Sewing simple cotton masks

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Sclass
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Re: Sewing simple cotton masks

Post by Sclass »

I have not. Waiting for my shock cord.

People are cutting filter inserts. I think even cutting a sheet and placing it inside the mask would work.

It is polypropylene fiber. My gut feel is you better stay on the lower end of the iron settings. Like Polyester? I’ll go out to the garage and shred a small strip up and put it on my iron. It’s pretty fleecy.

I wasn’t planning on ironing it.

Okay, just got back from the shop. Just discovered an iron makes a pretty nice electric hot plate. Ran the temperature up from 50C to 120C over a five minute period using the knob and a non contact thermometer. I watched the fibers under 10x magnification as I did it. The fibers from the outside layer (the more fleecy side) don’t melt. The inside (the quilted stippled side) looked like Swiss cheese at 100C. The upper layer melted but the underlying fibers were still intact.

That tight inner layer seems to be the “business end” of this cloth. I think the melted holes are a bad sign.

I was toying around with fusing the edges using and iron instead of sewing. Sewing punctures the cloth and creates a seam that can leak. But after seeing what 100C does to the inner layer I think I’ll sew then seal the seam with fabric glue kind of like how one seals a tent seam.

I noticed my blue Walmart shopping bag looks a lot like the inner layer of the Filti under magnification. Non woven polymer fiber with little melted stipples to hold it together. I think I’ll use this as my outer layer.

Good luck!
I’m shocked this stuff works so well I shredded it apart and there really isn’t much there.

There is the separate detail that the heat may electrostatically depolarize the material. This stuff is supposed to be statically charged and it attracts dust. I don’t know if heating it diminishes this property. We could try rubbing it on the cat and seeing if it picks up her hair after ironing.

Bottom line, I’m not going to be heating it.

horsewoman
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Re: Sewing simple cotton masks

Post by horsewoman »

This is a new (to me) style of mask. The pattern is a little bit more complicated, but very intriguing! I'm going to make such mask on the weekend, if I can unearth some batting from the chamber of secrets that is my fabric storage :)

https://youtu.be/UaZBm_V8Flg

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Sclass
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Re: Sewing simple cotton masks

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Yes! I saw that video and downloaded her pattern. I was wondering why she didn’t put batting under the chin. She must have found it worked better.

I may make one of these. The fit looks very good and the surface area looks large for easy breathing.

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jennypenny
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Re: Sewing simple cotton masks

Post by jennypenny »

I like that a lot, but it makes me laugh because the pattern is similar to the one I have for sewing a diva cup. Never thought to use it for this. I guess the purpose of holding in the body's ejecta is kinda the same. :lol:

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Sclass
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Re: Sewing simple cotton masks

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Oh no. I just looked up what that meant.

horsewoman
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Re: Sewing simple cotton masks

Post by horsewoman »

I did not have to look it up, but I have been wondering how exactly one sews a diva cup!

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Re: Sewing simple cotton masks

Post by jacob »

@horsewoman - DW made that including a nose clip made out of the lid of tomato can. It fits my big nose much better than the first version posted in this thread. I'm still waiting for the pattern for a genuine plague doctor mask.

Does anyone know how these homemade masks compare to the single-use surgical masks that seem to be widely available now?

Jason

Re: Sewing simple cotton masks

Post by Jason »

Before this thread, I would have thought a diva cup was the glass that Mariah Carey drank out of. How I long for those days of innocence.

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Re: Sewing simple cotton masks

Post by jennypenny »

Sorry, didn't mean to derail the thread. The pattern to which I was referring was for the homemade pad that accompanies the diva cup.

@j--To me, the biggest difference is fit/comfort, assuming your homemade mask has a comparable filter. If your mask has a pocket, you can insert a surgical mask as the filter. I prefer the masks with ties and a neck loop so that I don't have to touch around my face to remove the mask. I also like letting it hang around my neck when I don't need it up on my face.

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Sclass
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Re: Sewing simple cotton masks

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@jacob
I think it really depends on the quality of the surgical mask. I have a box in my garage that say the fabric is rated as n95, that is 95% of particles .3um or above get caught. But the seal around the cheeks kind of defeats the filtering ability. The elastic ear loops are too weak to create a seal.

There are a lot of fake surgical masks out there now. There are a bunch of tests like blowing out a lighter, or tearing the fabric, or burning the fabric as shown on YouTube. These will identify a paper mask versus a polypropylene mask. But the real test is a laser diffraction particulate counter. My understanding is brokers buying ppe in China are carrying handheld units to QC suspect masks.

Looking at the fabric on my box of surgical masks (left over from my late moms care) shows they melt and don’t burn. The fabric is hard to tear. Permeability is low using the blow test. They have the blue on the outside and white on the inside that repel water. But are they N95 rated fabric like the package says? Dunno.

