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How useful is a moisture meter?

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Jul 18, 2018
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I’ve periodically thought about adding a moisture meter to my tool collection, but I wonder how useful they really are for turning. I hear lots of folks talk about waiting for turning wood to get to a certain moisture content, but wonder if we are working with thick blanks, do these really tell us anything beyond where the probes are reaching? Is that number indicative of what’s going on inside the blank? I’d love to hear folks’ impressions, and perhaps brand name endorsements as well. Thanks!
 
Weighing your wood and writing the date and weight on the piece every couple of months is the simplest and most reliable means of assessing dryness. When the weight stops changing you're done, having reached equilibrium with your storage place's humidity. A nice electronic parcel scale works very well for this, plus has the added benefit that I actually know what my Fedex shipments weigh before I send them.

I have and use a meter on flat work all the time, checking that wood from the lumber yard is actually close to what it's supposed to be is often quite useful. I have a pinless version that can read to a couple of different depths, but an inch or so is the limit, for testing 8/4 boards. Obviously not useful for a 10" thick blank. Also doesn't work well on round objects, like rough-turned bowls. Pin-type meters will work on wood as thick as you care to drive the pins into. (several inches is still a stretch), but then you end up with holes in your workpiece, Unless you're turning strainers that can be problematic.

A digital scale is simple and reliable, with the downside that you need two data points to begin to know what's happening. With 40-50 roughed out bowls sitting around at any given time I never have an issue with getting a couple weights.
 
Like Roger, I, too, rely on weighing (in grams) my turned wood projects and blanks to assess dryness , it works quite well. I also have a pin-less moisture meter on the cheap to spot check flat lumber as I bring it in from outside, and get a comparison percentage (get a reading when it comes in the shop, then get another after it's been in a week or two, to gauge how it may have stabilized)
 
I've owned 2 of them. I turn mostly and do some flat work. I found them useless. It was interesting finding out the percentage difference between wood in my shop and wood in the house but for all practical purposes I didnt see any value. The first cheap one died. I bought the second when they went on sake but used it so little when a guy was at my shop and asked about meters I gave it to him.
 
I use mine initially when turning after I have made a few cuts because they only give the surface MC. It verifies the blank is dry or still containing some moisture. To determine if a rough out is stabilized I use a scale and monitor the weight loss. I could also monitor the blank this way and not need to use the moisture meter. The meter I have is SBC(?) brand that looks identical to the AccuMASTER XT sold by Lowes for around $30. Final, nice to have, but not a must have. A scale to measure weight is a must have IMO.
 
I do both methods for measuring roughed out blanks. I try to measure the mass shortly after roughing and then at some later point(s), and this is very reliable. Where it doesn’t work is if you have forgotten to measure the mass in the last several months and want to turn a piece from that batch, even if you mass it now you won’t know if it is dry for several weeks when you can measure it again. In this case I like a cheap pin meter. I can stick the pins into to a few tenons of bowls I know to be dry and then compare to the bowl in question. If the readings are the same the bowl is close enough, but if they differ then you know to wait, and can go ahead and record the mass for future reference.
 
Roger's comments above are "spot on". If you really need to know the exact moisture content of a piece of wood for some reason, learn how to do an oven dry test. The test will give you very precise MC and you can do it with a good scale and a microwave.
 
I use mine to test lumber brought in from other sources, to monitor kiln drying and occasionally to poke a bowl tenon. Driving long pins into hard wood is difficult and you really need a slide hammer like the one I got with my Delmhorst. I mostly go by weight changes for turning and rely on time to allow projects to reach equilibrium with the shop atmosphere.

If you are waiting for thick blanks to dry out before turning you can wait a long time and if not well sealed they can degrade considerably. I would suggest roughing them out and testing the moisture content of the inner surface you have opened up with a basic short pin meter. If the wood is still drying you will see a gradient from low to high moisture between the surface and core. If the moisture content is suitable you can turn to completion, if not leave them oversize, put them on the shelf and weigh them periodically.
 
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I agree with others regarding the evaluation of roughed out bowls; serial weights is the way to go.

I seldom twice turn, and am interested in getting an idea of the condition of a blank before I start a project. I buy a lot of my square blanks from estate sales and though waxed they may be 10 years old. I also buy 16/4 boards from lumber yards.

