How to waterproof styrofoam and how to waterproof polystyrene for outside use

Protect polystyrene with a layer of water proof PVA and a layer of dry sand which you pour onto the glued surface.

Use a roller to apply the glue.

Do two or even three layers, leave each layer to dry. make sure the previous layer is properly dry before applying another layer or you will seal in the moisture from the previous layer.

This method makes polystyrene durable enough for long lasting out side use.

You can also now paint it with any paint you like and it will not melt the polystyrene.

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