To the guy using "styrene" to build his "mush" helmet....if you are using any reasonable primer....I use Rustoleum Automotive primer...it should not dissolve styrene at all. If you are talking about styrofoam....yeah that would indeed dissolve with most solvent paints. You can seal it with white glue or if you want a harder barrier or hard coating, go with Styro spray 1000. It is a epoxy base coating that dries slowly....about 4 hours,to full cure in 24 hours. It leaves a high gloss surface when dry and is kind of self leveling so it seals and masks some imperfections in surfaces. Costs about $45 US, per quart,shipped from www.industrialpolymers.com....hope that helps.