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Wood moisture question - plharrison - 05-30-2024
I just bought 2 live edge slabs of walnut to make a table top. I've gotten the moisture down from the low 30's to the high 20's with a fan. Pretty slow work. We live in Georgia where our humidity is pretty high. How low does this need to be before I start working with it?
Thanks!
RE: Wood moisture question - jteneyck - 05-30-2024
(05-30-2024, 01:42 PM)plharrison Wrote: I just bought 2 live edge slabs of walnut to make a table top. I've gotten the moisture down from the low 30's to the high 20's with a fan. Pretty slow work. We live in Georgia where our humidity is pretty high. How low does this need to be before I start working with it?
Thanks!
What's your indoor RH? If you're running AC it's likely 50% or lower. 50% RH is 9% MC, so it would not be good to take a slab in the high 20's% MC into that environment. A guy I know who cuts and sells slabs claims anything below 20% is good-to-go. On the other hand, I've heard from several people that slabs they bought from him cupped and/or split. The outdoor equilibrium moisture content in GA according to the Forest Products Lab is about 13% most of the year. It sounds like you have the wood indoors. I suggest you sticker it outdoors, in the shade with a roof on top but open on the sides/ends, in a location where the wind will blow through the sides. You didn't say how thick the slabs are, but 4/4 stock should be air dry in a couple more months. 8/4 will likely take until Fall, maybe even late next Spring.
I would not bring them indoors until they are well less than 20% and preferably below 15%. Uncontrolled force drying of thick slabs never turns out well.
John
RE: Wood moisture question - CStan - 05-31-2024
I hope you're young... it's going to take a while...
RE: Wood moisture question - plharrison - 05-31-2024
Thanks John. Not sure what the relative humidity is in my basement shop where they are currently. They are 1 1/2" thick. I should have mentioned that. I realized this was going to take a while which is fine. Not planning anything that needs to be done immediately. I do have an outdoor covered porch on the second level with a lot of room to leave them outdoors. Maybe I'll give that a try. A Georgia summer has very high humidity so that will be interesting.
RE: Wood moisture question - plharrison - 05-31-2024
I'm not young! LOL, I knew this was gonna take a while!
RE: Wood moisture question - JosephP - 05-31-2024
Even with a high RH outside, if you have air moving over it whether that is a study breeze or a solar-powered fan, you can still get dehumidity of the wood down.
RE: Wood moisture question - rwe2156 - 05-31-2024
If you've got a basement, I'm assuming you're in the N GA mountains, correct?
Anyway, I'm in NE FL and air dry EMC here is 16% +/- depending on the wood species. IOW the lowest we can get air dry is 16%.
I don't work with slabs but I know they are notoriously bad about cupping. The thing is not so much the absolute MC but equal exposure both sides. I would sticker them with thick stickers like 2" to give plenty of air flow.
Personally I wouldn't be comfortable with 20%. I think the only way you're going to get there is a) move the slabs inside a climate controlled room or b) kiln dry. You can determine which option is best for you, but I do know there are heat driven as well as solar kiln plans out there and they aren't hard to build.
Some depends on how you're going to use them.
RE: Wood moisture question - jteneyck - 05-31-2024
(05-31-2024, 07:09 AM)plharrison Wrote: Thanks John. Not sure what the relative humidity is in my basement shop where they are currently. They are 1 1/2" thick. I should have mentioned that. I realized this was going to take a while which is fine. Not planning anything that needs to be done immediately. I do have an outdoor covered porch on the second level with a lot of room to leave them outdoors. Maybe I'll give that a try. A Georgia summer has very high humidity so that will be interesting.
I looked up the EMC for the cities listed for GA in the Forest Products Lab document on that topic.
![[Image: AP1GczPYq6kPXcUY4orJCwvbxtV6qTwurws5V4G9...authuser=1]](https://lh3.googleusercontent.com/pw/AP1GczPYq6kPXcUY4orJCwvbxtV6qTwurws5V4G9JusLTk8XjMFQwJ8ScwNnLvraCdHQe1eFtqu46pVpKM50RgzUFuma7EL2uZvJdjVjjDKisK5WcYydhFKwtbceeL6xpQHe1Pkq5Q0VAOa7qlrYmjYMu5iTXQ=w943-h345-s-no?authuser=1)
It's hard to believe it's that low in Savannah in the Summer, but the FPL is a reputable outfit.
I don't know what the RH is your basement, but I would bet it's pretty high if you aren't running a dehumidifier. You can still get drying at 70% RH, even higher, if you move air across the wood. This is exactly how kilns work. You start out at high RH and then lower it as the wood dries. Indoors/outdoors, doesn't matter, but moving air over the wood is needed in any case to make it efficient. 6/4 walnut will air dry in my area in less than a year. FWIW, the EMC where I live is not much different from where you are, at least according to the FPL data.
John