I’m making a Queen Anne tilt-top table from mahogany. The table top is 32 inches in diameter, 3/4-inch thick with a raised lip (i.e., it is a dished top) that adds another 3/8ths. The top is made of four butt-glued boards. I got it all sanded and scraped and put on the first coat of oil-based stain this morning. It looked great. Ten hours later, the top has curled in the cross-grain direction. Opposite sides are about 3/4 inch higher than the middle.
Help! How do I get it flat again?
The wood is in the same garage workshop it has been in for months, but the air is whatever exists outside–rainy some days, sunny others.
Replies
The same thing happened to me recently. On a 32 inch glued up piece of cherry I had edge glued 5 pieces with ( I think) alternately flipped growth rings. I'd gotten each dead flat on the jointer and had let everything equilibrate in my 60 degree, 50 % RH shop. Three days latter it was cupped in the center. There were no veneers involved and it wasn't fastened to anthing.
I had to rip it down the middle, flip it and reglue it.
In my experience mahoghany is more stable than cherry.
Sorry, but I am not certain what to tell you.
Frank
rensberger-
This works for me when I have a cupping problem. On a sunny day take the table top outside and place it cup side down on the lawn in a sunny place. Usually, within 1- -2 hrs. , the top will be straighten out. The cool damp grass underneath and the heat from the sun on the other side is what does the trick. If you leave it unattended to long it will start to warp the other way. I've done this inside in the winter with good results using a damp towel underneath the piece and one or two light bulbs on top. More'n likely you'll have to cleat the bottom to keep it flat untill it's fastened down permanently. My experience has been with square or rectanglular tops. Seems like it would work with a round top also.
It sounds to me like a classic case of moisture cupping. Solid wood usually needs to be sealed on both sides within a relatively short time frame to prevent cupping. Even plywood can twist and cup if one side is completely sealed off while the other is free to absorb moisture without constraint... like a cupboard door or something like that. Anyway... Oil-based stains and finishes create fantastic moisture barriers. Which is why they are much less forgiving when it comes to cupping and warping post-finish if one side has been left unsealed.
lostarrow's fix sounds like it would work. I've had to cleat cupped solid wood before to counter water damage related cupping.
Regards,
Kevin
I think Kevin is right about moisture cupping
I have had glued up panels curl up on me when left laying on my bench top " the top side draws more moisture than the bottom side " now I leave my panels leaning against something so the air can get to both sides and have no more problems with cupping.
It doesn't take long for something to cup" I was making a blanket chest- I haven't applied a finished yet- and left the lid on the chest over night. The next morning it had cupped almost a 1/4 in. . I stood it on end in the shop for a week to equalize and now it is as flat as it was before.
I have seen a lot of tables cup from not being sealed on both sides" the side that's not sealed draws more moisture than the sealed side"
If you could get it in some where that is low humidity and let it equalize out it may flatten out- I finish both sides the same even If it doesn't show
Many thanks to you and to Kevin and Lostarrow for the quick replies.
I figured it had to be a moisture differential, but was afraid to try anything too drastic. I put a little weight, maybe five pounds, on the convex side last night and it was pretty well straightened out by morning. My theory is that the mechanical stresses forced the concave side to expand and absorb moisture.
I quickly screwed on the cleats that go on the underside and it has kept its flatness
It's oil-sealed on both sides to the same degree. Now I'm wondering what it will do with seasonal moisture changes. Mahogany is pretty stable, but a board that is nearly three feet wide is going to stress those screws, I imagine. An antique version of this table that I saw appears to have been screwed through small, round (not slotted) holes and show no cracks. Do any of you have experience with this?
I doubt you are finished seeing problems from this glue-up. I would always use a slotted hole when screwing a tabletop down. Somebody else might have lucked out, you may not.
I've run across a batch or two of lousy H. Mahogany (in terms of stability). What we are getting now is nothing like what was available 100 years ago. Don't assume that the reputed 'stability' of a species will let you get by with rushed or shoddy, ill-advised construction methods.
Shoddy ? you talkin to me ???
Nah, but I've twice made the mistake that I think you are about to make. Severe cupping one day, flat the next, probably cupped the next, maybe flat in three days. I'll wet the concave side and that'll flatten her out (and she'll stay that way?). The result was definitely shoddy and went in the trash heap - the whole damn thing.
You can WISH in one hand that the top would quit moving and you can poop in your other hand. I'll take odds on which one fills up faster. Sometimes woodworkers have a hard time accepting that there's not a 'fix' for everything. We're problem solvers by nature.
