Post G22-008: Plastic cloche surprise, not all plastics are created equal.



In my last experiment, I showed how well a Ball (mason) jar worked as frost protection.  In the coldest part of the night, the inside of the jar stayed 10 degrees F warmer than the outside.  I thought that was exceptional performance for a lightweight uninsulated glass container.  My explanation is that the glass traps long-wave infrared.  And so, this works for the same reason that my radiant-barrier frost protection works.  It prevents the garden bed from radiating heat energy off into space.

Long-wave infrared absorption would explain why glass worked well but polyethylene sheet was a near-total failure.  A sheet of ordinary window glass will absorb about 86% of long-wave infrared, and reflect the rest.  Polyethylene, by contrast, was reported to be almost completely transparent to infrared.

Accordingly, where a glass jar works well as a garden cloche, I figured that a plastic jar would not.  And that’s what I tested last night.

Never let facts get in the way of a good argument.

There’s just one problem:  Different plastics have different infrared absorption spectra.  And it took me a while to track that down.

Using Wein’s Law, the spectrum of radiation emitted by my 50 F garden subsoil would peak somewhere around:

  • 10 microns (micrometers) wavelength
  • 10,000 nanometers wavelength
  • 1000 waves per centimeter.

Those are three ways of saying the exact same thing.

So I wanted to find out how different plastics behaved with respect to long-wave radiation somewhere in that vicinity.  That’s where most of the power from the upwelling long-wave radiation from the garden bed will be concentrated.

I never did find exactly the data that I wanted.  But I came close.  And, as it turns out, polyethylene’s absolute transparency in that region of the spectrum is the exception among plastics, not the rule.

The chart below show the absorbance spectra of various common plastics, with the long-wave infrared region highlighted.   Note that the line for polyethylene is almost completely flat in that region.  It absorbs almost no long-wave infrared.   But PETE plastic, just below that, in fact absorbs infrared strongly right at the frequency where infrared from the soil will have its peak — wave number of 1000.

Source:  Figure 9, “Identification of black microplastics using long-wavelength infrared hyperspectral imaging with imaging-type two-dimensional Fourier spectroscopy“, Kosuke Nogo, Kou Ikejima, Wei Qi, et al., DOI: 10.1039/D0AY01738H (Paper) Anal. Methods, 2021, 13, 647-659

The upshot is that when I condemned all plastic for this use, I was too hasty.  Avoid polyethylene, for sure.  But, assuming the glass choche works as I have described it, PETE plastic ought to work reasonably well.  Not as well as glass, but certainly not as poorly as polyethylene.

As an odd little footnote, Mylar plastic — the kind used to make space blankets — is the same stuff as PET/PETE plastic — polyethylene terephthalate.


Below is a photo of a quart Ball jar (right) and the thick-walled PETE jar that I’m going to test.  That was as close as I could get to the same size and shape as the Ball jar.  FWIW, the PETE jar originally held salad dressing.  You can see that it’s much thicker than (e.g.) a typical disposable water bottle or soda bottle.


When I tested that last night — two temperature loggers on a raised garden bed, one covered with the PETE bottle, one un-covered — sure enough, PETE works pretty well.  But not as well as glass.

At the very coldest part of the night, the PETE jar provided between 4 and 6 degrees F of protection, or about half the maximum protection observed for the glass jar.

The lesson here is that when I condemned all plastics for use in frost protection, I was too hasty.  Polyethylene sheet is a terrible choice, from the standpoint of trapping long-wave infrared.  But PETE’s OK.  Not quite as good as glass, but pretty close.


Post #1460: COVID-19 trend to 3/17/2022, hitting bottom?


Data source for this and other graphs of new case counts:  Calculated from The New York Times. (2021). Coronavirus (Covid-19) Data in the United States. Retrieved 3/18/2022, from”  The NY Times U.S. tracking page may be found at

The U.S. now stands at 9.4 new COVID-19 cases per 100K population per day, down 17% in the past week.

By eye, it looks like we’ve reached the end of the down-slope of our Omicron wave.  Or very nearly.  Continue reading Post #1460: COVID-19 trend to 3/17/2022, hitting bottom?

