Air-Dried Oak for Furniture
In theory, kiln-drying is better; but people have successfully made furniture from air-dried hardwood. April 20, 2011
Question
I also have some air-dried red oak that I would love to put in production. I live in central Illinois and the wood has been in a garage for 15 months stickered every foot w/ 1" stickers. The wood is a little over an inch thick. I checked it with a moisture tester and it tested 11% with about 4" freshly cut off the butt end. Will this be stable enough to build furniture with? I was also thinking about rough cutting the boards leaving them 1" longer than I need and putting them in the attic of the house for a month to dry some more. Is this a good or bad idea?
Forum Responses
(Sawing and Drying Forum)
From Gene Wengert, forum technical advisor:
Oak changes size quite a bit when it's MC changes. For furniture, you need nothing wetter than 7.0% MC. There is nothing wrong with air drying, but for furniture, the wood must dried a bit more. The attic idea is great, if the weight is not too much. As always, this approach will not kill insects.
From contributor I:
I'm doing the same thing with hickory to use for a 7ft bar. It is between 9 and 15% but I don’t care if it splits or cracks as that will add to the look I want. I’m not sure about the bug problem.
From the original questioner:
The oak that I have fell down about two years ago on our farm. I had my brother in law saw it up on his sawmill with the idea of making a bedroom set with it for us and hopefully passing it down to our daughter when we are done with it. I thought it would be a cool thing to do. So I really don't want to take any chances on having any problems later down the road with the higher moisture content. I think I may take the Doc's advice and do the attic thing.
From contributor B:
Take a good look in the Knowledge Base, type in "drying wood" and you will have a lot of info not presented here. From what I can read from it, you should be okay if you air dry well then put it in your home to acclimate for a while before you machine it.
From contributor P:
Certainly, Gene's opinion carries more weight than mine, but I build furniture with lumber from 12%MC and lower. Another thing you need to remember is that lumber dries from the outside in so the middle of the board is always wetter than the outside surfaces. I always get a higher reading on my moisture meter in the middle of the board than I do when I check near the ends, so I always check the middle of the board. Also, does your moisture meter have a compensation chart? Mine tells me to deduct 1% from the reading for red oak so if it says 11% it's actually at 10%.
Another thing I do is to plane the lumber down to 1" thickness, then restack with stickers and let it dry some more. My theory is, if the lumber is a little thinner, the moisture in the middle of the board will now be closer to the surface and able to escape a little faster.
You said your lumber is a little thicker than 1" so you should have some room to play. Also, air dried lumber doesn't dry perfectly flat and so a board that is only 1" thick might actually have high points at 1-1/8". So you should have room to plane it down to 1" without causing any problems. It will take down some high points but still leave enough lumber left to plane it down again if there is any further movement when the remaining moisture comes out.
Planing it down to 1" thickness also gives you a good look at the wood grain in the boards. Not only does it give you a chance to admire the beauty of what you might have, but it also helps when choosing boards for your project. I also run a dehumidifier in my shop which I think helps this process.
From the original questioner:
Thanks for the input. I actually did plane the wood down this weekend but not all the way. I was thinking this may speed up the drying process also. It does seem like a good idea. How long have you been letting your lumber sit after you have planed it before you start using it? I don’t run a de-humidifier like you do. Also to answer your question about the moisture meter mine does not have a conversion table. I know I will probably get laughed at but the meter I used came from harbor freight. I don't know how accurate it is but I get the same number each time I check the same board. The moisture does get higher the closer I get to the bottom boards. The trim in the house read 6% I figured it was somewhat close.
From contributor E:
I've used both air dried and kilned and had success and failures with both theoretically meaning more design and construction issues by not allowing for moisture changes and movement.
The question I have is regarding the planing for faster drying mentioned and Gene you may be able to answer. My view of the planing is the wood is going to actually seal/sear from the planer and not opening cells more. If you think about it if you don't sand a planed piece of wood prior to staining the wood won't absorb the stain, so if you reverse this the moisture inside would have a harder time exiting the wood that's planed only.
From Gene Wengert, forum technical advisor:
Wood planed before drying will plane easier because it is wet. In any case, knives must be sharp to avoid burnishing the wood and feed speeds must be reasonable. I have never heard or seen that planing affects drying speed. The clearance angle must also be large enough to prevent the heel from rubbing.
From contributor P:
Ok, I will try to explain my theory, which is only a theory and I put it out here to be dissected, so have at it. Let’s start with a rough sawn board 4/4ths thickness and say six inches wide. If we were to let this board partially dry at least to the touch then cut it in half across the six inch face and look at the cut end, in the middle of the board, we can see moisture in the wood due to the discolorations. I am using a red oak board here so the colors are very noticeable.
