Three days ago, I finished handplaning a laminated ash workbench top (17 strips of ash – the final top dimensions are 72″x28.5″x2″), and I thought it was as flat as I could possibly make it. I then left it in my basement, where it had been sitting for months, while I had been working on it. Prior to finishing the workbench top, I had been running the basement dehumidifier nearly every day, but for the past two days, the weather was dry, so I left the dehumidifier off. I went down to the basement today to find that the workbench top isn’t so flat anymore, most notably at the sides, which are now off by about 1/16″. The humidity has increased dramatically this morning, but I didn’t realize how fast and how much it would affect the workbench top. [The dehumidifier is back on.]
What can I do now to “re-flatten” the top? Will the dehumidifier reverse the wood movement? Should I plane it again and seal it right away?
I appreciate any advice you can give me.
Replies
The top will probably flatten out again if you turn on the dehumidifier, but it may take several days, depending on how long it takes to dry out the air in your basement. Alternatively, you will probably find that the top will flatten out again once it has absorbed moisture uniformly. The edge strips, being the most exposed, absorbed moisture first, and moved more than the rest of the top.
If your basement is normally damp, and you were only planning to run the dehumidifier while you were making the top, you have a problem. No matter what finish you use, the top will absorb moisture from the damp air once the machine is off and the air becomes more humid. So you might be better off allowing the top to absorb moisture for a week or two, and stabilize as much as it will, and then reflatten it.
John White
Shop Manager for FWW Magazine, 1998-2007
My "new" bench is five years old (maple), it gets planed flat about twice a year. It is part of the maintenance of a bench, enjoy it.
I have found that any board, glued-up or natural, has to be elevated on stickers so the air cab freely reach all sides.
It will probably re-flatten itself in a few days.
Frosty
"I sometimes think we consider the good fortune of the early bird and overlook the bad fortune of the early worm." FDR - 1922
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