Wood moisture meter for firewood logs - any recommendations?

[sometimewoodworker]

Bl**dy hell! That's a lot of wood to process. Get yourself a chainsaw saw horse like this : The Handy THSHWCS 25cm Log Capacity Log Saw Horse with Chainsaw Support

And a hydraulic log splitter which, combined with a decent portable generator will let you split your logs "in the field"

Over priced and under built for something that can be nailed together from off cuts for a few quid if you really need one. When I was regularly having fun in a friend’s small forest we might well make one of those, quite a bit stronger though, each time we went. They may have taken half an hour, probably less, but had diagonal braces so wouldn’t rack as that one will, and at the end of the week they usually got processed into firewood.

But renting a log splitter, if you can, is a really good idea.

 

[Jameshow]

Is it me or am I getting through logs quicker this year due to lockdown?

Anyone else have the same experience??

Cheers James

 

[BEE13]

The law is changing requiring firewood to be sold to a required limit of moisture content. In fact it requires kiln drying, not air drying. The reason is to avoid pollution (particles PM2.5) so it's in a good cause. So, although it's only the sale of wet wood that is outlawed in if you burn wet or damp wood, you will be putting pollutants into the atmosphere. That's not ideal so best to avoid it.

To make sure you only burn dry wood, you can either air dry it for a few years (allow about at least a year for anything over 100mm thick) or you can get some idea with an *induction* moisture meter.

In a previous life, I was a Chartered Building Surveyor so have used moisture meters professionally (on wood & other materials) for nearly 50 years. Having said that, the meters I've owned have all been from Protim which are of professional quality and therefore expensive. However, I know how the technology works..

As has been said, a conductive or resistance type moisture meter only measures resistance between the pins. An inductive meter (no pins) will measure accurately in Wood up to 25mm (1") depth depending on the design and gives some info much deeper than that. Therefore, although it won't measure the exact centre of a l large log, it will give some idea as it avoids the impact of T the dry surface layer.

As an aside, if you are using a moisture meter to evaluate the drying of a rough turned bowl, an inductive meter not resistance or conductive meter should be used.

B

 

[OBr]

Hi

I've got a woodburner coming soon. Can't wait! So I'm just getting together the peripheral bits and pieces I'll be needing, one of which is a moisture meter. I guess it doesn't have to be super accurate. But on the other hand there's no point getting one that's too far out...

Any recommendations?

Many thanks

I use a moisture meters fir my wood turning it’s a Dr Meter MD812 which I find is very useful. I also buy firewood logs that have been dried. They should be below 20% moisture content I believe to confirm with pollution regulations. I would advise you get one. To be honest just go for a reasonably priced. Mine was £14.99.

 

[Sundial Colin]

To calculate moisture content, take a clean log off the pile, weigh it and record. I use the kitchen scales. Put it somewhere to dry, airing cupboard, greenhouse, oven at end of cooking session etc. Weeks later weigh again, and record. Continue until consecutive weight are the same. Then use the equation; (wet weight - dry weight x 100 ) / wet weight = moisture content as a percentage. Quite accurate. Ps. With that amount of ash to come down an electric/ hydraulic log splitter is a no brainier.

 

[Concizat]

I have a Machine Mart 5 ton log splitter at my place in central France where the winters are probably much like Wales but colder.
I find it invaluable although it struggles sometimes on thick dry logs but mine are mainly oak. I also have their saw horse but that gets rarely used as it's easier to cut the logs in situ . I have a cheap moisture meter from ebay which is handy for checking the moisture content of logs bought in .
I would say that a lot depends on your age/fitness level as to how you process your wood but if ,like me, your the wrong side of 80, then anything that makes life easier helps!!

