# How can I measure the moisture content of my firewood to ensure good efficiency and clean burning?

It's clear that firewood that hasn't been well dried is more polluting and less energy efficient, hence the existence of various schemes to ensure firewood suppliers provide dry wood.

Is there a way to measure the moisture content of my firewood without specialist equipment?

It can be possible using drying piece of sample wood,

Dry pieces of wood in the oven or in another way . Make sure that pieces should be well cut. Logs have varying moisture contents, depending on tree age, time since felling and position in the seasoning pile. The moisture content also varies from the middle of the log to the ends. You should use 3 to 5 pieces logs, of varying cross sections and Densities/”weights”. Cut each piece straight across the middle and split down the length. Discard everything except one small piece from each log.

``````weight 1=Take the pieces, weigh them on accurate kitchen scales and note the total weight
Weight 2=Place in a low oven (less than 100 deg c) overnight. Weigh again and note the total weight.

The calculation for moisture content is as follows:

Weight of Water=Weight 1 – Weight 2

Then:
Moisture (%) = Weight of Water / Weight 1 x 100
``````

Here is a worked example:

`````` Weight 1 = 1.7 Kg
Weight 2 = 1.36 Kg

Therefore 1.7-1.36=0.34

0.34/1.7x100=20%
``````

As said elsewhere, you can experiment with moisture from 25% down to 19% and see what works best in your stove, fire or burner.

• Great answer, thanks. Out of interest, are you aware of any reason why wood could be considered too dry? May 23, 2013 at 8:29
• I don't think wood could be considered too dry. It will burn faster and cleaner, but if you have good control of the airflow, you should be able to control at what rate it burns. Also, depending on the climate, the wood always has some moisture content anyway and any measures to keep it below humidity (like drying it in the oven) would certainly lower the overall sustainability factor. Also, very dry wood can ignite outside of the stove, when it is stored too close to the stove, but the preventative measure of choice would be a safer storage place, not greener wood. May 25, 2013 at 5:23
• The problem of having wood stored for too long isn't that it is "too dry" but that some of the burnable oils evaporate, leaving less energy in the log. Feb 8, 2014 at 21:08
• @HighlyIrregular Just for the sake of argument. If you dry too well your wood then cram it it some container, the dry wood will absorb water, expand and destroy your valuable container. It also can happen that you want to limit the heat of your fire (to avoid some chemical to occur) and adding water inside is an efficient way to do so Jun 23, 2015 at 19:08

Here's an example of a device that measures the moisture of wood electrically, via resistance. While the electrical measurement will bequick, I'm sure that the procedure described by Yadav Chetan provides a far more representative result.

• .... "without specialised equipment" - I read it to late. Oh well.
– mart
Aug 7, 2013 at 9:14

I suggest the following:
1) Take a jug with a scale and fill it with water water. Measure the amount of water. That's the starting value.
2) Put a piece of wood inside the jug and let it swim. Measure at the scale the new volume. That value minus the starting value is the weight of the peace of wood.
3) Press the piece of wood under water an measure again the value at the scale. Thats the volume of the peace of wood.
4) Divide the weight and the volume to calculate the density. The density is directly connected to the content of moisture.
So let the water games begin :)

• Thanks for the interesting answer! Unfortunately, even though I'm no expert in wood, I'm still about 99% sure that the assumption "The density is directly connected to the content of moisture." is incorrect. A few years back I had some firewood obtained from old hardwood power poles, and it was very clearly more dense than other wood; it was very dry, and for its size very very heavy, and boy did it burn well once it got going... Mar 5, 2015 at 9:36
• Hi Highly Irregular, as you can see in the link, their is a correlation of the content of moisture and the seasoned firewood.<(engineeringtoolbox.com/weigt-wood-d_821.html) But their is of course one exception for the method I (and heureka: Archimedes ;) ) supposed: the wood must have a less specific weight (lass that 1 kg/l) than water has, so that it can swim. Mar 7, 2015 at 13:40
• Looking at the data, I don't see any correlation that would be useful to the technique you're describing. Mar 10, 2015 at 23:50
• @Highly Irregular: Density is definitely connected to the tree species. Mountain mahogany, for instance, will sink even after it has dried for years. Jun 19, 2015 at 5:41

Wood can be "too dry" . It loses waxes and esthers that contribute heat (energy)

• Can you point me to some more information about this? Thanks! Jan 28, 2014 at 21:35
• Hi Roger, and welcome to Stackexchange. This sounds interesting, but for it to be a good answer it'll need some more detail, and ideally a source for the information. If you want, you can edit your answer to include this using the "edit" option just below your text. Jan 28, 2014 at 22:55
• I found some information about wood being too dry: woodheat.org/firewood-too-dry.html Mar 18, 2016 at 10:05

take one sample of that firewood then burn it, a burning firewood which is moist will tend to produce a bubbles at the other end caused by the combination of the moisture content of wood and the gases it accumulated during the burning process .