painting polystyrene planter

I am using a used polystyrene box to plant some succulents in. I am hoping to make it look like a stone trough.

Does anyone know how one goes about painting polystyrene surfaces. The finish needs to be weatherproof since it will be outdoors.

Any practical advice will be much appreciated. Thanks.

Ms Flowers

 

Acrylic paint is waterproof when it is dry. And to achieve effects it is perfect because it only takes 30 mins tops to dry.

I haven't painted polystyrene so don't know perhaps you have to give it a rough sand down to get it to key on properly.

 

You could acheive the stone effect by adding sand or fine grit to the surface beneath the final coat of paint.

 

Is it really polystirene?

I had good results in the past mixing fine plaster powder with specific polistirene glue (it's used to stick insulating panels, comes in largish pots, say 1 l or more, very thick paste, and smearing it all over with a spatula. You could add as it was suggested grit or sand to make it rougher, them paint with acrylics and finish with clear water proof flatting (water based flatting is less resistant than oil based one... but a world more pleasantto use). It should be water proof, but may suffer from hot-cold extremes.