Post #G21-050: Simple solar dehydrator, quantifying failure.

This is just a brief followup to Post #G21-049, where I decided to make a simple solar food dehydrator out of a plastic tote.  My goal was to turn the last few batches of tomatoes into sun-dried tomatoes without using electricity.

My first attempt, shown left, was a failure.  I loaded in about six pounds of tomato slices, and despite optimal weather, and a working temperature just under 118, the tomatoes were nowhere near dry.  I finished that batch in my electric dehydrator.



For my second attempt, I used just 2 pounds of tomatoes, and weighed them at  start and end of the day.  In one sunny day, this simple solar dehydrator managed to remove about one pound of water.  Again, the tomatoes were nowhere near dry enough to let stand overnight, so they became part of a batch of tomato sauce.

I think the upshot is that this simple setup will never be usable for drying tomatoes on its own.  A pint (pound) of water per day just doesn’t cut it.  It needs a rethink.

Why does it fail?

First, it doesn’t fail for lack of energy input.  I did the math before I started.  Best guess, at this time of year, in my latitude (about 37 degrees north), about 250 watts of energy should make it through the four-square-foot lid of the box.  That’s enough energy to evaporate six pints of water per day.

Some of that will be reflected back out of the box.  Some will be wasted as heat lost through the surface of the box.  But that still seems to be more than adequate.  I figured that energy would essentially “cook” the water out of the tomatoes.

Second, it doesn’t really fail for lack of temperature.  Despite being ventilated, the interior of the box gets up to about 120F.  That should be an adequate temperature for drying vegetables.  In fact, I don’t want it to go over 140F for drying vegetables, because that affects the quality of the resulting product.

I think it fails for lack of air movement.  As it stands, the only air movement is from the thermal siphon created by hot air rising up the clear chimney pipe.   That’s a gentle flow of warm, moist air.  Stick your hand over it, and it feels as if someone where gently breathing on your hand.

Best guess, that provides one full air change in that box every five to ten minutes.  But it doesn’t really provide any active air movement over the surface of the food.  Although the air going up the chimney pipe might be moving at 0.5 to 1 miles per hour, the air sitting on the food itself is, for all practical purposes, still. provides a calculator for evaporative losses from swimming pools based on, among other things, wind speed above the pool.  That’s not exactly the situation I’m in, but it’s enough to give some sense of how much air circulation matters.

Let me use a typical 20″ box fan as my benchmark.  A typical fan of that sort can push air at nearly 5 MPH on low.  Based on the swimming pool calculator, for the default values (which I take as typical conditions), evaporation with a 5 MPH breeze is just about three times higher than evaporation in still air.

That’s interesting, because every do-it-yourself direct solar dryer that I can recall did nothing more than provide slow, passive air movement via air vents.  They are all variations on a simple glass-fronted box.  (Direct solar dryers are those that put the food directly into the light, as this dryer does.  By contrast, indirect driers use sunlight to heat air, and pass that heated air over the food.)  Near as I can tell, all direct solar food dryers dry the food in more-or-less still air.

Further, when I take the pool calculator above, at the typical conditions used there, merely blowing 5 MPH (2.23 meters per second) air over my two trays of tomatoes should — by itself, with no added heat — remove about a pint of water every eight hours.

It’s almost as if I could dry food just as well by sitting it on top of a running box fan.  As long as the air circulated by the fan was reasonably dry.

And, sure enough, you can do that.   Alton Brown (of Good Eats) makes dried fruit using a box fanAt least one person has replicated that and says it works well.

I think the next step is obvious.  I need to add some sort of forced-air circulation to my solar dryer.  That will take electricity, but not very much.  A small box or window fan on low uses maybe 25 to 40 watts.

Post #G21-049: Simplest solar food dehydrator, works with Nesco dehydrator trays.


This started out to be a little treatise on solar dehydrators, ovens, and kilns. And I may yet write that.

But my goal, right now, is to make a small solar food dehydrator that will work with four 13.5″ diameter trays from my Nesco electric food dryer.  That’s “a batch of tomatoes” for me.  The upside of using those trays is that I can always finish off the drying using the electric food dehydrator.  It is, in effect, hybrid solar-electric food drying.

There are lots of plans for sturdy, well-made, functional solar dehydrators available.  And all of them were way more than I needed, and far more than I cared to fabricate.  I mean, why spend hours making something that you can buy for a few bucks?

