Category: Making

Projects that make or build something.

Post #G14: Garden update

Source:  My garden.

If you have no interest in gardening, skip this.

Squash Vine Borer.  Looks like the SVB season is over.  I spend a lot of time walking around my garden, and my last sighting was 7/25/2020.  My first was 7/5/2020, making the SVB season just about exactly three weeks long.

My spraying regimen — I would term it spinosad with a side order of neem — appears to have worked so far.  In the sense that none of my many cucurbits is showing symptoms of SVB infestation.  Yet.  So that’s 0.008% spinosad solution (made up from concentrate), sprayed on the stems of my cucurbits every five days or so.  In the late evening, to avoid the bees.  Plus one random spraying with 100% neem (the variant that contains the insecticides, not the “hydrophobic extract” that’s just oil), more out of paranoia than from any thought-through plan.  I’ll have to keep up the spray for another week or so to account for the lag between egg-laying and hatch-out.

Powdery mildew.  I have that on nearly all my cucurbits now.  I should have been taking preventive measures, but I didn’t, so now I’m playing catch-up.

I tried baking soda (sodium bicarbonate) solution, once.  Recipe given in earlier posts.  I tried potassium bicarbonate solution, once.  Just substitute K for Na in the recipe.  If those had an effect, it was fairly subtle.

So I’m pulling out all the stops and following the hydrogen peroxide regimen as outlined on The Rusted Garden blog.  See the video above.  (Seriously, look this guy up on Youtube.  He’s in Maryland.  If you’re not envious of his garden, you’re a far better gardener than I am.)

This involves pruning out any leaves that are badly hit with powdery mildew, then spraying daily with a dilute solution of hydrogen peroxide.  (Around) 4 to 6 ounces of 3% hydrogen peroxide per gallon of water.)

If nothing else, this is certainly cheap.  A quart of 3% H2O2 is $1.29 at the grocery store, and is enough to treat my entire garden four times.  I’ll post in a few days and report back the results.

Ongoing, I’m also pruning my squash and pumpkin plants.  It never even occurred to me to do that.  (I’m kind of a laissez-faire gardener, which is another way of saying, I do as little as possible.)   But after listening the the logic behind it and seeing the results on The Rusted Garden, I’m all in.  As with the mildew issue, I’m running behind, so this will be an ongoing process.

I’m planting mid-season replacements for some of my cucumbers.  That’s another thing I’ve never done before.  To me, you plant in the spring, you harvest in the fall.  But apparently that’s not what smart gardeners do.  In this case, my Spacemaster 80 cucumbers were incredibly productive, until the simultaneous effects of bacterial wilt and powdery mildew got hold of them.  They are now such a mess that I’m pulling them out and replanting.  Apparently, with warm soil and a bit of fertilizer, there’s plenty of time to have them grow up and produce cucumbers before first frost.

Cucumber beetles and bacterial wilt.  Today I was 4/4 (attempts/kills) when inspecting my squash and pumpkin blossoms, long-nosed pliers in hand.  (As described in Post #G13).  I think that I have seen no new cases of bacterial wilt these past few days, but it’s hard to say, as it takes some time for the plant to die off.  In any case, I’ve gone from finding dozens in one pass through the blossoms, to consistently finding maybe four or five.  Tentatively, I think I’m winning.

Timing is fairly key to this operation.  The limiting factor is grumpy bumblebees.  If I get out there at 7 AM, there are bumblebees  just kind of sitting in the squash blossoms, zoned out.  My wife swears that bumblebees sleep in squash blossoms.  (Aww!)  I, by contrast, thought that was way too cute to be real.  A quick google search shows that she’s correct.  Not only do they sleep in flowers, but squash blossoms are preferred due to size and configuration, and squash blossoms provide considerable protection from the cold.  Snug as a bee in a blossom, no joke.  The upshot is that I have to wait for them to get up and go to work before I can patrol for cucumber beetles.

Tomato ripening is now occurring generally across my tomato plants.  Slowly.  My cherry tomatoes are ripening a few at a time, and some Rutgers tomatoes are finally turning pink.  Still going slowly, though, that’s for sure.

And the deer have not yet returned. As evidenced by the fact that I still have standing sunflowers, above.  On net, I’m crediting Bobbex deer repellent.  It really stinks!  I think the motion-activated radio comes in a close second (Post #G07).  I don’t know if it scares the deer, but it sure manages to scare the pee out of me every time I inadvertently trigger it.

Post #G13: Garden update

Not everything in my garden is a problem.  I just tend to talk about the issues that I’m trying to solve.  I’m attempting to achieve some balance here.  Topic below, in order, are:

  • Deer (success),
  • Birds (limited success),
  • Cucumber Beetles (apparent success);
  • Squash vine borer (possible success, possibly too soon to tell),
  • Powdery mildew (no success at all, yet, but I’ve learned to prune my squash).

Continue reading Post #G13: Garden update

Post #747: Can Kents clarify KN95 chaos? Updated

Source:  Depositphotos.com

Update 2:  This didn’t work, at all.  Not even a little bit.  See Post #790 for details.  You can’t use the odor of cigarette smoke to test mask filtration.

Update:  See postscript at bottom.  The ability of genuine N95 masks to filter smoke particles is well known and well documented.  In that light, my proposed “sniff test” for KN95 masks looks fairly promising.  To the extent that a mask reduces the odor of cigarette smoke, then it is filtering out virus-sized particles.

In Post #740, I noted that my local convenience store had “KN95” masks for sale.    I’ve heard a rumor that one of the local hardware stores is also selling such masks.  (I plan to check that out soon.)  And I exchanged emails with  neighbor who is in the process of purchasing some KN95s, from a couple of different sources, for daily wear at work.

In theory, wearing a KN95 gives you the same protection as an N95 respirator.  So, in theory, upgrading from a cloth mask or similar to a KN95 is a smart thing to do.

