Several costumers have used a hot wire on foam, but Ashton recommends caution when using a hot wire because it can release noxious fumes which can make you dizzy. She also recommends avoiding a hot wire if you tend to have a lot of allergies.
Dawn McKechnie uses a hot wire when working with dense or extruded styrene/insulation along with an Exacto, case cutters, or #6 woodcarvers J hook.
Charles Galway uses a hot wire when he has to cut simple curves (not compound curves) in foam (nichrome wire, with something like 6 to 12 volts running through it, maybe 1 to 4 amps.) He uses nothing hotter than a dull red incandesence.
Ashton and her foam partner are able to achieve very good, organic curved surfaces with just electric knives and scissors. "Sometimes you just have to go over an area and refine it and smooth it out many times, which can be messy because it creates lots of tiny foam scraps that pick up static electricity," Ashton says. "I've pretty much discontinued using the hot wire."
While hot wires are great for getting pretty small detail, you are really trying to make an impression from far away, which is what makes foam spectacular, Ashton points out.
Ashton has never used a hot wire to cut foam, only for carving small detailed areas about 2 to 3 inches (5 to 7.5 cm) or less. She uses scissors or scalpel for any larger areas. Ashton does not have any sustained experience using a hot wire on dense, rigid, or styrofoam.