Post #1412: A simple heated outdoor faucet (tap, spigot, sillcock, hose bib) cover.


This post shows you how to take a few off-the-shelf parts from your local hardware store and make a plug-in heated cover for an outdoor faucet.   This will take you about two minutes to assemble, and will cost you about $17, including some spare light bulbs.  The only tool you need is a knife.

It’s not rocket science:  Add a candelabra-bulb socket to a standard foam faucet cover.  Screw in a night-light or similar incandescent bulb.  Hang it on the faucet.  Plug it in.  You’re done.

I was motivated to install one of these by a recent 11F night, after which water would only trickle out of my outdoor faucet, suggesting it was very nearly frozen solid.  Given the damage that a burst pipe can cause, this seemed like a cheap bit of insurance.

I guess the target audience for this post is people like me:  Southerners, facing a few bitterly cold nights a year, who would rather not mess with trying to winterize their outdoor faucets the proper way.  I’d rather run an extension cord to the faucet than hope that the 60-year-old sillcock shutoff — that hasn’t been used in at least 30 years — will work without leaking.

The only value added I’m bringing to this, other than pointing out the obvious, is that I’ve tried three wattages and recorded the results.  Having tested it, you can be assured that you’re not going to end up with a flaming piece of styrofoam attached to your house, and you can pick the wattage that meets your needs.

  • 15 watt incandescent:  60+ degrees F over ambient temperature
  • 7 watt incandescent: 40 degrees F over ambient temperature
  • 4 watt incandescent: 28 degrees F over ambient temperature.

The long and the short of it is that even a 4 watt incandescent bulb is adequate for any nighttime temperature I might expect in Northern Virginia.  The 15-watt bulb was clearly overkill, so I’m not even going to include it in the parts list below.  YMMV.

I think that seven-watt night-light bulbs are almost universally available.  The only constraint is that, for the wattages listed, they have to be old-fashioned incandescent bulbs.  You’re using them for the waste heat, not for the light.

(You could, in theory, make this work with LED bulbs, but just don’t go there.  To get the same amount of heat, you’d have to find ones that actually consumed 4 to 7 watts, not ones that are listed for a light output equivalent to 7 watts.  In other words, you’d need to by LED bulbs listed at 40 to 60 “watts” of light output.  As I said, just don’t go there.)


Parts, tools, and assembly.

Parts, left to right:

Home depot reference: , $4.


Pick one:


Ace hardware typical reference., $6 for four.


Home depot reference, $7.

Instructions:  Use the serrated knife to cut a small (1/8″ wide) slot in the bottom of the Styrofoam faucet protector.  Bend the metal fitting that comes with the candelabra socket to spread it out a bit.  Press the cord for the candelabra socket in place.  Snug it up.  Screw in the bulb.  What you see below is the inside of the faucet protector, fully assembled and lit.

One clear drawback is the need to run an extension cord out to the faucet cover.  But, with a power draw so low, the cheapest, flimsiest outdoor extension cord will do.

You might want to wrap any junctions (e.g., where the extension cord and lamp cord meet, or where the switch is on the lamp cord) with electrician’s tape or other waterproofing material, depending on how exposed they are.  Otherwise, that’s it.

Post #1394: The U.S. CDC: Argh.

I saw this headline in today’s Washington Post.  It appears that the U.S. CDC is almost ready to maybe sort of recommend that you wear a good mask, not just any mask.

I guess, as pictured above, they’re looking back on the entire history of the pandemic, assessing where we now sit, and asking whether or not they might, possibly, at this stage, as a last resort, recommend an easy, cheap, and effective method for radically reducing the population’s exposure to COVID-19.


If you read this blog, you know I’ve been strongly in favor of use of high-filtration masks for a long time.  Since before the CDC even recommended wearing masks.  Just search the “mask” category and you’ll see what I mean

With this latest near-pronouncement from the U.S. CDC, I hardly even know where to start.  In the interest of saving time, I’ll skip the rant, and remind you of a few useful things.

1:  An N95 isn’t just better than a standard blue procedure mask, it’s vastly better.

2:  If you insist on wearing a cheap blue procedure mask, at least learn the “tucked and tied” technique.

3:  Leave the KN95s on the shelf.