I have a pin & pinless combo unit. I seldom use the pins. A useful tool to me, but not essential.
 
Pin meters are useful if you want to assess the moisture gradient through the thickness of the wood, but they do leave holes (not a problem if in a waste area) and are limited to how deep you can drive them. Pinless meters give an average measure of the moisture content but are limited as to depth. I am not aware of any pinless meters that will measure to the center of a 4" blank.

Pinless meters give readings of specific gravity which is compared to the listed specific gravity for each species and compensated for moisture content, so they can be thrown off by samples of unusual density due to growth characteristics. The most reliable indication of moisture content is obtained by oven drying a sample and comparing to its initial weight, and the most practical method for most turners is periodic weighing until equilibrium moisture content is reached.
 
I use a pin meter. For me it is less work than weighing.
Weighing will be more accurate on thicker pieces.

Controlled environment is the key to drying Wood. The table below from the forestry service shows EMC you can achieve in your environment.I keep the drying room humidity at 50% so my wood will dry to around 9%

56D6420F-D3D3-4F4D-9C78-5FE8AC778CF6.jpeg
 
equilibrium
I noted that several of the replies used the term "stabilized" instead of the more accurate term "equilibrium". I go by "Hoadley's Understanding Wood" which never uses the term stabilized.
I have been using an obsolete mail scale (obsolete only because the manufacturer stopped making the plug in modules for mail rates) and like Roger detailed I weigh each piece and keep an individual record and reweigh after a day or 2 gradually increasing the time between weighing. The group drying process and the finished reassembled natural edge coasters.
DSCN0328.JPG 21103-7coaster.JPG
 
You could do without a moisture meter. I use a moisture meter on every bowl block in the waste corners, and I do so to get an idea of what kind of MC I'm dealing with. This is useful information to know. If my moisture meter conked out, I'd buy another.....

Determining current MC and determining stabilization are two separate things. The only true way of determining stabilization is done by weight. Monthly weights are the best way to observe the stabilization process accurately. Time is your friend in this process.....this means you just have to have plenty of patience to do this right. I decide a roughed bowl is ready for 2nd turn after a minimum of 3 months of unchanged weight. For many roughed bowls, I wait 4 months, or more, during winter months. If you're not absolutely sure.....it's never a bad idea to give it extra time, just to make sure. Don't be hesitant to give dense and heavy roughed bowls a little extra time, over lightweight and porous bowls.

There are incidences where a roughed bowl will actually gain a few grams during winter, or rainy months. Take this into consideration, and allow for it. For instance, if a roughed bowl weighs month by month, 1lb 1.6 oz, 1lb 1.6 oz, 1lb 1.8 oz, 1lb 1.6 oz, and 1lb 1.6 oz......I'd consider that bowl stabilized.

The real trick is to not get too anxious to work on a bowl......have lots of roughed bowls in progress. You need to have plenty of other stabilized bowls to work with while you wait for that "special" one to stabilize. I stress here.....time is your friend in the stabilization process.....don't get too antsy to finish turn your bowls.....have plenty of other work you could be doing while you wait.

-----odie-----
 
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I noted that several of the replies used the term "stabilized" instead of the more accurate term "equilibrium"


Stabilization and equilibrium are terms that describe the same thing.....and, both would be correct.

-----odie-----
 
The only use I would have for one is for the furniture I make. I always let the wood 'adjust' to my shop for months before I make anything. For bowls, I turn green and let them warp. Love the warped shapes.

robo hippy
 
Stabilization and equilibrium are terms that describe the same thing.....and, both would be correct.

-----odie-----
Stabilization is defined as unlikely to change where as wood is likely to change.
Equilibrium is defined as balanced as in moisture content between the wood and it's current environment.
So that does not appear to be the same thing unless you have some way to stop the inevitable seasonal changes in humidity.
 
Stabilization is defined as unlikely to change where as wood is likely to change.
Equilibrium is defined as balanced as in moisture content between the wood and it's current environment.
So that does not appear to be the same thing unless you have some way to stop the inevitable seasonal changes in humidity.

