I’m building a blanket chest for my niece out of maple. The top is a solid panel (3/4 x 24″ x 42″) made up of 4 pieces that I jointed on the edges and glued together using a few biscuits (to help out with alignment). After the panel dried, I sanded it and set it aside until the bottom part of the chest was finished so I could cut it to final size.
The panel has been laying on a flat surface in my basement shop for 2 weeks. This weekend I noticed that it had cupped severely. There’s almost a full inch of air beneath the center of the panel when it’s laying “flat”. I’m pretty sure this one is a lost cause and I can rebuild another quickly enough, but I’m wondering where I went wrong. I used the same wood to build some raised panels which haven’t moved at all.
Other important details:
The wood was purchased from a reputable local dealer. I bought it kiln dried, cut to dimension (4/4 about 8′ long), and straight as an arrow. All of it is plain sawn. The ends were painted red when I purchased them. I used 2 of the 5 boards for the lid and the other 3 to make some raised panels. I have noticed no movement in those panels. I cut the maple to a rough length for the lid and after it was glued it was left flat and untouched for about 2-3 weeks. I did not put anything on the ends of the panel to “seal” the grain. The humidity level in my basement is roughly the same as it is outside. Last week we had 4-5 consecutive days of 90% plus humidity here in Alabama. Today, it’s 35%. We see DRASTIC fluctuations in humidity this time of the year. The maple in the raised panels has been assembled and complete for over a week now. They were put together before the 4-5 unusually humid and mild December days we had last week.
My guess is that the exposed end grain soaked up some of that wet air last week and well…the wood just did what it does. I should have put something on the ends to prevent that from happening. I’m pretty new to woodworking and this is my first attempt at panels. Is there something I’m missing here? Have I diagnosed the problem correctly? Are my raised panels going to explode any day now?
Thanks for the help and Merry Christmas!!!
-Curt
Edited 12/22/2008 10:04 am ET by marti038
Replies
Your "mistake" was probably in laying it flat, so that the exposed side picked up moisture while the underside stayed relatively dry. If you stand it so that both sides are equally exposed to the air, it may very well straighten itself out. But in the future - always store panels so that they get air equally on both sides. Even if it's only overnight storage.
David Ring
http://www.touchwood.co.il/?id=1&lang=e
Curt ,
You said you left the top laying flat , not sure if you stickered the top but most likely the top laying flat could only allow air movement on the top side and there is a chance the one side was allowing the moisture exchange and not the bottom . You could try turning the top over and let it sit long enough to allow it to equalize .
No Worry about the panels , while in a frame it is unlikely they will curl .If you had left the panels out and layed them flat the same may have happened to them also .
good luck dusty
Wide panels are always potential candidates for cupping, caused by eneven drying, or wetting, of one side. You may be able to save your panel by placing it concave side down over a source of moisture, like a lawn on a sunny day, or a damp towel in your shop. You could also rip it along the original glue lines and reassemble it with the growth rings alternating up/down, so any bowing in one piece is roughly cancelled out by bowing in the opposite direction in the next. (Some folks insist this is a necessary assembly technique, others insist it isn't. I say "understand it and use it where appropriate.")
You can help prevent the problem in the future by using quartersawn wood, sealing all sides of the panel as soon as it's assembled and/or storing it in a dry area on stickers so it gains/loses moisture on both sides at an even rate.
Mike Hennessy
Pittsburgh, PA
Thank you all for the comments. Makes sense now. Experienced eyes are always a big help.
I did glue the panel so that the growth rings were alternating which added to my confusion. It sounds like I goofed by laying it down. Hopefully I'll be able to straighten it out.
"...reassemble it with the growth rings alternating up/down, so any bowing in one piece is roughly cancelled out by bowing in the opposite direction in the next."I've heard this before, but wouldn't that just give you a wavy surface as boards cup alternately on one side and the other?BruceT
The original poster said that he did indeedy alternate the growth rings. The issue is that the panel was left flat on a surface during a high humidity spell, so the exposed side swelled when the other didn't, because it was laying on the table.
It's true, if the wood cups and the growth rings are alternated, the wood would end up wavy. However, IF is the functioning term. If the rings are not alternated the whole piece stands a chance of cupping, which is even worse. So the standard practice is to alternate the rings to minimize cupping, then try to prevent it to start with. See my work at TedsCarpentry.comBuy Cheap Tools! BuildersTools.net
View Image
"So the standard practice is to alternate the rings to minimize cupping, then try to prevent it to start with."
That may be the standard practice in some woodworking circles, but it is not standard practice everywhere and in every case.
A significant number of workers, for example, select for looks first and pay no attention to growth ring orientation. In other words, growth ring orientation is completely random.