In the end, by far the simplest and most cost-effective approach was to buy an $18 clear plastic tote from Sterilite (r).  That, plus a few bits of junk lying around the house, an hour of time, and I had a functional, sanitary, minimal-effort solar food dehydrator.

If the thought of drying your food in a plastic box turns you off, I’ll note up front that Sterilite (r) says that all of their products are made with food-safe plastics.

I’ll document this while my first batch of tomatoes is drying.  I’ll update this evening with an analysis of the results from one day’s drying in this solar dehydrator. The upshot is that this setup will partially dry trays of tomato slices in one day.  But it won’t dry them completely in one day.  In the humid Virginia climate, I’m not willing to let half-dried tomatoes sit overnight, so I moved the trays to the electric dehydrator and finished the job.  This simple dryer reduces but does not eliminate the use of electricity for drying produce.

Upon reflection, given that I’m going to have to use electricity as part of this process, it’s obviously smarter to start the tomatoes in the electric dryer, then finish the half-dried tomatoes in the solar dryer.  I haven’t done that yet, but I lay out the logic behind that in the “power calculations” section at the end of this posting.

Background 1:  Solar food drying works even in humid climates.

My rolling solar food dehydrator worked pretty well  (Post #G21-048).  A day in the sun greatly reduced the time needed to finish the drying in an electric dehydrator.  On the face of it, that little bit of solar “pre-drying” saved about 4 kilowatt-hours, or roughly the electricity needed to dry a large load of laundry.

If nothing else, I now feel better prepared for the zombie apocalypse.   If society collapses, there will be no lack of dead cars out here in the ‘burbs.  My future-dystopia food preservation plan is all set.

The real benefit from this test is that it shows that solar drying is possible in Virginia.  Many reputable websites (e.g., state extension service website) state plainly that solar drying is not practical in humid climates.  I now realize that statement probably applies to unassisted, open-air solar drying.  If you put your food in the equivalent of a solar oven, it will dry, even with the high relative humidity we face here in Virginia.

Drying vegetables in my car works, but it’s less than ideal.  Not just because it looks odd.  It’s inconvenient to load and unload.  The car only gets up to 115 F, whereas the preferred drying temperature for vegetables is 140 F.  And I might actually want to drive that car at some point.

Background 2:   This ain’t rocket science, but a bit of calculation is in order.

In theory, any enclosed object with clear cover could be used for solar drying.  At least to some extent.  One can, for example, use a cardboard box and a piece of plastic wrap to create a pizza-box solar oven.

The interesting thing about a solar dryer is that it’s not a solar oven or solar kiln.  Unlike an oven or kiln, you don’t want it to get very hot.  For drying vegetables, you’d prefer to keep it under 140F.  That means the demands on the materials, insulation, and so on are all relatively minimal.  For example, double-paned window glazing is almost unheard-of in a solar dryer.  You just don’t need it.

Under those conditions, I ought to be able to made an adequate solar dryer from any simple enclosed box.  It needs to have at least one clear face, and some ventilation. But it doesn’t otherwise have to be exceptionally well-built or well-insulated.

The size of the clear face of this box determines the energy input, which in turn determines how much food can be dried in a reasonable amount of time.  The bigger the window, the larger the mass of vegetables you can dry at once, within a reasonable time.

My typical batch size is about 6 pounds of tomatoes.  When I work through all the math (typical summer insolation in this area, losses through the clear window, energy required to boil a pound of water), I estimate that I need 3.5 square feet of window area merely to evaporate off six pounds of water in one sunny day.  Given the inevitable conduction-radiation-convection energy losses that any hot object has, surely I’ll need more than that.

But this tells me that I need a box with a window that’s at least 3.5 square feet.  If I hope to get these tomatoes done in a day or two.

There are a lot of excellent, well-engineered solar food dryers out there.  But almost all of them were a) big, and b) required a lot of fabrication if home-built.  They were, in effect, complete overkill for a person who wants to dry a few batches of garden vegetables per year.

One of the simplest you’ll see is this product, the Dehytray.  It really is nothing more than a black plastic box with a clear lid and vent holes.  It was developed to help third-world farmers preserve their crops more easily.  I found the simplicity (load it and put it out in the sun) appealing.

Source:  Dehytray

Were it not for the fact that these are $140 each, I’d have gone with that.  I’m sure this thing is built to last a lifetime in third-world conditions.  But as with most of the designs I’ve seen, this is overkill for my needs.

But the general concept — you can dry food in a plastic box with a clear lid — that’s the direction I’m headed.  I really don’t need anything fancier than that.

Building a food dehydrator using a clear plastic tote.

