Particleboard Warping in Cold Weather
From Contributor O:
Contributor L is right. Another way to deal with it is to have a sheet of 1/4" or 1/2" as a cover sheet for your PB stack. It will moderate the differences (in EMC) between the stock and your shop. As panels in process are left overnight, ensure that no hot air blows on them by a cover sheet of cardboard, or that air can get to both sides of any panel. This should keep it all flat. If you are laminating or veneering, make sure all those materials also get the same treatment, or else your completed panels are at risk of warping or seams opening up. Iíve been there.
Years ago, I took over a shop that did a lot of pre-hanging of W Pine 6 panel residential doors. Once the weather cooled off in late fall, the shop guys would reject 20-25 doors per day as warped to return to the manufacturer. As I looked at the problem I could see that every door would warp (ends of the door would rise off the stack in the racks) in the unheated and damp warehouse. Flip it over, and the next day it warped the same as the others. The exposed faces were dying out, shrinking, pulling the doors out of flat. We put 1/4" cover sheets on the stacks and they stayed perfectly flat. The reject rate went from 25% to once the doors were pre-hung and air could get to all sides, they stayed flat. Even on the jobsite, we could minimize returns from the jobsite by insuring the doors were stored properly.
From contributor G:
We had the same problem. Our solid wood was being affected also. We added a couple hanging humidifiers that have their own 1/4" water lines supplying them - problem solved.
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