1:  An N95 isn’t just better than a standard blue procedure mask, it’s vastly better.

Here, I’m just repeating a part of Post #938, from almost exactly one year ago.

Here’s a simple question.  Even if you think you really, truly understand masks, take 15 seconds to see if you can get the correct answer.

Question:  An N95 respirator (mask) filters out 95% of airborne particles.  A procedure mask with ear loops filters out about 30% of airborne particles.  (That’s based on an actual test of those masks as published more than a year ago in JAMA).   Let me loosely call that an “N30” mask.  Roughly speaking, how much better is an N95 mask, compared to an N30 ear-loop procedure mask?

  1. Obviously, it’s about three times better, because 30 x 3 = 90, which is close to 95.
  2. Obviously, it’s about 14 times better, because (100 -30)/(100 – 95) = 70 / 5 = 14.
  3. Obviously, this must be a trick question.

The answer is B, it’s 14 times better.  Why?  The mask rating (N30, N95) shows you what the mask keeps out.  But the viral load you inhale isn’t about what the mask keeps out.  It’s about what the mask lets through.  It’s about 1-minus-the-mask-rating.  And in any given situation, the ear-loop surgical mask will let through and expose you to 70% of what’s floating around.  While the N95 exposes you to 5%.  And 70/5 = 14.

In case you still don’t quite get it, let me do the math the other way.  How much better is that N30 ear-loop surgical mask, compared to wearing no mask at all?

Question 2:  Assume that you need to inhale 100 copies of COVID-19, at a sitting, in order to get infected.  Assume that you are going to inhale one cubic meter of air, at a sitting.  How dense can the COVID-19 particles in the air be, before you inhale enough to get infected, based on wearing:

  • No mask.
  • N30 mask (ear-loop surgical mask, worn loosely)
  • N95 respirator.


Question 2, same math, but rephrased.  Suppose there’s a room filled with COVID-19 aerosol.  Suppose that, without a mask, you can sit in that room for no more than 10 minutes before you get infected.  How much more time does your cheap, blue ear-loop surgical mask buy you?  That is, how long could you sit in that room and remain uninfected, wearing an ear-loop procedure mask? And then, how long wearing an N95 respirator?


  • No mask — 10 minutes.
  • N30 mask (ear-loop surgical mask, worn loosely) – 14 minutes (10/.70)
  • N95 respirator — 200 minutes (10/.05).

That cheap blue mask buys you a whopping four additional minutes of time, before you get infected.  Which not only makes my point, but which shows you why you want to stay away from close, crowded situations, mask or no mask.

Sure, a loosely-fitting ear-loop surgical mask is better than no mask at all.  But not by a whole lot, in the overall scheme of things.

I hope you now get why I’m so persnickety about masks.  The difference between a good mask and a poor mask isn’t a little bit.  It’s a lot. It’s an order-of-magnitude difference in performance.


Still wearing those 20-cent blue procedure masks that you bought a year ago?  Can’t bring yourself to pay a whopping 89 cents each for genuine 3M N95 respirators, even though the 3Ms are good for hundreds of hours of normal use before the filter material clogs? Or maybe just just plain don’t like N95s of any sort, despite the wide variety available?

Then you should at least learn the tucked-and-tied technique.  By itself, this improves the filtration ability of the typical surgical style mask from roughly an N30 to roughly an N60.

Takes a few seconds to do.  Costs you nothing.  Doubles the effectiveness of the mask.  What’s not to like?

Or watch that directly in YouTube.

In the U.S., KN95 is a style of mask, not a legally-enforceable filtration standard.

The CDC will be doing nobody any favors if they recommend using an N95 or KN95 mask.  I’ll go so far as to say that adding KN95 to the recommendation is simply an incompetent mistake.

In the U.S., N95 is a U.S. standard maintained by the U.S. National Institute for Occupational Safety and Health (NIOSH).  A NIOSH-certified N95 respirator must fit tightly to the face, using straps that pass behind the head (never ear loops), and, when properly fitted, filter out at least 95% of of the hardest-to-filter particles (0.3 micron).