In practice, not so fast.  I’ve started looking into the “KN95” mask market, and it is complete chaos.  I guess that’s no surprise.  That’s more-or-less of a piece with the entire Federal response to COVID-19. Continue reading Post #747: Can Kents clarify KN95 chaos? Updated

Post #G07: With my luck, the local deer are all Garth Brooks fans.

Source:  Clipart-library.com

This is one of my occasional posts on gardening.  In it, I’m going to explain how to take an off-the-shelf plug-and-play motion sensor and turn it into flexible device for deterring deer.

As anyone who gardens in this area will tell you, deer are pests.  Cute as all get-out.  But pests, nevertheless.  And, unfortunately, either they can’t read, or they just don’t obey signs.  So unless you want to feed the local deer, either you erect some serious fencing around your garden, or you do something else to convince your local deer to feed elsewhere.

What I describe in this post is one of several deer-deterrence measures I have taken.  They seem to be working so far.  But I haven’t seen any elephants in my yard recently, either, and that doesn’t mean I’ve found a good elephant repellent.

Background

 

Source:  USDA

At the end of March, I decided to put in a big vegetable garden.  Just to have something to do during the pandemic (Post #580).

I recycled my “MAC” signs into raised beds.  Figuring, if there was no longer a MAC ordinance, I’d have to get signs reprinted anyway (Post #G05).  And that’s how things did shake out, this past month (Post #706).

 

Above, that’s the same garden, today.  Note the complete and total absence of deer!  The red arrow points to my latest deer deterrent.  That’s a trash bag covering up an indoor motion detector.  That’s what I explain next.

Making a flexible deer scarer.

There are some things that absolutely will keep deer out of your garden.  A tall and sturdy fence.  A shorter fence, if you can plant enough shrubbery around it to prevent the deer from jumping it.  A two-layer electric fence.

I didn’t want to do any of those and/or they were illegal and/or my wife didn’t want that in the back yard.  Not that I can blame her.  Nor was I willing to buy a few hundred dollars in supplies, and put in hours of labor, to produce a few tens of dollars of vegetables.

Any cheap and easy deer deterrents are likely to be, at best, partially effective.  I’m not going to run through all the commercial and home-made deer deterrents, except to say that a) there is little agreement on effectiveness of most of them, and b) the conventional wisdom is that deer will get used to just about any un-changing device designed to scare them.

I had several deer deterrents in use, and they seem to be mostly effective.  This includes Bobbex deer repellent, a Yard Enforcer motion-activated sprayer, some older ultrasonic “pest scarers” that seem to be useless and/or broken.  Liberal use of blood meal throughout the garden.  And, of course, the classic of low-end DIY deer repellents — bars of Irish Spring soap. (Manly, yes, but deer hate it too.)

I decided to add a motion-activated noise/motion device of some sort.  Just something to startle the deer as they chow down on my string beans.  But didn’t really find what I was looking for as a commercial product.  So I decided to make one.

My first attempt failed.  I tried to make one out of a cheap motion-activated floodlight.  Figured that, in place of the floodlights, I’d just put in some screw-in sockets, and then plug something into that.  But modern motion-activated floodlights are all (or nearly all) designed to turn off during the day.  Basically, a) they don’t work in daylight, b) everything that I tried to block the daylight also messed up the infrared-based motion sensor, and c) I ended up ruining the unit when I tried to drill out the wired-in cheap light sensor (literally, just an LED).

Not only did I not figure out how to defeat the nighttime-use-only problem, those require a lot of additional parts, and they require having an electrical box.  And the cheap one I got from Home Depot was clearly going to require a lot of sealant in order to be weatherproof.  And, owing to the electronics of the motion sensor, there are limits on what sort of electrical/electronic device you can control with that.  All in all, too complicated and too clever by half.  But designed for outdoor use.

Here’s what saved the day.

Source:  Amazon.com

My second attempt worked perfectly:  I used an off-the-shelf plug-and-play indoor motion sensor.  What you see above is an indoor motion sensor with a roughly 25-foot range.  It has no problem working in daylight.

As importantly, this device has no problem “seeing” right through a thin plastic bag.  So all you need to do, to use this outside, is set up whatever you are going to set up.  Then put a white garbage bag over it, to keep the rain off the electronics.

What’s more, it’s electrically bulletproof.  Some light controls used electronics to turn the lights on and off, and so have significant limitations at to the type of device they can control.  (E.g., some on-at-dusk, off-at-dawn controllers can’t deal with compact fluorescent bulbs).  But this device uses a physical relay to turn the electricity on and off (you can hear it click).  That means there are no restrictions (other than total wattage) as to the type of electronics it can control.  And it can handle up to 1200 watts.  That means you can use a wide range of household devices as noise-makers.  For example, I could plug my Shop-Vac into this.

With this part in hand and tested, the rest of the deer-scaring device is straightforward.  Put a stake in the ground where you want to use this.  Run an outdoor extension cord out to your garden, plug this in, mount it to that stake.  Plug the device of your choice into this.  (Or use a multiple tap, and plug in several devices).

Then cover the whole assembly with a white plastic trash bag. When a deer walks by, it will now trigger whatever device you have plugged in.  For the amount of time you choose.

For my first round, I’m following a recommendation I’ve seen in several places, and have hooked this up to a radio.  Then I put the radio in a small metal garbage can.  That keeps the water off the radio.  I have it set, very loud, to WMZQ.  Now when a deer tries to walk up to my beans, it is greeted with one minute of loud country music.  Which then stops.  And if they are still there, it runs for another minute.  And so on.

It’s far enough into the yard that I don’t think I’ve created a neighbor-annoyance device.  But if you’re standing right next to it, the effect is pretty startling.

The nice thing is, if the deer get used to this, I can just change out the radio for something else.  Maybe a weed whacker next time?  And there are all kinds of sound-and-motion possibilities using a Shop-Vac exhaust.  Maybe some flashing lights.  Plug in a three-way tap and operate three devices, subject to the 1200 watt limit.

