Thin films based on polymer poly(isobutyl methacrylate) (PIBMA), doped with carbon black particles deposited on steel plate substrates are proposed as dirt reference standards for cleanliness accreditation methods, particularly for instruments based on laser ablation. The films were made with the spin-coating method, obtaining layers with thickness between 4 and 17 μm. Carbon black particles with sizes smaller than 100 nm and concentrations between 1 and 27.6 mgr/cm³ were used. Characterization of the films was made by using absorbance measurements and laser ablation-induced photoacoustic.Facultad de IngenieríaCentro de Investigaciones Ópticas