The BI article I posted

https://www.businessinsider.com/the-mat ... ing-2020-4

Paints a really bad picture for cotton cloth performance. (Edit - if you believe the article, the two layer Kona cotton mask is N7 if there is such a thing as opposed to N95). They show a laser based handheld particle counter in the photo. I tried building one of these for biodiesel QC that used a laser pointer and Fraunhofer diffraction but it had issues...I cannot recall why I gave up on the diy. Maybe the Fraunhofer model didn’t handle particle size distribution and count at the same time. If I recall right you can get a pattern by shining a laser through the sample and looking at the 2d spot pattern on a screen behind it. Perhaps this is a way to indicate pore size on mask fabric like a double slit experiment? At least you can have a relative measurement of pore diameter and spacing between say a cotton quilters fabric and Filti.

I recall trying all this stuff on screens years ago...senior brain. Let me run out to the shop and see if I can make an interference pattern with cloth. I’ll post it up if I get a positive result. This maybe a good way to check relative filtration abilities on different cloths.

An interesting Filti anecdote. So I bought Filti and I haven’t seen masks with it. I use some P100 respirators from my shop instead. I did send some Filti to my dad. His wife made masks for him and my half sibs. They said their seasonal allergies went away when they sewed the Filti into their existing masks that were made of quilters cotton. FWIW.

My understanding is real hepa filters rely partially on electrostatics to capture particles. They’ve somehow put a polarization on the polypro fibers in there. I think it’s pretty hard to beat these melt blown textiles when it comes to these nanotechnology effects.

Luckily we can get these materials in vacuum bags, HVAC hepa filters, car covers that promise breathability but dust impermeability, or even cut up surgical masks which seem to be the material of choice for 3d printed masks.

Good luck and stay safe.
Last edited by Sclass on Mon May 25, 2020 11:56 am, edited 2 times in total.

Jason

Re: Sewing simple cotton masks

Post by Jason »

jennypenny wrote:
Mon May 25, 2020 11:43 am
The pattern to which I was referring was for the homemade pad that accompanies the diva cup.
I can understand the appeal of the Trikini, but this seems a bit extreme.

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jennypenny
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Re: Sewing simple cotton masks

Post by jennypenny »

Sclass wrote:
Mon May 25, 2020 11:45 am
Luckily we can get these materials in vacuum bags, HVAC hepa filters, car covers that promise breathability but dust impermeability,
I read that those can contain fiberglass particles, so they should be used inside of other covers to offer some protection from the fiberglass.**

We've noticed the same thing with the filti masks. Makes cutting the grass much less annoying.

**edit: Is that right? You'd know more than I would.

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Sclass
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Re: Sewing simple cotton masks

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Yeah, I hear vacuum bags contain fiber glass. I've not used one...maybe I shouldn't be suggesting them. The burn test may ID glass fibers. Glass fibers will melt differently than poly fibers when heated. They melt, but not nearly as easily as plastic ones.

Okay, so I ran out to the garage and got some swatches of cloth and started doing my "optics" experiments. Here are my results. They're a little backyard scientist but hopefully you can be inspired to try your own gentleman scientist project with a laser pointer and see the effects for yourself. I really wasn't able to capture the beautiful interference patterns I can see IRL with my digital camera but there is some indication of the difference between Filti and other common cloths.

I taped a sheet of copy paper to my bathroom door. I shined a green laser pointer through the cloth from 1m back and projected the transmitted pattern on the door. I clearly observed an interference pattern. Kind of a generalized double slit in 2D. Basically a grid of holes in a plate. The image is not shadows. The bright spots are caused by interference effects of the laser's coherent light interacting with itself as it exits the holes on the opposite side of the cloth. I took photos with my cheap camera 1m back. In theory, the pattern is related to the pore diameter and spacing.

the setup
Image

cotton bedsheet. strong x-y repeating interference pattern consistent with weave. lots of light transmission in the middle because cloth is thin. easy to distinguish bright spots (intensity maxima and minima)
Image

cotton t shirt. anisotropy of pattern not as regular as the bedsheet. but you can still observe woven pattern creating interference.
Image

walmart melt blown poly shopping bag. the pattern is more or less regular. not showing a preference in the x or y direction like the woven cloth. the fiber matting is more or less random in this weave. I still see minima and maxima but not as clearly as the woven cloth.
Image

filti. advertised N95 equivalent. Note no hot spot in the middle. This cloth lets less light through in general. less interference pattern if any at all. I see smaller spots that are fuzzier and blended together which I interpret as smaller holes approaching the Rayleigh limit and likely tighter spacing of the holes. This eliminates the interference pattern seen on the woven cloth.

Image

Again, hard to see in the photos but easy to replicate at home with your fabrics. cool things you can do with a laser.