Masks may then be further certified for medical use by the FDA.  Masks certified for medical use must meet additional standards, including resistance to splashes.  It is completely possible to have a NIOSH-certified N95 that is not suited for medical use.  Most or all NIOSH-certified N95s sold for industrial use — such as the ones you can easily purchase at your local Home Depot or other hardware store — filter to the N95 standard, but are not certified for medical use.

In the U.S., KN95 means nothing.  It’s a Chinese standard, and has no legal meaning in the U.S.  Anybody can make a mask and sell it as a “KN95” mask.

Practically speaking, in the U.S., KN95 refers to a style of mask, not to a guaranteed level of filtration.  A mask that will fold flat, unfold into some sort of cone shape, and use ear loops rather than behind-the-head straps.

I have tried several KN95 masks over the course of the pandemic, and none of them worked well enough to use.  They all fit too loosely, allowed too much air to leak around the face seal, allowed my glasses to fog, and were generally insecure due to loose-fitting ear loops.

My point is, the things you can buy in the drug store labeled “KN95” are in no way a substitute for a NIOSH-certified N95 respirator. Not even close.  I sincerely hope that some CDC bureaucrats will get out from behind their desks, walk into a few hardware and drug stores, buy a few packs of what are routinely sold as “KN95” masks in the U.S., and assess them for air-tightness and likely filtration ability.  And come to the realization that, as I just said, the typical KN95 in America is not even in the same league as a NIOSH-certified N95.

In theory, the FDA had, at one time, a list of certified Chinese manufacturers whose masks could be used in U.S. hospitals under an emergency use authorization.  The FDA has long-since cancelled that EUA, and so, technically speaking, there are no KN95 masks certified for medical use in the U.S.

The bottom line is that, for the average consumer, you have no idea what you are buying when you purchase a KN95 mask. For myself, at least, every one I tried failed due to obvious air leaks.  And that doesn’t even begin to address the actual filtration ability of the cloth itself, which you have no way of testing, and which was never tested or certified by an U.S. agency.

Maybe if you’ve never worn a properly-fitted N95, you wouldn’t know the difference.  But once you’ve worn an N95, and realize that absolutely no air is supposed to leak around the mask, you will instantly reject any hardware-store KN95s on the basis of lack of air-tight fit.

If you must use an ear-loop mask, I’d recommend a made-in-Korea KF94, such as the LG Airwasher.  (KF94 is a filtration standard more-or-less equivalent to N95 in terms of particulate filtration.)  If it’s genuinely made in Korea, that provides a known filtration ability, and the ear loops are adjustable for tight fit.  Of all the masks that I asked my daughter to try, that was by far the most preferred (Post #1246, What mask should I wear?  We have a winner).

And at the end of the day, it’s all about wearing the best mask that you are willing to wear.

Post #1381: SNOVID-19.

I can’t help but smile when I hear the term “snow day”.  It’s a conditioned reflex, the result of having gone to school in the South.

But now there’s a new perspective on that old joy.  After a couple of years of complaining about hanging around the house and not doing much because of COVID, I now find that hanging around the house and not doing much because of snow is totally different.  It’s unironically fun.

Thus proving that mental attitude is all in your head.

It’s a snow day here in Fairfax County, VA

This is God’s way of shouting at us “Do Not Go Back to School”!  (That’s per a a friend of my wife’s, a schoolteacher who isn’t much looking forward to in-person classes with Omicron).

People from northern climates laugh at the degree of disruption a little snow causes in the South.  But, having seen it from both sides — grew up and live in Virginia, but spent several long, cold winters in Chicago — I can tell you that snow in the South is just a completely different beast from snow in the North.

It’s slipperier.  And that’s a fact.

Wintry mix is our favored form of precipitation this time of year.  It’s a random combination of snow, sleet, ice pellets, freezing rain, and rain.  The weather forecasters aren’t quite sure what will be hitting the ground at any particular moment.  The only thing they agree on is that whatever it is, you can slip on it.

(My wife often said that Baskin-Robbins should offer a flavor of  ice cream by this name.  It would come pre-marketed because everyone in this area hears that term all season long.)

We get wintry mix so often in this area because the temperature is typically just about freezing when it snows. Might get snow, might get rain.  You never know until it gets here and makes up its mind.

