Masked and Anonymous

There’s no way I’m the only person who has had this idea. But I don’t see a lot of talk about it, so it seemed like it was worth exploring.

Breath masks are not 100% good for anything, we are told, and viruses are much smaller than most filters catch – but the mask might catch inbound or outbound droplets and that could make all the difference. 0.3 microns is the upper end of useful, and that’s the range HEPA (High Efficiency Particulate Air) filters are designed to catch. So, I believe that puts HEPA filters into the “might be useful” category.

That’s a central air recirculating system filter pack; there’s a huge stack of them for sale at the hardware store, $20 a pack. It’s a .3 micron filter (but the packaging is a bit dodgy about how well it is expected to perform at that size) It’s designed to catch pollen, cigarette smoke, very small bugs, and droplets that some virus sufferer coughed into the air near you. I’ve used these filters before, for a bunch of things (filtering silver nitrate before I switched to my vacuum filtration system with the bucholtz flask) – they’re just hot glued into the cardboard frame and you can de-frame them in seconds.

After that, you grab your glue gun and some string and you have a HEPA mask.

The air conditioning filters are really great to work with because they have a mesh of fine aluminum wire embedded in the layers, so you can shape it and it’ll keep its form. I realize it looks like crap but the air was only coming through the filter and not around the edges. So, that’s a win.

There’s another good source of HEPA filters and that’s vacuum bags and vacuum pre-filters. This is a pre-filter from my old Filter Queen(tm) vaccum that died and was gotten rid of years ago. Naturally, I still have the pre-filter because I’m a packrat.

I feel a bit bad about this; I really just threw it together. A bit of hot glue on the top, and glue the sides to the bottom, then add a string. I appear to have misplaced my nazgûl cloak, so I just wore the jacket I was wearing while turning some wood – everything was covered in dust. So I dusted my old glasses (those are not what I normally wear) and hat and set the camera up with remote and flash sync. I was lazy with the mask, too – it’s held on with nice big dabs of spirit gum. It’s literally glued to my face. Surprisingly, with all that surface area and the very light filter material, it was very comfortable except I kept banging my “beak” into things.

A friend of mine who is involved in a “maker space” says that a bunch of the crew have been making cloth filter masks for workers who need them. Now, they are going to have pockets where you can slip a piece of HEPA material from wherever you can find it.

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I hope things don’t get so bad that I want to wear a mask to the grocery store or something like that. But, if I do, I’ve got a really nice full-face 3M chemical mask that I used to wear when I was mixing up collodion (ok, mostly when measuring out cadmium bromide) – it’s got activated charcoal chemical filters on it now but I could easily hot glue some folded HEPA material over the inlet area of the filter bodies. I also have a powered filter mask that I wear when I’m grinding lead off of wrought iron, but the fan motor makes a weird whine and it’s like having an air conditioner attached to your face – no fun in the winter.

Back in the day, I would have painted my entire backdrop sweep a nice charcoal gray to make the picture more somber, but it seemed like a waste of a half hour and a half gallon of paint just for a throwaway shot.

Spirit gum is funny stuff. I believe it’s just pine tar in ethanol. It’s got to go back deep into theatrical history. A lot of the time, these chemical formulations are hit upon and they endure far past what ought to be a sensible time. For example, why are they still using gutta percha for root canals, instead of some kind of nice, neutral, gooey silicone? When I was doing wet plate photography, I made my own varnish the way they did in the 1860s, by dissolving gum sandarac (sandalwood tree sap) in everclear – you can’t buy process ethanol in Pennsylvania because of the stupid quakers – which I had to buy down in Maryland when I visited my parents. Anyhow, it was nice to smell spirit gum again, it’s been a while.


  1. MattP (must mock his crappy brain) says

    Common air filters are not HEPA.

    MERV (not to be confused with MIRV) is a rating of how well the filter can perform down to 0.3um, but the most common filters are MERV 9~12 which only go down to 1.0um and what you’ve got is MERV 11. There have been multiple independent efforts to insert pieces of MERV13+ filter into pockets in reusable cloth masks to improve their effectiveness, and I’m thinking there were some people working to make 3D printed cages/skeletons for the filter media with silicone/TPE edging to provide a proper seal on the face. One could probably print custom-fit half-face respirators and filter holders/cartridges, but haven’t looked to see if anyone has done that yet.

    The comfy 3M half-face respirators with the bayonet/twist-on filter cartridges will already have electrostatic pleated filters with P95 or P100 rating if the cartridge is not meant exclusively for filtering chemical vapors, so adding a bit of flattened MERV11 in front of it won’t do much. Have been using a 3M 6200 half-face respirator equipped with N95 cartridges for several years when cutting grass, raking leaves, grinding, or welding as just a few minutes of mild exertion in cold dry air or heavy dust/smoke leads to several hours of wheezing and coughing with mucus filled lungs. Still not great for disease control as the one-way valves would not stop the user spreading anything they pick up elsewhere.

  2. kestrel says

    I thought Real Men used duct tape… :-D

    Very fashionable. I predict our vacuum cleaner bags are going to be re-purposed.

  3. voyager says

    Lately, I’ve seen plenty of people wearing masks, but none so fabulous as yours. Not just anyone can carry off that look, Marcus.

  4. says

    Thank you for the explanation. As you can tell, I was a bit waffly about the claims of the A/C filter. Looking at the back of the package there was a bunch of stuff about how it could catch .3 micron but it didn’t say how often or how well. That immediately armed my bullshit detector.

    My shop mask is the 3M versaflow with the pump mounted at the bottom of the mask. They run about $600 on ebay but it turns out that the cost is mostly the battery. Some fire department sold 6 of them “new in the box minus battery” for $100 apiece and I got 2. It turned out that a USB battery can drive them just fine if you pair the wires up right.

  5. says

    That looks amazing.
    Masks are mainly for protecting others. the surgeon fixing your broken leg isn’t afraid of catching a broken leg from you, they’re afraid of introducing all sorts of nasty into an open wound. Basically most people don’t know if they are Covid 19 positive and a simple cloth mask means I’ll keep all of the potentially highly infective fluids to myself. Of course that doesn’t mean I’ll reduce my viral shedding to zero, but by a lot. The one positive effect they have for the wearer is that you cannot touch your face.
    I keep wearing masks and gloves for shopping. Setting an example. Also they’re cute.

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