Other workers will say orientate the growth rings so that the bark side of every plain sawn plank that goes into a panel faces one side. In other words, do not alternate the growth rings. This sets a different problem to the waviness inherent in the alternating growth ring philosophy but, as some will say in response to the cry of, "how do you cope with the cupping", that you deal with it if it's necessary.
Yet other workers, and I am one that advocates this practice, say you should assess every job on its merits and decide on a strategy of growth ring orientation according to the needs of the job in hand.
Now, if I ran a mass manufacturing furniture business and had to create hundreds of solid wood panels with the least problems likely to occur, I'd go for short, narrow strips, alternated growth rings, finger joints along the edges and each end of the strips and hydraulic clamps and something like a UV or radio frequency setting glue. In the US the end result of this type of construction is commonly misnamed as a "butcher block" panel.
That's one extreme, and at the other you have the designer craftsman that takes a comparatively long time to carefully select grain for match, growth ring orientation and so on. This type of worker allows time to consider how to deal with the likely wood movement that will occur due to their particular selection and construction choices. Slainte.Richard Jones Furniture
Thank you for the enlightenment, richard. The few times I've struggled trying to find the best matching grain pattern, I was so bent on alternating the rings when the application would never be exposed to elements that would cause cupping. I ask myself just how important is this alternating rings issue, but always fell back on the standard procedure just to be on the safe side. Apparently that was all for naught.
Live and learn, eh? =)See my work at TedsCarpentry.comBuy Cheap Tools! BuildersTools.net
View Image
Ted:I do hope you don't mind me mentioning it, but the addition of links to your tools business and carpentry business is not quite in keeping with the spirit of the forum, particularly with the accompanying photograph. And, they appear with every post.There are many folk here on Knots that are engaged in relevant commercial activities but you would not know it from their forum posts. Phillip Marcou is but one of many examples.Some members of the forum have started a thread which basically says, "check out my new web site", which seems perfectly fine.If every poster included a mini ad with every post, the forum would get pretty tedious! I know yours is quite tasteful and certainly muted in character, but shouldn't we nip this before we see a trend?Best wishes,Hastings
Hastings old buddy, I think you should perhaps have given me a slap before you mildly remonstrated Ted. After all, for many years now, every one of my posts has contained a link to my website.
How can I infer there is a wry smile intended in this post? I guess I just did. Slainte.Richard Jones Furniture
Richard,These day's there are few places to get respite from the almighty marketing machine —slippery slope and all that.Your link is your signature and you would not know the difference were it not for the underlining.Besides, Ted should know that any message that starts with "cheap tools" is not for this forum. Does he not know that Knotizens only buy the best?Have a great holiday and successful 2009.Hastings
"wouldn't that just give you a wavy surface as boards cup alternately on one side and the other"
To some extent (depending on how wide each section is), it does. That's why some folks rail against the method.
Still, everything has it's place. If done properly, the waviness is barely noticable, while the bow that would result without it would be comparatively huge. It's not always the best solution, but sometimes it is, so it's good to know about.
Mike HennessyPittsburgh, PA
"That's why some folks rail against the method."If they rail about panel-making methods, perhaps that's just their stile. :)Thanks for the response,Merry ChristmasBruceT
You say it was laying on a flat table. Was there any air space between the table and the panel? If not then the side towards the table could not release or asorb moisture the same as the exposed side. Try just turning the panel over on the table and when it flatens out then raise it up on some stickers to give at least an inch of airflow under it. If it was flat when you put it on the table at first then it should flaten out again. The trick is to let both sides be exposed to the same conditions.
Rich
The Professional Termite
Curt, It sounds from your description that the wood gained moisture on the top during those warm moist days on the top side.
The last thing I would do is add more moisture to the other side. That might bring it back more straight, but then once you finish making something and it comes inside, the shrinkage will come back, an probably cause you some problems.
I would concentrate heating only the convex side, while keeping the concave side covered. If you have a source for radiant heat, like a fireplace, or stove, or heat lamps etc. Even using a blow dryer on the humped side should do it. That side will give up some of that gained moisture without changing the other side, and you will be closer to where you want to be.
As for the moisture absorbing through the end-grain. Wood absorbs and gives up moisture readily across the grain, which sounds exactly what yours did.
Marti,
No need for panic just yet. Undoubtedly the problem is due to you not stickering the panel so that air is unable to circulate evenly all round resulting in uneven stress .
I would merely set it on two or three 1x1's (straight sticks) with the concave face up this time, or if you could do as Keith suggests and maybe speed things up a bit.
I have spent a lot of time doing solid carcass work and I always stickered the panels or components until they had been assembled into the piece-even if overnight and especially if the weather is due for sudden changes or as they were waiting to be worked further. Especially pertinent when dovetailing bigger panels for chests etc. So this is what I would advise you to do in future rather than over-focus on alternating growth rings etc.
On the other hand, if you are in a screaming hurry, and you have sufficient spare width, you could just rip and re-join-but this time be sure to sticker that panel....
