The Surfboard Blank is the foam core of a surfboard that is usually wrapped in fiberglass and resin. The most common surfboard blanks are made up of polyurethane foam, although EPS foam is becoming more common as well. These blanks are commonly formed in a mold and then shaped by hand or by machine before they are glassed and ready to surf.
There is always experimentation with new surfboard blank materials as shapers try to maximize performance out of their equipment. One notable "new" material being used in surfboards is Varial Foam which is a material that has come out of the aerospace industry.