Basically, anything you can plug into a standard wall outlet, and that doesn’t draw too much current, can serve in place of the radio.  Which means you can keep it fresh, for your deer.  And keep them from getting used to this deer deterrent.

 

Post #648: Instructions for making a Filtrete™ mask liner

EDIT:  See Post #807 for a vastly simpler approach to making a mask liner for a typical cloth mask.  Even if you decide to pleat it (as below), the methods in that later post are much easier than what I show below.

EDIT:  By contrast, If you want to make a stand-alone Filtrete mask (not a mask liner) See Post #780 for a better way of creating a high-quality aerosol-filtering mask.  What you see below is an OK retrofit for existing cloth masks.  But if you can find a mask that makes a good seal against your face (e.g., a 3M dust mask),  you’d be better off following the instructions in Post #780 and upgrading that tight-fitting mask so that it filters aerosols.

To see all posts on masks, use the drop-down search menu and pick “masks” as the category.

The white object above is what you are going to make.  The blue “single-use” disposable mask is there to show the size, and to clue you in that the you’re going to make a piece of Filtrete™ into something resembling the body of a pleated surgical mask.

Continue reading Post #648: Instructions for making a Filtrete™ mask liner

Post #646: Second mask liner for distribution

This white cloth above is my second and final design for a mask liner.  (The blue single-use mask is just there to show the size).

This is a piece of Filtrete 2500, encapsulated between two sheets of thin spun-bonded polyester cloth (a.k.a, floating row cover) using fusible interfacing to bind the polyester layers at the edges, then stapled to form a pleated sheet in roughly the same format as a standard surgical mask.

The idea is that you would wear this inside your tight-fitting cloth mask.  I am leaving a generous allowance of excess polyester cloth so that you can trim the edges to get the best fit to your own mask.  And so that you can find an expedient way to attach this to your own mask, in the correct position, without poking a hole in the Filtrete material.

There is no nosepiece on these.  If your cloth mask does not have a nosepiece, you should make one for it.  There are instructions for that all over the internet. You will want to position this so that the top edge of the Filtrete material is located under the metal portion of your mask nosepiece.

The pleasant surprise here is that, as constructed, this is incredibly breathable.  You pretty much don’t notice that it’s there.  (Which is, in fact, what 3M advertises about their filters.  They trap 0.3 micron particles without adding materially to the back-pressure in an HVAC system.  The MERV-13 material I have obtained, by contrast, seems to have a lot more back pressure.  So I’m going with Filtrete until I run out of it, if that ever happens.)

If , upon examination of one of these, you have any fears about inhaling a stray fiber, please attach you own thin cloth backing to the whole assembly.  This is just three pieces of non-woven polyester (or possibly polypropylene fiber).  But if the idea of breathing though this bothers you, modify it, or don’t ask for one.

If you have a mask with a filter pocket, pick out the staples and you will have a 6.75″ x 6.5″ piece of Filtrete 2500, encapsulated in spun-bonded polyester.  As long as a piece that size will do you, I don’t even have to offer something for those of you with filter pockets in your cloth masks.  Just undo the staples.

In fact, if I see little enough demand, I’ll use two pieces of Filtrete (r).  That should, in theory, capture 95% of 0.3 micron particles.  And as I said, it’s amazingly breathable, so that there seems little danger that you will breath around this, rather than through this, if you use it in a filter pocket.

For now, I’m going to advise you not to wash this material.  I know that washing N95 masks compromises there filtration ability somewhat.  I have no clue what washing does to Filtrete.  Do what hospital workers are now doing to re-use N95 masks. Drop this is a paper bag and leave it alone for a few days.  Virus particles that you may have picked up with self-destruct over time.

I need to tweak some details.  I’ll probably make this a little less wide than my single-use masks (6.75″), because I don’t want my pleats to compromise the fit of your mask.  I may also rethink the size of the pleats. But this the general idea.

The construction of these is still slow and fussy, but I’m betting I can get better at this as time moves on.  But right now, I have zero stock, and it’s going to be a while before I have a considerable supply of either of these mask liners.

If you have a mask with a tight-fitting nosepiece, this is a better option than my first mask liner.  In fact, I’m only going to offer the first one with a nosepiece, and strongly encourage people to use this design instead.  It uses less material, and it doesn’t have the cheap commercial mask material impeding the breathability of it, so, plausibly, with this design, more of your breath goes through the cloth, not around it.

In short, it’s a better design.  And, if for whatever reason, the way I’ve pleated this does not work for you, you can pick out the staples, redo it, and re-staple it.  You could probably even just tape your pleats in place.

I make no guarantees as to the effectiveness of this mask liner, if any.  I will only state that I have in fact made this out of the materials that I say I have made this from.  Most importantly, if this in any way compromises the fit of your own cloth mask, do not use it.  Minimizing air leaks is by far the most important aspect of mask use.  Better that your cloth mask filters most of your air, however it does, than that this mask liner gives you filtration that you don’t use, because it disturbs the fit of your mask.

I’m probably going to do one more variant on this that merely shapes the material into a rough conical mask, and does not have the pleats.  That would have lower risk of disturbing your cloth mask fit.  But that’s another level of difficulty.  And, frankly, I hope I am too busy making these first two designs to have the time to come up with a third.

I’m now going going to make the following offers, on some commercial platform (likely Google Forms, maybe SurveyMonkey).  I’ll set that up today and post the link here.  My offers, to Town of Vienna residents and small businesses, are the following.  You may ask for:

  • A few single-use masks, just like the blue mask in the picture above.  Trust me, when I call those cheap, it’s an insult to the word cheap.  The nosepiece, as-is, is completely inadequate, and if you use these for any purpose as stand-alone masks, you should tape a piece of wire over the embedded nosepiece and use that to shape the mask to your face.
  • A few of the white mask liner pictured above.  Unless I get feedback calling for other sizes, I’m only making one size.  It’s not difficult to make those in any size.  If you just want a piece of Filtrete, in any easy-to-handle form, for the filter pocket of your mask, order some of these.
  • A few of my first design, with nosepiece, but only for individuals who do not have a cloth mask with an adequate nosepiece.   E.g., if the only thing you’ve got is a bandana, order that one, and wear your bandana over it.
  • If I fall behind, I’ll start offering these as kits.  I’ll give you the parts, you do the pleating and the stapling.

