Acetone is a relatively non-polar solvent (as compared to water, which is highly polar), and Styrofoam is made from polystyrene and foam. Due to their similar polarities, acetone can dissolve the carbon-hydrogen bonds of Styrofoam.

Can you touch acetone and Styrofoam?

Any surface of the styrofoam touching acetone will dissolve. SAFETY NOTE: Now here is a bit of a caution. These are strong chemicals with a lot of fumes.

What will break down Styrofoam?

The acetone is a solvent that easily breaks down the polystyrene, releasing the little air pockets trapped inside and leaving very little residue at the end. In other words, when you combine Styrofoam and acetone, the polystyrene will completely dissolve!