O.K. Guys, I need some help.
I am in the process of building a console table out of cherry. I glued 2 pieces of 4/4 flatsawn cherry together for the top (each piece was 8 1/2″ wide X 48″ long). My glue up was nice but not perfect so I brought it to a cabinet shop and had them sand it on a wide belt sander. When I left there the top was perfectly straight and flat. I got home, set it on top my workbench (wrapped in cardboard), and was horrified to find a week later that it has cupped about 3/16″ across it’s width. Now it looks like a coopered door. I really don’t want to sand it again, it is already at 13/16″ thick. Can I wet 1 side to draw the cup the other way? I’ve read about this but never tried it. If so, which side do I wet? Any advice would be much appreciated.
Birdy
Replies
You might wet it and get it straight, but it is hard to predict. When you look at the end of the boards, can you describe if the heart would have been above the top or below it, and which side the cupping is to.
If you are looking at the annual rings, they tend to straighten out as wood is drying. If wood is taking on moisture, they should tend to cup more toward the heart.
Did both sides get sanded? If your cardboard was dry, I would not have expected any change while covered.
Did you only sand the face? Was this kiln dried, or air-dried lumber?
I usually advise against wetting wood. I would rather place the wood in front of a radiant heat source to the convex side, and dry that side out some.
Notice. Don't try to go too fast, and try to quit a little early, as there will be a delayed reaction, and over drying will cause small surface checks.
If you can see that the surface is straight, but you can still feel some heat, cover it with plastic sheeting, to stop moisture loss.
If I were to guess, I would bet that, if you only sanded the face, the heat from the friction of sanding caused that side to give up some moisture, causing the sanded side to go concave. If this is not the case, try to describe in as specific terms as you can what has happened.
Hey root,
Sorry for leaving a few facts out. Both sides were sanded equally, and yes, the boards are trying to straighten out from the direction of the growth rings.
Thanks,
birdy
Birdseyeman,
First of all, I would have to agree with all the points that Rootburl made. And trying to wet the other side is not going to fix the problem.
Rip the thing into 4 parts (separate the glueline and halve each of the original planks) and re-glue them paying attention to alternate the growth ring patterns. If you lose too much width by ripping, you just have to introduce a new wider piece into the new glueup.
It's water under the bridge already, don't waste time trying to "fix" it any other way.
DR
You have gotten good advice so far. I would never try to glue up such wide boards to make a top, especially with them being so thin. Although it may seem to be a sacrilege to do it, you need to cut each board in half (or even into three pieces) then reglue it, alternating the growth rings. It will be much more stable over the life of the piece. Have you ever seen a butcherblock made from wide boards? There's a reason for that.
If you really need the look of the wide boards, you could start with an MDF core, apply solid edging wide enough to accomodate any profile you will be using, and veneer both sides.
Hello Birdey,
Don't panic just yet.Ring is suggesting going overboard, whilst Rootburl has hinted at the most likely culprit in his last paragraph.
I suggest you set that top down on a couple of battens so as to raise it a couple of inches or so and let the air circulate all round more or less evenly top and bottom. Set it concave side down, somewhere in your shop where there is some air movement and give it a couple of days- unless you are frantic to complete the job, that is. If that is the case and you go ahead and rip and rejoin you might get the same if those boards have uneven moisture content one side to the other, and , as you have said, you lose some more on the thickness.
I can hear some of you guys saying "this guy is from another planet", or something , but that is what I do when that problem crops up -usually when I have glued up some panels and neglected to separate them for a period- the top one may warp.
Birdy, you asked for "any" advice... so here goes. I'm sure the other responses are from more experienced craftsman than me... And I've been down the rip & glue again road for thicker panels. But sometimes for thin panels (less than 1 inch) I'll place it concave down on my shed floor (on a blanket) then put lots (LOTS) of weight across it. Leave for a couple of days. Then take the now flat panel and immediately apply a finish (I use lacquer) and then (in the case of table tops) fix it down onto the base with numerous button fixes. Havn't had anything re-bend on me. So far!
Just an idea....
Good luck,
Richard
Rich,
That sounds like it may work. I'm definitely not interested in ripping into smaller pieces and re-gluing. I would start over from scratch before I did that.
Thanks to all for the great ideas.
Birdseyeman
Bird,
Don't panic, or be horrified. In my opinion, 3/16" over 16" isn't a lot. I'd guess that the side of the top that was away from the benchtop either drew or lost a little moisture while it was lying there. If a weather system came thru your area in that period of time, that is likely the culprit. I'd go with the advice you were given to get it up on stickers, or stand it on end, so air can circulate around it for a couple days.