Proceed at your own risk. However, I wouldn't let fifteen board feet of lumber be a project killer. Find some better mannered stock and chalk this one up to experience.
His top cupped from moisture - I don't belive HE sealed the bottom like the top- the bottom took on more moisture expanded and cupped the top. I'm not to dam sure but I think I told HIM that If he could get it to dry out it may flatten.
Why would you want to wet the other side- so it would delaminate?
Hell I just fell of the Turnip truck -I'm just a weekend woodworker that's worked in cabinet shops for 20 + years
I learn one of these days
I hope
If you read more closely, I'm not advising any remedial techniques other than to build a new top. I wouldn't trust a panel that cupped 3/4" in a day (for whatever reason). At a minimum, the panel has proved it's unruly nature. Somewhere in this series of posts, I gathered that this was for a paying client, so I would even more stridently suggest starting over from scratch.
In other words, the topped if F'd up. I'd build a new one. I think in one of my other posts I mentioned something about not letting 15 bd. feet of lumber risk ruining what sounds like a nice project.
If this was a nine foot long dining table top made from a few thousand dollars worth of extremely fine stock then obviously a wait and see, or even a more aggressive approach, might be called for. But it's not.
Learn a lesson, build a new top, and move on is still my suggestion. That this suggestion should be taken FWIW is implicit in a message board.
The fact that "his top cupped from moisture" is hardly a revelation, but you present that as if it is some mitigating factor.
Anybody who has been involved in a woodworking business, certainly anybody who is a proprietor in a business, knows full well how much more trouble sending out a potetially troublesome piece can be. The cost in lost goodwill and customer complaints down the road far outweighs the cost to build a new top for a project of this size.
I would not pick a moment when the panel is flat (maybe the stars aligned themselves properly at the same moment the relative humidity was just perfect), screw it down, slap finish on it, and hope.
Like I mentioned in my other post, I've done it and really regretted it. Maybe you've had better luck, or had more time to spend fooling around with and tweaking cupped glue-ups. And that's not a bad thing; maybe you manage your time better than I manage mine.
I generally try to price my work to keep these occurrences from becoming a financial disaster. Doing this lets me deliver the best piece that I am capable of building with my meager talents.
The beautiful thing about the advice I'm giving is that being cautious and conservative is rarely bad advice when it comes to furniture making.
Edited 6/7/2003 8:49:29 AM ET by CHASSTANFORD
"If you read more closely"- the top was flat before the stain was applied. Also the top had not cupped 3/4 but 3/8. Might help to read my first post again also.
If it was the woods" unruly nature" to cup then shouldn't it have always been cupped from the start of the project?
From my "meager talents" once you have a panel flat it will stay flat unless something changes how the wood takes on moisture.
So even if you use cupped stock and it is milled flat and glued up in a panel it will stay flat unless something changes the way it takes on and releases moisture.
What makes wood move? isn't it moisture if not it must still have roots in the ground and still growing.
So why should we throw away $200 worth of Mahogany when theres nothing wrong with it?When it just needed to equalize out the moisture.
" Maybe the stars aligned themselves properly at the same moment the relative humidity was just perfect"? Maybe its was a" Revelation"?
Yea that's it a "Revelation"
It sounds like really you did everything right. I wonder if lying flat on the bench was the problem. I think the same thing has happened to me. I wounder if it isn't a beter idea to just stand the panels on end after glue up?
Frank
Laying the panel on something where the air can not get to both sides - yes I have had them cup.
I've had limited experience with cupped glued panels. But... I've yet to have one stay flat without having permanently mounted cleats once it has cupped once. Well... I should qualify that as once it has cupped badly once.
I've got an oak coffee table in my living room that was once damaged in a flooded basement. I inherited the project from a helper who left for another job and never came back to get the coffee table. The only real problem, other than the top, was the moisture staining on the legs. But the top.... maaaaaaaan, it was cupped pretty badly. I tried everything I could think of and nothing worked. I finally just cut a piece of 3/4 birch ply to fit just barely inside the legs and side rails and screwed the heck out of it while the top was clamped flat. That worked. But, I have never removed the ply scab to see if the top has now decided to remain flat.
Regards,
Kevin
Your experience sounds essentially like mine.
When they cup badly, and I think the specimen in this post fits that description, it's bad news.
I'm sorry I brought it up. It was my first post to this list, and I had no idea how emotionally invested some subscribers can become. I solved my problem before the first reply came online.
I am not a professional woodworker, just a weekend carpenter. I was making this piece for myself. I've made exactly six pieces of furniture in my life, not counting a bunch of Norm Abrams's Adirondack chairs.
