Cleaning of the S.Stefano Church Portal by two Short Free Running and Long Q-Switch Nd:YAG Lasers S.E.Andriani1, I.M.Catalano1, R.Laviano2, F.Vona3, G.Daurelio4, G.Stea5 1Unità di Ricerca INFM - Dip di Fisica, Università degli Studi di Bari- Laboratorio di Ricerca per la Diagnostica dei Beni Culturali Università di Bari, Italy,andrianiedo@yahoo.it 2Dip Geomineralogico, Università degli Studi di Bari, Bari, Italy, 3Soprintendenza per il Patrimonio Storico Artistico e Demoetnoantropologico della Puglia, Bari, Italy, 4Private Senior Researcher in Laser Material Processing & Art Restoration, Palo del Colle (Bari), Italy, 5Private Geologist, Sannicandro di Bari, Italy The deterioration of materials is a natural process: ALL MATERIALS DEGRADE IN NATURE “…the aim of the cleaning, by the point of view of preservation, is the removal of harmful substances : soluble Salts, black crusts, lichens ecc…, but it must preserve the original color, natural layer (oxalate) and the superficial layer of the stone material” (NorMal 1985) Laser Cleaning… “Technique that remove, selectively, soiling from the surface of an artwork and “pick off” remnants of dirt without overcleaning ” ADVANTAGE Non Contact Selectivity Immediate control High precision: localized action Solid state Laser Nd:YAG (L nss; =1064nm) SHORT PULSE (Q-SWITCH) LONG PULSE (NORMAL MODE) 200s 1ms PHOTO THERMAL ABLATION Sublimation (continuously) Thermoelastic Phase Diffusion of heat Probable PHOTO-THERMAL DAMAGE 4 10ns PHOTO MECHANICAL ABLATION Explosive vaporization Plasma expansion Shock Wave Probable PHOTO-MECHANICAL DAMAGE Prelievo Microimage 100x Nicol // FT-IR Microimage 100x Nicol // SEM+EDS PRIMA PRIMA SEM+EDS a) b) DOPO DOPO Microimage SEM 335x Microimage SEM 910x Microimage 100x Nicol // Microimages 100x Nicol//: after laser Nd:YAG cleaning L= 20s F=7.11 J/cm2 L=70ns F=2.87 J/cm2