Essentially a specialized rasp, the cutting edge of a Surfoam looks similar to a cheese grater attached to a handle. It is commonly available in DIY stores, such as Home Depot or Lowes.
Although a sharp blade is useful in the general shaping of foam—and a hot wire is helpful with etching or carving—the Surform excels in smoothing out and shaping foam.
A common use I make of a Surform is in the shaping of hills. After gluing tiles of foam together, I run the tool across the surface. Putting my weight into it, I can shape gentle or steep slopes. Dig in a bit, and I can create furrows or gulleys.
As revealed by the accompanying photo, the surface of the shaped foam is rough. It works fine for plowed fields or drought-stricken soil that’s buckled under the heat. For a smoother surface, a light rub of sandpaper will provide a smoother surface. You’ll need patience, though, as you cannot press the sandpaper too forcefully or you’ll tear up the foam.
With a little practice, you can make gentle slopes–and completely hide the joint lines where multiple layers of foam are glued together.
Be prepared for a mess, however. As you work, you’ll find small, static-electricity-charged dust and particles sticking to everything surrounding your work area (including you). One trick to minimize your problem with foam particles is to mist water over the work area and your tools. But make certain to wear a dust mask, too.
This is a great tool for your workshop. It takes a bit of elbow grease, but you can get great results.