moisture meters

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JWD

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Hi everyone,
I've started to buy timber that isn't pre-milled and i think its about right i get a moisture meter to make sure i know what i'm buying.
I've looked at old threads on here and done a little bit of research.
Anyone who uses one periodically and can recommend a cheaper option, your guidance would be very greatly appreciated.

There's one on axminster for £20 and it says +/- 2% which is more than adequate for checking that wood is stable isn't it?

Also what are peoples ideal wood moisture content for working with? i know in the states its between 6-9 but can vary greatly depending on state

Thanks for your input all

joe
 
Wood will settle (for a while) at its equilibrium, that is when it is equilibrium with its surroundings. When wood is green it contains a lot of water, some of this is sort of loose and is easy to dry. There is a huge amount of water bound up in the individual cells of the timber, water that is necessary for the cells to function as cells.this is the stuff that is difficult to persuade to leave. It is a slow process that can be speeded up to some extent by by controlling the environment the wood is kept in. This is the basis of the kiln, and is a great deal more involved than heating it and dehumidifying. Well it is if you want some useful timber at the end of it. In a centrally heated Home, you want to be fairly low, 10% ish or better. In a less controlled atmosphere 15% could be considered dry. Bare in mind boats are often made of wood and they float on water! Whatever figure you decide is right you will need to be aware that the wood will always strive to reach an equilibrium with its surroundings and this may mean that it will take water into its structure after you have taken pains to achieve a lower level. All changes in moisture level may produce changes in dimensions. Good joinery techniques and choices made very early on in a project in terms of timber choice and milling will help to mitigate this, as will choice of Finnish that can help to isolate the timber to some extent from its surroundings. If you walk round a timber yard with a meter, you need to be aware of a number of issues. The yard are often almost outside or actually outside, and therefore the humidity in the air is likely to be high in this country at least. Temperature is involved in the moisture reading and the meters are calibrated usually for a particular species and at a temperature usually about 20 deg C. When I used to have to work for a living I used a moisture meter many times a day every day. I still have my meter, and I remember it cost me about £700 when I bought it about 15 + years ago so I do wonder how good the cheap ones are. Mine was not the dearest on the market at the time, although I guess the technology could have got cheaper over time. A meter is useful to take relative measurements, as in has it got drier over the last week/month, but don’t rely on it to provide you with a definitive moisture content. There is only one accepted method to determine absolute moister content expressed as a percentage, and it is a destructive method that involves weighing a sample, totally drying it and doing the maths. There is also a similar method using a pressure device, a sample of wood or dust and calcium carbide, that reacts with the water in the sample to produce acetylene gas, the pressure of which is displayed on a meter fitted to the top of the device. This method is often used with brick or concrete dust from buildings. However, a moisture meter has its uses when used as a reference to show trends. Unless you cut your timber and measure in the middle of the very fresh cut you will likely get a different reading from the outside edges of the timber. If you mill your own timber, do it in good time, oversize, and allow it to stabilise ideally in the conditions that it will eventually live in, to allow it to move. You may be surprised how much it can move when you have released the stresses in it by cutting it, and that’s before the moisture element comes into play. If I’ve been teaching my grandmother to suck eggs so to speak, then I apologise unreservedly. Hey if it was easy, we wouldn’t want to do it (hammer)
 
Id be more tempted to buy an wave one, than a resistive one.
I know a branded one will cost about 10x the figure youre looking at, but unbranded can be had for about USD 40 from asia.
 
thanks for your input guys

John the overall message i've got form your wise words is that i shouldn't focus too much on accurate moisture readings and instead focus on giving the timber i've purchased time to stabilise before i use it, is this roughly correct?
My workshop is an non-insulated 2 car garage (single brick) with good ventilation - none of my tools have rusted over time so it must be relatively consistent...
if lets say i'm making slab tables or benches with 'kiln dried' slabs - how long do you reckon i should leave them to settle in their new surroundings before milling them? i did always assume kiln dried meant stable enough to work without worry of any major warp/cup/split risk but maybe i'm just being hopeful :(

another point i wanted to ask was: does anybody use moisture meters for once turned bowls to see when they're dry enough to finish? i've got literally a whole tree's worth of oak that's only going to become firewood otherwise and i'd like to see what i can make from it.


Julianf - may i ask why? thanks for the input!
 
JWD":rhd0gmll said:
Julianf - may i ask why? thanks for the input!

Ive used the pin ones before just on firewood, and the result, whilst accurate (in the area where the probes are stuck) does not tell you anything more than that - it it gives you the reading on that very specific area.

I once pulled a log from the pile, stuck the probes in, and did not really believe the content was as low as i was being told. So i split it, and tested the inner areas, and, sure enough, it was just the outside that was dry.

I cant really see how the inside and outside of a lump of wood are ever going to be the same, unless it has been aclimatised for long enough for there to be even moisture the whole way through - and a probe meter wont tell you when this is anyway.

I gave up using it for firewood.


The wave ones have more hope of getting you a non-surface reading. Ive not purchased one of the cheap-from-china ones, but im tempted to do so. I know i have an IR thermometer here that was the cheapest i could possibly find (less than £10 inc delivery from the far east!) and it worked just as accuratly as the £300 IR camera we had at work (obviously it did not take photos, but the temp readings were the same). So id be tempted to just buy a £25 device and see how i went.
 
ps. there are videos comparing the £200 plus wagner (or whatever it is) to one called a "dr meter" - they both come out about the same.

I dont know how much the dr meter is, but if you look at the device, this -

https://www.ebay.co.uk/itm/T8-Xinbaokey ... SwMGVaZhR4

is either a deliberate copy, or, i suspect, came out of the same factory in china. So you have somthing that is (i think) probably comperable to a £200 device for £27 delivered. Its even a couple of quid cheaper on aliexpress...
 
Your kiln dried timber will I’m sure be stable to work provided it’s kept at what ever level it was when it came out of the kiln. Your workshop is likely to not be hugely different from the humidity outside and so it is likely your wood may take on more moisture at this time of the year. Relative humidity in my workshop area of my house is stable it is heated a little and I use a dehumidifier to maintain normal to dry levels consistently. You may not experience any problems with your timber. There are so many variables and we just attempt to stay one jump ahead. 2 boards from the same tree can behave very differently when worked.
My moisture meter has both pins and the wave penetration. Both are useful but the wave pen3tration is only a centimetre or two at most. The inside will always be different.
If you are talking about completed bowls but not finished, then a moisture meter could be used, but if you are using one with pins, then you are going to mark the surface. You could weigh them and record the weight on a piece of paper. Re weigh them every week or so Record this weight until the weight doesn’t change, at which point it has reached its equilibrium value. At least until you take it indoors (hammer) if you try to achieve a consistent wall and base thickness you will have more success with final drying. Some people soak green bowls with lemon oil, which is very thin and penetrates the wood fully, and is said to help. Not tried it myself but Mark Sanger uses it a lot. Good luck.
 
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