Moisture Meters

Moisture Meters

A firewood moisture meter is perhaps the most important stove tool for helping you to get the most out of your stove.

Your firewood moisture meter can help you make sure that you are getting well seasoned wood. Although there are many firewood suppliers out there who know their business and when they say that their firewood is well seasoned it is. You may well find that some of these more professional firewood suppliers are booked solid; so you should try to get your orders in with them over the summer. Your firewood moisture meter will help to confirm that their wood is well seasoned and let you gauge exactly how well seasoned it is. Conversely; there are also firewood suppliers out there who supply firewood, claiming it is seasoned, when in fact it is far from it.

Without a moisture meter the first you may know that their wood is not dry enough may well be when you notice that your wood burning stove isn’t giving out much if any heat at all and that the window is getting tarred up.  It doesn’t just stop there;  burning unseasoned wood will tar up your chimney (increasing the risk of chimney fires) as well as reducing the life of your wood burning stove, liner and/or chimney flue itself. Burning unseasoned wood is inefficient and results in high levels of particulates, which is bad for your health and often makes NASTY problems for your chimney sweep.
In terms of how much heat you get out of your wood stove, the moisture content of your firewood is probably the single most important thing to consider, (the moisture in the wood has to be boiled off before you get the expected kilowatt per hour rating-which is based on dry wood) which is why a firewood moisture checker is so important.

Firstly it makes sense to check with the supplier what type of firewood you are getting (see wood burning properties here (Wood Burning Properties), it may be well seasoned, or the supplier may give you an assessment of the dryness of the wood anywhere from freshly processed to partly dry. If you have a firewood moisture meter then you can tell exactly how wet the firewood logs are, although of course there will be other tell-tale signs i.e. no cracks in the end grain and a ‘wet’ smell.

Buying Wood

Next time you get a firewood delivery take out your firewood moisture meter and before your supplier unloads, grab a couple of logs, split them in half with your axe or hatchet and take a couple of moisture readings. If the firewood is well seasoned then it should have a moisture content of 20% or lower, a few logs at around 25% isn’t too bad as long as most of the load is under that.

                                     testing firewood moisture
                                                Picture 1: Moisture meter 
To take a moisture reading, all you need to do is push the two pins into your chosen piece of firewood. As you can see above, this piece of firewood is at 17% moisture which is ideal. You should aim for around 16-17% moisture for firewood which is easy enough to achieve.

If the firewood is a lot wetter than this, then it is not actually seasoned firewood; it’s just a load of wet chopped logs that will one day be seasoned firewood after you have dried & seasoned them yourself 🙁 . If after having used your firewood moisture meter the wood turns out to be wet and the supplier is claiming that it is well seasoned, you should either pay less for the wood and store it up until it is dry, or send it back.

It is possible that some firewood suppliers are not aware of the issues, or do not know how to properly season wood for wood burning stoves.
They often come armed with a multitude of freshly prepared stories to get you to accept their unseasoned wood and might say that freshly felled wood is “Ok to burn straight away” (this is incorrect !! ) or that it has been a wet winter and it had been hard to season the firewood logs properly. However,  seasoning firewood properly and then delivering  it, is basically their job description and you should hold fast against accepting these fairytales.  

 Seasoning your own wood

You can also use the firewood moisture meter to see how well your firewood is seasoning, which stacking techniques work best, etc. When you are processing and seasoning a lot of firewood it really makes sense to do it in the most effective way possible. For example, it is possible using a small, a single log thick, stack of firewood on a south facing section of wall to drop the moisture from around 55% when first felled, to around 17% in around 4 months!

To take an exact moisture reading you need to measure the moisture on the inside of your piece of firewood: the firewood will be drier on the outside where the wind and sun have had their effects. So split a piece of firewood down the middle, push the two pins on the end of the moisture meter into one of the freshly split faces of the wood (not the end grain and not the outside faces of the wood) , ideally near where the middle of the piece was before you split it and press the On button. The moisture reading will appear on the screen as a percentage.
Just an example you can find Stihl Wood Moisture Meter Customer Reviews on Amazon here > http://www.amazon.co.uk/product-reviews/B004NQ0RL4
Remember as linked to in paragraph 3 above some wood burning properties can be see here in another of our wood category posts here. (Wood Burning Properties)