Help! Determining wood's dryness by periodically weighing it.

[David Wadstrup]

Hello,

I cannot wrap my head around this and would love some advice. Does anyone here have a grasp on the logic of determining whether a piece of wood is dry by monitoring its weight? I have a number of small-ish pieces of boxwood that I've been periodically weighing for the last 10 months. They came to me "semi-dry," and were previously stored outdoors, but under cover -- in an unheated shed, I think.

I weighed them in grams for the first time in early April '21. I weighed them a second time in early June, at which point they all had LOST a little weight. I attribute this loss in weight to me bringing them indoors. I weighed them again in August and they had all GAINED a little weight. I attribute this to the humidity of summer. I forgot about them for a while and re-weighed them all in December, at which point they had LOST weight. I attribute this to winter's dryness. And I weighed them again just now. They all LOSS even more weight and now weigh even less that they did when I first weighed them back in April. I should note that I live in Maine and have no control over the forced air heat in my upper floor apartment. It's usually in the low to mid 70's indoors(which I hate) and my hygrometer reads 10% pretty much all of the time(I don't think it goes lower as I've never seen a reading in the single digits.) This is all to say that it is warm and DRY. The wood is stored on a wire rack.

I conclude from this trend that my boxwood is dry and ready to use -- that the variations in weight I've noticed are due to seasonal fluctuations in relative humidity rather than the wood continuing to dry. I believe this because all pieces GAINED weight in summer's humidity(between June and August) and LOST it again with the onset of winter. Is my conclusion correct? I am unsure because I wonder if I have enough data. Today's weights are all lower than they have ever been, but my first weighing took place in April and after they were brought indoors. Does a piece of wood that GAINS weight in the summer indicate that it is dry and ready to use? Do I need to see another season of weight gain to be sure? I ask because I'd really like to get these pieces of wood out of my living room. I'd like to box them up and put them in storage. Moving environments, and storing them in a cardboard box would, of course, mean I couldn't weigh them again as my readings would then not have a relationship to the ones I've been making for the last 10 months. I don't need to use them at present as I'm still looking for shop space. Can I assume they are "dry," box them up, and not worry about it?

Has anyone here ever judged dryness by regular weighing? And, if so, can you please explain the process to me?

Thanks very much!

[Richard Coers]

In the simplest form, the wood is acclimated and dry when it stops loosing weight.

[Kevin Jenness]

I think you can conclude that the wood is dry enough to use, maybe too dry depending on what you plan to use it for. It may still be losing weight now, but at 10% relative humidity the equilibrium moisture content is probably something like 2 or 3%.

[Maurice Mcmurry]

I always weigh each piece of wood after air drying before it goes into the kiln. I slowly bring the wood up to quite hot (bordering on torrefied). Weight is a very accurate way to get an idea what is going on with your woods moisture content. When it stops loosing weight in the kiln you know it is getting dry. After cooling and some time in the shop you can know exactly how much moisture your "dry" wood is picking up.

[Scott Winners]

I agree with Kevin, your wood is dry enough that it is chasing EMC (equilibrium moisture content) with the change of seasons. If you need to box it up for a couple years it will probably be fine, but it may need to re-acclimate out of the box before it is ready to go after that. Depends on the temp/humidity swings in the storage area.

[David Wadstrup]

Thanks, everyone! Glad to hear the consensus is that it is "dry." And thanks, Scott, for the expression "chasing EMC" -- it perfectly captures what fully "dry" wood does.

[Maurice Mcmurry]

I have read about free water and bound water in wood. With an accurate scale and some data collection I have been able to get an idea what final drying temperature is best for stability. So far I have tried Walnut, Maple, Black Locust and Ebony. I finished the last batch at 214 degrees for 48 hours. The wood is very stable and less vulnerable to humidity changes.
I am also getting an idea which chunks of wood will survive baking.