Question: Coronavirus & home sewn masks?

So, I went to my sewing box this evening to see what fabric I had - very little, it turns out, as I think most of it is in storage. The only piece I have is a long strip of cotton which is about an inch (aka 2.5 cm) narrower than a standard disposable surgical face mask, so I assume that's not really going to give enough lateral protection. Do you think I can machine-stitch 2 pieces together to make it wide enough (bearing in mind that I also need to make a lot of pleats), or would the seam be a weak point, virus ingress-wise?
 
Wits_End said:
Do you think I can machine-stitch 2 pieces together to make it wide enough (bearing in mind that I also need to make a lot of pleats), or would the seam be a weak point, virus ingress-wise?
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You could use the sort of seam used in jeans and pyjamas. I've just looked it up and it's called a flat felled seam, and there are lots of videos showing how to do them. The downside is that would make that part bulkier, so might make pleating across it more difficult. Would it be better to use the strip the other way around, so the seam goes across it - then it wouldn't interfere with pleating?
Am I making any sense?

Edit: or how about, instead of looking at new fabric, cutting up an existing garment or a teatowel?
 
Here's a question: I have a few of the surgical masks. A few weeks ago, a social worker I know told me these are only good for 4 hours and then should be tossed. This morning I washed a number in very hot water and soap and they are now air drying. I actually wear a surgical mask, and then on top of that I have a cloth mask which I have sewn which provides a nice tight fit. So here's the thing: are these surgical masks still effective when washed?
 
Perrier said:
Here's a question: I have a few of the surgical masks. A few weeks ago, a social worker I know told me these are only good for 4 hours and then should be tossed. This morning I washed a number in very hot water and soap and they are now air drying. I actually wear a surgical mask, and then on top of that I have a cloth mask which I have sewn which provides a nice tight fit. So here's the thing: are these surgical masks still effective when washed?
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I don't know of any data on that and there probably is none. But I think you can be pretty sure that unless you can see through them more they will still prevent a high proportion of virus particles getting into public space if the wearer speaks or coughs. As to whether or not they would protect the wearer I think that is much more doubtful but if it were me and the only option I would still wear one.
 
Perrier said:
Here's a question: I have a few of the surgical masks. A few weeks ago, a social worker I know told me these are only good for 4 hours and then should be tossed. This morning I washed a number in very hot water and soap and they are now air drying. I actually wear a surgical mask, and then on top of that I have a cloth mask which I have sewn which provides a nice tight fit. So here's the thing: are these surgical masks still effective when washed?
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Check out Ian Lipkin's interview*; they were investigating whether washing masks at "56 degrees centigrade for 30 minutes" would be enough.
I assume this is based on the following data from WHO [https://www.who.int/csr/sars/survival_2003_05_04/en/]
"Virus survival in cell-culture supernatant

  • Only minimal reduction in virus concentration after 21 days at 4°C and -80°C.
  • Reduction in virus concentration by one log only at stable room temperature for 2 days. This would indicate that the virus is more stable than the known human coronaviruses under these conditions.
  • Heat at 56°C kills the SARS coronavirus at around 10000 units per 15 min (quick reduction)."
Personally I'm not sure why they are looking at 56 degrees centigrade for washing masks --- why not heat them to a higher temperature (say 74 degrees) for a shorter period of time?

I hadn't noticed the stability of the virus at 4°C (fridge temperature!) "Only minimal reduction in virus concentration after 21 days" @Jonathan Edwards
Anyone got reliable data for stability of virus on food e.g. fruit such as pears! I might be peeling them after reading the above data, regarding the stability of the virus, from WHO!

Interview with Ian Lipkin:
51.30 minutes
56 degrees for 30 minutes
*http://www.microbe.tv/twiv/twiv-special-lipkin/

 
Jonathan Edwards said:
I don't know of any data on that and there probably is none. But I think you can be pretty sure that unless you can see through them more they will still prevent a high proportion of virus particles getting into public space if the wearer speaks or coughs. As to whether or not they would protect the wearer I think that is much more doubtful but if it were me and the only option I would still wear one.
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Well, that's vaguely what I've been wondering for weeks. If, as recommended, I were to bag it immediately after wearing, but then leave it for, say, a good couple of weeks to see whether I develop any symptoms and nothing happens, presumably I could assume that either I didn't have Covid and therefore there are no contagious germs on the mask, or there are, but they've evaporated or whatever they do in the meantime. Presumably any moisture on the mask will have dried out by then. Is there really any reason why you shouldn't re-use it in a casual situation like just being outside? Is there a flaw in my reasoning? I must admit that it had never occurred to me to risk washing them, because I didn't think they would withstand it.
 
