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!
"Some glue, some brads while the glue dries, and that's not going anywhere!"
Norm
(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.
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.
"Some glue, some brads while the glue dries, and that's not going anywhere!"
Norm
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.
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.
(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.
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.
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