# Cabinet door cupping?



## dummkauf (Jun 11, 2010)

Question for someone a bit more knowledgeable than myself. I am working on a dresser/changing table for my 7 week old son to match the crib I built for him. There is 1 door on the dresser which has cupped and has me a bit baffled as to why? The center of the door is 3/4" curly maple and trimmed with 3/4" cherry with some biscuits between the 2 to help hold them together. I glued the door together about 3 months ago and it has been sitting in my shop for about 1.5 months. The day before my son was born(he showed up 4 weeks early) I installed the top drawer and the door. At the time of installation the door was still perfectly flat and fit in the cabinet perfectly. The next day my son was born and I didn't get back out to work on it until last weekend, and much to my dismay the door had cupped out and the corners stick out from the cabinet a little less than 1/4". I could push the corners in without too much effort, but the door has definitely cupped. I've currently got the door off and some weights on top to hopefully flatten it, but I am not sure why this happened, or if it will happen again after I get if flattened again(assuming I can get it flattened), so I am looking for any ideas on why this happened?

Info on the wood:

- the curly maple board in the center of the door I purchased back in April for the crib. This board was left over from the crib and all the curly maple in this dresser comes from left overs from the crib, so I'm going to assume that the wood has acclimated to my shop by now.

- The cherry was purchased a couple months prior to the glue up and also should have acclimated to the shop.

- The door was flat up until I installed it on the dresser, and was flat for a couple of months post glue up.

Any ideas why this happened and how I can keep it from happening again if I get the door flat again?


Pic from right after I installed the door, no cupping yet, don't have a pic of the cupped door right now.


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## dummkauf (Jun 11, 2010)

also, before anyone asks, by the time he's out of the crib and old enough to abuse the furniture in his room, this dresser will be confiscated and placed in Dad's bedroom, and replaced by something with either much cheaper lumber, or possibly an Ikea special


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## Steve Neul (Sep 2, 2011)

If the door was laid on a flat surface to where air could only get to one side could have made it cup. Cupping is normally caused by the moisture content getting higher on one side of the board than the other. The side with the crown has absorbed more moisture out of the air than the other or something has caused the cup side to dry more than the other. Your best long term solution would be to put the door in front of an electric space heater with the crown side facing toward the heater and dry that side. Don't set it close enough to get it hot and check it frequently. When the door is flat keep it somewhere where air can circulate around it until you can put a finish on it. If you need to rush it you can dampen the cup side but with this method the door might cup again later.


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## cabinetman (Jul 5, 2007)

If the location was changed after mounting the door, the MC in the area could be different. Warping in general is attributed to movement when drying. Obviously that door was targeted on one side. You may try just acclimating the door again. If you try to flatten it, you would have to over correct, and hope that the springback is flat.








 







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## Midlandbob (Sep 5, 2011)

That's way too wide for a solid wood panel to stay flat unless it was perfectly quarter cut.
You would commonly make a door that wide with two raised panels loose in a frame. This would allow for the wood movement with the seasons.
It cupped when the winter dryness changed its shape.
You can get temporary cupping if one side of a panel is at a different humidity but again you design to avoid the problem. In that circumstance , it would recur if you dampened the cupped side to expand it. Not a good solution in most constructions.
The other way to get a door that wide would be to veneer a 1/2 or 5/8 inch ply like a quality birch. This could be built into a narrow cherry solid wood frame.


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## dummkauf (Jun 11, 2010)

Steve Neul said:


> If the door was laid on a flat surface to where air could only get to one side could have made it cup. Cupping is normally caused by the moisture content getting higher on one side of the board than the other. The side with the crown has absorbed more moisture out of the air than the other or something has caused the cup side to dry more than the other. Your best long term solution would be to put the door in front of an electric space heater with the crown side facing toward the heater and dry that side. Don't set it close enough to get it hot and check it frequently. When the door is flat keep it somewhere where air can circulate around it until you can put a finish on it. If you need to rush it you can dampen the cup side but with this method the door might cup again later.


That's what's interesting. It's been laying flat on a shelf for well over a month, and it was still dead flat when I installed it. It didn't cup until it had been installed on the cabinet.


