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Moisture meter

Glenn Lefley

Glenn Lefley

Joined
Jul 10, 2017
Messages
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Location
Windermere, British Columbia
Looked in back threads but did not find much. Need advice on type of moisture meter to purchase. Not a cheap one, but one I can check wood I buy that says its kiln dried. Lately receive wood, and when I put it in my dehydrated with just the fan on getting bad cracks. Wood states it's 8 %, I'm thinking not even close. When I weigh a 700 gram pc lost 35 grams in a day.
 
I have a sawmill and did have lumber drying kilns at one time. In 1995 I bought a Electrophysics pin meter and a Wagner L609 pinless meter. Both are still working well, but I normally only use the Wagner just because I don't like pin holes in wood.

I have checked the meters against oven dried wood samples. Sometimes the Wagner reads 1% high on some species. The Electrophysics is always right on.

I've also tracked the MC of wood in our house for years. It normally runs from 7% to 9% winter to summer. In turn I know if my turning wood is in this range it will not move (much) when I bring it into the house.

My recommendation is a Wagner pinless, your choice of model.
 
I purchased my Mini Ligno E moisture meter back in the late 1980's......and, it's still working fine. This one has progressive light bulbs that light up, and two range settings.....they now have a digital readout. This is a pin type meter. Use it where you know it will be waste material: on corners of bowl blocks, and on the bottom of bowl blanks in the round.....no problem. It seems to get better, or more consistent accurate readings on the end grain, over the long grain.
Mini Ligno E moisture meter (2).jpg
The moisture meter is only important to get a general idea of the moisture content, and it will help to know this when roughing a bowl for seasoning. The higher the MC and expected tendency to warp, the thicker the roughed bowl should be. The thicker it is, the longer it will take to season......but, this is the price to pay for avoiding excessive warping and cracking. (Woodturners will go to extremes to avoid the time element......but, nothing works as well as accepting the fact that Father Time is the one thing that can work for, or against you......if you don't give him his due!) After roughing, weigh monthly until the weight stabilizes.....usually 3-4 months of unchanged weights, or within 5 grams, or so. It isn't necessary to know the exact MC of the wood after its stabilized......it is what it is, and will be determined by the ambient atmosphere at your location.

-----odie-----
 
A moisture meter is the best tool for checking the moisture level in stickered lumber where it's not feasible to weigh it, but in my opinion it's not the best option for rough turned bowls. Knowing that a rough turned bowl is at or near EMC is more important that knowing what the percent moisture content is.

As Odie already mentioned, you can weigh a roughed out bowl periodically and when the weight loss stabilizes to within a few grams then you know that it is as dry as it is going to get in your local climate. Odie mentioned not messing with Father Time (or Mother Nature) and that's good advice.

Here is a graph that I posted in a thread four years ago. I generally weigh rough turningis in grams, but this was an extra large coring (about 19" diameter and roughly 2" thick) and I had to use a larger scale for the initial weight. Note that the vertical scale doesn't go to zero so don't get overly excited by the magnitude of weight loss.

[You might need to click on the image to see it full size]

index.php



You might want to read the full discussion so here is a link to the thread: Need Info on Moisture Meter
 
Check out Bills link above.
There are also these threads

http://www.aawforum.org/vbforum/showthread.php?t=6671

http://www.aawforum.org/vbforum/showthread.php?t=2827

I have been using a Mini Ligno E for about 16 years it has two pins.
I use it to check airdired wood before I use it and I use it to check air dried bowls before a second turning.
I push the pins into the chuck tenon so the holes get turned away. This is measuring the moisture deep in the tenon where the long grain of the bowl is. While not perfect it gives a pretty accurate assessment for bowls approaching 8 %.

Quick and easy. Takes out the guesswork.
 
I have a really cheap moisture meter and don't recommend it other than it has been fun playing with it just to sort of see if what I did before I got the meter was in the ball park. I much prefer to weigh my bowl blanks. Moisture meters don't read very deep so I don't really think they would be very useful to measure bowl blanks. However that's purely based on my limited experience with meters. As far as the pin holed go I doubt you will ever see them. They don't cut the wood they just spread it. With a little moisture they would close back up and never be seen. I use mine to check flat stock that I use for hand mirrors and I've never seen a puncture hole. I don't particularly pay attention to where I stick it in the board. I will try sticking it in a plain area that I know will show and let you know what happens. May take a week or more because i have to leave for demos in the next few days and won't be back until Monday.
 
