glue ups cupped

[steve vanosdol]

I recently made 4 54"x20"x3/4 glue ups using 4-5 boards out of walnut. I used my straight line rip saw to rip the boards and I biscuit joined them with 2 biscuits per board. Once glue was dry I ran through my planner to surface to 3/4" thick. All was good and the panels looked great, were flat and at the exact dimensions.
Customer took panels to his shop and then a few days later has called me and said that the panels were severly cupping and he had to cut the boards apart and reglue.
Any ideas on what would cause this? I have done many other glue ups with no issues but none this wide.:confused:

[Jim Andrew]

Personally, only time I have had that kind of trouble was with wood that was not completely dry. He should have let the panels acclimate to his shop, they would probably have straightened up.

[Michael Dunn]

I always let the boards acclimate to my shop for 7-10 prior to milling. Then I alternate the growth rings. Smiley, frown, smiley, etc... There is some debate about this method, by it's worked well for me.

After glue up I clamp the boards to my assembly table or a bench to resist any desire to move due to change in moisture content.

[Bradley Gray]

Walnut is especially bad to warp if not dry enough. Did you supply the walnut?

[Dave Zellers]

If he left the glue up sitting on a bench so only one side was exposed to the air, that would do it.

Always put it on stickers or cover the top so both sides have equal exposure. Even overnight.

[Judson Green]

I'm guessing your in a area where you are heating, yes? Assuming you are using kiln dried lumber. Your client most likely didn't have air circulating on both sides of the panels.

Ha Dave beat me by one minute. My thumbs just aren't fast enough.

[Dave Zellers]

Beat you by 1 minute!:cool:

[J.R. Rutter]

Agree with uneven moisture due to one side being exposed and one side not. I've had panels change the direction of cup in a single day just by changing the face that is exposed, especially this time of year when the air is dry.

[Judson Green]

And the thing of is, your client need not have cut apart the panels, just should have repeated his/her mistake on the other side. Might have taken a bit longer though.

[William Nimmo]

i had the same issue the two times I made panels out of walnut. took several months for the wood to lay back down, but it did. This has never happened on another species of wood and I have been doing this for 20 years. Growth rings were alternated and air flow was consistent around the wood. Has me stumped

[steve vanosdol]

Yes the walnut is mine and it was dried. I didn't alternate grain direction because I've never done that before and I was more concerned with getting pieces that matched each other. My shop is heated but I keep it about 55 degrees, Im wondering if he has a lot warmer shop and possibly dryer shop. Im thinking this time of year RH% could get as low as 10% and if he had only one side exposed as some of you mentioned, that might just do it. I made some more panels and I'll bring them into my house which is heated with wood stove and I know its dry and very warm in here and I'll post what happens.
Thanks for the responses.

[scott vroom]

Were you given the chance to personally inspect the panel before he ripped it? I'd want to know precisely how much cupping occurred. If I received piecework that didn't meet the agreed standard, the first thing I'd do is call the supplier and offer him a chance to inspect it.

[Myk Rian]

Nothing to do with the cupping, but 2 biscuits isn't enough.

[scott vroom]

Nothing to do with the cupping, but 2 biscuits isn't enough.

Isn't enough for what?

[Myk Rian]

Isn't enough for what?
If you have a 54" panel with only 2 biscuits, you might as well have none at all.
I would put 5 or 6 in them.

[Chris Fournier]

I always let the boards acclimate to my shop for 7-10 prior to milling. Then I alternate the growth rings. Smiley, frown, smiley, etc... There is some debate about this method, by it's worked well for me.

After glue up I clamp the boards to my assembly table or a bench to resist any desire to move due to change in moisture content.


If you are gettinig good results then that's good but your practice of clamping your panels to a bench is not a great idea unless you cover the open face. If you don't cover the open face then you are encouraging cupping, not preventing it. Treat both faces the same!

If a glue up is sound then you should be able to let it do its thing. If you think that you can clamp a glue up flat, you may be able to, for a while but ultimately that wood is going to do what it wants to.

[Patrick McCarthy]

". . . . but ultimately that wood is going to do what it wants to. Which is what convinced me that all wood is female!!!

[scott vroom]

If you have a 54" panel with only 2 biscuits, you might as well have none at all.
I would put 5 or 6 in them.

For strength or alignment?

[Peter Quinn]

I see biscuits in an edge grain glue up as little pockets of unwanted moisture and not much else, I avoid them in favor of good cauls and clamps. I've taken to the practice of standing panel glue ups on edge to acclimate and equalize post glue up, little tip I got from a veneer guy, a few screw jacks makes it easy, then both broad faces are in the same environment. Stickers are not much better than nothing in the short run unless a fan is moving some air, moisture evacuates a lot quicker on the up/exposed surface. Clamping to a bench strikes me as counter productive, like trying to talk a strong willed child out of their favorite flavor of ice cream, once the mind is made up it rarely bends. All panel movement issues come down to moisture, too much, too little, or too much change too fast all give variations of the same results. I've had it here with clients that claim there is a problem with the work but don't give the maker an opportunity to inspect the problem. But client management is at least half the struggle of most businesses not least of all wood working. And luckily its usually just the pepper on the soup. Hope this works out for you.