Yes, I get it......however, we're discussing layman's terms here.....and, stabilization is a commonly used term. You just have to apply the meaning of the term as it's used, not the technical definition as it's not used.

-----odie-----
 
Thanks all for the thoughtful replies. I have been, and will continue to simply weigh my wood and wait for a couple of months of no significant change. I’ll save my pennies and refrain from buying a moisture meter.
 
Yes, I get it......however, we're discussing layman's terms here.....and, stabilization is a commonly used term. You just have to apply the meaning of the term as it's used, not the technical definition as it's not used.

-----odie-----
Here is a definition for "layman's term, "simple language that anyone can understand" or should that be misunderstand.
 
I have one from when I 1st started with wet wood - you know how it goes with something new, you read a lot of info and many dead end. MM’s for turning are a dead end. Kinda fun to check wet blanks before I turn for the heck of it, and after wet turning to get an idea of how long the piece will take to dry, but I never got detailed about it. Weight tells me everything, not just part of the story.

Havent messed with quick drying methods much, no beads and only a few mw pieces, so I’ve not thought through whether wt would really work. I see potential for over-drying since the equilibrium point is for the immediate environment (beads or mw) and not the external environment, and have not tested either method with a MM by cutting and checking various depths, which is probably how I would approach it. Get an idea of time vs wood thickness.
 
Weight tells me everything, not just part of the story.

Yep....this is the bottom line, Doug..... :)

Just how someone does use weight as the measurement, is a variable. On these forums, I've observed those who believe days without weight change is the determining factor. Others may find what they believe is stabilization (or equilibrium!) to be a matter of a couple weeks, or a month. What I use is monthly weights, and I've come to conclude is even KD wood will sometimes change in weight (depends on who, where and how the kiln drying is done), let alone wet unprocessed woods.

Since we know that, for us, successfully drying woods is (or should be!) a slow process, then monthly weights makes the best sense. Different species, and different levels of moisture content will dry at different rates. We also know that (generally) the drying process for wet unprocessed wood will be faster at first, and will gradually slow down during it's weight reduction. (This will also depend on the immediate environment in one's shop, as well as the general climatic conditions of the region......as, well as the kind of wax coating used, or none at all using shavings, beads, paper bags, or whatever.)

For me, a minimum of 3 months processing time, without weight change, is the basic requirement for determining stabilization. Note here, that I also use anchorseal on any roughed bowl with a MC of about 14%, or more. (I find that anchorseal is not needed with a MC of less than 14%.....and, this is where a moisture meter comes in handy!) My "anchorseal" is the wax solution available from CSUSA, and it purposefully slows down the drying process. This is what you want, if you want to minimize cracking. Using Bill Boehme's wording, "internal stressing" is what causes these drying cracks, and slowing down the process is what minimizes it by allowing the surrounding wood to adapt to these internal stresses....

When I first started turning I had plenty of problems with drying my wet roughed bowls......just like everyone else does......but slowing down the drying process to a crawl, and monitoring it over an extended time frame is exactly what results in the most successful outcome.

I am adding my previous post (edited) for further clarification on the process:

I use a moisture meter on every bowl block in the waste corners, and I do so to get an idea of what kind of MC I'm dealing with. This is useful information to know. If my moisture meter conked out, I'd buy another.....

The only true way of determining stabilization is done by weight. Monthly weights are the best way to observe the stabilization process accurately. Time is your friend in this process.....this means you just have to have plenty of patience to do this right. I decide a roughed bowl is ready for 2nd turn after a minimum of 3 months of unchanged weight. For many roughed bowls, I wait 4 months, or more, during winter months. If you're not absolutely sure.....it's never a bad idea to give it extra time, just to make sure. Don't be hesitant to give dense and heavy roughed bowls a little extra time, over lightweight and porous bowls.

There are incidences where a roughed bowl will actually gain a few grams during winter, or rainy months. Take this into consideration, and allow for it. For instance, if a roughed bowl weighs month by month, 1lb 1.6 oz, 1lb 1.6 oz, 1lb 1.8 oz, 1lb 1.6 oz, and 1lb 1.6 oz......I'd consider that bowl stabilized.