I chose this particular tote, below, as the basis for my food dehydrator.  It needed to be large enough to accommodate four dryer trays, and it needed to have a top of at least 3.5 square feet in area.

I went to about an hour’s worth of effort to build this.  But I bet I could just chuck the trays in, leave the lid ajar, and it would still dry the food.

What I’m trying to say is that if you start with a food-safe clear plastic box, it should be no surprise that it’s not very hard to build a working solar food dehydrator.

Source:  Target.

First, Sterilite (r) says that all of their products are made with food-safe plastics. Even with that, I’m a little concerned that the hoped-for 140F operating temperature might cause me problems. But they make everything from polypropylene and polyethylene.  A working temperature of 140F should cause no problems with those materials.

Second, I know this isn’t UV stabilized, so it will eventually rot from sun exposure.  But, again, I’ll be using this for a few days per year.  I’m sure I’ll get years of use out of it at that rate.

Third, it’s large enough to accommodate four 13.5″ diameter Nesco dryer trays, stacked two deep.  (Interior Dimensions at bottom: 31 1/2″ x 16 5/8″ x 6 3/8″).  By using those trays, I always have the option of finishing the drying process in my electric food dryer.

Fourth, the top is approximately four square feet.  Per my earlier calculation, in theory, on a clear day, at my latitude, that will let in enough energy to evaporate the six pounds of water required to dry my tomatoes.

Fifth, ventilation can be accomplished by cutting through the relatively soft plastic.  If I’m careful, I won’t really even ruin the tote for other uses during the rest of the year.

Sixth, beyond a couple of holes for ventilation, it needs:

  • Something dark and insulated for the bottom
  • Something reflective and insulated for the sides.
  • Something to prop it up so that the top faces into the sun.
  • Screened vent holes and other items to encourage air flow but keep bugs out.

I bought the tote yesterday, and put the dehydrator together in about an hour today, from stuff I had lying around the house.  Here are some views of the final product.

The body is the $18 tote, purchase from my local Target.

The shiny stuff is Reflextix (r) insulation.  More-or-less, it’s a tough, aluminized bubble wrap. I cut two sheets to size and folded the corners so that they cover the bottom and sides of the box.  The only reason I used that material is that I had a piece of it sitting around.  Anything that would insulate the bottom and sides, and would not taint the food, would work.

The spacers between the trays are pieces of furring strips.  Again, anything that won’t taint the food would do.  I’d shy away from using PVC pipe, owing to the potential for high temperatures, but I’m not sure there’s any science behind that.

Not shown, I lined the bottom of the inside with a cut-up brown paper grocery bag.  I originally thought I’d need that dark surface to capture sunlight.  As you can see, the box is full enough that not much sunlight makes it to the bottom.


Ventilation is the hard part.  I could not even make an educated guess for the amount of ventilation this needs.  But that’s easy enough to change if I got it wrong.

The only thing you want to be sure to include is a good-sized chimney of some sort.  That’s the plastic pipe at the top of the picture.  The “draw” of the chimney is what directs the flow of of air into the holes at the bottom, over the produce, and out top of the chimney.

For ventilation, I cut three holes in the top, roughly 1.5″ diameter, using a drill with a hole saw.  (You could just as easily cut rougher holes with a utility knife.)

I attached pieces of cloth netting over the lower two holes (using tape).

In the top one, I placed my chimney.  In this case, it’s a lightweight piece of plastic pipe.  (It’s a piece of a fluorescent tube bulb guard for a traditional T-12 fluorescent bulb).  Anything that’ll carry the hot air up, and can stand up to some moisture, would have worked.  I would bet that a piece of carboard, taped up to form a tube of some sort, would work just fine.  There’s really nothing to attach it to, so the lighter the better.  In this case, I made a “pipe collar” out of a couple of pieces of cardboard, ran the pipe through that, and taped the cardboard to the top of the tote.