 

[tinfoil]

I've forgotten where this is from unfortunately, but I suspect the class will find it amusing and informative:

Wood Beechwood fires are bright and clear If the logs are kept a year,
Chestnut’s only good they say, If for logs ’tis laid away.
Make a fire of Elder tree, Death within your house will be;
But ash new or ash old, Is fit for a queen with crown of gold.
Birch and fir logs burn too fast Blaze up bright and do not last,
it is by the Irish said Hawthorn bakes the sweetest bread.
Elm wood burns like churchyard mould, E’en the very flames are c old
But ash green or ash brown Is fit for a queen with golden crown
Poplar gives a bitter smoke, Fills your eyes and makes you choke,
Apple wood will scent your room
Pear wood smells like flowers in bloom
Oaken logs, if dry and old keep away the winter’s cold
But ash wet or ash dry a king shall warm his slippers by

 

[stevek]

If you have Ashtrees to split you should be very happy, Ive just split a good few ash rounds and they split really easily when fresh, Ive found most wood will split better when fresh, but the Ash was lovely.
As to looking after your chimney etc,,well we had our log stove connected to stainless twin wall flue stacked inside our old brick chimney and for 20years used to burn anything I could find, worktops, mdf an old shed,,it all went into the stove wet or dry,,I then thought I had better get the flue swept and some miserable old git took £20 of me to shove a brush up and down and took out a few handfulls of soot,,,a few years later we started to have serious problems with the flue not drawing, turned out that the installer had used a mild steel connecting piece to join into the pot, this had rotted away and the whole twinwall stack had fallen over inside the chimney..anyway I was convinced that a flexable flue would be best and the really intresting thing is that when we lifted out the old Selkirk Twin wall sections they were as clean as a whistle,,stained as you would expect but no build up of anything in 30ft of flue that had burned mostly rubbish for over 20yrs! I sold them on ebay!
I think one of the best things you can buy is a cheap flue thermometer, just to give you an idea of the flue temp, Im sure these are helpful.

 

[Cabinetman]

I have been buying offcuts from the Timberyard I use, always soaking wet/green and now of course they aren’t allowed to sell it which is a problem for me, I always put it into my home-made kiln to dry it out as to be honest I’m not organised enough to buy a year ahead. 20% for me doesn’t work I don’t know if it’s my fire but it’s too damp I prefer it down to about 10 or 11% like my offcuts from the workshop. Bright and cheerful. Moisture meters are ok but you need to split the wood and measure in the middle as it may still be wicking out, and cheap ones, always take the battery out between uses or it will be dead when you come back to it. Ian

 

[sometimewoodworker]

I've forgotten where this is from unfortunately, but I suspect the class will find it amusing and informative:

Wood Beechwood fires are bright and clear If the logs are kept a year,
Chestnut’s only good they say, If for logs ’tis laid away.
Make a fire of Elder tree, Death within your house will be;
But ash new or ash old, Is fit for a queen with crown of gold.
Birch and fir logs burn too fast Blaze up bright and do not last,
it is by the Irish said Hawthorn bakes the sweetest bread.
Elm wood burns like churchyard mould, E’en the very flames are c old
But ash green or ash brown Is fit for a queen with golden crown
Poplar gives a bitter smoke, Fills your eyes and makes you choke,
Apple wood will scent your room
Pear wood smells like flowers in bloom
Oaken logs, if dry and old keep away the winter’s cold
But ash wet or ash dry a king shall warm his slippers by

A really good wood that is missing from your list is hornbeam, it’s one of the main species that fuelled the industrial revolution and was well known long before that. I’ve copiced stands where the original tree was around 800 years old, that dating based on the centre distance of the ring of trees. It has one of the highest calorific values for a given volume and burns slowly.

 

[OldWood]

I was going to put his in as after thought but realised no one had mentioned it and maybe this is important. Does any one had any knowledge of what the fungus is that is infecting ash and should particular care be taken against it - further ash is a nice wood; is it suitale for working with once infected?

I'll back up Jerome's picture - pallets, pallets and more pallets. That is exactly what the OP should be aiming for. Incidently I got an inexpensive humidity meter off Ebay some years ago and use predominanly for checking turning wood - I did a test early on with wood in the house and logs stored for a extended time to dry out in the house and found it much more accurate and consistent than I expected.

I don't back-up AFFF's recommendation of a steel framed saw horse. I'll go as far as to say that that is b****y stupid as you can never be sure that the chainsaw will not come in contact with the horse - it may well be a glancing cut but against steel that will knacker the blade and you also don't know where else the saw might go. Mine was made some 25 years ago of ~5 x 11/2" timber suitably cross braced and it has to odd scuff/notch or two, but nothing has suffered. I certainly would not buy that SF one as there is no cross bracing on the legs and it will wobble horribly.