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## dummkauf (Jun 11, 2010)

cabinetman said:


> If the location was changed after mounting the door, the MC in the area could be different. Warping in general is attributed to movement when drying. Obviously that door was targeted on one side. You may try just acclimating the door again. If you try to flatten it, you would have to over correct, and hope that the springback is flat.
> .


And no, the location has not changed. It's all been sitting in the same garage for several months. Only change so far has been the season outside(garage is temperature controlled too)


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## dummkauf (Jun 11, 2010)

Midlandbob said:


> That's way too wide for a solid wood panel to stay flat unless it was perfectly quarter cut.
> You would commonly make a door that wide with two raised panels loose in a frame. This would allow for the wood movement with the seasons.
> It cupped when the winter dryness changed its shape.
> You can get temporary cupping if one side of a panel is at a different humidity but again you design to avoid the problem. In that circumstance , it would recur if you dampened the cupped side to expand it. Not a good solution in most constructions.
> The other way to get a door that wide would be to veneer a 1/2 or 5/8 inch ply like a quality birch. This could be built into a narrow cherry solid wood frame.


Yeah, i was hoping I'd get away with it. And looking at it again today, I think I might just get some kind of a catch to install to hold it closed. If I can find something with a strong latch I can install on the shelf behind it I might be able to keep it pulled in and pretty close.

I'm still baffled as to why the cupping occurred after installation and not while it was sitting on the shelf, but maybe it was just the winter season changing the humidity too.


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## Steve Neul (Sep 2, 2011)

dummkauf said:


> That's what's interesting. It's been laying flat on a shelf for well over a month, and it was still dead flat when I installed it. It didn't cup until it had been installed on the cabinet.


That is what makes woodworking interesting. Its often unpredictable. The board may have been poised to warp and keeping in on a flat surface kept the moisture content balanced. 

If you wouldn't mind the appearance you could use a router with a fluting bit and make some verticle relief cuts on the back side of the door. This should reduce the pressure and help the door flatten out.


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## TimPa (Jan 27, 2010)

dummkauf said:


> That's what's interesting. It's been laying flat on a shelf for well over a month, and it was still dead flat when I installed it. It didn't cup until it had been installed on the cabinet.


When you installed it, the inside surfaces only played against the somewhat trapped air that was inside. the outside surface had to play against the ambient air. i've never seen weight work to combat cupping. 
i think you're going to have additional issues with that door like cross grain (rails/panel) possibly opening up your miters down the road. you may consider a new door, if you do, make your panel thinner and floating in a frame. good luck.


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## dummkauf (Jun 11, 2010)

At this point I think I'll wait and see what happens with it as I think I can get a catch to help pull the door in flush for now. If I'm going to re-build the door I can always do that in the future if needed too. And I could also just cut the trim off that door and run the same piece of maple through the planer to thin it down too at that time.

I've been googling this, and rediscovered Krenov's cabinets. I had forgotten about his cabinets since I always associate him with hand planes, but now that I think about it, I've seen some decent sized cabinets he built with solid wood doors. Did he just get the perfectly quarter sawn boards mentioned above for all his work, or is there some other magic at work there? From what I can gather he pretty much used air dried lumber exclusively, is stability a difference between air dried vs. kiln dried lumber? While I am certainly not building at Krenov's level, I am still subject to the same wood expansion/contraction as everyone else on the planet :/

Or maybe it's just that stubborn German blood in me wanting to make it work the way it is :icon_smile:


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## Midlandbob (Sep 5, 2011)

The most likely cause is just the change in moisture in the wood due to drying in winter or a change in location like moving from an downstairs shop where it is a bit more cool and humid to upstairs in a heated home.
Wood continues to cycle in shape in different humidities forever. No reasonable technique will change this. 
if you can push the door flat with not too much force, you could put cleats on the inside of the door to apply forces opposing the curve. 
Did the door change much in width? a door that wide might change by over 1/4 inch causing problems for the cross grain frame.
if you use cleats be sure to make the side hole a bit oval to allow movement. You can prestress the cleats with a slight curve oposite to the door. 1x1 stiff wood like oak would oppose quite a bit.
Standard designs have developed to take the movement of wood into consideration. Violating them will almost always lead to problems to force learning the limits of wood structures.


