Question
So per usual it gets cold outside, my 3/4" 4x8 pb I have in the shop starts warping. I keep the shop at 65 at all times including when we are not here during the work week. I turn the heat down to 60 when we are not here. The top 4x8 sheet warps the width, and length dimensions. After I cut panels out of full sheets each panel has a warp in it. I don’t have a problem with any melamine products.
Forum Responses
(Cabinetmaking Forum)
From contributor L:
The relative humidity in your shop is below the equilibrium level for the particle board. If the board is exposed to the dry shop air, the top of it will dry more than the underside creating the warp. Hot air blowing on it from a furnace will make it worse. The ideal solution is to humidify your shop. Melamine is less prone because the surface has a water resistant resin keeping the moisture in. Try covering the particle board with a sheet of melamine board or plastic for a short term solution.
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.
