"One of the most obvious things
that distinguishes polystyrene from other types of foams is that it will be
eaten away by many other products, including permanent markers, spray
paints, lacquers and fiberglass resin. This is because all of those
products contain one or more of the solvents which will dissolve styrene,
such as xylene, methyl chloride or liquid styrene. Urethane and
polyethylene are not soluable in most of the common solvents, so their foams
will stand up to most other prop shop products."
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