To summarize the construction:

  • Start with an appropriately-sized Sterilite (r) tote.  I used the one depicted above.
  • Find something to insulate the sides and bottom a bit.  I used a couple of layers of Reflextix (r).  You need something that can take the humidity and a little bit of heat.  It’s not completely clear that you need to do this, but you guarantee a higher ultimate working temperature if you do.
  • Get four thin sticks about as long as the box, to use as spacers for the trays.
  • Cut three holes in the top, about 1.5″ in diameter.
    • Cover two of those with something to keep the bugs out.  I used pieces of tulle (cloth netting), taped in place.  Window screen would be fine.  Any sort of fine mesh would work..
    • Fit some sort of chimney in the third hole, maybe 2′ to 2.5′ long.  I used fluorescent bulb tube guard, but anything lightweight that will take the heat and moisture will do.  (The ideal chimney length is whatever will fit diagonally in your tote, so that you can stow it when you’re done. )
  • To fabricate the chimney, I cut a piece out of the side of the tube guard, at the bottom, so that air could get in even if the pipe rested on the bottom of the box.  And I slit a couple of pieces of cardboard to make “pipe collars”, slipped those over the tube, and taped the cardboard to the top of the box.  So my chimney rests on the bottom of the box, runs through a hole in the lid, and is held in place by a couple of pieces of cardboard, slit so they’d slip over the pipe.

None of that is hard.  Any sort of reasonable substitution is acceptable.  The only rules are that the materials need to stand up to moisture, stand up to a bit of heat, and can’t be made of things that might taint the food.

Operation so far.

I started out at 40 minutes before solar noon, ambient temperature 75 F, clear sunny day, 39 degrees north latitude.

It took 18 minutes for the interior of the box to reach 100 F.  After an hour, it seems to have stabilized at 118 F.  (I expect that to go up as the food dries, as much of the energy entering the box now should be absorbed in the conversion of water to water vapor).

There’s a steady stream of warm, moist air coming out the chimney.

This appears under-ventilated, given the size of the load.  There’s some visible condensation on the underside of the lid.  I probably need to add another chimney.

That said, this clearly works.  The 118 F is a little lower than I’d like, but well within the range of temperatures acceptable for dehydrating vegetables.  Water is in fact clearly being removed from the tomatoes, at a temperature that will not cook them.

I’ll come back to this in late afternoon to summarize how my six pounds of tomatoes slices are doing.

I now wish that I had weighed the trays before starting.  The next section of this posting is based solely on how the tomatoes looked.

By the end of the solar day, the tomatoes were only partially dried.  The top racks looked about half-done, with the thinner slices just starting to turn leathery.

By eye, they looked about the same as the trays that I left on the dashboard of my car for a day.  That would make sense, as the car got up to 115 F and the clear-tote solar dryer got up to about 118 F.

The bottom trays showed minimal evidence of drying.  The obvious lesson here is that I can’t stack the trays two deep in this cheap little solar dryer.

Even if I had just a single layer, it looks like it would take at least two days to get the tomato slices dry enough for storage.

This means that all-solar drying with this cheap little dryer depends on my willingness to leave the partially-dried produce overnight.  I’ll have to think about that some.

With the right climate, people surely do that.  Direct sun-drying of tomatoes — just laying them out on screens to dry in the sun — is said to take four days to two weeks, per The Spruce Eats.  Any directly sun-dried tomatoes have, by defintion, sat for a few days in a partially-dried state.

But the experts say that only works in an arid climate.  Here’s what the University of Minnesota extension service says about sun-drying produce (emphasis mine):

  • Sun-drying is not recommended in Minnesota due to our high humidity and cool night temperatures.
  • Foods dried in the sun can take 3-4 days to dry; if the humidity is high, as is generally the case in Minnesota, the food will mold before it dries.
  • Sun-drying requires constant exposure to direct sunlight during the day and a relative humidity of less than 20%. These conditions are found only in areas like the Sacramento Valley of California or in Arizona.

Given the high relative humidity inside the tote, and the high relative humidity outside in Virginia, the only way I’d consider doing that is bringing it into the house overnight.  But even with air conditioning, relative humidity in my house never gets close to 20% in the summer.

In short, I’m not going to start with raw tomatoes, use this solar dryer for a day, and leave the resulting tomatoes overnight.  They remained too wet for me to be comfortable doing that, even if I brought them inside.

As it stands, I put the trays into the Nesco dryer overnight, and they were all done the next morning.  I err on the side of caution when it comes to food safety, so that’s probably how I’ll end up using this.  Part-solar, part-electric drying.

Other types of solar dryers can get the job done in a day.  That’s the claim for the best indirect solar dryer — where a large glass-covered box is used to produce hot air, which is then piped over the produce.  With that piece of equipment (and maybe a lower-humidity climate), you can get solar drying done in a day. That’s just more equipment than I want to use for my occasional batch of dried vegetables or fruits.

So, in Virginia, with this dryer, I can reduce but not eliminate the use of electricity for making dried tomatoes.  Given how easy it is to use — stack the Nesco trays in and put the lid on — I’ll certainly keep using it.

