XPS Foam (Extruded Polystyrene)
Owens Corning / Dow
Overview
Closed-cell extruded polystyrene rigid foam board (pink/blue insulation board). Widely available at hardware stores as insulation. Machines fast and clean for prototyping, architectural models, cosplay props, and lost-foam casting masters. Much less dust than EPS (beadboard).
Properties
Difficulty
beginner
Flexibility
rigid
Layer Adhesion
poor
Enclosure
no
Heated Bed
no
Dry Storage
no
Pros
- Machines very fast — 3-5× faster than wood
- Near-zero chip hazard (fine dust only)
- Closed-cell — minimal moisture absorption
- Inexpensive — hardware store pricing
- Can be bonded with foam-safe adhesives
- Available in large sheet sizes
- Re-melts with heat for simple forming
Cons
- Melts at 95°C — low heat tolerance
- Dissolves in acetone, styrene, gasoline — must use foam-safe finishes
- Not structural
- Flammable without FR additive
- Fine dust is irritating — dust collection needed
- Breaks under point loading
- Cannot be finished with polyester resin (dissolves)
Best For
- Architectural scale models|Stage prop fabrication|Cosplay armor and props|CNC training and bit testing|Lost-foam aluminum casting|Surfboard cores|Wing cores for RC aircraft
Avoid For
- Structural parts|High-temperature environments|Contact with acetone/polyester resin|Food contact|Load-bearing applications
Storage
Store flat and dry. Keep away from heat, flame, and solvent-based coatings. Use foam-safe spray (Plasti-Dip, latex paint, or water-based coatings) for surface sealing. Fine dust — use dust collection and light filtration.
Brands
Owens Corning FoamularDow Styrofoam Blue BoardKingspan Kooltherm