This isn't meant to be a quantitative measurement but I think it has some value for doing relative comparisons between different fabrics for filtering ability. Easy to try for yourself. My camera cannot do justice to the actual pattern projected on the door.

edit - finished my lockdown lunch and decided to try to get some better images using a superior camera. I moved the laser and cotton fabric back 2m from the screen and got this image. Took a close up. You can really see the fringing in this image. This is dense cotton quilting fabric. The laser punches through makes a beautiful aperture array interferogram.

Image

I tried the same setup with Filti and just get green fog. No fringes. No pattern whatsoever. Looks just like a blown up version of the Filti image above...no structure. There are a number of explanations, the distance between holes is much smaller than the distance to the projection screen, the holes are so small we are not getting any smearing in the image - i.e. Fourier transform of narrow window makes a wide intensity pattern on the screen...I think this is called Rayleigh limit after the guy who discovered it. All point to Filti being a well engineered fabric for lots of perforations and small ones to boot. There is a huge material difference between conventional fabrics and purpose built filter cloth.

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Sclass
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Re: Sewing simple cotton masks

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Ohh man. This.

https://youtu.be/3XE3OgcgXyE

I’m playing home lab and then I find this on YouTube. This is why I cannot form an interferogram with Filti. There is no straight path through it. It just looks like a translucent piece of plastic in front of the laser. The cotton quilt fabric has holes like Swiss cheese or a window screen. By the time the light gets to the other side of the Filti the coherence is reduced by transmission through the tangle of clear fibers. The electron micrograph in the video says it all. Trying to get a fringe pattern on Filti is like trying to X-ray crystallography on glass. Won’t work.

Not sure what this all means for a QC method using interference. I guess one can see the difference between a Walmart polypropylene bag vs. quilters cotton. But Filti is the show stopper. It’s all over eBay in small sheets now. It maybe worth the money if you’re going to sew masks.

I do find Filti a little bit laborious to breathe through. The blue paper towels were worst in this respect. I ended up using mine to clean my garage after they nearly suffocated me.

One day my shock cord will arrive from China and I’ll make some more masks.

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Re: Sewing simple cotton masks

Post by jennypenny »

I love the filti. It's so much better than inserting other makeshift filters. It adds a little bulk but I'm able to sew over three layers (outside, filti, liner) including the pleats with no problem. I don't have trouble breathing through it. The only slight issue is that it's a little hard to bend the filti layer with the pipe cleaners I've been using as the nose piece. It works, it just takes a little more effort.

I don't think you have to sew the filti into the mask. The ends don't seem to fray. I think you could cut pieces to work as inserts into pocket-type masks. That way you don't need as much fabric.

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Sclass
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Re: Sewing simple cotton masks

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Finally my shock cord arrived from China. It took 3 months and the pandemic is already nearly over. Not really, heh...the infection plots knocked my socks off this morning. Just when I thought it was safe out there. So I have my Filti for the inside, Walmart shopping bag for the outside, shock cord and cord locks. Stainless steel wire for the nose bridge.

I decided to use stainless steel wire for the nose bridge. Harbor Freight lifetime supply for $7. After cutting with wire cutters I needed to grind the little sharp point off with a file. I didn't want this poking through the mask. The nose wire is critical for getting a good seal around the nose and cheekbones. I see a lot of fabric masks out in town and they have a big gap at the nose. No good for aerosol protection. It doesn't matter what kind of high tech cloth you use, big leaks defeat the mask.

The elastic shock cord is also a lifetime supply @ $12/100m roll. It'll disintegrate before I use it all. I'll have to come up with uses for it. Funny I was down at Walmart and the sewing section has elastic cordage back in stock. It is specifically labeled "for DIY masks". I like strapping the mask behind the neck and head like a professional N95. Then I put a cord lock on for tension adjustment. This helps with the seal. It is uncomfortable but effective.

I guess same for the Filti. Bought too much. I made six masks and used less than a yard. I have several yards because I bought the $30 roll which was the smallest at the time. Thankfully it is incredibly light and I've been sending it in the mail to friends around the country who got caught without masks. I can send about two sheets 8.5"x11" sheets in a business envelope for surface postage. The Filti layer is just sewn as the inside layer. I was thinking of doing the pockets/replaceable filter thing but the Filti is cheap enough that I can dispose of the entire mask periodically. I use a non toxic kid's glue on the inner seams to seal leaks because the needle and thread open up some pretty big holes in the fabric.

For the outside I use blue Walmart shopping bags. I think these cost me $0.99 while I shop. Cheap enough. They are blown polymer fiber bags with no weaving. Some people are using them as filters but I think they are too porous. It is much more breathable than the cotton bedsheet material I was using before. Together with the Filti it is extremely breathable. Much better than the masks I posted earlier in this thread. The outside layer is kind of glossy and may offer some abrasion and splash protection. I should check it for water repellency.