I had joined four pieces, all from the same board, cut it to a circle, routed out the dishing, sanded and scraped the whole thing to my satisfaction and put it aside for several weeks. It stayed flat, so I figured it was okay to proceed.
I stained both sides (tung oil and dye) and left it on the bench for a day, not appreciating that the sun coming in a large nearby window would strike only one side. The next day it was badly cupped. That's when I looked for advice and came to this site.
Before getting so many answers, I shaded the window and put some weight on the convex side, figuring the stretching of the concave side would allow water to intercalate faster. Just water from the air, it being quite humid at this point.
I was right. A day later the thing was perfectly flat without the weight. I screwed on the cleats then. They're part of the design of this kind of piece. I have since gone back to enlarge the screw holes to slots so that if the wood moves seasonally, it will be less likely to split.
Frankly, the piece looks great, very close to the original, which is owned by the Metropolitan Museum of Art.
Good for you glad it worked out.
I just didn't see why you should rebuild the top when there was nothing wrong with it before you stained it .
I love that style of furniture - can you post a pic.? would like to see it
I'm sorry I brought it up. It was my first post to this list, and I had no idea how emotionally invested some subscribers can become.
Chalk that up to some of us having experienced extreme frustration at one point or another trying to get a cupped panel to flatten out. Your post dredged up unpleasant memories for some of us. LOL
I'm glad that your project worked out. And I'll second the request that you post some pics. I'd love to see it.
Regards,
Kevin
Okay. I just grabbed a shot and am posting it here. (Distortion in the image makes one leg look longer than the other, but I assure you all three are the same size.)
Oh my! That's very nice work! That looks exactly like one I saw a couple years ago on The Antiques Roadshow that was worth a LOT of money. One of the twin brothers (I forget their names) was doing the appraisal and from the looks of it he was barely able to control himself because he was so excited. LOL
Regards,
Kevin
Thanks for all the kind comments. I live in a 1732 house and would like to furnish some of the rooms in period furniture. But I can't afford the kind of stuff that shows up on Antiques Roadshow or in antique shops. So I'm making reproductions.
Well, I'm not antique expert or anything... But, if all your work is the quality and look that the table appears to be, I should think you've potentially got a bright and possibly prosperous future making reproduction antiques. As always, attention to detail is what separates the masters from the wanna be's. And it is obvious that attention to detail is one of your strengths.
Keep up the good work.
Regards,
Kevin
Great table very very nice- I really like that style
Great job
Nice work indeed , and the top looks flat from here HaHa.
Thanks for triggering such a lively discussion topic , amateurs like myself can always learn something by reading along.It's not what you chew, it's how you chew it
While this seems to have worked out in the end, please don't take a half-inch (or so) of movement in a panel in one day as something you can simply dismiss, regardless if it moves back to flat as quickly as it cupped.
At a minimum, you should pause before working a panel any further. If that workpiece was destined to be a case side, or say the writing surface of a slant front desk for instance, I absolutely would not have used it.
Edited 6/9/2003 6:29:45 PM ET by CHASSTANFORD
Rens,
Very nice table. As you undoubtedly noticed, it didn't take much to flatten the dish, so to speak. So it shouldn't take a whole lot to keep it relatively flat. Even if it does curl a little, so what? That will just add interest to the piece. Some of the nicest looking antiques I've seen were wobbly, battered,checked, stained and chipped. Some of my new work is that way too.
Clampman
Edited 6/8/2003 10:50:25 PM ET by clampman
Um... I hate to pick nits... but, if it's curling up then the top side is releasing moisture while the bottom isn't, causing the top side to shrink relative to the bottom side. I've had boards and even plywood go both ways... depending on the relative humidity in the air and the relative moisture of the wood. Whether the wood is giving off moisture or absorbing it, the end result is the same. Your solution of letting air get to both sides is the best one IMHO. Once a piece of wood has been secured thru construction of stablized thru thoroughly sealing both sides, it will usually stay put. In my experience it pays to spend a little extra time to finish up that part of the project (whether finishing or construction) before calling it a night. Much better to face it the next morning with a little less sleep than to walk in refreshed only to find a cupped piece of wood where the night before there was a flat piece.
Regards,
Kevin
This top is realistically probably toast (as a unit that is; you can rip it down and start over). The next time you glue one up, make sure you prop it up on edge. Don't lay it flat. Let the stock for wide glue ups sit in your shop for at least two to three weeks before you lay a hand on it. It's never a bad idea to skim plane new stock on both sides when you first buy it. Sticker it, don't let fans blow on it, and let it sit for a few weeks.
Well it's certainly hard to argue with success. You've built a nice project.
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