The real trick is to not get too anxious to work on a bowl......have lots of roughed bowls in progress. You need to have plenty of other stabilized bowls to work with while you wait for that "special" one to stabilize. I stress here.....time is your friend in the stabilization process.....don't get too antsy to finish turn your bowls.....have plenty of other work you could be doing while you wait.

-----odie-----
-----odie-----
 
I have two moisture meters myself - one with pins and one without. I like to use them for a general idea of the wood MC, but do not really rely on them to tell me if a piece is dry or not. I use the scale method when drying wood. I have a decent scale I use to get the weight in grams, and record that. Each week, I weigh and record until I get successive weeks with little to no change in weight. Then I consider it ready. It is still often several weeks (or more) before I get back to the piece. I have a problem that seriously disrupts my shop time - I like to eat and have a roof over my head, which means I have to work a real job during the week! :cool: My shop time is generally limited to weekends, although some evenings I am able to get out there and work a couple of hours or so.
 
I have one and use it all the time to determine when my rough turned or once turned blanks are ready for the next step. Yes, I know it's not as precise as weighing them but, I've used it on hundreds of bowls and works great for me. When a once turned blank gets to about 13% in the bottom inside center and on the tenon I move on to finish it. I know it's a "surface" MC measurement but when I do sometimes check the bottom MC after I've turned off the tenon I seldom find it varies by much at all. I saw a chart once, not sure where, that stable MC for where I live is 13-14% so I've stuck with it since then. They all sit flat when they leave my shop and a natural edge bowl will sit flat or wobble just a little bit as the environment MC changes no matter what starting point you have. It's wood. It moves.
 
I saw a chart once, not sure where, that stable MC for where I live is 13-14% so I've stuck with it since then.

I'd like to take a look at that chart, Randy......very interesting indeed!

I've always felt that stabilized MC for around here in Montana is around 12%. (I guess each moisture meter might calculate a little differently......so that might introduce some variance.) I've gotten KD wood that metered as little as 6%, but most commonly KD boards are anywhere from about 10% to 14%......probably depends on each individual facility, and the climatic conditions of where they are.....I suppose.

I've always assumed that, eventually, any wood that is less than 12%, will eventually increase until it reaches that mark. That could take some time, I guess.....and, I've never really tested that theory. Anyone here actually run some hands on testing of this theory?

-----odie-----
 
Odie, here's a link to one at the Dept of Agriculture US Forestry Service site. Chart begins on page 6. I think I found a few others with similar data. The "science" of MC, which I know nothing about, gets very complicated and the variables re temp, RH of the environment, etc made my head spin. Seems anything in this world can be reduced to and explained by long math equations. The net for me was that about 13% was a reasonable target for my area. I get lower than 13% on a lot of my pieces by the time I get to finishing them. Max 13% in the thickest parts is when I take them off the shelf and start the next steps.

 
It really depends on in-service conditions. Here in VT wood in an open shed will average around 12-14% mc, but interior woodwork can vary from 5-6% in the winter with wood heat up to 10% or so in the summer. I try to keep my shop between 35-50% rh year-round, which correlates to about 6-9% mc. The numbers aren't important in themselves but matching finished work to in-service conditions can be, especially for segmented work.

Most commercial kiln operators aim for 6-7% mc for lumber, but thick material like bowl blanks can be harder to dry and monitor. Kiln drying is temporary - once out in the world wood will equilibrate to its surroundings like the sponge it is.
 
Kevin, good points and a big part of how/why I settled on the process I have. I can only control what I do here. After that I have no idea, or control, on where the piece will be used. I recently shipped pieces to the Seattle area and to CA. Very different environments. Will they be indoors? Will they be on a patio table on the porch? Will they sit on a mantle above a warm fireplace? In a bathroom next to a steamy shower door? No idea and all of them will impact the piece MC and how it sits on a table. So, do what I can here and that's all I can do.
 
Kevin, good points and a big part of how/why I settled on the process I have. I can only control what I do here. After that I have no idea, or control, on where the piece will be used. I recently shipped pieces to the Seattle area and to CA. Very different environments. Will they be indoors? Will they be on a patio table on the porch? Will they sit on a mantle above a warm fireplace? In a bathroom next to a steamy shower door? No idea and all of them will impact the piece MC and how it sits on a table. So, do what I can here and that's all I can do.
Good points. As a cabinetmaker I generally know what conditions a piece will wind up in and plan accordingly. Glued joints that open up and drawers that stick become obvious quickly. Most turned work will hold up fine in a range of conditions, but I have seen discussions of segmented pieces that went south because the lumber used dried out after finishing.
 