I also would recommend that you do not go down the electric hydraulic log splitter route but go petrol as from personal experience the electric ones just do not have enough power.

There was also a comment about dried hardwood being destructive on chainsaw blades. Yes wet/green wood cuts easier, but I've never found drier wood a problem.
Rob

 

[emjaiar]

I’ve never had a problem with cutting dry well seasoned timber. The main thing with chains is to keep the oil tank replenished, check tension/tightness frequently and whatever you do keep it away from dirt. The best skill you need to learn is how to sharpen a chain, you may have to do it more than once during a long cutting session. The more you can process the wood the quicker it will dry out. If you’re splitting manually get a maul, not an axe.

 

[Krome10]

Lots of helpful and useful info in the above. Thanks a lot for all the help

 

[Krome10]

Hi

Back with a further question about moisture meters for firewood, and more generally for all wood. I've been looking into it further and discovering what a minefield it is. The main thing I've learnt about is the difference between "wet basis" and "dry basis" readings and how this skewers readings and makes half a mockery of the whole thing! Not many meters specify whether they calculate on a wet or dry basis. And a fair few manufacturers don't seem to even know the difference.

It's very relevant now to the firewood industry. I've learnt that the new legislation stating firewood to be sold must be less than 20% has based that figure on a wet basis calculation. Yet most meters calculate on a dry basis. WB at 20% = DB at 25%. Mix all those facts together and you get a right old mess!

I've been discussing the ins and outs of this on an arborist forum. I've returned here to ask more generally about woodwork. Living in an old house and loving old knackered furniture, woodworm has often been something I've had to think about and you often hear that it thrives in xx% MC timber, and bnuggers off from timber with xx% MC. I don't think I've ever heard mention of whether these %% are dry basis or wet basis. And that makes me think it's all a bit of a guessing game when it comes to assessing wood for woodworm too.

Any thoughts from wood experts?

Cheers

 

[Krome10]

Any thoughts on this? I can't thin of a better place to ask or a better bunch of people who understand wood so well. So I'd be really interested to hear some opinions RE moisture in wood and dry basis/wet basis meter differences.

Or would it be better as a new thread?

Cheers

 

[Sgian Dubh]

Any thoughts on this? I can't thin of a better place to ask or a better bunch of people who understand wood so well. So I'd be really interested to hear some opinions RE moisture in wood and dry basis/wet basis meter differences.

The benchmark method for ascertaining wood moisture content is the oven dry method, and this is method used by kiln operators, for example, that really need accuracy to within very fine limits. The methodology, as I assume you know, is to weigh a small sample of a piece of wood of unknown moisture content, then dry it until no more weight is lost which equals oven dry, i.e., there is no water left in the wood as either free water or bound water. Then the sum used to calculate the MC of that dried sample is:

MC% = ((WW – ODW) / ODW) X 100, where
WW = Initial wet weight of the sample, and
ODW = the oven dry weight

Therefore, as can be seen, the moisture content of the wood before it was oven dried is calculated using the dry wood weight as the base line. In other words the calculation works out the moisture content based upon how much heavier the wet sample of wood is compared to its weight when fully dry.

I've never heard that wood moisture meters read MC on either a 'dry' or 'wet' basis. As I understand it good wood moisture meters provide their readings through electric signals that pass from one sensor to another that are read and interpreted by a computer chip to provide the reading. They are, as far as I know, set up (calibrated) against the bench mark oven drying method and I assume the meter (computer chip?) has within it some sort of programme to read and interpret the signals, i.e., wavelength or electrical strength, plus a wood species selector of some sort on better meters to provide the estimated wood MC percentage. In use then, a wood moisture meter can only read the wood it's testing, so that piece of wood is not oven dry, so the readings given have to be based on a similar sample that was oven dried at some earlier point, and data from that earlier definitive testing programmed into the meters a company produces.

