How to Sand Polystyrene
- 1). Shape the foam before sanding using a series of hand-held woodworking tools such as handsaws, files and rasps. Cut the foam into the shape desired with the saw, then rip away large portions of the foam to generally shape it with the files. Go over the foam with the rasps to further shape the material until you're prepared to finalize the shape with the sandpaper.
- 2). Sand the polystyrene foam down further into its general shape using a 100-grit coarse sandpaper to remove as much of the foam material as possible. Run the sandpaper over the foam form, scraping away the polystyrene in layers until only detail sections remain to be finished. Switch the sandpaper whenever the granules begin to become clogged by foam particles to avoid creating jagged edges in the foam.
- 3). Use a sanding block pad to shape large flat or gently curving areas of the foam. Avoid using the blocks on sections of the foam that contain small details; the block may flatten detailed areas.
- 4). Use fine-grit sandpaper to perform finishing work on the foam, lightly sanding the surface smooth, or sanding into small detailed curves or edges that the coarser sandpaper or sanding block would otherwise remove. Wipe the foam surface with a clean cloth, then run a second piece of scrap foam over the surface to remove any foam residue.
