PVA as a sealer - drying time on plywood?

[harryagain]

Paint on PVA sealed surfaces often fails to adhere well. Doesn't "key" to the smooth impervous surface.

[Jon Parker]

Folks,

Rebuilding a caravan, rain due tomorrow, must finish get window seals on tonight as nowhere to store it undercover.

On 3.6mm bare ply which I have coated with a 50/50 mix of PVA and water, how long before I can paint that plywood please?

Thanks JP

[stuart noble]

If using a water based paint, as soon as is the pva is touch dry. For a solvent based paint it needs to be bone dry

[stuart noble]

"Keys" to glass well enough :-)

[Cursitor Doom]

The pain manufacturers commonly recommend doing so, presumably for that reason. I use PVA neat, though.

[tabbypurr]

but not to slick pva. Its ok if you don't put too much on, but its easily overdone.

NT

[Cursitor Doom]

There's nothing to stop you scuffing it up a bit with a piece of say 240 grit wet or dry; doesn't take 5 mins/sq mtr.

[tabbypurr]

Yes there is. PVA on plaster can't be counted on to form a uniform slick, so sanding will break up the plaster surface. And why wuold one create such unnecessary work?

Only in newsgroups & fora do such questions get discussed.

NT

[Cursitor Doom]

Eh?? What's plaster got to do with it? This thread's about PVA on plywood and that's what my remark was addressing.

[Cursitor Doom]

I should have been a bit more precise. I only use PVA as a foundation for painting wood which is going into bathrooms and other wet areas.

[tabbypurr]

When I've used it as a primer its usually been to hold the substrate together, which means plaster.

NT

[tabbypurr]

it's water soluble

NT

[Cursitor Doom]

As are a lot of modern paints - until they dry out.

[Cursitor Doom]

For applying further plaster, fine. But for painting over raw substrate I'd sooner use a proper stabilising solution.

[tabbypurr]

how is that better?

NT

[Cursitor Doom]

Specifically formulated for such purposes!

[stuart noble]

PVA is the basis of many different products, all allegedly specially formulated. Mostly bollocks I suspect. I mixed Gyproc joint filler and neat pva to finish off a job at the weekend because I couldn't be bothered to go out for a single cartridge of Gripfil.

[tabbypurr]

that doesn't tell us how its better, or even if its better

NT

[schetrumpf]

tonight as nowhere to store it undercover.

how long before I can paint that plywood please?

A friend said a tip for putting down ply which will get wet (in my case the base of a trailer) is to just seal the edges with PVA. Product advise to s eal was with a 1 to 3 mix with water. The edge is quite thirsty and when it s done still leaves a roughness for purchase of the paint. I kind of agree about pva on a smoothish surface taking any paint off because the paint may not penetrate the pva'd surface - a thinned coat of paint on the untreated ply seems to the best way to get subsequent paint to adhere.