Carbonization (a thermochemical process) produces dark marks. Foaming, a partial degradation creating gas-bubbles with in the material, scatters the light and produces light marks. Additives can help improving absorption properties. Applicable laser sources are Nd: YAG-, Nd: Vanadate- or fiber lasers.

Harmonic wavelengths of 532 nm (green) and 355 nm (UV) can be used for bleaching and photo reduction processes. UV-induced photo reduction is often called „cold marking“, as there is no noticeable heating of the material.