Fiberglass sheet is a composite of glass fibers in an epoxy matrix. It is also known as glass fiber reinforced plastic (GFRP) or E-Glass Epoxy Composite. Laser processing of fiberglass sheet is possible with a 9.3 or 10.6 micron CO₂ laser, with no significant difference in quality produced by the two wavelengths. The 1.06 micron fiber laser is not used for processing this material as the wavelength is not readily absorbed. Laser cutting of fiberglass sheet with a CO₂ laser produces a blackened carbonized edge that can be cleaned with a solvent. Laser marking of fiberglass sheet with a CO₂ laser carbonizes the surface of the epoxy creating a dark visible. Laser engraving is typically not recommended, as the process produces significant discoloration and deposition.