Trish said:
You could use the sort of seam used in jeans and pyjamas. I've just looked it up and it's called a flat felled seam, and there are lots of videos showing how to do them. The downside is that would make that part bulkier, so might make pleating across it more difficult. Would it be better to use the strip the other way around, so the seam goes across it - then it wouldn't interfere with pleating?
Am I making any sense?

Edit: or how about, instead of looking at new fabric, cutting up an existing garment or a teatowel?
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Yes, that occurred to me in the wee hours of the morning, when I was lying there unable to sleep. I think I can probably remember how to do them after my Home Economics teacher drummed it into me decades ago. Existing garments would be mainly of the T-shirt type, I think, and therefore less useful than a cotton weave. Alternatively an old pillowcase or something, but those are usually polycotton, which again might not be as good.
 
FMMM1 said:
Check out Ian Lipkin's interview*; they were investigating whether washing masks at "56 degrees centigrade for 30 minutes" would be enough.
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I think Lipkin is addressing a different issue from the one @Perrier raises. If there is virus on a mask washing in hot water may kill the virus but the mask may no longer be any good as a filter. That would certainly be a worry for some of the disposable materials. I don't see it as much of a worry for shirt material. On the other hand I agree with @Wits_End that there doesn't seem a to of logic in washing masks. I am not washing the one I have used whenever outside in public for a fortnight or so.
 
Putting my biologist hat on for a moment, I agree that air drying for several days could be a good alternative to washing, and that re-use of medical masks should then be safe. And it seems this is backed up by the various tests done on materials and virus survival.

However the concept of “bagging” masks up concerns me. Leaving the masks in a plastic bag might prevent them drying fully, and so allow other nasties to grow. So the masks are probably best left unwrapped (or wrapped in a fabric bag), so that mould or bacteria don’t get a chance to grow in the damp!
 
Jonathan Edwards said:
I don't know of any data on that and there probably is none. But I think you can be pretty sure that unless you can see through them more they will still prevent a high proportion of virus particles getting into public space if the wearer speaks or coughs. As to whether or not they would protect the wearer I think that is much more doubtful but if it were me and the only option I would still wear one.
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Yesterday on newsnight they had a care worker on who was talking about wearing the same mask all shift (and possibly multiple shifts) the doctor (it's hard to know if the experts really are experts!) who they asked talked about the masks being good for about 5 hours as they degrade and get damp etc. But that was for someone who was a care worker in close contact with people, I suspect the use of a mask where people are keeping a distance in a more general situation will be quite different in requirements (and acceptable performance).
 
Sly Saint said:
couldn't you do them in a microwave oven?
https://regenexx.com/blog/coronavirus-episode-12-does-a-microwave-kill-coronavirus/
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If you mean putting the mask in the microwave oven, there might be a problem unless you also put something containing water in the microwave too. And the mask itself may not actually heat up unless it is wet. As I understand it the microwaves act by heating up water molecules. If there aren't any, as when you switch a microwave on with nothing in it, it can destroy the microwave oven - I did it once. It went bang and stopped working.
From my trusty friend google:
If you microwave plain clothes such as cotton T shirts there will be almost no effect and but you can cause the oven to fail since there is no load to dissipate the microwave energy and it might self-heat the microwave tube (magnetron).
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Edit: I wonder whether you can iron a mask.
 
Trish said:
If you mean putting the mask in the microwave oven, there might be a problem unless you also put something containing water in the microwave too. And the mask itself may not actually heat up unless it is wet. As I understand it the microwaves act by heating up water molecules. If there aren't any, as when you switch a microwave on with nothing in it, it can destroy the microwave oven - I did it once. It went bang and stopped working.
From my trusty friend google:


Edit: I wonder whether you can iron a mask.
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This a Blue Peter, don't try this at home one!

Take a saucepan of water at 74 degrees centigrade and an electric slow cooker. Place mask on the base of the slow cooker and put the saucepan on top. Turn on the slow cooker. Maintains the heat at about 74 degrees centigrade for a while i.e. to try to kill the virus.
We don't have results of tests which kill the virus at different temperatures, so we don't know if this works.
 
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