Phenolic Balsa-Foam is available in three different densities: 7, 12 and 20 lbs. per cubic foot. Aside from weight and hence, hardness, all 3 densities are essentially the same. The same techniques can be used except that the hardest, 20 lb. density offers much more resistance to cutting or shaping tools, and techniques such as punch cutting or impressing the foam may not be practical with the harder material.
Hot Wire cutting does not work with Balsa-Foam because it is very resistant to heat. It is resistant to heat up to 300 F. There is also no need for a hot wire because, unlike polystyrene foam for which the hot wire method was developed, Balsa-Foam can be cut easily with a knife or saw.