LASER-INDUCED BREAKDOWN SPECTROSCOPY AS A DIAGNOSTIC-TECHNIQUE FOR THE LASER CLEANING OF MARBLE

Laser cleaning studies were performed on samples of ancient Pentelic m arble covered with black encrustations by employing a Q-switched Nd:YA G laser. Elemental analysis by laser induced breakdown spectroscopy (L IES) has been applied as a real-time diagnostic technique for the clea ning process, with the aim of safeguarding against potential damage. I n addition to the elemental composition, this technique can also provi de information on the depth and morphology of the crust when combined with ablation rate studies. In this way the choice of the optimum lase r parameters for effective cleaning is facilitated. The analytical and structural composition obtained by LIES compares well with the result s obtained by traditional analytical techniques, such as scanning elec tron microscopy, energy dispersive X-ray analysis, Fourier transform i nfrared spectroscopy and optical microscopy. This indicates that LIES can be used as an autonomous on-line diagnostic technique, providing i nformation necessary for accomplishing the efficient laser cleaning of marble artefacts. (C) 1997 Elsevier Science B.V.