I was reading an article about an individual that glued up some 1/4 inch door panels to make doors for his cabinets. He worked on these for a cabinet he was building.
He put the project aside for a week and when he came back the panels had cupped 5/16 of an inch. He tried bending them back with clamps, it helped but didn’t fix it. So if you ever run across this issue, here is the solution:
First identify why the cup happened. If you leave the panel out on the workbench, especially with wood stock that thin, one side is going to be exposed to the air’s elements and the other side isn’t. Changes in humidity are likely to occur, affecting both sides differently since one side is face down.
If there is more moisture in the air, it will cup on the downside, looking like an upside down U. If the air is drier, it will cup upwards, looking like a U.
Reversing the cup is possible by putting the cupside upward and putting weight on top, then give it some time to let the moisture content to equalize. You can try spraying water on the concave side as well.
If the panels are resawn, they are more prone to cup because of the tension on the interior of the panel that will be created from the process of exposing the resawn material’s insides to the elements, elements that wouldn’t have penetrated as deeply into the material until it was cut open and exposed.
Also, whenever the wood is resawn, it will act as a rubber band does when it is in a stretched position and then let go. It will loosen and create cupping in the wood. There is another thing to try as well.
You can lay the panel on a table or level surface with the cup side down, with a wet towel underneath. It works better with a little weight on it. If you have a heat lamp, this will help it to cup the other way, but you need to monitor it so that it won’t cup too much the other way, but it will level out.
You won’t really know exactly when to stop the process until you take the lamp off of it and then let it cool off for say, half a day or so…
This can be done for about any panel, not just 1/4 inch thick. Of course, you would have to have a sizable lamp, almost tanning bed size, in order to take care of a 4×8 sheet of wood. But I don’t think I would do this to a panel this size because once you cut it up you may not have such a problem with the pieces.
DO YOU HAVE a woodworking project or tip that you would like to submit to WooDesigner and get it added to our site? Then go to the contact tab below OR at the top of this page and let me know. Just make sure you are able to give us step by step instructions on it, as well as images as you see here, and we will put it on this site just like you have read on this page! As long as it is clear and concise like you just saw, it will go up. Your name will be credited to the project, as where you live. (Please include that.) Also include the type of lumber you use for the design. We look forward to hearing from you! (Take note that the tip and images and instructions have to become ours. I do hate that so much but in today’s society so many will sue, and yes, you can sue for a lot of money over images.) The tips will need to include YOUR IMAGES that you take. They can’t be images from somewhere online. Remember, we have to go through these images and if they aren’t your own, we will not be able to use them. This is illegal and it won’t be tolerated and you will be banned from this community by being blocked. We can get sued for this, and just one bad apple can ruin our community.
Ted Leger –
Comments or questions are welcome.