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## everyday (Jan 6, 2013)

i like this ,batterymag.co.uk


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## jimmyjames (Nov 23, 2012)

Maybe the board was.planed when it was cupped and now it dried and cupped the other way...


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## Midlandbob (Sep 5, 2011)

I have two books of Krenov's work. I reviewed both and generally know his work pretty well. He uses frame and panel doors for wood that might move/warp a bit. He does have quite a few cabinets with solid doors. All of the doors that I viewed that had no frame were made with very stable woods and all were almost perfectly quarter cut.
Current college of the redwoods grads do use veneering well and large flat doors are often birch ply or even MDF with veneer and possibly a solid wood edge.
I hope your door fares well.


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## Lola Ranch (Mar 22, 2010)

Dummkauf,

The way the door was constructed, it was doomed to fail sooner or later. The solid panel of the door should have been allowed to "float" in a dado grooved into the outer frame. Solid edge banding on solid end grain (perpendicular grain attachment) will always fail if there is not allowance for the wood to move.

Lots of beginning woodworkers fall into this trap.

Woodworking 101, Rule #1: Wood Moves, Rule #2 Wood moves more across the grain than with the grain. Rule #3 unless you use plywood and veneer. Rule #4 if you use plywood and a veneer you have to "balance" the panel or it will warp too

Bret


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## jeffsw6 (Nov 24, 2012)

dummkauf said:


> Any ideas why this happened and how I can keep it from happening again if I get the door flat again?


No one has really mentioned paint. The purpose of paints and other moisture barriers is part aesthetic and part .. moisture barrier.

If you put water seal on your deck regularly, the deck boards may last a very long time. If you don't, they will warp and pull themselves right out of your joists even if fastened every 12" to 16" with screws, and this will happen incredibly fast even to pressure-treated lumber!

So one way to reduce lumber movement is to apply a moisture barrier such as paint.


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## Lola Ranch (Mar 22, 2010)

jeffsw6 said:


> No one has really mentioned paint. The purpose of paints and other moisture barriers is part aesthetic and part .. moisture barrier.
> 
> If you put water seal on your deck regularly, the deck boards may last a very long time. If you don't, they will warp and pull themselves right out of your joists even if fastened every 12" to 16" with screws, and this will happen incredibly fast even to pressure-treated lumber!
> 
> So one way to reduce lumber movement is to apply a moisture barrier such as paint.


Kind of defeats the whole reason for using aesthetic wood if it is painted. Paint might delay the wood movement but painted wood still moves.

Bret


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## dummkauf (Jun 11, 2010)

Lola Ranch said:


> #4 if you use plywood and a veneer you have to "balance" the panel or it will warp too


Could you elaborate a bit more on "balancing" the panel? I'm curious what you are referring to. I've been under the impression plywood is inherently stable and not prone to warping.


As far as the paint suggestion, no, I will not be painting this dresser.


This is still just a slight cup, so I am going to try adding a couple cleats to the back to flatten it out, and then we'll see what time does. From the sounds of it I will likely wind up rebuilding the door at some point, so I've got nothing to lose at this point by adding some cleats and waiting to see what happens(maybe I'll get lucky and there's some sort of magical vortex in my house that stops wood from moving  )

Out of everything that could go wrong on this project, the door is probably the easiest piece to remove and rebuild if needed.


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## Lola Ranch (Mar 22, 2010)

dummkauf said:


> Could you elaborate a bit more on "balancing" the panel? I'm curious what you are referring to. I've been under the impression plywood is inherently stable and not prone to warping.
> 
> 
> As far as the paint suggestion, no, I will not be painting this dresser.
> ...


Balancing the panel refers mostly to plastic laminate applications but could apply to veneer added to only one side of a plywood or composite wood door. A backer panel needs to be added to the back side to balance it or it will warp. Not really needed if the panel is a table top or something that is securely fastened down.

Bret


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## cabinetman (Jul 5, 2007)

Lola Ranch said:


> Balancing the panel refers mostly to plastic laminate applications but could apply to veneer added to only one side of a plywood or composite wood door.


An example of "balance" would be with plywood and the cores available. With a veneer core, there will be an odd number of total plies. From the center layer, the same thickness and type of layer is added to each side right out to the faces, as you can see in this example...
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