In hindsight, it might actually be more energy-efficient to pre-dry the tomatoes in the electric dryer, and finish them in the solar dryer.  Rather than the other way around, as I did here.  See below.

Afterword:  Some power calculations.

In this trial, I deliberately used the same quantity of tomatoes that I would normally run through my electric dehydrator.  That works out to be about six pounds.  That means that, in theory, I need the same total energy input with this solar dryer as I would normally use with the electric dryer.

The Nesco dehydrator that I use runs at about 400 watts.  And I have to believe it was designed to give the optimum level of ventilation as it runs.  Last time I ran a batch of tomato slices through that, in the humid outdoor air of Virginia, it used 8 KWH of electricity, which means it took about 20 hours to dry the tomato slices completely.

This little solar dryer, by contrast, runs at about 250 watts, as near as I can calculate.  Starting with data on summertime ground-level insolation in my area, for an average summertime daylight hour (spanning four hours before solar noon to four hours after solar noon), I calculate that about 60 watts of energy per square foot makes it through the plastic, into the box.  For roughly four square feet of free area on the top, that works out to about 250 watts.

Not all of that energy goes into removing water.  Both dryers will suffer energy losses from conduction and convection.  The Nesco, being far more compact and (presumably) designed for optimal ventilation almost certainly has lower losses than the solar dryer.

Factoring in energy losses, this little solar dryer is at best half as powerful as the electric dryer I use.  (And, separately, it clearly had too little ventilation, as evidenced by condensation on the inside.)  So it’s no surprise that it could not dry the full batch of tomatoes in one solar day. 

Given the estimated power input, it’s right on the edge of plausible that this simple solar dryer could do half a batch in a day.  In other words, stack the trays one deep, not two deep as in this trial.  That means that two of these might possibly provide a complete substitute for my electric dryer.

Maybe a better possibility is to use this solar dryer as-is, but use it to finish the tomatoes, not start them.  If you’ve ever tracked the drying process, you know that as the food dries, the drying slows down.  In this scholarly article on food drying, the conventional wisdom is that two-thirds of the drying time is used to remove the last one-third of the water.   As a consequence, the last few hours of electric food drying are the least efficient, in terms of water removed per KWH of electricity used.

(As an aside, that same article also notes how energy-inefficient food drying is.  “Most common drying processes use extensive quantities of energy at relatively low efficiency. Energy-wise, drying is a wasteful water removal process …”.  That high energy use is the very thing that started me down this path.

Combine that with the observation that my little solar dryer was overwhelmed with the water from the raw tomatoes.  It was not sufficiently well-ventilated to avoid condensation from a full (four-tray, six pound) load of tomatoes.

My final observation is that the dryer the tomatoes are, the safer it is to leave them out overnight.  If I had a batch of tomatoes that was two-thirds dried — leathery, say, with no visible moisture — I’d consider leaving those out overnight.

When I put that together, I can almost certainly dry my tomatoes more efficiently by combining solar and electric drying in the reverse order of what I just did.  I should use the electric dryer first, remove the bulk of the moisture, then finish the half-dried tomatoes slowly in the solar dryer.  Maybe something like four hours in the electric dryer, followed by two days in the sun.

Let me summarize:

  • This solar dryer, as currently constructed, can’t dry a full load of tomatoes in a day.  It’s too low-powered.
  • I am not willing to let the partly-dried load of tomatoes sit overnight.  After a day in the sun, they were still too wet for me to be comfortable doing that.
  • Therefore, I will use some electricity as part of this drying process.  This is inherently a hybrid solar-electric system.
  • Upon reflection, given that I am going to use electricity, I should use that first.  It’s smarter to dry the raw tomatoes for a few hours in the electric dryer, then finish the partially dried tomatoes in the solar dryer over the course of one or two days.

That’s obviously the next thing to try.

Post #1219: Bought a Prius Prime


That’s the plug-in Prius.  So far, my wife and I like it.  A lot.

This car is a plug-in hybrid electric vehicle (PHEV).  It’s a standard Prius gas hybrid that also functions as a fully-capable electric vehicle (EV) with limited range.

In a nutshell, this car combines good electric-vehicle performance, easy at-home recharge, no range anxiety, and all the bells and whistles that you expect to get with a modern car.

And it was cheap.  Toyota offered $5000 worth of incentives, the Federal government chipped in $4500 worth of tax credits.  Net of both, the car cost $22,000.