If it doesn't flatten out on its own, I'd just screw it to the case, in a way that it can move with changes in humidity. You should be able to easily pull it flat, and the fasteners will hold it that way.
Just my opinion, but the idea of ripping wide boards, and rejoining them, is a production-oriented practice to avoid having to select/ discard unstable, or less than uniformly dried, wood that has been acquired from many sources. By ripping to 3" width, you do eliminate many variables, also the need to be selective in choosing your stock in the first place. I dislike the distracting appearance of many narrow strips of wood joined to make a wide panel. Looks cheap, to me.
Regards,
Ray
I readily admit being in a production situation and therefore having a certain slant on things. If I get a callback to a customer whose cabinet top has cupped, I have just lost whatever money I made on the whole job. If I was making furniture for friends and family it would be a whole other perspective.
The cupping problem that was brought up is a really common one, but it takes a very experienced craftsman to look at the boards and know which ones are going to give trouble in the long run. Depends on so many factors that are even difficult to define on paper, an almost instinctive reading of the boards as well as knowing where they came from, etc.
If you have the luxury of time to play with it, then sure, try to straighten the top. But I personally would have it ripped and reglued and out of the clamps within an hour.
DR
ring,
We're gonna have to agree to disagree on this one, I believe.
Like you, I'm doing this for a living. In my 30th year now. I build custom reproduction furniture. To be authentic, I can't be ripping up wide boards into narrow strips, and I've never yet had a call back for warpage. I'm using lumber that is either kiln dried and acclimated to the shop, or that I've had cut and dried myself in the attic of the shop. Nothing really mystical about selecting stock,, mostly a matter of having it around long enough to relax. Really squirrely pieces of wood will generally let you know they are gonna be trouble while you are milling them, or within a day or two afterward.
Rather than spend the time ripping gluing then re-sanding, I'd spend my time doing something else productive while the cupped panel rests and flattens out on its own. You know, like assembling the rest of the piece. Come time to put the top on, it'll likely have regained equilibrium, and flattened itself. If not, 3/16" cup can easily be pulled flat in assembly. and held there by screws, clips, or buttons, allowing for future movement.
Regards,
Ray
Hi Ray,
I think the key words you used were "reproduction" and "authentic". On that point I take your comments as being totally on the mark. In any case, if your still in the business after 30 years you've got to be doing something right, even if it's not identical to what I'm doing. (I've been at it for 35.) I enjoyed the exchange of views.
DR
ring,
Yeah, as my old man used to say, "There's more'n one way to skin a cat."
Regards,
Ray
Ripping into narrower boards is only a last resort. The most likely reason for the warping was the way you treated the panel after having it sanded. Panels should always be stored in a manner that allows air to freely circulate to both sides. Either set it on some stickers or stand it straight up and down on edge with the edge raised off the floor.
There is every likelihood that if you now sticker the panel it will tend to loose most of its warp. A little warp is generally not a problem if you have the top supported on some sort of frame. If you can flatten the panel by pressing down in the center, you can do the same during assembly with using proper attachment techniques.
In the shop I was involved with, we left panels in their cauls until will needed them.
The simplest soultion.....
On a bright sunny day take the table top outside and place it cupped side down on your lawn in a location where the sun will be shinning on it. usually it will only take 2-3 hrs in the sun to flatten out. But if you don't keep track of it, it will curl up toward the sun in short order. When it's flattened out, take it back in the shop and put some weight on it until it to hold it cools down. If it doesn't stay flat, you might have to screw a couple of cleats to the underside to hold it flat.
2 or 3 hours in the sun and that nice cherry top will be alot darker than the rest of the piece. Make sure the frame and legs get equall time to keep the color even.Andy"It seemed like a good idea at the time"
mostly all good advice! wood moves. you can flatten it join it ect. but it will swell and change over time. 3/16 will be pulled out when you fasten it to the base. thats why we use buttons or elongated holes w/ screws to let the wood move. i have a cherry shaker gate leg table in my living room. the thing is more then 150 years old and the drop leaves are 18" wide and one board. the leaves are cupped. when i removed the top to do some minor restoration work it was dead flat. about 3 days later it was cupped a bit. the screws pulled it right back down....
cheers
lee
If the cup is not excessive,once the top is finished and installed on the support structure,the problem may disappear.I would put the first fastening screw in a tight hole on the width center line of the top.The other needed fasteners would be in slotted holes to assure that all wood movement takes place from the center line to each side.
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