Hey Mook, You know, you are one of those few people who regularly post on this site that I seem to always agree with. However there is always a first. While I will agree with your suggestion that stickering the KD wood in a humid shop will allow a balanced gain. I would rather keep any KD wood at its lowest MC level, rather than give it a chance to reach air-dry level while making it through an unconditioned shop. I think a better solution would be to just cover the parts with plastic sheet anytime you are not working with it. Wrapping it in plastic is best, but I don't think it really takes that much for the normal process, if you just cut down on the circulation of humid air across the parts. I am sure that you know, but I will add for any new WW's, that a piece which is made with drier wood will normally just tighten up if it gains MC after completion, but when it goes down after it is made, that is another mater. Wait a minute. Did I just disagree with you for agreeing with me? I may be confused. ha, K
I thought I would update you all on this panel. Taking your suggestions I simply moved the panel upstairs in my house where the climate and humidity are more stable and where both sides of the panel were exposed. The panel went back to it's original form after a day or two.
In the mean time, I had already assembled a second panel to replace this one as I expected it was "too far gone". I was wrong. Anybody need a maple panel ready for sanding?
I'm sure I can use it sooner or later. I'll be sure to take better care when I store it and other pieces in the future. I appreciate all of your comments.
Sincerely,
Curt
Thanks for the update. Glad it worked out for you.
GeorgeYou don't stop laughing because you grow old. You grow old because you stop laughing. - Michael Pritchard<!----><!----><!---->
<!----><!---->
Hang onto that 'extra' panel. I've got an entire section of "panels gone wrong" leaning against the wall in my shop. Sooner or later, they all get used. I even used a seriously cupped panel, over 1", as the raised panel in a bowfront cabinet door. I had that panel for about 6 years before finding a good home for it. Only small scraps make it to the burn pile.
Jeff
"you could just rip and re-join"
Philip,
Wouldn't this just repeat the problem? If I understand what's happened the cupping was caused by the moisture level in side A (the top) being higher than the level in side B (the bottom). If he rips and rejoins he will have a flat panel for a while. But the moisture level in side A will still be greater than in side B. Eventually the moisture levels will equalize then he will have a panel that is cupped in the opposite direction.
Better to just let the panel stabilize.
Best wishes, GeorgeYou don't stop laughing because you grow old. You grow old because you stop laughing. - Michael Pritchard<!----><!----><!---->
<!----><!---->
You could be right. I have done rip and re-joins at times and found the process effective. Maybe it's to do with taking some stresses out, waving boards around in the air, clamping all again and leaving the assembly in the clamps (which allows air to circulate all round) which does it.......Philip Marcou
Curt, you might find the discussion on panel glue-up considerations at my website useful. On the other hand it may be far too much bloody information: but that discussion is only an extract from the full discussion I have created and saved elsewhere on that subject, ha, ha--- ha, ha, ha. Slainte.
Richard Jones Furniture
Relax.
Okee Dokee
=)
View Image
Edited 12/27/2008 1:21 am by Ted W.
Hello Ted:
I think your signature is much better, and for whatever reason you changed it, I certainly thank you and I appreciate it.
I am afraid you misunderstood the irony embedded in the cheap tools reference in my response to Richard. A member going by the name of Riverprof made a brief but memorable appearance on this forum some time ago and his various threads and posts were the genesis of the comment. I am sorry you took this the wrong way.
Finally, the absence of complaints do not necessary indicate satisfaction. I find people will put up with a whole lot without voicing their dissatisfaction; I am just not one of them. I really dislike ALL CAPS posts too!
I posted to you publicly because I was uncertain of how other people react to these mini ads (if I might characterize them such). If I was out of line, then folks here are pretty quick to weigh in. It was means to test the water.
Well, I hope you are no worse off for the experience. One of the features of the Knots forum is that one can block posters. But that would have been far too easy a solution.
I wish you well for 2009.
Hastings
I probably got a little over-bent about it. Just stopped by to delete that post.
Also, I am better for the experience. Thanks ;)
View Image
Edited 12/27/2008 5:41 pm by Ted W.
Hi Ted ,
Your not going to tell the guy's over at BT how we roughed you up , are you ?
Heck , Forestgirl hasn't got a hold of you yet , She is like the OSHA of Knots , keeper of the kingdom , direct hotmail to the moderators , She will keep us in the right folders especially jokes .
Make sure you get access to the Cafe for off topic discussions (not woodworking ) just like BT woodshed post to sysop er such just ask .
Seasons greetings
dusty,boxmaker
Edited 12/27/2008 6:53 pm ET by oldusty
Maybe shell get all three of us for stealing this thread ;-)
Yeah, I guess we get a little roudy over there at bt. Contractors, ya know.
View Image
This forum post is now archived. Commenting has been disabled