Here's a link to Wagner's website where they discuss their moisture meters - it might be useful to you. Still, you've got me curious about what you mean by the difference between meters that read MC on either a 'wet' or 'dry' basis. Can you expand on that? Slainte.

 

[Krome10]

Hi there

Firstly, thanks for the great response - a pleasure to read And secondly, apologies for my delay in replying...

Rather than try to explain it myself, I'll quote from one of the articles on the net I read:

"The moisture content (MC) of a piece of wood is defined as the weight of water expressed as a
percentage of the weight of the wood either the total (wet) sample weight (wet basis) or the
dry wood weight (dry basis). All fuel calculations are carried out on a “wet basis” (MC wb ).

"The wet basis moisture content is a measurement of the proportion of the sample which is
water expressed as a percentage of the total sample. For example if the wood in a sample
weights 50kg and the water in the sample also weight 50kg, then the total MC of the sample
would be 50% as half of the sample is water.

"The MC wb = (the weight of water in a sample/ total initial weight of the sample)x100

"'Dry basis' is expressed as the percentage of the oven dry weight of the wood. For example, if the
wood in a piece of timber weights 50kg and the water also weighs 50kg then the dry basis moisture
content is 100%. The main advantage of this method is that the oven dry weight of the wood remains
constant. This method is the standard used by many of the organisations doing research on wood, as well
as building surveyors and architects. (It is rare to use dry basis measurements when talking about
woodfuel).

"The MC db = (Weight of water in a sample/ oven dry weight of sample)x100"

I hope that helps. Googling "wood moisture content dry basis vs wet basis" will bring up others.

As I mentioned above, firewood must now legally be under 20% MC. But that's on a wet basis, whilst most meters measure on a dry basis. Or don't specify. 20% MC wet basis = 25% MC dry basis. And so problems are occurring whereby people might complain about a firewood delivery where their meter says the MC is above the legal 20% level, when in actual fact it might still be below.

It's funny that some cheap meters claim to be quite accurate (+/-0.5% for example), and yet don't specify whether they calculate on a wet or dry basis, and don't allow selection of wood species. Putting those two things together can throw the accuracy off by quite some amount; possibly even into double figure % off the mark.

Hope someone finds this interesting, and if not it's at least helped me clarify my thoughts and kept me awake a little longer trying to write it in some kind of half-sensical manner!

Cheers

 

[Sgian Dubh]

Hope someone finds this interesting, and if not it's at least helped me clarify my thoughts and kept me awake a little longer trying to write it in some kind of half-sensical manner!

I do find it interesting, and appreciate your response. I've already done some research and also came across your question and the ensuing discussion at Arbtalk (I think it was) - or at least I presume it was you because of the way the question was framed there, i.e., similar or the same text.

What is interesting to me is that the 'wet basis' for calculating wood moisture content seems to be based on an erroneous assumption of the wood's dry weight.
To quote your text it reads:
"The wet basis moisture content is a measurement of the proportion of the sample which is
water expressed as a percentage of the total sample. For example if the wood in a sample
weights 50kg and the water in the sample also weight 50kg, then the total MC of the sample
would be 50% as half of the sample is water."
The assumption here seems to be that a piece of wood weighing 50 kg after drying for a while, e.g., as a stack of firewood under a roof in an open sided shed has no moisture in it which is obviously incorrect. In such circumstances it simply won't dry to the point where there's no moisture in it because it's impossible to air dry a piece of wood to the point where there's neither any free water nor bound moisture remaining. i.e., it's not oven dry. It seems to me that as the oven dry weight of that wood sample is unknown it's not possible to accurately calculate the moisture content.

The truth is that in almost every region of the UK air drying wood outside without cover is unlikely to ever get the wood down to much below 20% MC. Putting it under a roofed shed open at both ends to encourage air movement will, given time, usually bring the moisture content down to somewhere around 15 - 18% MC. Those numbers for air dried wood MC I've just given are based on the 'oven dry basis' for calculating its MC; this being the benchmark method seems to be the only reliable one that can be used. Slainte.

 

[dzj]

Tap two logs together like rhythm sticks. If they produce a ringing sound, they're fine.
If it's more like a 'thud', then they're not dry enough.
A very scientific method.