If you don’t want to take some for free, please donate some money to some Vienna-oriented charity.  My best guess is that (e.g.) the economic situation for local small business is not going to improve any time soon.

I’ll have an order form up as soon as I can figure out how.  I’m not going to put it on this website because I realize that lot of people don’t much like what I’ve had to say, and I don’t your dislike of me to stop you from asking for one of these.  And if you know any Vienna business that still have public-facing employees (i.e., not delivery people, but anybody who has to talk to customers in person), consider pointing them to this order form.  When I figure out how to do it.

Again, I make no claims or warranties as to effectiveness.  Use at your own risk.

Christopher Hogan, Ph.D.  chogan@directresearch.com

Post #644: First mask liner for distribution

This is the first model of “mask liner” that I am offering to anyone in the Town of Vienna who would like them. I will go learn Google Forms tonight and set up a form for requesting these, tomorrow.

The base of the mask liner is cheap commercially-made “single-use” mask, not suitable for use by hospital workers.  That’s the blue mask pictured above.  I then pleat a piece of Filtrete (plus thin cover cloth) and staple that over the outside of the mask.  Finally, I add a stiff full-length metal nosepiece in the form of a galvanized wire.

Here, so as not to waste the Filtrete, I used a piece of printed cloth.  The actual masks will be plain white on the outside.

My intention with making mask liners is that you would wear this under your regular cloth mask.  The small size and weak elastic makes these potentially quite “leaky”, and this really should be used with a tight-fitting cloth mask pressing this against your face.

In an emergency, you could wear this as a mask, by itself, but that’s inadvisable due to the potential for air leaks.  If you were forced to do that, you would be well advised to add a couple of pieces of string to the loops on the nosepiece, then tie those behind your head and pull this more tightly against your face.

Surgical-style masks like these are compromised by air leaks, so the nosepiece is important.  If your existing mask has a good metal nosepiece and fits snugly against the bride of your nose and cheeks, order the version of the mask liner that does not have a nosepiece.  The additional nosepiece will just be in the way.  And wear this so that this mask liner is held snugly to your face by your existing mask nosepiece.  If you have a mask that lacks a good nosepiece, then order the version of the liner that includes a nosepiece, as pictured above.

I make no warranties as to how well these work.  I make no warranties that they work at all.  You use these completely at your own risk.

The theory behind this is that it should help filter out smaller particles, of a size that cloth mask is probably unable to filter well, if at all.  In particular, Filtrete 2500 claims to catch 77% of particles down to 0.3 microns.  Two layers should, in theory capture 95% (but I have not tested that yet for breathability).

Surgical masks do not seal to the face the way respirators do.  No matter what you do with a surgical mask, short of literally taping it to your face, you will breath some unfiltered air.  And the harder it is to breathe through the mask, the more air will go around the mask.  So I have tried to keep this as breathable as possible.

These take longer to make than I had hoped.  So I’m not sure how fast I can make them. At some point, if you have a stapler, it might be more expeditious for me to mail these out as kits, rather than assembled.  All you need is a stapler, four clothespins, and (if you need the nosepiece) a few pieces of high-quality tape.  I would supply the rest.

Do not wash these masks.  Washing reduces the filtration ability of most high-quality filtering material.  You should treat these masks exactly as hospital workers now treat N95 respirators for re-use.  Wash your hands, carefully take it off your face (without touching your face), drop it in an open paper bag, and leave it for a while.   The virus self-destructs over time.  How long is a while?  If you are phobic, leave it for three days.  Otherwise, two days.  So if you plan to be out every day (which I think is bordering on crazy unless your job requires it), you’d want two of these, to use in rotation.

How long will these last?  I suspect that the elastic will break early on, but as long as you are using these under a tight-fitting cloth mask, that’s just a nuisance.  The filter material should be good for hundreds of hours of breathing, but I have to do a calculation to determine just how long it should last (based on the rated lifetime of the original filter assembly, and so on).

My intent here is that this would be used when (e.g.) on a weekly shopping trip.  Or when going to the doctor.  I don’t really see these as suitable for use on an 8-hour shift, day after day.  I don’t think they’ll last that long, owing to the generally cheap construction.

I’ll have the form up tomorrow to allow you to order this, or order a kit of materials to make these, or just order up a piece of Filtrete, if you have a cloth mask with a filter pocket in it.  Likely, I’ll ask you to pick your up off my front porch.  If you’re hesitant to take this as a gift, then donate a few dollars per mask to some worthy Vienna-centric charity.

Whether or not Filtrete will work, as advertised, in this case, is purely an act of faith.  For all the world, the stuff looks like a pleated piece of paper with some fibers on one side.  But you have to trust something.  I trust 3M.

That said, you get no guarantee from me.  It should work, but there is absolutely no way to test that, under the circumstances.

Finally, extra points for any old-timers who recognize the brand of tape measure.  Ya’ can’t hardly get those any more.

Post #___: Expedient masks, part 4: My niche.

Source: 3M

You can find numerous plans for sewing a mask. I’ll present one below, from Instructables, that I like for its simplicity and efficiency.  And for the fact that I see that other like-minded people also point to that design.

And I do, in fact sew.  I own a sewing machine.  And I do … big stuff:  slip covers, drapes, and so on.

Which, if you really know sewing, gives away the fact that I’m not good at it.  I could not set a zipper if my life depended on it.  I think Velcro (R) is God’s gift to  mankind the ham-handed.