This morning, it’s 30 F with high humidity.  And so, we’re actually getting just snow.  It melts as it hits, then piles up, and as a result, we end up with a thin layer of slush everywhere, covered with snow.  That will be freezing to ice in random areas throughout the day, and will freeze uniformly tonight.  Tomorrow morning, anywhere that hasn’t been shoveled and salted will have a uniform coating of snow-over-ice.

Let me contrast this with a typical Chicago snowfall.  Typically, it’s 20F or so, everything is already frozen solid, and 4″ of powdery dry snow comes down.  It doesn’t melt.  It doesn’t stick to anything.  People sweep off their sidewalks and life moves on.

Having driven on roads in both areas, I’d trade their coefficient of friction for our coefficient of friction any day.

Finally, hills.  Midwesterners in general don’t have to cope with them.  For sure, they just plain don’t have them in Chicago.  Around here, though, they are a fact of life.  And once you find yourself sliding downhill, on the frozen slush hidden under the snow, there really isn’t much you can do about it.

Bottom line, I’m leaving the car in the garage today.  And the power has gone out now.  So I will just enjoy sitting around the house doing nothing.  For a change




Post #1353: COVID-19 trend to 12/17/2021


In the U.S., the winter wave continues to be mainly a wave in the Northeast states.  That area is now worse off (in terms of new cases per day) than it was at this time last year.  Rhode Island is still the only only state with new COVID-19 case rates in excess of 100 / 100K / day. Continue reading Post #1353: COVID-19 trend to 12/17/2021

Post #1318: IED


I enjoy crossword puzzles.  And I’m not ashamed to admit it.

My puzzle habit was formed during ten years of daily commuting from the suburbs to downtown Washington DC, via DC’s Metro system.  Now, after more than three decades of puzzle-solving, I have an appreciation for the subtle science and exact art of crossword-puzzle making.

Filling in a hard crossword puzzles requires an odd assortment of skills.  It becomes roughly equal parts of:

  • Knowing the structure of language (e.g., plurals usually end in “s”).
  • Straight-up trivia (e.g., Pierre is the capital of South Dakota).
  • Current pop culture (e.g., Grammy winners).
  • Older pop culture.
  • A good sense for puns, alternative word meanings, and the like.

Much of it has a unique crossword-puzzle slant, owing to a chronic need for vowels.  For example, ONO (Yoko), ARLO (Guthrie), OCALA (Florida) all appear in crosswords far out of proportion to their importance in the real world.  As do the many, many vowel-rich four-letter rivers of Europe (e.g., ODER, YSER, URAL, ARAL, AARE, …) .

The popular-culture aspects of crossword puzzles typically don’t age well.  It’s hard to pick up a 20-year-old book of difficult crossword puzzles and fill them in.  The world has moved on.  Pop-culture names and terms familiar to every well-read reader in 2001 are seldom on the top of the tongue two decades later.

That said, they are never truly current, either.  It takes a while for any new pop-culture phenomenon or phrase to work its way into the day’s crossword puzzles.  So what you really get in crosswords is pop culture with a lag.

Which brings me to IED.  That was in a puzzle I worked yesterday, with the clue “hazard to troops”.  It was, in that sense, a perfect crossword puzzle word.  Lots of vowels, and a term that every U.S. resident would have absorbed over the past couple of decades.

But IEDs haven’t been in the news of late.  Which is a good thing.  And I can only hope that this clue and answer will be completely mystifying to some puzzle-solver a couple of decades from now.

My point being that sometimes the news ought to be about what hasn’t happened recently.  We ought to see a great big headline stating that “No American troops died in Afghanistan over the past two months”.  Or that we failed to spend $20B propping up a corrupt and unpopular government over that same time span.

But that sort of obvious good news just isn’t what the popular press is all about.  Too many other things that are better click-bait.  U.S. casualties that didn’t occur are the sort of thing that will only sink into our collective consciousness a decade or two from now.  If then.

Meanwhile, I’ll continue to enjoy the absence of the IED from our popular press.  Even if that word is still in crossword puzzles, for the time being.

Post #1316: The universal state budget surplus of FY 2021 and the economic boom of FY 2022.


In Post #G21-058, I stumbled across an interesting finding.  More-or-less every U.S. state had a large (often record) budget surplus for FY 2021.  As far as I can tell, this has gotten exactly zero notice in the popular press.

