Laser-Induced Breakdown Spectroscopy of Cinematographic Film

Abstract

Laser-induced breakdown spectroscopy (LIBS) was used to characterize the composition of black-and-white silver-gelatin photographic films. LIB spectra of samples and reference gelatin (of various gel strengths, Bloom values 225 and 75, and cross-linking degrees) were acquired in vacuum by excitation at 266 nm. The elemental composition of the gelatin used in the upper protective layer and in the underlying emulsion is revealed by the stratigraphic analysis carried out by delivering successive pulses on the same spot of the sample. Silver (Ag) lines from the light-sensitive silver halide salts are accompanied by iron, lead, and chrome lines. Fe and Pb are constituents of film developers, and Cr is included in the hardening agent. The results demonstrate the analytical capacity of LIBS for study and classification of different gelatin types and the sensitivity of the technique to minor changes in gelatin composition. In addition, LIBS analysis makes it possible to extract important information on the chemicals used as developers and hardeners of archival cinematographic films.