filter vacuum bag, maybe?
This is how to insert a filter piece. 5”x5” square, best material available.