Foam: it is used by furniture and vehicle manufacturers, mattress makers, shipping companies, and hobbyists all over the world. It is an amazing product that provides, paradoxically, both cushiony softness and hard rigidity, depending upon its composition. Yet, as pervasive as this material is, it is practically invisible. Tucked out of sight and covered with upholstery, plastic, and other covering materials, it can be a seat cushion, a memory foam mattress, a surfboard, an insulation board, or an RV tabletop. Its light weight and durability make it a magical material for construction in many industries.
For the hobbyist, foam is a fantastic material. It can be shaped, molded, or sculpted into many shapes and projects. With just a few tools, the hobbyist can easily cut thick foam into extraordinary shapes and sizes.
Cushiony foam comes in many forms: polyurethane, high density, high resilience, closed cell, latex rubber, memory, Supreem, and Rebond, to name the most common. Most of these types of foam cut very easily with a common household appliance: the electric kitchen knife. Even thick foam (up to 6" thick) can be cut easily with an electric knife, making smooth, even cuts. For vertical cuts, a vertical guiding edge can be easily devised with boxes placed directly upon the foam in the appropriate place. Of course, it is important to use two tables or flat surfaces to support both ends of a piece of foam that is to be cut, with a channel beneath to allow the electric knife to pass freely and without interference below.
Of course, the pros don't use household electric knives. They use much more expensive foam cutting saws that have a flat base on the end of the blade that is angle-adjustable, with a 6-12" blade that will handle fairly thick foam jobs.
Rigid foam also comes in several forms: polystyrene (used, for example, in coolers), polyurethane foam board. This type of foam is primarily used for its insulative and rigid properties. While thinner sheets of rigid form can often be cut by scoring it with a utility knife and snapping it along a rigid surface, thicker sheets of this product require a bit more finesse. A foam saw will do the trick, but most individuals don't have a foam saw in the garage. Instead, many hobbyists in recent years have constructed a hand-made hot wire saw to cut this this type of foam.
A hot wire saw works by heating a wire to the point that it will vaporize foam that it contacts. It can be made cheaply, or it can be purchased online from many vendors. It makes clean, crisp cuts on even the thickest types of foam.
For a small investment of an electric knife or hot wire saw, anyone can use foam in all its shapes, densities, and sizes. Viva foam!