And I now am hearing that a lot of people that don’t sew.  Doesn’t surprise me, really.  But we have an army of unemployed people.  So I’m making it my mission to help the sewing-challenged.

This is America, folks.  Think Apollo 13.  Have you never asked yourself, why in the world did NASA sent a roll of duct tape to the moon?  Can you even conceive of what it cost to do that?  And they planned on bringing it back?  They can eject an entire Saturn V first stage to self-destruct in the atmosphere, but the friggin’ duct tape had do be able to make the entire round trip?  Do you have any notion of what it takes to get a pound of material to the moon and back?  (Let alone a kilogram, which is why America had the best space program, right?)

I digress.  Got duct tape?

My role for the next few days is to put together a few high-protection masks, for the maskless, with minimal sewing.  Duct tape, 3M products, furnace filters, and such like.  Because, if you’ve been around, you know that if it’s 3M, it does what it says it does.  May not be the cheapest, but clearly the best.  This is no time to screw around with generics.

So this is the mask blog for rednecks.  Or maybe old rednecks.  If you don’t sew, but still occasionally refer to the big hardware store at Fairfax Circle as Hechinger’s, you’ve probably found the right place.

If mainstream America has the comfy fabric-store masks, what you’re going to get here is your basic hardware-store mask.  I aspire to channel Hyneman and Savage for the next couple of days.  WWMG.  What would MacGyver do.

But with the serious and ultimate goal of producing an N95-equivalent mask. 

Trust me, if you want comfortable masks, go with something that somebody sews.  So this may or may not be the most effective source for mask plans.  The best mask is the one that you’ll wear.

But if you’re among the paranoid — and, seriously, that’s hard even to define these days — even the most nervous of nervous Nellies would accept an N95-equivalent. Even if it’s ugly, and really not a lot of fun to wear.  And maybe then they’d leave the real ones for the pros who need them.

So I’m going to do non-sewn masks.  That’s what I see as the unfilled market niche.  These will not be as comfortable as sewn cloth masks.  They are going to be every bit as much of a pain in the … face as real masks.  But they are going to be a lot more scientific.

Tomorrow’s task is to replicate a 3M 8511 mask, from MERV-rated cloth and … not sure what else.

Got any good ideas, within what I have outlined above?  Email me:  chogan@directresearch.com

Post script:

Here’s what I believe to be the best sewn mask I’ve come across so far.  FWIW.  When I saw another MERV-mask maker mention this, I knew it was the right design.  Note that she has a design with a pocket for a filter.  So, if you have a high MERV filter at home, you could plausibly get the best of both worlds with this.  I find this an admirable design due to its simplicity, depth of face coverage, and attention to critical details like the nosepiece.  If you don’t have elastic at hand, think something like kitchen cotton twine would probably work.

Source:  Image used without permission, for which I apologize.

  • Mask 2:  DIY Cloth Face Mask.  By
  • Cloth:  Tightly woven cotton or cotton/poly.  Cotton recommended.
  • Layers:  2
  • Ties:  Elastic, over ears.
  • Metal noisepiece:  Yes, continuous wire, sewn in, floral wire or other thin wire.
  • Design:  Single piece of cloth with elastic feed through “drawstring”-type channels at side.
  • Methods/skill level:  Knowledgeable craft sewer.
  • Steps:  14
  • Number made:  73
  • Interesting quote:  “Surgical masks and some cloth masks will block 7 micron particles.”

Post #595: Expedient masks, part 3: Expedient mask prototype

Rapid conversion of dust masks to MERV-8, proof of concept.

 

I just heard that the Mayor of Los Angeles has asked everyone to wear masks in public.  So, now more than ever, we need effective masks for everyone.  I reviewed what’s for sale, and a) it ain’t much, and b) likely, most of it is gone by now.

Just breaking:  Looks like the CDC is finally going to issue guidance to wear masks in public.  Thank goodness.  I’ve just been told that Laredo, Texas will now fine people for being in public without a face covering.

Maybe the Army Corps of Engineers can produce and distribute a few optimized mask designs, with the idea that its within their mandate as sort of reverse Roemer’s Law.  A bed not filled is a bed not built.

In Post # 593, I showed the key tables from a scholarly article on home-made respiratory masks.  That analysis looked at the air-filtering properties of various types of cloth.  And, in fact, you could achieve particle filtration equivalent to a surgical mask, merely by using two layers of tightly-woven a tea towel.  But that two-tea-towel mask would have generated much higher back-pressure than a surgical mask (i.e., hard to move air through it).  That would have resulted in moving a lot of air around the mask (at the edges), rather than through the mask.  So, likely, you’d end up inhaling significant amounts of unfiltered air.

Return to Post #593 for the discussion MERV standards for air filters.  There was a reason I included that.  Some people (and other people) (and even some doctors) (and some nurses) have already come to the conclusion that the obvious material for home-made masks is the fabric inside of furnace air filters.

At the end of this, I’m going to make something that I think is obvious.  Take a dust mask — one with no guarantee of filtration at all — and tape a piece of MERV-8 cloth over it.  That should provide excellent protection against droplet transmission.  The shape of the face seal is formed by the factory-made dust mask, and is far better than I could achieve by hand.  The filtration is performed by the MERV-8 material, which should be adequate for droplet protection.  It uses a minimal amount of the MERV material.  I believe I could get this down to maybe — well certainly under 5 minutes a mask.  And if I can swap out MERV-16 for MERV-8 and still breathe through it, the same techniques would allow me to mass-produce N95-equivalent masks.

Seriously, I think this is a way to help solve America’s current shortage of masks for the public.  So this is my last plea:  If you know someone in a position of responsibility, please pass this along.  Because this way, not only do you have a mask that protects others.  This way, if I up the MERV level, you have a mask that protects you.  Using filtering materials that are outside the hospital supply chain. 