Weighing can be better than using a moisture meter but you must have a controlled or known environment to know what moisture content you get when the wood stops loosing weight. Wood stops loosing weight when it reaches equilibrium moisture content with the RH. To know the apximate MC you have to use a chart like the one below. You also have to keep charts on each bowl and when it gets to the lowest weight you have to wait an extra record period to see if the weight gets lower. The record keeping is something could never get in the habit of doing.
EE2E8DBF-9CAA-4A4C-840A-4E0B81DD0921.jpeg
 
I have a pin type moisture meter that got free when we bought our fireplace. pin type and works well. I only use it to get a initial number. I have a postal scale and I use weight to determine equilibrium. There is listing by some government agency that has the average MC depending on area. I'm changing computers and don't know where it is right now on this computer, but it does exist. the chart gives average MC for each month based on area. I'll try to locate it later, but weight is the best way in my opinion.
 
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A pin meter is measuring the resistance of the wood and moisture between the pins. The measurement could be dependent on many variables such as wood species and pressure applied.
I use mine as a relative meter by first setting a dry measurement of my kd workbench which is in the shop environment.
I guess you could do this with a series of dry thin samples of the types of wood you normally turn. This would give a quick test of where the surface of the blank is.
Stu
 
So, the issue isn't whether or not to poke holes with a pin meter, if that really happens, but to understand you're really only checking the surface and NOT the interior of the wood. I fell into that trap with a piece of Maple I'd harvested locally. The Pin Moisture Meter told me it was pretty dry and I smooth turned it, finished it and set it up on a shelf. About a month later someone asked me how I got it to look that way? "What Way?" Kind of a cross between a banana and a potato chip. Yeah, pretty warped. Smooth turned it before it was dry. Of course I told whomever was asking that it was the plan.

Get a scale and weigh things until the piece stops loosing weight. That means it's ALSO stopped loosing moisture. You'll be happier.
 
I think this discussion in one form or another shows up about every nine months (mmm is that related to...no couldn't be) . We are not dealing with a medium that can be accurately measured in thousandths and be expected to stay there. Wood moves and no matter what finish is used it will still move . This movement is even greater when the environment changes--rain,drought,A/C,no A/C,cold. So the only thing important to what we do is to get to EMC and the way to get there is like Odie said "time". I use the weight method and when it stays the same or within 1 GM for 4-5 days it is time to do the second turn. Note that if there is still some moisture to be reduced the thinning of the item and at that point movement will be minimal and not visible to the human eye.
 
hockenbery said:
Weighing can be better than using a moisture meter but you must have a controlled or known environment to know what moisture content you get when the wood stops loosing weight.
Click to expand...

True, but I don't care what the final MC is. When the weight stabilizes I know that the wood is dry. On average, we are fairly dry here interspersed with brief periods of rainy weather. Since I keep my wood in a controlled environment that is heated and air conditioned, what is going on with the weather outdoors has much less impact on the indoor weather. Besides that wood very slowly responds to changes in absolute humidity. The reason that your chart includes temperature is that it is actually making a conversion from RH to absolute humidity.
 
I use a moisture meter, but just for a relative number - I also weight blanks because the pin type meter is about as cheap as they come. I weigh the blanks when they’re roughed and write the weight and the mc according to the meter on the tenon. If there’s a lot of blanks, the accounting can take a while, so in between weighings (about once a week - I weigh about once a month) I just take a mc reading and write it on the tenon next to the last weight if its changed.
When I say the meter is cheap, I’d be surprised if I paid more than 12 bucks for it about 10 years ago - don’t remember where it came from. It’s truly a wonder - measures moisture, locates studs, is a metal detector and has another function that I don’t recall and haven’t yet found a need for. The metal detector has come in handy. While it probably isn’t all that accurate or sensitive, I’ve found it to be consistent, and the stud finder easily outperforms the one that cost 5 times more.
I love it when cheap works. Perhaps there should be a thread on cheap products/solutions that have been useful...
 
