Bowed MDF

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SimonStevensCanes

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I have nearly completed a built in desk that features a trough (with "lids") along the back for wires. The trough becomes just a lid in the middle to allow access for a radiator that the desk sits on top of. I had planned on adding vent holes, but not got around to it yet. The lid is made from MDF and painted on top. I put all the lids in place last night and this morning the radiator lid has bowed upwards in the middle.

I'm surprised that MDF would warp like this, presumably this is caused by only painting one side, rather than the MDF being previously stored in a cold workshop?

Am l likely to be able to fix the warp? Presumably the horse has already bolted and painting the other side of the lid wouldn't help. Heating/Drying from the painted side?
 
It can be remedied - paint it all around, and if you want to 'force' the bow back into shape, you can weigh the piece down, or even bow it in the opposite direction until it straightens out.
 
with Sammy's reassurance that I could force it back in to shape, I figured before painting the other side (turns out I couldn't be pineapples to do that either) I'd just give that a go. I over bent it back in the other direction for a few hours and then weighed it down in place and by the morning it's straight and has stayed so since. I guess MDF is rather pliable 🤷🏻‍♂️.
 
with Sammy's reassurance that I could force it back in to shape, I figured before painting the other side (turns out I couldn't be pineapples to do that either) I'd just give that a go. I over bent it back in the other direction for a few hours and then weighed it down in place and by the morning it's straight and has stayed so since. I guess MDF is rather pliable 🤷🏻‍♂️.
could be wrong, but I see no reason that it would not re cup over time without a bit of support
 
Cool, glad it worked out!

Painting both sides would give you peace of mind but if it ever cups again, you know what to do.
 
Architect i worked with mentioned once that mdf is not structurally stable, ergo bent or twisted can be straightened by weigh.
Screwed down to the desk it will straighten over time.

Maybe add some more fixings.
 
You can straighten any board by milling a saw kerf down the middle on the concave side, glueing in a snug fitting slip or batten and then clamping the board to a flat surface until set. Generally MDF is not a good material if left 'free floating' - it likes to warp.For quality veneered furniture I find blockboard to be the most stable of all.
 
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