What’s not to like? Continue reading Post #1219: Bought a Prius Prime

Post #G21-047: Canning lid shortage revisited mid-August 2021

This post is about the ongoing shorting of lids for home canning in the U.S.  The only value-added here is that I’ve been tracking this for a while, so I can give some perspective on how things are evolving.

Briefly, U.S.-made disposable lids are much harder to find now than they were when I posted on this back in May.  In my area, I found one retailer (Tractor Supply) that would ship them to store for pickup.  On-line, they are still available from Amazon, but almost nowhere else.  On-line prices appear unchanged to up slightly.

By contrast, there is no on-line shortage of foreign- (i.e., Chinese-) made lids.  Prices appear to be falling, with some Amazon offers now in the $0.15-$0.22 per lid range, for lids in bulk.  That’s down from about $0.30 when I checked back in May 2021.

U.S.-made re-usable lids (Tattler, Harvest Guard) are unchanged in price, but only the more expensive ones (Tattler, about $1 per lid) are freely available.  The less-expensive Harvest Guard lids appear to be back-ordered by about a month.

U.S.-made disposable lids

These are almost entirely Ball, Kerr, and Golden Harvest brand.  These are all made by the same company, a subdivision of Newell Brands.  That corporate conglomerate ownership is discussed in Post #G21-009.

There may be some store private-label brands that are U.S. made, but I have never been able to verify that.  I read one on-line source suggesting that Walmart’s house brand of lids (Mainstay) appears to be made by Ball/Kerr.  Not sure if that’s true or not.

How has the market changed since my last post:

Back in mid-May, these were still sporadically available at at least one of my local Walmarts, and I was able to show that they were in-stock and on the shelf in about 15% of U.S. Walmarts (Post #G21-025).  Where they were not in stock, Walmart was willing to ship you up to three packages (of 12 lids) for a reasonable price.  In addition, these were frequently available at my local ACE Hardware and some of my local grocery stores (Post #G21-020).

Currently (8/18/2021):  Nothing is on the local store shelves.  These aren’t even listed on the Walmart website, and haven’t been for at least a month.  On every shopping trip my wife and I take to any retailer that sells canning supplies, we check for lids.  Near as I can tell, there are no packages of lids for sale on the shelf in any bricks-and-mortar retailers in my area that I frequent.

Checking all the retailers in the area, Tractor Supply says they can have some for me at my local store (Manassas, VA) in two days.  And if I were willing to drive quite a bit, there are two packages on the shelf in Marshall, VA.  But they won’t ship them directly to me.  So, apparently Tractor Supply has some ready for distribution to their stores, in some areas.

The best I can get out of any of my other local retailers is a “call store first” notice from Southern States.  All the rest of the places I could drive to, that I know stock lids, show nothing.  Not even boxes of bands-and-lids, which work out to about $0.50 per lid.

On-line?  Amazon still lists what appear to be legitimate vendors offering U.S.-made lids in large lots for around $0.70 per lid.  Uline (an industrial packaging supply firm) listed them back in May, but no longer lists lids.  I haven’t stumbled across any other on-line mainstream retailers offering genuine Ball lids.

Foreign-made disposable lids

Much of what you are offered on line consists of Chinese-made lids.  Some companies are up-front about it.  Many of them try to hide that.

Basically, if it’s not brand-name Ball, Kerr, or Golden Harvest, based on what I’ve seen, chances are you are looking at Chinese-made lids.  Almost no matter what the website marketing the lids has to say, or however many American flags they display on their web page.

I’m only looking at Amazon.  At least there, the vendors seem to be required to disclose that lids are not American-made.  Based on the comments, some quality problems were evident for quite a few of these imported lids.  And, because the manufacturers have largely figured out how to game those ratings, even if you see high ratings, you’re taking a gamble no matter what the average rating says.

How has the market changed since my last post?

The only change I note is that foreign-made lids are getting cheaper.  The typical offer is now around $0.22 per lid for lids in bulk, and I am seeing a few offers for as low as $0.15 per lid.  I’m pretty sure that’s trending cheaper than when I looked back in May.

U.S. made re-usable lids.

The original and more-expensive brand (Tattler) appears to be available in any quantity.  These run about $1 per lid/seal, but those are both re-usable.  The cheaper knock-offs (Harvest Guard) are available for about $0.76/lid.

How have things changed since my last post?

The Harvest Guard lids are now back-ordered by about a month, based on the Harvest Guard website.

Post #G21-046: The carbon footprint of home-made tomato sauce

In this post, I estimate the carbon footprint of my home-made spaghetti sauce.

