Repair a Broken KN95 Mask

There is a preception that the COVID-19 pandemic is winding down, at least in the USA. So we were able to get some face masks from Amazon at what I thought was a very good price (40ยข each) a few months ago. One brand worked great. We ordered more of another brand. The second brand seemed to have elastic ear loops that were very short. I broke half of them simply in the act of attempting to put them on the first time. So I decided to try and fix them. Why bother? Well, they are otherwise unused, and I like to experiment with this sort of thing.

On 4 (50%) of the masks that I tried to wear, the elastic loop broke immediately. This is not baseball; a .500 average is terrible.
The weld between the elastic and the mask itself was what failed. Light shines through the white rear filter layer.
I’m going to attempt to reattach the strap. I have a 40-watt soldering iron, a can lid to put under the weld, and aluminum foil to put over the strap as I weld it. I will position the strap and foil with my left hand, and apply the soldering iron with my right. Sorry, I can’t show it, because I’m also taking the picture.

I found that it works best to press the iron against the foil firmly, but very briefly – like 1/4 of a second. Longer, and you might burn through the whole mask. If the weld doesn’t take, you can always try again, but if the a hole is burned in the mask, you have to throw it away.

This is what the weld looks like. It was actually quite strong. I pulled the aluminum foil off too quickly – a sliver of it is sticking to the top of the weld.
And the back side.
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