Bowed work piece after painting

[markblue777]

Hi all,
I painted a door I made for one of our bathroom cabinets I made but whilst it was drying it bowed (and I mean like a lot of bow from and "l" shape to "c" shape type bow) It was made out of 8mm tongue and groove pine boards that were glued together with a 6mm piece of ply on the back to make them a bit more rigid.

I think it happened because I painted the one side with two coats and when the paint dried it had like a spring effect on the wood or something and made it bow. I put some weights on it and put some thicker battens on the back and it straightened it out to an acceptable level.

Obviously I want to avoid this happening again so should I just have painted both sides equally (eg one coat front then one back) or should I have just used thicker battens from the beginning. Im thinking thicker battens but not 100%

Cheers

Mark

 

[Racers]

Its because you glued a dynamic material (the wood) to a fixed one (the ply) any expansion of the wood will result in bowing.
Its why frame and panel door where invented, the loose panel is held a slot allowing movement with out bowing or affecting the size of the door.

Pete

 

[markblue777]

Hi Pete,
Oh right it was quite amazing how much it bowed over the space of about 1 hour. it literally turned into a semi circle I was quite surprised.
The panel door style would not go with the rest of the design in the bathroom so was limited to what to do.
I will post some pic in the projects section

Cheers
Mark

 

[Racers]

I would make it out of MDF and cut groves in it to simulate boards.

Pete

 

[Sheffield Tony]

Oh right it was quite amazing how much it bowed over the space of about 1 hour. it literally turned into a semi circle I was quite surprised.

Presumably the T&G absorbed water from a water based paint, making it swell ? I used some pine panelled cabinet doors from a DIY shed once, and the water based paint caused the panels to swell so much they pushed the frame joints apart. Then when dry, they shrank back leaving bare wood lines. Don't think I'd use water based paint next time.

The panel door style would not go with the rest of the design in the bathroom

Presumably semi-circular ones will go even less so ! Even if the door flattens out as it dries / under some weights, in a bathroom it will curve whenever things get steamy.

 

[markblue777]

I flattened it out and then coated it in a marine lacqure so should help protect it within the bathroom environment. I used the same stuff on the bath panelling and seems to be ok so far.