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My daughter decided she wanted to making something out of wood, and the resulting wagon for toys is being painted with leftover household gloss paint in various colours (mainly by me as it's "stinky"). Since we started painting, she's thinking about decorating on top of the gloss paint with a wide range of colours. So far the project has used solely materials we had to hand, and that means her paints if we want plenty of colours; the best by far are acrylics.

Is there a reasonable way to use these over gloss?

The gloss should be quicker and harder drying than artist's oils, discussed here though I haven't handled the latter for decades. The piece is also small enough that we can warm it to speed up curing (even in an oven, but in full sun the air inside my van can reach 40 °C and it can go weeks without being driven). As this is a kid's project, it's likely to get some rough handling, but doesn't have to last forever. I have water-based varnish (for wood) here, and I've often used oil-based paints over water-based successfully in DIY, but water-based over oil-based less so. oil-based

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  • My understanding is that for artist oil paint, it isn't a matter of solvents evaporating. The oil oxidizes to polymerize, which takes a long time to complete for the full thickness. A covering of acrylic paint prevents that. But I also don't think typical "oil-based" house paint uses the oils used in artist paints (the "alkyd" in the description is a modified polyester resin). So to the extent this is answerable, it probably requires info on the paint formulation and how much time has elapsed since painting.
    – fixer1234
    May 26 at 16:24
  • @fixer1234 that would make sense if artists' oils are based on linseed oil. I'm sure they were once and presumably they still are. The most recent coat went on about 5 minutes ago. If I do well, it will have a week to dry at room temp before she want to decorate it. And because I'm using odds and ends of paint (I happened to have a few bright colours, different brands) it's several formulations.
    – Chris H
    May 26 at 19:32
  • The question of longevity is only answerable with the exact formulations, but since it's not intended as an artwork, this doesn't seem as important a requirement as the bond between the two is. Aren't these gloss paints usually so full of solvents that the polymerization of the oils (which I would venture is significantly less than in oil paints) is sped up dramatically once applied?
    – Joachim
    May 27 at 13:11
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    @Joachim artists' oils are essentially a mystery to me, and the only polymerising oil I know is "boiled" linseed oil for wood finishing. I think gloss paints mainly rely on solvents but judging by the smell it takes a few days for the last traces to evaporate in a warm place. The bond is indeed the most important thing. But that's both the initial bond - does the detailing acrylic sit nicely on the surface or bead like water on a surface wet with oil - and the final bond - does it abrade easily. When I put the next coat on I may quickly paint a test piece.
    – Chris H
    May 27 at 15:11
  • I think the answer is "it depends". It sounds like you don't want to prime before the acrylic because you used colorful paint for the base (although you could prime just the spots where the acrylic will go). If you can get the acrylic to stick without beading up, you could add some protection after the acrylic is dry with a clear coat.
    – fixer1234
    May 28 at 16:06

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The acrylic will have a hard time sticking to the glossy surface no matter what it is made of. That is why sanding to roughen the surface and then priming are a thing.

Add to that lower adhesion the properties of oil based paints mentioned in the comments, slower drying being the main one, your top coat will be fairly fragile compared to the base.

The proper and most permanent approach would be to stick with the stinky paint. Anything else in this case will be hit or miss.

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