Can firewood be too dry?
Firewood can definitely become too dry; while it will still burn, of course, it will burn at a hotter temperature and thus burn out faster. It can actually make your wood stock worse if you only have over-aged wood; you’ll burn through it much quicker and mid-winter you will struggle.
You can easily leave your firewood to dry for about two years but much longer and you start to run the risk of it becoming too dry. You want the firewood to have moisture content around 10-15%, anything less will burn too fast and hot, whereas anything more will struggle to burn.
If you are finding what you’ve measured to be quite low on the outside, it will be much wetter on the inside naturally. You can always chop off some of the outsides of the log to use as kindling, as extremely dry wood is great to start fires but not to sustain them. The inside of the log can become the sustained piece you need to last for a while.
Can firewood be too old?
Yes, when firewood has been sitting out for more than three years it can be safely deemed too old to use as the sustaining log in your fire. These older pieces of firewood can be great when cut down into kindling, as they will burn really fast and really hot.
In this sense, it can be argued that even though the firewood is too old to use as the slow-burning log it can be used in other ways. The most practical use of them would be to chop them down into a variety of sized kindling. You can easily break them down into tinder and kindling and save yourself the hassle of doing it later.
You can never actually reduce the moisture content to 0%, which would then spontaneously combust, so it’s never a good idea to get rid of wood because it’s too old. It will be more work to reduce down in size, but it is not a waste and will be a good saving when you need to build a fire in your wood stove.
Can Firewood season too long?
Yes, you can season your firewood too long if your sole purpose for the firewood is to be slow-burning logs. The wood will not necessarily be worthless if you try to season it for a long time, as you can put in some extra work and utilize the wood for kindling.
Granted many variables come into play with the storage of the firewood, the climate you live in, the type of firewood, and the environment you store it in. If the wood is left on the ground, it will take longer for the wood to dry, specifically the wood on the bottom of the stack.
Hardwoods will season slower than softer woods as well, so keep this in mind when factoring in how long to leave them. If you live in a humid climate you may also run into trouble with how long the seasoning process needs to take.