How Dry Is Dry?

[Rick500]

I'm thinking about buying a piece of about 4" x 4" x 20" cocobolo that's been air drying for at least three years. There is no opportunity to actually measure the moisture content.

If it's been air drying for three years and has been stable for that amount of time, is it likely dry enough to resaw and use? Or is there no way to tell without getting a moisture meter on it?

[orgmorg]

Hard to say, being as thick as it is. If you plan on resawing it, do so, but do not use it right away. Stack it in a nice dry place, with sticks between the pieces for air flow. A dehumidifier will speed things up nicely. I would wait a few weeks with the DH, a few months without it.

[fryovanni]

4" thick Cocobolo can be a mother. I doubt it is dry after 3 years(from my experience Cocobolo tend to be a slow air dryer). To be honest any wood over 8/4 is generally risky to me because you can't get a good read on the moisture at the core. Oily wood like Cocobolo tend to be have a bit more risk. You also have to consider compression and decompression. Wood that is dried thicker sometimes has fine(hard to detect compression cracks), and may also have stored up compression that does not show up till you saw because it is thick enough to hold its shape till you saw it. There are other concerns that I associate with thick wood(not so much coco) like worm holes that are deeper in the wood. I would not recommend using dehumidification. Just air flow is good. If you want to take a little risk and speed the drying process, you can warm the room temp a bit, but faster can be risky after it is below about 20%. Kiln drying schedules for some woods call for modified drying rates to get through the compression and decompression stages faster, but that is a controlled schedule.

So my personal first choice would be to buy thinner well dried cuts and laminate vs buying thicker. That is just me though.

Peace,Rich

[orgmorg]

I would not recommend using dehumidification. Just air flow is good. If you want to take a little risk and speed the drying process, you can warm the room temp a bit, but faster can be risky after it is below about 20%.

Rich, does this pertain mainly to dense exotics, like cocobolo?

My experience is solely with domestic stuff, where below 20% is where you can speed up the drying, and above is where you have to control the drying speed more.

You bring up a good point about the wood moving when resawn.

I have too often tried to squeeze one more piece out of a thick board, and ended up with stock that was too thin after trueing up and thicknessing.

[Rick500]

Thanks, guys. I decided for now to let that particular piece go. I'll get some thinner, drier stuff.

[fryovanni]

I would not recommend using dehumidification. Just air flow is good. If you want to take a little risk and speed the drying process, you can warm the room temp a bit, but faster can be risky after it is below about 20%.

Rich, does this pertain mainly to dense exotics, like cocobolo?

My experience is solely with domestic stuff, where below 20% is where you can speed up the drying, and above is where you have to control the drying speed more.

You bring up a good point about the wood moving when resawn.

I have too often tried to squeeze one more piece out of a thick board, and ended up with stock that was too thin after trueing up and thicknessing.

Your right that you can usually hit wood with higher heat and lower humidity as it becomes dryer(tougher). I don't generally like to force the drying process, short of air flow. Even though the shell is tougher and can take more stress without splitting it does add stress and risk(and these are spendy woods). You also have to figure you understand how much stress is on the wood at that point(below 20% your in the later stage of core and shell pressures, but I often find Cocobolo is slower to realease its core moisture). If you are familiar with drying though and are ok with pushing the wood harder, then you can usually get away with hotter, dryer air as it becomes dryer.

I have found cocobolo to be problematic when it come to either being case hardened or just very slow to release core moisture. I have had boards(4/4) that were seemingly dry when I bought them, had then in my shop for a couple years+, and then re-sawed to find the core moisture read 18%. This was supposed to be air dried wood(it is possible it was overly agressively kiln dried* it was not sold as KD). Maybe it was dried in a very hot dry climate(I suppose that could lock up the shell), or maybe it has to do with its oily nature?

[orgmorg]

OK, I think I get it, now, thanks.

Ya, most kiln dried wood I have brought into my shop has ended up around 16% after a few weeks. It gets really humid here in the summer. I have gotten into the practice of just using air dried wood, and keeping it around 14 to 16% in the shop which is still not so well insulated, then bringing it in to a more climate controlled room until it gets down to the MC I want before I use it.

It seems like too many changes in moisture content is not a good thing.

[fryovanni]

OK, I think I get it, now, thanks.

Ya, most kiln dried wood I have brought into my shop has ended up around 16% after a few weeks. It gets really humid here in the summer. I have gotten into the practice of just using air dried wood, and keeping it around 14 to 16% in the shop which is still not so well insulated, then bringing it in to a more climate controlled room until it gets down to the MC I want before I use it.

It seems like too many changes in moisture content is not a good thing.

I like to not change moisture contents any more than nessasary too. I bring everything into my shop/storage area which winds up aclimating the wood to 6-8% according to my moisture meter. I pretty much only use wood that I have had for a couple years(in my shop), not that that is a requirement but I have enough wood stocked up that it is easy enough to do so. I have found case hardened wood from my stockpile and it really irritates me(it is not as easy to detect* usually only reads a few percent off). I have gotten to the point that I compair the moisture reading of several billets when I want to check a billet to use. I find the readings are always darn close unless something is wrong with a billet.

If I do find a problematic billet. I surface its faces, and then resaw and sticker and weight it. Which works most of the time. Sometimes you can resaw a board that is case hardened and it will just look like a potato chip in about an hour(those make good firewood generally).

Peace,Rich