[glenn bradley]

If he left the glue up sitting on a bench so only one side was exposed to the air, that would do it.

Always put it on stickers or cover the top so both sides have equal exposure. Even overnight.

I agree that it sounds like a material handling issue after the fact.


I'm guessing your in a area where you are heating, yes? Assuming you are using kiln dried lumber. Your client most likely didn't have air circulating on both sides of the panels.

Ha Dave beat me by one minute. My thumbs just aren't fast enough.

Well, you both beat me by a full day :p


I didn't alternate grain direction because I've never done that before and I was more concerned with getting pieces that matched each other.

There is much debate about this but, I too position material for appearance, not growth ring orientation, and do not have problems.


Were you given the chance to personally inspect the panel before he ripped it? I'd want to know precisely how much cupping occurred. If I received piecework that didn't meet the agreed standard, the first thing I'd do is call the supplier and offer him a chance to inspect it.

I agree that at least a picture of the problem emailed to you would have been appropriate. Now you don't know if you have a problem, they have a problem, or what. This makes it impossible to judge what you did (if anything) to contribute to the claimed issue and therefor you have no way to adjust. Your method sounded fine to me. I do not use biscuits but, have used splines on larger panels. The often reported mishap there is that the glue is not fully dried prior to planing and then, once the glue is fully dry, dips or deviation appears where the swollen material now rests as dry. This condition did not enter into the discussion so I must be rambling . . . .

[Judson Green]

Please pardon my curiosity if you feel it's inappropriate.

I just keep wondering why your client outsourced this relatively small project. Especially when they seem to have the skill and the means of which to accomplish it. I mean they would have to cut them apart, face joint, edge joint, glue back together (with more walnut due to kerf loss and edge jointing, assuming the panels needed to be 20"), be perfectly lined up (if the length is to be maintained), and some where in the order of things, rethickness planed. And now no longer ¾" thick.

That's a lot of work and ya gotta be pretty good at to keep, or at least close to, the size required.

[steve vanosdol]

Judson, I wondered the same thing. I appreciate all the input. I still havent put a panel in my house to see what happens-been busy with many other issues. I will post results soon.
someone posted they would put 5-6 biscuits, is that per board? Seems like an awfull lot to me. Im not sure I needed them at all but used them for what I though would be extra strength.

[J.R. Rutter]

On biscuits: If you can clamp a panel reasonably flat and/or flatten it afterwards, then you don't need biscuits. For long grain joints, the only reason to use them is to register the faces. I agree with Peter that they just create pockets of moisture that can cause problems on down the line when the wood shrinks to equilibrium. It can't be said enough that the only reason that wood changes shape on its own is moisture related.

[Mel Fulks]

The "moisture pocket biscuit thing "had never occurred to me. But I have used them without any glue other than the incidental from application to edge surfaces, just for alignment. Usually we would do that only in the case of unusually long pieces of wood where it is not as practical to use sprung joints. I have never used the clever devise Michael posted a link to ,I don't doubt that it works, I think spring clamps are a lot cheaper and work fine.

[steve vanosdol]

I made another panel with bicuits and set it inside near our woodstove for 4 days now and it has remained flat. Still can't explain why the ones that were picked up by client cupped. Thanks for all the input.

[keith micinski]

http://www.sawmillcreek.org/images/misc/quote_icon.png Originally Posted by Chris Fournier http://www.sawmillcreek.org/images/buttons/viewpost-right.png (http://www.sawmillcreek.org/showthread.php?p=2191964#post2191964)
". . . . but ultimately that wood is going to do what it wants to.



Which is what convinced me that all wood is female!!!

And this is officially the funniest and best thing I have ever read on this web site. Thank you!!!

[Charles Lent]

Steve,

Now take that flat glued up panel and lay it flat on a concrete basement floor or against a concrete basement wall for 24 hours. I'll bet it warps considerably. Your customer didn't likely do this, but he could have put it somewhere where moisture got to one side and not the other. Even if he laid it flat on a dry workbench, but in a humid basement the humidity would swell the top side and not the bottom.


Patrick,

I loved your comment too.

Charley

[Jay Park]

Steve, were the boards resawn or milled heavily right before glue up?

Wood dries (even KD wood) with a gradient of moisture from the outside to center.
If the boards was resawn, that could leave one side w/ more moisture, which would cause cupping.

Jay