And if you can suggest ways to do this better, or have an idea for a better design using MERV-rated furnace filters, email me (chogan@directresearch.com).

Let me now list the advantages of the MERV-based mask.

  1. It has a known level of filtration, the MERV rating.  With cloth, you have to guess.
  2. You can achieve a N95 level of filtration with a (rare) MERV-16 filter.  This would provide protection against aerosol (airborne) transmission.
  3. You can filter out some small droplets with a MERV-8 or higher.  This would provide protection against droplet transmission.  You can get almost all of them with a MERV-13 or so.
  4. Most American homes have some supply of these in the basement, so there is a large supply of this material readily available and already distributed to homes.
  5. The only tool required to extract the cloth from filters and work it into shape is a set of common household shears.
  6. The MERV-8 cloth is easy to work with (well, sort of), if somewhat fragile.
  7. FWIW, except for Filtrete (R) filters, I believe that the material in MERV-rated furnace filters is in fact melt-blown cloth, the same stuff that is in masks.

And so, while I could talk about how to sew a cloth mask, for that, I think I’ll just just put that off, for the time being.  At some point, that will come back into play, because I would need sewn bodies for my MERV-based masks.  But for now, let me just convert a dust mask that I have, and see how that works out.

I’m not even going to review MERV.  Refer back to Post #593 if you want to brush up on it.  For now, you’ll just have to take me at my word that MERV-16 requires 95% removal of particles down to 0.3 microns, in one pass.  Just line N95.  And we can work backwards from there.

For the record, I know MERV-8 ain’t great.  You can see the specs here.  But its what I happen to have.  MERV-8 only guarantees to trap 70% of particles between 3 and 10 microns in size.  And only 20% of those those 1 to 3 microns.  (Aerosols are those 5 microns and below).  But a MIRV-12 — readily available for home use, traps a minimum 90% and 80%, respectively.  And, you can double up the fabric, get two passes, and presumably raise those to something like 99% and 96%, respectively.

(And MERV-16 is basically the same spec as N95:  It gets 95% of particles down to 0.3 microns.  But I just got my hands on a MERV-16 filter, and I don’t think I could breathe through the material..)

So this is a proof of concept.  I.e., I’m wrecking a relatively low-valued MERV-8 filter.  Once I’ve fine-tuned this, I’ll move up the MERV scale.

Section 1:  Converting a MERV-8 pleated filter, and common dust mask, to a MERV-8 mask.

You’re going to take a standard home air filter, MERV-8, cut it out of its casing, leave the wire backing in place, cut out a rectangle, mold it around a common dust mask, trim and tape in place overtop the dust mask.  Then replace the elastic with something more substantial.

Tools and materials:

  1. MERV-8 or better home air filter
  2. Kitchen shears, large scissors or similar
  3. Sharp razor blade (optional)
  4. Packing tape, duct tape, Gorilla (R) tape, or similar.
  5. Piece of cord (shoelace, parachute cord, kitchen twine, garden twine).

1  Remove the filter from the cardboard casing, taking care not to damage the fabric.

You can’t peel them out without damaging them.  I learned that the hard way.  Take a pair of scissors and cut them out, cutting right through the metal mesh on the back.

On mine, the carboard on the face was randomly glued to the fabric.  Don’t pull that off.  For now, just cut around it, leaving chunks of cardboard on the fabric surface.  You can cut them down later, and either leave them or carefully get them off the fabric with a sharp razor blade.

Step 2:  Roughly flatten the fabric and wire assembly.

Leave the wire mesh attached.  I tried removing the fabric from the wire, but a) it was tedious and b) being as careful as I could be, I was still damaging the fabric.  I would prefer to work with the fabric alone, but that’s not gonna happen.

Step 3:  Cut roughly to size.

Carefully roll the mask in one direction, mark, then roll it in the other dirction, and mark.  Give yourself maybe a half-inch seam allowance all the way around.

Step 4:  Roughly shape the filter material by wrapping it round one fist.

Check for fit against the mask shape.  Fine-tune as needed.   Avoid creating “folds” in the material, to the extent possible.  I have a large fold at the bridge of the nose that may, to small degree, compromise the filtering, but … when I look at it, it’s not obvious that it does.

Once you are comfortable with the fit, trim the excess.  It’s OK to be a bit sloppy because you’re going to cover the joint between the two materials with plastic tape in the next step.

Step 5:  Attach the filter material to the dust mask.

Lay down a ring of tape on the mask seal.  This is just small pieces of high-quality tape.  It’s important that these overlap a bit, because these are going to become, in effect, the new mask seal.

Lay the dust mask into the shaped filter/mesh assembly, start in one place, and tape it all around.  When you are done, take a couple of strips of tape about 1″ wide, and just tape your way around the circumference of the mask.  Just to stabilize it, and make sure it sticks.

Step 5:  Replace the elastic with a cord of some sort.

Knot the cord, tape it to the mask.

6:  Put it on on, bend to adjust fit as necessary, and tie tightly.

Time and materials summary:

This entire process took me an hour, and left me with enough MIRV-8 material to make, looks like, maybe another 7 or 8 masks, with a lot of waste (because the mask min dimension is just over half the MERV-8 sheet that I got from my 14 x 30 x 1 filters.

Performance:  Yeah, it works.

I’ve been wearing this for an hour now, and it’s hot, uncomfortable, and it stinks a bit of plastic..  Which is to say, behaves like just about every other face mask.

I was worried that I would compromise the mask seal, but I don’t think I did.  For one thing, my glasses aren’t fogging up.  I don’t notice any leaks with a wet finger held near the edge (and sharp exhalations).  And, when I exhale, I can feel my hot breath diffuse out the lower part of the mask.  I want it going through the mask, not around the mask.

Back pressure is fine.  Not at all hard to breath, despite narrowing the breathable area somewhat with the plastic tape  .As it should.