So, I understand that the moisture meters are inaccurate because the surface (or just below) will be dryer than the interior. This is why wood cracks, right?
Right after rough, initial turning I coat liberally with anchorseal, the entire piece. I also add a layer of blue shop towel with more sealer over that, for the likely crack areas in Oak, especially.
That slows the rate of water loss so that the surface is not much different than the interior. That’s my understanding anyway.
When the blanks are measured to be about 11%, the same as my workbench, I consider it stabilized. I then move most of the stabilized pieces to the house. I figure it likely the piece will end up in heat and a/c.
usually those pieces sit for a few months before last turning.
Thats been working well for me, makes sense to me.
Is my logic way off here? I’d rather not do the weight thing. Just too much attention and record keeping for me.
 
Sounds like a workable process @Marc Banka. IMO the quicker you put the piece in an hvac environment the better (I bag and weight mine as soon as I stop cutting and place in the house). My reasoning is a consistent environment provides a more consistent drying process - less variability of the drying process piece to piece, so that you can then, if needed, make changes to other aspects of the process. In short, reducing the # of variables.

My weighing process is quite simple and not much time. Record date and wt on blue painters tape on the bag, weight again whenever, record date and weight. It doesnt require a set schedule. Prefer bags to the mess and time of any sealer, but sealer works.

I may have ~ 20-25 pieces drying at a time (none right now!) and 1/2 of those may be done, no attention required.
 
I think getting into the dryer environment sooner is better because it is dryer. I have limited space in the house for drying, so have ’on deck’ shelves .
I wouldn’t have thought the paper bags to be as effective as sealers. Good to know it works so well.
Largely, the drying timing is academic for me, most of the time. I have more than 100 bowls and platters drying.
My methodology is, when wood is plentiful in freshly cut trees I spend my time with the saw. I cut it all, and rough turn it all. This gives me sore muscles and lots of bowl blanks.
 
So, I understand that the moisture meters are inaccurate because the surface (or just below) will be dryer than the interior. This is why wood cracks, right?
Right after rough, initial turning I coat liberally with anchorseal, the entire piece. I also add a layer of blue shop towel with more sealer over that, for the likely crack areas in Oak, especially.
That slows the rate of water loss so that the surface is not much different than the interior. That’s my understanding anyway.
When the blanks are measured to be about 11%, the same as my workbench, I consider it stabilized. I then move most of the stabilized pieces to the house. I figure it likely the piece will end up in heat and a/c.
usually those pieces sit for a few months before last turning.
Thats been working well for me, makes sense to me.
Is my logic way off here? I’d rather not do the weight thing. Just too much attention and record keeping for me.

If it works, it works. Where it might not work well is with very slow drying species and thick blanks. Wood dries because there is a moisture content gradient between the surface and core. If you had a thick blank of white oak or some dense exotic a surface meter reading of 11% might be far from the core mc. Bringing a piece like that into the drier house prematurely might invite problems by increasing the moisture gradient. Periodic weighing gives a more definite assessment of whether the piece has achieved equilibrium with its surroundings. I do the same as you with roughed out domestic woods unless I am in a yank to use a specific piece, in which case weighing is helpful.
 
When I first became interested in wood turning Mike Mahoney's process made sense to me, or looked like it would work for me. He had a room with bowls stacked up around the walls. He had a place he could go to where everyone could get rid of their cut down trees and he could 'shop', if you will and keep his supply of cured blanks at the level he needed.

I love turning green wood so after a tornado and a couple of ice storms lately, I've been wide open roughing in pecan, black walnut, birch and a little cedar. Probably over a 100. I have plenty of blanks several years old so I never use a meter or weigh. I use a sealer then store the blanks outside on shelves but under a roof.

That said, if I start really cranking out bowls or run across wood that I really want or need to get a bowl out asap, you all have convinced me that weighing is the way to go.

Now I just need to talk mama out of her postal scales...
 
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