You’ll hear people casually assert that home-canned food is good for the environment.  The idea is that it avoids (among other things) the fossil-fuel use associated with transporting food.

But as an economist, I guess it’s my lot in life to point out that nothing is free.  Home canning uses a significant amount of fossil fuels.  Home-canning of foods with relative low energy content leads to a significant amount of fossil fuel consumed per edible calorie preserved (see Post #G22).  It can also generate a non-neglible carbon footprint, owing to the fossil fuels used.

Each quart of sauce I make generates a bit over two pounds of C02 emissions.  But that is heavily dependent on a couple of things. Continue reading Post #G21-046: The carbon footprint of home-made tomato sauce

Post #G21-045: Embracing my inner rutabaga.

Part 1:  A farewell to squash

I pulled up my summer squash plants yesterday morning.  These plants held up well and produced a reasonable yield, but their time had come.  And so I called an end to summer squash season.

The members of my family took the bad news remarkably well.  If I didn’t know better, I’d almost think they were tired of eating summer squash.  Inconceivable!

In any case, yields had fallen to next-to-nothing. At some point, that garden space could be put to better use.

I would continue to try to grow some if I could preserve it well.  But as far as I can tell, available methods for preserving fresh summer squash are largely unappealing.  Canning fresh squash safely is difficult-to-impossible to do at home.  (And supposedly safe recipes include more than half an hour in a pressure canner, so I’m not sure the end product would be worth it.)  Freezing them degrades the texture, and the slicing/blanching/cooling/freezing process seems both labor- and energy-intensive.  That said, I’m going to try freezing my last remaining squash to see how that turns out.  I’m not desperate enough to try drying them other than as a novelty.  (Squash chips, anyone?)  Pickling (lacto-fermentation) is always on my list, and I’ve already put up couple of half-gallons (per the simple instructions in Post #G23). That’s obviously not fresh squash when you are done, and you have to refrigerate the end product unless you can (preserve) them afterward.  Standard (vinegar) pickles/relish/bread-and-butter pickles, ditto.

The final factor was the effort involved.  In hindsight, those summer squash plants required a lot of space and maintenance for relatively modest yield of edible calories.  To recap this growing season, keeping these plants alive required dealing with:

  • A fungal disease of unknown origin, never fully identified (Post #G21-036).
  • Squash vine borer (Post #G27 and see the afterword below).  This year I lost several plants despite repeatedly spraying the stems with spinosad.
  • Cucumber beetles, which showed up early this year (Post #G21-027) and have been present ever since.  Despite what the academic sources say, there is no distinct “season” for them here.  I never did find any systematic way to get rid of them (Post #G21-032).  My sole method of control is to squish them on sight, which is satisfying but ineffective.
  • Birds that ate all the male squash blossoms.  I ended up using metal and/or netting cages to protect individual male blossoms.  That worked (Post #G21-042), but meant that I had to hand-pollinate the new female blossoms every morning, in addition to managing the protections for the male blossoms.
  • Squash bugs.  Keeping these in check was made somewhat easier by use of a lint roller and an inspection mirror (Post #G21-034).  But that still meant eyeballing all the leaves in the entire squash patch on an almost-daily basis.
  • Powdery mildew.  I guess this was the last straw.  I fought this to a standstill last year, having found a formula that would knock it back pretty well once it was established (Post #G20 shows the results).  I wasn’t willing to do battle at that intensity again this year.  Instead, I’ve been cutting off any infected leaves, but that has turned out to be just a holding action.  The mildew can grow faster than the new leaves can.

Not to mention staking, pruning, watering (they wilt so easily in the heat), fertilizing, and so on.

And so, I’m throwing in the towel on summer squash for the year.  In theory, in this climate zone, I could re-plant for a fall crop.  I’m not going to bother.  FWIW, my favorite variety remains early prolific straightneck.  That variety accounted for maybe a third of my plants and 90% of my yield.   Zucchini and patty pan were failures by comparison.


As if to celebrate my squash liberation, I spotted a squash vine borer (SVB) yesterday  afternoon.  And I didn’t have to care.  It was loitering around my winter squash, but those with solid stems are (in theory) resistant to borer damage.  The upshot is that hollow-stemmed summer squash are still not yet safe from the SVB.

I found a lot of conflicting evidence on the SVB when I first did my research.  For the record, the 2021 SVB season here has run from June 16 (Post #G21-033) to (at least) August 8 (yesterday).

