Foam Core Board, or foam board, is comprised of a polystyrene foam core laminated between two pieces of white cardstock. Laser processing of foam core board is possible with either a 9.3 or 10.6 micron CO₂ laser with no discernible difference in process quality. The 1.06 micron fiber laser is not recommended for use with this material as the wavelength is not readily absorbed. Laser cutting of foam core board with a CO₂ laser produces a clean color-free concave edge where the foam retracts slightly from the edge, leaving the cardstock unaffected. This characteristic can vary depending on the material thickness. Laser engraving of foam core board ablates the cardstock surface exposing the polystyrene foam underneath. Laser marking of foam core board is typically not recommended as the laser does not produce a contrasting mark on the material.