Unusual Use of a Moisture Meter

[DuaeGuttae]

I debated whether to put this question in the ongoing garden thread, but it pertains more to the function of a moisture meter, so I decided to go with the gear thread. Bear with me, please, folks.

This summer I made an attempt to grow some fun-colored popcorn kernels for my children. The variety was Glass Gem Corn. It was a terrible gardening year in Texas due to record-high temperatures for all of May, June, and July and just plain miserably high temperatures in August and September. All this was coupled with exceptional drought. Anyway, I had a tiny harvest of Glass Gem Corn. I’ve saved seeds from it, but I want to get the rest of the kernels to a proper condition for popping.

I tried just six kernels a week or so ago when I was heating oil for another purpose, and I would say that I had mediocre to poor popping. I assumed it was because my kernels were too dry, so I added a teaspoon of water to my stash and let it rehydrate for a few days. We made a second attempt yesterday with five kernels, and the results were no popping whatsoever. At that point, I thought, “maybe my kernels are too wet actually.”

I had earlier read an article about popcorn where someone actually used a moisture meter to test the level of dryness. I have to give her credit for acknowledging that this in not an accurate test, but she tested known “good” popcorn and her own homegrown popcorn and compared the two results. Here’s the link for anyone who wants to see.

Popcorn Not Popping? Why & How to Fix it.

Popcorn not popping? There are 2 reasons for that. It's either too wet or more likely, too dry. And you can fix it. Here's how ...

www.theartofdoingstuff.com

I decided to do the same yesterday, and I got my storebought popcorn that pops coming in at 15% and my Glass Gem Corn at 19%, so I have the jar open on my mantel now to dry down further, and I figure I’ll test till it gets down to the same level as my popping corn that pops.

My question is about why the moisture meter measures the two separate popcorn kernels. I put the two kernels on and then used my palm to make a connection between the two, and that’s when I got my readings. It’s my (very limited, almost non-existent) understanding of a moisture meter that it measures the conductivity between two points. The less resistance there is, the more moisture, I think. Is my hand, therefore, creating a conductive link between the two kernels and allowing it to take some sort of measurement?

Can someone more knowledgable than I about electricity (which would probably be practically anybody here) explain the moisture meter to me in layman’s terms. Even if I’m not getting an accurate reading on popcorn with it, would it actually produce a repeatable moisture measurement that I could use to help gauge the proper curing of my popcorn, or is it somehow silly to try?

 

[Newbie78]

The moisture meter simply measures resistance.

if you want moisture accurately, do it by weight. Weigh say 50 seeds. Then put them in the oven at a somewhat low temp for a long time, idk? 6 hours, 12 hours? 24 hours? Weigh the seeds again. This method will be much more accurate than the resistance method.

 

[stoveliker]

Yes, your hand (moist skin surface) is providing the channel between the two. That means that what you measure now and what you measure tomorrow (after a teaspoon or oven) will be incomparable, because your hand conductivity will be different depending on temperature, RH, sweat, IR exposure (sun), etc. etc.

Moreover, this method adds a ton of issues to an already "approximate" method (weighing as above is far more precise, but takes time).
The problem with 2-point resistance measurements is the contact resistance. You are *not* only measuring the resistance of the sample (wood or corn) but the resistance of the contact between metal and wood gets added. And that might not even be the same for both contacts. With the corn you added a contact between pin and (inhomogeneous) corn, AND between the corn surface and your hand. Neither inside nor outside of the corn will be very uniform in electrical properties, so sticking pins in there will give some random contributions to this contact resistance.

Now maybe in TX your hand will always be "cracked-skin-dry". Maybe the RH is so low that the surface of the corn is also always the same dryness. Then, if you make sure that you stick the pin in in the very same way (through the germ?) for each measurement, you can minimize the randomness.

Still, I'd simply weigh corn. Count 100 kernels weigh them. Count 100 other kernels, weigh them. Do that a few times, and see what the variability is between their weight. That gives you a baseline precision (average + error range).
Then dry them, and weigh again.

My $0.02

 

[DuaeGuttae]

Thanks for the replies, @Newbie78 and @stoveliker. They were both very helpful. I just needed to understand what was going on with my hand making the connection.

The quantity of corn kernels I’m talking about here is less than one cup, so I’m not going to go to great lengths to try to figure out the perfect moisture content. I don’t think I could do a weight comparison between my kernels and the storebought ones because my kernels are not as large, so 100 of each batch would have quite different weights. I have the jar of homegrown kernels open on my mantel now to try to dry down some more on the assumption that they aren’t already too dry. I don’t know if that’s what they need, but they will dry since it is very dry in my house at the moment. We’ve been having a cold front here. The temperature didn’t even get out of the thirties yesterday, and even with a very rare damp day outside, I think the relative humidity inside had dropped to 29% the last I checked. We have a console humidifier that we’ll start running soon, but I’m also drying down some bean seed inside, and I’m going to give that a little more time to benefit from our dry air before I make efforts to up the humidity.

If a trial of popcorn kernels fails again, I’ll just grind it into cornmeal, which had actually been my original plan in growing it. It was only after the harvest was so small that I thought I’d pop it instead. We might just have a really small batch of cornbread one night the next time I make chili. If this cold air keeps hanging around, I can see myself making another pot pretty soon.

Or, maybe just maybe, I should make a special batch of cornbread to go into the stuffing for our Thanksgiving turkey. That might be the perfect use for a small batch.

 

[ezequias]

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