When we look at the board, most of the moisture content appears to be toward the center of the board. This implies that the outer edges dry faster. If this is true, then the moisture in the middle of the board has to work its way to the outer surfaces of the board before it can be evaporated into the open air. If we plane the board down just a little, we shorten the distance the moisture needs to travel before it can reach the open air.
We already know a thinner board dries faster than a thicker board, so if the board is half dried, and we plane it down to make it thinner, it only makes sense we'll speed up the drying time of the remaining portion of the board because we've shortened the distance the moisture needs to travel before it can be evaporated into the air.
Of course, many thoughts, at least in my head, make sense in theory. If testing is done, or in this case probably has been done, we must accept the results of the testing. I also have added a dehumidifier to go along with helping my theory. If a dehumidifier removes the moisture in the open air, then naturally the air will stabilize at that new Relative Humidity level. But if we have lumber with moisture in it, and dry air all around it, the moisture will want to travel toward the dryer air. If this is true, then the moisture in the lumber will be higher than the RH and will need to move toward the dryer air to help stabilize the environment, thus helping to extract the moisture from the lumber faster. At least those are my theories, now feel free to dissect it.
I might let my lumber sit for a month or more before I use it after I have partially planed it. In my case, I am not waiting on any one stack of lumber. I have five stacks of lumber in my two car garage, which is not making my wife very happy at the moment, and another eleven stacks of various species of lumber in my basement workshop and yet three more stacks in my mother's basement who lives next door. So in my situation, I have plenty of other lumber to work with.
From contributor B:
Well, it seems fairly obvious these things are accurate. The only question left is how much are you going to plane off in the name of drying the board faster? Shavings can dry pretty quickly. It reads like you want the wood now while the wood wants to be dry later. Without a kiln, the wood wins. Too much kiln and you both lose. So let it set and air dry way too long if that is the option and you will have some good wood; and let it acclimate in the house for a month or so before you use it. There's hardly a guarantee that anything will be perfect, but we do what we can with what we have.
From contributor P:
For me it's a two prong process. Usually I'm in a hurry to see what the wood is really going to look like, so I plane it down a little and then wait. It gives me a chance to try and dream up a good application for the wood based on what I see coming out of the wood grain. It also gives me a chance to double check how dry the wood really is. When I plane lumber down, it seems dry at first, but when I take the first few cuts off the top, I can sometimes feel the moisture still in it. Since a board can vary in thickness by as much as 1/8th of an inch. Planing it down to 1" or 7/8ths of an inch isn't too bad and still leaves room to clean it up some more later if I have to. Planning it down by an 1/8th of an inch isn't really going to help with drying all that much, but I think it does help.
From the original questioner:
Here's one more question I will throw out there. When I planed down the oak last weekend I was surprised to see some of the boards had insect holes bored in them. They were an 1/8th inch in diameter or so. I never really noticed them until they were planed. This wouldn't bother me so much if the wood was kiln dried but because it’s not, what do you think the chances would be that there are any bug eggs in there that would hatch and get into my house? I mean wouldn't you think after 15 months of setting around air drying if there was anything in there it would be hatched out by now? I had wanted to kiln dry it from the start but the only guy who I knew of that has a kiln only starts it up when he has enough wood for a full load. I just got tired of waiting so I chose to air dry now I'm wondering if that was such a great idea.
From contributor P:
Most of the bug holes I encounter are near the edges and I just trim the board up to get rid of them. I once found a board that had a boring bug in it. I know this because I left it overnight and found a small pile of sawdust on it in the morning. I removed the pile of sawdust and within an hour, there was more dust. I removed the dust, then poured a small amount of alcohol into the hole and let it sit. After several hours still no dust so I continued to sand it then let it sit over night again. In the morning there was no dust so I filled the hole with wood putty, sanded again and sealed the entire surface with shellac to finish the project. I've never seen anything else from that project in the way of sawdust or bugs.
My theory was that if I filled the hole he was in with alcohol it would drown him or as it evaporated, it would help to suck the moisture out of him and any eggs thus drying them out and killing them. That was my theory, not sure if it's the correct method, but I've never had any further problems in over two years.
Peter
From Gene Wengert, forum technical advisor:
The lyctid powder post beetle is the one insect that is active in dry oak. It makes holes 1/32 to 1/64" in diameter. So, your holes are from a different insect that will not be active in low MC wood. If the wood is a bit wet, the insect could be active and spread to other wetter wood, such as other wood or wood debris in the air yard. Clean your air yard of all wood trash. Please make sure that the holes do not weaken the wood too much.