The plastic tape is a little itchy, and I can feel a couple of the seams.  But I actually think the plastic tape, the overall metal mesh, and heavy-duty tie, in total, results in a pretty good seal against my face.

Tomorrow I’m going to review what other MERV masks are out there, and either improve this one, or build one of a different design.

And keep in mind, there is no obvious barrier to do this with MIRV-16 material.  The only real hitch there is that few domestic furnaces or air cleaners use MIRV-16.  And MIRV-16 — at least in terms of the specification — matches N95 for capture of 0.3 micro particles, and such.

I, Christopher Hogan, PhD., place this posting entirely in the public domain.

 

Post #594: Expedient masks, part 2: What can you buy

Source:  Amazon.com

As our Federal government stumbles toward a public mask policy at a glacial pace and with off-the-cuff advice, let’s see if we, the people, can get ahead of the game on this one.

The just-prior post already established that a reasonable home-made mask will do just fine for protecting others.  This next series of posts is about protecting yourself.  

And this post is about what you can buy, right now.  Its about expedient masks, meaning anything you can buy or make to serve as a face mask, that would (we hope) never be used by health care workers.  Anything other than real medical masks — either N95 (or equivalent hardware-store P95) or proper, certified surgical masks — such as might be used in a hospital.

Upshot:

If you want to buy a plausibly-effective sanitary mask, right now, for wearing in public, it looks like your sole option is disposable “surgical” masks bought through Ebay.  As discussed below, these are not actually proper certified surgical masks, and some of them are in fact simple “single-use” masks, as described in my just-prior post.  You can order the same thing through Amazon, but typical wait times are about a month.  I list out the features you want to see in those masks, if you buy them, below.

Caveat emptor:  I just looked at Ebay, and there are clearly a lot of unscrupulous sellers, and a general air of on-line panic shopping.  If you absolutely have a need for these, consider it.  But be aware that you may well be wasting your money.

In addition, anybody who is in the business of throwing away N95 or P95 masks (respirators) should read this analysis of how long an N95 may be re-used.  The answer is, putting aside the issue of sterilization, a long, long time.  Which is good, because (e.g.) the screeners at Dulles Airport have been asked to re-use their masks on a permanent basis.  So, even if you don’t re-use them now, it’s probably time to start separating them from the rest of the waste stream and retaining them.

What’s off-limits, what’s available on Amazon

This post is about masks that you can buy, right now.  And, separately, how you might modify them to improve their filtration capabilities.  I’m not going to spend a lot of time on this, because I suspect that when CDC issues guidance that Americans should wear masks when in public, anything for sale will disappear from the shelves.

I am sticking with Amazon, for the time being, because they appear to be doing things responsibly, as discussed below.  As I read it, right now, if you see it for sale to the general public on Amazon, that’s because it’s not needed by the US health care system.  That is not uniformly true of places like Ebay.  So I’m only going to look at items that are for sale on Amazon.  I may check availability of those same items on Ebay.  Clear enough?

I spent some time explaining the technical jargon in the last post, so I am going to feel free to use those terms around here without explanation.  Just refer the last post.

But this is not about protecting yourself, at the expense of the health-care workers.  In my last post, I explained why hospital workers need N95 masks and you don’t, under the section on aerosol transmission of disease.  So let me list not just the things you can buy, but the things you shouldn’t buy.

N95, P95, P99, P100:  NO. 

Source:  Wikipedia

If you stumble across anything rated N95 or P95 or better, just leave it alone, unless you plan to purchase it for donation to your local hospital or fire and rescue unit.  You should not be able to find these for sale now, but that’s only because responsible companies have withdrawn them.  (See Home Depot in just-prior post.  I don’t think the Federal government has taken any action to make the sale of these (to other than medical/fire/rescue providers) illegal. This class includes not only classic N95 “masks” as above, but (e.g.) anything like the P100 paint respirator pictured at the very top of this posting.

Again, you don’t need it.  Health care workers and fire and rescue units are going to need them.  See my prior post on why health care workers need them, and you don’t.

Surgical masks certified for medical use:  NO.

Source:  Wikipedia.

I’m not sure if you can find proper certified surgical masks for sale or not, but ditto the remarks above on N95s.  Leave them for health care workers.  Please see the prior post for a discussion of the difference between single-use masks and surgical masks, and the filtration standards.

Note that several large-scale controlled clinical trials show that surgical masks are just as good as N95 respirators at preventing flu infection among hospital workers.  An excellent summary is here, at Smart Air.  So, in a pinch, you bet hospital workers would use those if N95 respirators are not available.

Read my just-prior post for the difference between certified surgical masks, and “single-use” masks, which you can buy, and which are not critical to the US health care system right now.

Things that look like surgical masks but are not certified for medical use, available on Amazon, and are probably “single-use masks”, not surgical masks (defined below):  I would say, yeah, for now, probably YES. 

Wait times are long (typically one month) on Amazon, but this same sort of produce appears widely available (for now) on Ebay with short delivery times promised.

Source:  Amazon

What makes me say that?  Amazon is one of the responsible vendors who have pulled all masks that can be used by medical personnel and first responders.  Anything like that, their pages now have this wording:

Available only for hospitals and government agencies directly responding to COVID-19

For example, Amazon has withdrawn not only N95 respirators, but high-quality nuisance dust masks as well.  They have withdrawn surgical masks that appear to be certified for medical use.  (Note that those masks list their actual filtration rates, whereas the ones that remain for sale do not.)  To me, that suggests that they really have gone through their inventory and pulled out anything that would be useful to medical providers or first responders.

I have to infer, then, that if Amazon doesn’t say that, then there has been some professional judgment that the item in question is not needed by health care workers.  I am not 100% sure about that, but at some point, I have to believe that Amazon knows its business, and has done the right thing, and has stopped sale of all items that would be useful to health care workers (as Home Depot has done.)