I too use the weight method and finish turn once the weight stabilizes. Here in Whitehorse, Yukon it is considered a dry climate. Many of the turnings I produce end up being sold in the lower provinces of Canada and those environments are far more humid than here in Whitehorse. I find when to stop weighing becomes a guess if I know the turning is being shipped south because it will adjust itself to whatever environment it will end up in (regardless of finish.) I have an Electrophysics pin meter and never use it. It is a crap shoot as I have had a couple of reports of hairline cracks forming after a few months.
 
Robin Thompson said:
I too use the weight method and finish turn once the weight stabilizes. Here in Whitehorse, Yukon it is considered a dry climate. Many of the turnings I produce end up being sold in the lower provinces of Canada and those environments are far more humid than here in Whitehorse. I find when to stop weighing becomes a guess if I know the turning is being shipped south because it will adjust itself to whatever environment it will end up in (regardless of finish.) I have an Electrophysics pin meter and never use it. It is a crap shoot as I have had a couple of reports of hairline cracks forming after a few months.
Click to expand...

Interesting, Robin........If I understand what you're telling us here, your bowls which originate from your dryer climate are getting hairline cracks when they are relocated to a more humid climate?

I've found that cracks usually happen with a reduction in moisture content, and not the other way around......so, this is a little confusing to me. :confused:

Much of the wood I get is KD, or processed elsewhere, and as low as 6% MC.......much of it between 8-12%. Even though it's expected that some of this wood will gain some MC, I've never had any trouble with subsequent cracking, because it gained some slight MC while acclimating to my location. When I season my own wet roughed bowls, they acclimate downward to around 12%. To my knowledge, there has never been any problem, and my bowls are spread out pretty diversely withing the lower 48 states. (I did have some problems with cracking, and uneven warping between dissimilar woods, back when I was making laminated bowls in the 80's and 90's......and, it's one of the main reasons why I don't do those anymore. :()

-----odie-----
 
odie said:
Interesting, Robin........If I understand what you're telling us here, your bowls which originate from your dryer climate are getting hairline cracks when they are relocated to a more humid climate?

I've found that cracks usually happen with a reduction in moisture content, and not the other way around......so, this is a little confusing to me. :confused:

Much of the wood I get is KD, or processed elsewhere, and as low as 6% MC.......much of it between 8-12%. Even though it's expected that some of this wood will gain some MC, I've never had any trouble with subsequent cracking, because it gained some slight MC while acclimating to my location. When I season my own wet roughed bowls, they acclimate downward to around 12%. To my knowledge, there has never been any problem, and my bowls are spread out pretty diversely withing the lower 48 states. (I did have some problems with cracking, and uneven warping between dissimilar woods, back when I was making laminated bowls in the 80's and 90's......and, it's one of the main reasons why I don't do those anymore. :()

-----odie-----
Click to expand...
I've been told by my shipper that he had a lot of trouble with things being shipped in the winter. Goes out with kiln dried number. Frozen at shipping site. -35c in airplane , then up to plus 20 at the post office same day. Cracks appear. It is the sudden freeze thaw cycle in the shipping process that a lot of people forget about and then things show up later.
 
Glenn Lefley said:
I've been told by my shipper that he had a lot of trouble with things being shipped in the winter. Goes out with kiln dried number. Frozen at shipping site. -35c in airplane , then up to plus 20 at the post office same day. Cracks appear. It is the sudden freeze thaw cycle in the shipping process that a lot of people forget about and then things show up later.
Click to expand...

Yes, I can see that, Glenn.......extreme temperature swings does seem to add an additional aspect, especially so for wood with a high MC. :D
 
There are several finishes that do not perform very well when subjected to extreme temperature changes.
Many a musician back in the day would travel from one gig to the next hauling the equipment in an unheated trailer. If you brought the equipment into a warm location and opened the guitar case while the instrument was still frozen and exposed to the warm indoor temperature the finish would crack across the surface. As the surface warms quickly the underlying substrate is still frozen which cause a thermal shock to the piece. When a package arrives in the mail and it has been sitting on your porch for several hours it would be advised to let the package slowly warm up inside the house before opening the package if it contains an item that may be fragile or susceptible to thermal shock.
 
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