The permeability is crucial. First it makes the mask less exhausting to wear. Secondly it lowers the pressure drop across the filter material which will discourage the air from taking easier paths around the face via leaks.

So here are some photos. I made 6. It was a nice afternoon project. I will be using these as the disease winds down. I don't feel comfortable in public with the rubber industrial respirators I usually use. They're effective but I get a lot of funny looks.

elastic shock cord

Image

nose bridge wire and tools

Image

Inside of mask. Filti HEPA cloth.

Image

Outside of mask. Walmart shopping bag.

Image

My workstation.

Image

Drying the kid's glue.

Image

mask

Image

tsch
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Re: Sewing simple cotton masks

Post by tsch »

Has anyone decided on a protocol for how much re-use or cleaning they do with the Filti material? On the Filti site they seem to recommend these guidelines:
https://www.cdc.gov/coronavirus/2019-nc ... ators.html

While working on my second batch of masks, I decided to try doing a removable Filti lining so I could just replace it when I want to launder masks. (totally agree w/jennypenny, the edges of the Filti don't seem to fray).

But it occurred to me that maybe I should just make single-layer Filti masks and re-use the cord and nose wire when it's done. Might be a situation where disposable (after many hours of use) might be reasonable. And one later of Filti for summer sounds pretty good. Am I missing something?

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Sclass
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Re: Sewing simple cotton masks

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I’m treating my Filti masks as disposable. The only major cost is the time to sew one. I like the security of he sewn in panel rather than the filter pocket. Just a feeling, but I trust it to seal better than the sheet slipped in a pocket.

As for cleaning I don’t plan on doing it. Contaminants will get trapped in the mesh and won’t likely rinse out easily. Using heat may kill the virus, but it may damage the very small fibers in the cloth. If you look at the electron micrograph I posted the fibers look like they’ll just melt away if exposed to any hot air near the melt point of poly propylene. The fibers are very thin and don’t have much mass. They’ll be gone in a blink and you have no way of knowing they’ve coalesced into useless blobs if plastic.

A single layer mask is a great idea. I’m toying with hot gluing the seams rather than sewing. It may be faster and more effective than sewing. It’ll be ugly but an easier to make mask is easier to throw out periodically.

Maybe you’re right and the two pieces shouldn’t be sewn together. It may not matter. Think of it like wearing two masks...one atop the other.

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Re: Sewing simple cotton masks

Post by tsch »

Thanks! Hot glue is a good idea. (And thanks for posting those optics experiments a while back, very cool!)

My latest two trial masks were two layers of cotten fabric, sewn, with Filti in between as a removable layer.

Image

I used the Brittany Baily pattern, but hemmed the sides separately to be able to insert the filti layer. The result is usable for quick stops shopping and stuff, but I think too thick to wear comfortably for a long time or with any exertion.

But what about a fabric outer layer, nicely sewn and easy to launder—with a Filti layer tacked in along the edges. Easier to keep together for a while. I wonder if careful and minimal hot-glue could be peeled off. But then it would be almost as easy to just do a fast running stitch around the edges to put it in, and pull out the stitches when it's time to wash the outer layer and discard the used inner layer.

I do like the cotton outer layer for most situations. Long term looks tidier (there's no point in me wearing white anything.)

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Sclass
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Re: Sewing simple cotton masks

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@tsch nice mask.

I noticed the Filti is very easy to breathe through. It occurred to me that the outer layer of the mask serves for abrasion protection, structure and decoration. To protect the fleecy outside of the Filti, perhaps using another sheet of Filti just reversed so the shiny side pointing out will serve as an outer layer? The fuzzy side tends to catch on things. My guess is it’ll be easy to breath through. A double layer Filti mask may filter better too. I have notice that the Filti is really strong fabric while trying to tear up scraps. Light too.

An entire mask sewn from Filti in other words.

I’ve been sewing then gluing the seams to seal them up. I’ve seen some videos of people using hot glue. Some others are using heat sources like soldering irons and flat irons to fuse the materials as well. I recall seeing somebody using an ultrasonic welding device too. It just made me realize that sewing may not be the best way to construct the masks. It’s just the easiest and most convenient way.

Last night I made up a few masks for my wife. Her face is smaller than mine and the pattern I had used was too lose. I made some modifications to the original and it worked well. A couple of things I learned were to just bend the wire ends over instead of blunting them with a file. Also I stitched in the wire channel before putting in the wire. In the past I stitched around the wire and had a tough time stitching straight as the wire and mask squirmed around under the presser foot. And I broke a needle too when I struck the wire accidentally. It is a lot easier to install the wire after stitching the mask.

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