Cutting and shaping upholstery foam is a project anyone can do. Do basic projects yourself using upholstery skills to convert old, worn chairs, car seats or sofa cushions into comfortable seating by learning easy foam-shaping and cutting techniques. Even without sewing experience, you can complete foam-shaping projects in a day or two. Flexible polyurethane foam is versatile and you can cut and shape it to fit most projects.
Place a flattened cardboard box on the work area. This will keep the knife blade from scratching any furniture or floors.
Lay a sheet of polyurethane foam, that is medium in firmness, on the cardboard. The foam should be no thicker than 4 inches. More than that and the electric knife will not be long enough go through it.
Create a template out of cardboard. Lay used foam from the old furniture piece on the card board for your pattern. Trace around the foam ¼-inch larger than the old foam.
Place the cardboard template on the new sheet of foam. Use a felt tipped pen and place a dot every 12 to 18 inches on the new foam. Connect the dots and form a continuous line.
Cut the foam using a serrated electric kitchen knife with a sharp edge. An electric knife works well with many types of foam. Hold the knife vertically for ease of cutting. Cut along the felt lines or curves.
Clean up the cutting edge. If the foam is rough, or the edges fray, use scissors or a utility knife to trim. You can shape round untidy edges with an air sander using 24-grit sandpaper.
Spray silicone lightly on the foam if the blade becomes slow or sticks. Spraying the blades may be an alternative solution.