Reading a few reports of these surpluses, it seems like various sources of state tax receipts started to pick up around April 2021 and just haven’t quit since.  And nobody is quite exactly sure why, although the obvious suspect is all the spending power that the Federal government injected into the economy over the past 18 months.

Now here’s the weird thing, and the main conclusion that I’ve drawn so far:  We seem to be in a genuine economic boom.  I keep looking for signs that revenue growth will be petering out, now that we’re reaching the end of the pandemic.  But there’s no sign of that in sight.

At some level, it shouldn’t be a surprise.  The Federal government has just gotten through two years of the largest peacetime economic stimulus in U.S. history.  A good chunk of that was simply saved, presumably to be spent later.

And now, with all that free money burning holes in many pockets, the result is just standard Keynesian economics.  There’s a whole lot of new economic activity, with a side-order of inflation.

But you’ll have to judge for yourself.  As I say, this started out as a study of state budgets, and rapidly turned into an analysis of just how rapidly the U.S. economy seems to be heating up.

U.S. Treasury Revenues are clearly up.

Let me start with the most stable source of timely national information on economic activity that I know of:  The Monthly U.S. Treasury Statement.  If somebody’s making money from it, it’s a good bet that Uncle Sam is taxing it.  So, putting aside the big lump of revenue that arrives at tax time, Federal receipts provide a pretty good estimate of the pace of economic activity.

Source:  My plot, of data taken directly from the U.S. Monthly Treasury Statement.

No matter which perspective you take — two decades, or five years — we have clearly entered a period of rapid growth in U.S. Treasury receipts.

Flash GDP estimates are running to double-digit growth.

These get a little murkier, as they are no longer hard data, but are estimates from somebody’s economic model, fed by current data.  For this, I’m relying on the Atlanta Federal Reserve’s GDPNow estimate.

“The GDPNow model estimate for real GDP growth (seasonally adjusted annual rate) in the fourth quarter of 2021 is 8.5 percent

They also note that their model is well above the “blue chip consensus forecast” of real GDP.

Virginia’s general fund revenue numbers are running 10 to 15 percent above the same period last year.

Source:  Virginia monthly revenue letter, September 2021.

And, from what I can tell by casually checking a few other states, this is not unusual.  Seems like a lot of states have seen broadly-based revenue growth continuing well into FY 2022.

Whether or not state tax receipts will continue to grow is the question of the moment.

The fact that started me on this analysis — the large number of states with record FY 2021 budget surplus — has not gone unnoticed in the academic press.  Of the articles that have focused on this, the Pew Charitable Trust managed to hit the nail on the head.

Awash in Cash, State Lawmakers Ask How Long the Boom Will Last, dated July 26, 2021, by

Here’s a quote that pretty much sums it up:

“The growth trajectory—it’s higher than we expected,” said Adams of Idaho’s Division of Financial Management. “I don’t anticipate that it will continue at this pace. I don’t think anyone does, frankly.”

Kate Watkins, who leads the team that prepares revenue forecasts for the Colorado legislature, said she expects Colorado’s revenue growth to flatten out.

“In many cases,” she said, “we’re still waiting on data to validate what the story is moving forward, whether or not this is really kind of a blip or if it really is a sustainable growth trajectory.”

As I read it, the reason there’s no “smoking gun” is that revenue growth is quite broad-based.  Not only is income tax withholding up, so is sales tax, so are corporate tax payments, and so on.

Basically, we seem to be in the middle of an economic boom.  One that doesn’t seem to have gotten much attention.  But one for which the Federal and State tax data, and the flash GDP estimates, suggest is pretty substantial.

Amidst all the negative press regarding the President, I sure haven’t heard much about the U.S. being in the middle of rapid GDP growth.  The only sign of that has been the steadily falling unemployment rate.

But, as far as I can tell, that appears to be true.  I started out assuming that we were in the middle of some temporary bubble in state finances caused by direct Federal pandemic relief.  But now, that appears to be wrong.  For whatever reason — making up for lost time in the pandemic, spending all that free pandemic money, or who knows why — we’re suddenly in the middle of economic good times.