I’ve been trying to make laser cut jewelry with different woods. I practiced with draftboard, then tried birch plywood and walnut.
Whenever I paint the pieces, I give them a ton of drying time, and coat them with polyurethane spray. Still, days later the paint can be easily peeled off and the wood looks normal again. (I also sand before I paint anything). It’s like the paint just sits on top of the wood but is never really sealed off no matter what I try.
The Proofgrade material is already sealed, so your topcoat won’t stick. If you aren’t using Proofgrade, you need to make sure the material isn’t already sealed. This means sanding the surface you want to paint or stain to remove any sealant and then applying your own. As others have said, primer is required under paint on unsealed wood to seal the grain. I would primer, sand, and then paint on unsealed wood, or for a natural wood look, sand, seal, sand, and topcoat.
I agree with @ben1 and it’s the sealed PG material. You’re kinda defeating the purpose of using a sealed and finished wood and then painting it. (Not that there’s anything wrong with that if that’s what you want to do. ) You can either sand it more to remove all the finish, but it’d be more economical to buy unfinished wood and then finish it yourself.
That depends on what you’re going to do with it. Does it need UV protection? Does it need weather-proofing? Will it see a lot of wear of hang on a wall? Can the finish have a slight yellow color to it? How shiny, how thick does it need to be?
Finishing wood is a big topic that has been discussed, demonstrated and opined on for centuries. As a general starter finish I’d go with shellac or the wipe on poly @evansd2 has been using.
Watco clear satin finish wipe on polyurethane, to be precise.
I use as little as possible across two coats, literally wipe on and off as quickly as possible. The matte surface is forgiving and gives a nice feel after all is said and done. Given how little I’m using, it is probably not the most durable surface, but it’s perfect for light duty.