Will staright Plywood warp after coated with clear?

**Tegmark** · 27th January 2014, 11:39 PM

The 3mm ply from bunnings was straight when I brought it, & stayed straight at home that night & next day in cool weather lying flat & even when I cut the a4 sized pieces. The next warmer day 25C + (probably 30C in shed) & they warped. No tricks of any kind gets them perfect like they were when I cut them, they just go back to warped. Must be the moisture sucked out of them & warmth that has permanently ruined them.

My question is. If I had of sealed the pieces with clear straight after cutting, would they have remained straight? I could not be bothered spending the money on clear & new sheets unless I know from someone else's experience.

thanks.

**gms002a** · 28th January 2014, 01:09 AM

Make sure you coat both sides.

I was using cheap ($10/sheet) 3mm ply many times as backing for shelves. It warpes badly after coating one side, but when I do the other side it gets pretty flat again.
Also, I do few coats. I do both sides at once (use painter's pyramids). I got them at bunnings. Carbatec sells them too.
Painter's Pyramids : CARBA-TEC

Hope it helps

**Tegmark** · 28th January 2014, 08:23 AM

Originally Posted by gms002a

Make sure you coat both sides.

I was using cheap ($10/sheet) 3mm ply many times as backing for shelves. It warpes badly after coating one side, but when I do the other side it gets pretty flat again.
Also, I do few coats. I do both sides at once (use painter's pyramids). I got them at bunnings. Carbatec sells them too.
Painter's Pyramids : CARBA-TEC

Hope it helps

Thanks. So I will try again with new sheet. The already warped pieces don't seem to stay straight after coated both sides. Must be all permanently damaged from the dry warmth.

**Xanthorrhoeas** · 29th January 2014, 08:36 PM

One way to straighten warped boards, including plywood, is to wet some lawn on a sunny day and place the warped boards, uncoated side down, on the wet grass. The heat and water swell the wood on the underside and that straightens the board. Keep an eye on it so it doesnt go too far. Then take into the cool and coat the underside with clear sealer. That keeps the water in and the board straight. I have used this with a Kauri table top and even without sealing the underside the top has stayed flat afterwards.

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