An incredibly helpful and succinct discussion of single-use masks, surgical masks, and N95 respirators, along with considerable other helpful information (e.g., can you wash disposable masks) can be found at Smart Air.  If you want to get up to speed on what’s what, for actual medical supplies, that’s the place to start.

So, provisionally, I’m going to say, despite some misgivings, these are probably OK to buy.  I’m guessing that most of them are, in fact, “single-use masks” and not surgical masks.  If (note, if) those were manufactured to any standard, it would be a Chinese standard, and they would be able to filter out 95% of large aerosol droplets (3 microns), but would not filter something the size of a virus.  Proper surgical masks, by contrast, will filter out virus-sized particles.  Again, see Smart Air for a discussion of mask standards.

Even though these are not certified, and some appear to be poorly made, many of them do appear to have the right construction:

  • Three-ply construction, with
  • A layer of melt-blown fabric, and
  • A metal strip at the bridge of the nose.

To the extent that these are fairly good at filtering the air, that’s due to the melt-blown fabric and the nose piece.  See prior post for “melt-blown fabric”.  (You don’t know the quality/specs on the melt-blown fabric, but at least it has some, suggesting that it has filtering ability above-and-beyond what you’d get from just paper.) The nose piece is required to seal up what would otherwise be the largest air leak for the mask, right at the bridge of the nose.

Finally, multiple large-scale controlled clinical trials have shown that proper, certified surgical masks (not single-use masks) work just as well as N95 respirators at keeping hospital workers from catching the flu.  (Cite Smart Air). Whether or not whatever-these-are on Amazon — single-use masks or possibly uncertified surgical masks — would work as well as certified surgical masks is a complete unknown.  For sure, single-layer single-use masks, even if they were built to the Chinese standard, have no ability to filter virus-sized particles.  They would not have the filtration capacity of a certified surgical mask.

Check the delivery time before you buy.   The main catch here is delivery time.  That nice-looking white mask above?  I searched “face mask”, sorted by descending customer rating, and checked the earliest promised delivery time for the first 20 entries.  Median earliest promised delivery date was 26 days.  Three entries promised delivery within six days.  Two of those were of such low quality (by description and customer comments) that I doubt they would work.  The third was priced at about three times the going rate for masks.

The upshot on delivery is that a) for the typical product, it’s going to take a month, and b) anything promised for near-term delivery is either too poor to be useful, or (in one case) priced at several multiples of the going rate.

I re-sorted by descending price, and spot checked.  Even for very large orders (e.g., 1000 masks) first promised delivery dates were about a month away.

To summarize:  It appears that Amazon has stopped selling anything that has been judged useful to the medical or first-response sectors.  The only safe thing is to assume that whatever you are seeing on Amazon, at best, meets the Chinese standard for filtration for single-use masks.  If so, those would provide significant filtration against droplets, but limited filtration against aerosols and virus particles.  (I.e., they aren’t as good as real surgical masks).  Some of the disposable masks appear to have proper construction, per bullet points above.  If so, you could reasonably assume that wearing them would offer you some protection, but that is just an assumption.  The best of these have melt-blown fabric (the “filter” portion of a certified surgical mask), but you have no way of knowing what type of melt-blown fabric it is (i.e., how well it would filter air).  Even with that, you should expect about a one-month wait time for anything that looks worth buying, or feed the occasional price gouger who is promising an earlier delivery time.

Can you get them now, on Ebay?  Yes, that appears to be true.  If you go that route, look for three-ply construction, metal nosepiece, melt-blown fabric, and some claim as to bacterial filtration.  You have no idea whether the claim is right or not, but so be it.  A fair price appears to be in the range of $0.70/mask or so, in large lots.

Fabric sports masks:  YES, if you are wiling to modify it.  What you can routinely get does not appear very effective as a protective mask, because these are designed to “breathe”.  If you can sew, you can add a lining.  If not, you can try to add a paper lining.  You will definitely want to add a wire nosepiece to provide a tight fit across the bridge of the nose.

Source:  Amazon

At present, everybody says that any type of fabric mask is OK. Masks like that are frequently sold as pollen/pollution masks for outdoor exercise.  Amazon has a wide range of them. Most (perhaps all) are really not adequate for this task, consisting of a single layer of cloth.  Because these are exercise masks, they are made to “breathe”, which is what you don’t want, right now.

At the minimum, you’d have to line these with something.  Practically speaking, I think you’d have to resort to lining these with paper towels.  That provides some protection, but not much (see prior post, last section).  You would also want to take a bit of wire and either duct-tape it to the mask, or thread it through the mask, to provide a metal nosepiece for sealing the mask to your face at the bridge of your nose.

And, as with the disposable masks above, most have one-to-two-month shipping times.  I saw a handful with promised delivery times of a couple of weeks.  Weirdly, I did not find these on Ebay.  Maybe I just didn’t have the right search terms.

I’m not going to pursue these any further.

“PM2.5 masks”:  Eh, I’m not even sure what this means.

Source:  Amazon

There is a huge range of masks — some hard-surfaced, as the one above, some fabric, some hybrid — that are sold as anti-air-pollution masks.  That is, they claim to filter out particulate matter of 2.5 microns in size (PM 2.5).

Near as I can tell, as discussed in my prior post, there are no standards and there is no testing of these masks.  Some probably work.  Some probably don’t.  I have no way to tell.  I’m not going to discuss these further.  The few that I checked appeared to have delivery days 6 weeks away or so.

Caveat emptor.

Various loose-fitting masks and bandanas.  These protect others, a bit, but the lack of any seal means they provide very limited protection to you.

Source:  Amazon

And, of course, even these have promised delivery dates 6 weeks out.  These are single-layer loose-fitting cloth mouth coverings.  Better than nothing, but probably not as good as just pulling your t-shirt up so it covers you nose and mouth.  I don’t see value here.

Etsy hand-sewn cloth masks.

I did not pursue this option, but I would assume that some are available.

My next posts will discuss making masks.