That’s just over seven weeks, which is a good match for the duration of last year’s season (Post #G27).  Based on these two years, that seems to be the pattern for SVB season here in Zone 7 Northern Virginia.  The SVB arrives like clockwork at around 1000 growing degree-days.  We then have three weeks of multiple sightings per day, followed by four weeks of sporadic visits.


Part 2:  That’s one hot tomato.

It has been hot and dry of late in Northern Virginia (Zone 7).  My nearest weather station shows that we’ve had about two inches of rain in the past four weeks.  That, coupled with temperatures consistently in the 80’s and 90’s F means low soil moisture anywhere that isn’t irrigated.

I don’t need to look at the weather data to know it’s been dry.  My rain barrels are just about empty again.  While that’s not unusual (see post #G21-043 for a model using historical weather data), it is an indication of a consistent shortfall of rain.

Now we’re projected to a have a week of days with highs in the 90’s F.

This is unfortunate, in that I have a lot of tomato plants that are bearing fruit.  Not only does the high heat keep the fruit from ripening (see Post #G11), it stresses the plants, and may result in fruit drop.

This year I decided to follow the approach laid out by Gary Pilarchik (“The Rusted Garden Homestead”).  First, I put up a sun shade for my tomatoes by clamping a piece of floating row cover to my tomato stakes.  Second, I picked every pickable tomato, at the “breakers” stage or beyond.  In other words, any tomato showing any red or pink coloring came off the plants, to ripen in a paper bag in the kitchen.  Finally, I’m giving my tomato plants about an inch of water every other day. With dry soil and highs in the 90’s, I don’t think there’s any conceivable way I could over-water them.

Here they are, chilling out yesterday afternoon.  Shaded, watered, and picked.  That’s about the best I can do for them.

Part 3:  Embracing my inner rutabaga.

After two years of growing fussy above-ground vegetables, I’m beginning to think that maybe I’m a root crop kind of a guy.

This year I haven’t said a word about my value-destroying experiment in no-dig potatoes (Post #1173).  That’s because a) no pests bothered them, b) the deer didn’t eat them, c) the weeds didn’t grow over them, and d) I got a so-so yield of potatoes.

I might have watered them once during the season.  In short, it worked as advertised.

That was gardening as it exists in children’s books.  I planted a crop.  The sun shone, the rains fell.  The crop went about the business of producing food.  I harvested it when it was done.  And it will keep all winter, no preservation needed.

Likewise, I have been silent about my sweet potatoes.  That’s because they worked.  I started with three moldy sweet potatoes, and I now have maybe a hundred square feet of sweet potatoes growing.   What’s not to like?  They are easily propagated, grow like crazy, and need no attention other than occasionally directing a stray tendril back into the patch.  And they have pretty flowers, to boot.

Maybe I’ve learned my lesson.  I replaced my summer squash with beets, turnips, and rutabagas.  None of the glamor of a nice, showy zucchini.  But none of the drama, either.

And certainly none of the work.  This morning, for the first time in months, I got up and didn’t go to work in the garden.   I admired my sunflowers for a bit, then made a cup of tea and put my feet up.

Nothing wrong with that.  I’ll almost certainly get more calories per square foot out of those crops than I would from summer squash.

And yet, it’s unsettling.  It’s akin to what I felt with my first pension payment.  It just seemed wrong, somehow, not to have to work for it.  But I think I can get used to it.  With time, I will eventually come to embrace my inner rutabaga.

Post #G21-044: Stealth mildew and a farewell to squash

Squash vine borer, and an observation.

Source:  U Wisconsin Vegetable Entomology.

As was the case last year, the squash vine borer season has been slowly tapering off.  My last sighting of a squash vine borer was a lone female about six days ago, or circa 7/23/2021.

I’m calling that the end of the season, unless I see another one. Continue reading Post #G21-044: Stealth mildew and a farewell to squash

Post #G21-043: A model of a rain barrel system based on historical weather data


If you use rain barrels to water your garden, you will eventually realize that you don’t have enough of them. 

This post tells you that you never will.  But that’s OK.  Most of the benefit you will get from using rain barrels, you will get with the first few you install.

This post isn’t nearly as folksy as the introduction implies.  To write this, I first created as reasonably sophisticated model of rain barrels and gardens using four decades of daily weather data for Sterling, VA.  While the results of that model really only apply to my local climate, I think the more general lessons about rain barrels apply broadly to well-watered temperate climates such as the climate of Virginia.

Continue reading Post #G21-043: A model of a rain barrel system based on historical weather data