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Reply by Waldschrat

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Posted on How do I fix a Veneered chessboard that's backing "cupped"

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Waldschrat

505 posts in 2188 days


#1 posted 04-06-2009 02:12 PM

TopamaxSurvivor,

Well, I am not saying that it will not flatten out (its possible, but I think that is not the problem), but more than likely, at least from what it looks in the pic on the blog link, that it looks like it it had a higher moister content when the wood was pressed with the veneer, and I will tell you why I think that: I think the opposite is true. We need moisture to flatten this board out and when we do it is still a temporary fix until some sort of backing veneer is put on, to stabilize this panel.

The board is curved upwards (towards the veneer), which I would believe is caused by either one, or both of two thing.

A) the wood was moister when pressed, dried from the heat from pressing or by itself from less moisture in the air and shrunk, since one side is bound fest/fast by the glue and the veneer layer (which locks the wood from moving (at least mostly but not all movement) thus the side which is free to the air, dried quicker plus is more free to movement because lack of the backing veneer, shrunk, and the other side did not/could not, thus we have the bow in the wood.

B) the other think to cause this because it does have a solid wood core is the simple fact of what happens to wood when you leave a board sitting on a workbench over night, usually it will cup upwards because the air will will dry out the side exposed , and not the side which is sitting on the benchtop. To counter this simply lay the board the other direction and it will go straight again and if left long enough it will cup the other way. I doubt though that this is the problem, although you see why in most shops that I know, man made veneered boards are usually stored upright for this reason— on edge, especially when they are freshly veneered, and are still cooling down, it is very important that the just veneered panels are cooled evenly and depending on the type of adheasive (namely Thermoplast or Duroplast) if it should be stacked with muntins/sticks to allow air to circulate all around (so with thermoplasts, PVC or PVA /white, yellow glues) or completely covered with each panel stacked on top of each other with a scrap panel on top to stop air circulation and allow slow cooling (the Durplast kinds).

The only way to make this panel flat for permanent is to make a backing veneer of similiar wood type and thickness to keep this panel from going curved again, not the problem is, once I have thought of it is to see how to get the moisture back to where it was at when it was originally pressed, then at that specific moisture content, press the backing veneer on, so it will stay straight.

-- Nicholas, Cabinet/Furniture Maker, Blue Hill, Maine


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