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Marker and Pen Graffiti Cleaning on Diverse Calcareous Stones
by Different Laser Techniques S.E. Andriani1,2*, G. Daurelio1,2 , I.M. Catalano1,2 , A. Albanese1 1InterAteneo Physics Department “ M. Merlin “ of the University and Polytechnic of Bari – “InterDep. Center “Search Laboratory for the Cultural Heritage Diagnostic” - Bari, Italy, 2Consorzio Nazionale Interuniversitario per le Scienze fisiche della Materia- Udr Bari, - c/o Physics Department “M. Merlin” - Italy Contacts: Laser Cleaning tests on 41 new marker and pen types ( fluorescent, permanent , water-based , acrylic tempera, metallic paint , waterproof inks ), applied into laboratory on different litho- type samples (Chianca, Travertino di Roma, Tufo carparo fine grain, Sabbie), typical stones employed in much more monuments in Puglia and Italian architectures were carried out . The same ones , were exposed for twelve months to outdoor ageing, subject to sunshine, rain, wind, IR and UV solar radiations. Ablation experiments and tests by using different cleaning techniques each one in Dry and Wet condition (classic technique, Daurelio technique 1 and Daurelio technique 2 and others new techniques), two different Nd:YAG laser systems (Palladio by QUANTA SYSTEM and SMART CLEAN II by EL.EN.), three experimental modes N – Mode ( 1064nm – 150, 300 and 500 μs pulse duration), Q – Switch ( 1064nm - 8 ns pulse duration ) and SFR ( Short Free Running – 1064 nm – 40 to 110μs pulse duration ) were tested . According to the different ink types and stone substrate, Q-Switch laser cleaning ablation with optimized laser techniques are the best solution to marker an pen graffiti removal. The work is still in progress Abstract Sabbie Sabbie Tufo Carparo Tufo Carparo Travertino Chianca 12 months after Chianca Travertino Technique Daurelio n.1 This technique uses an integrated focused beam both in Dry and Wet condition, it consists of substituting a cylindrical converging plano-convex quartz lens (CL whit 25cm focal length) to classical convergent lens. New cleaning mechanism called “blade laser cleaning” was obtained. Classical technique This technique is the laser cleaning with the beam in air in Dry or Wet condition with a classical focuses lens (in this experimental work with a new lens L1 of 30cm focal length) Technique n.3 This technique combines classical technique and technique n.1 with “very Wet” condition, it is a “Bubble water laser cleaning”. Technique n.2 This technique consists of covering by a very thin wet layer of a mixture, composed by water and earth (oxides and salts of Iron and Aluminium) Technique Daurelio n.2 or by another surface absorbing “coat”, wet or dry. Travertino sample- Colour 26 Sabbie sample- Colours 9 to 12 F= 1.2 J/cm2 F= 8 J/cm2 Before DRY 1° DRY 2° WET Dry or WET Dry The best solution in 26 colour removal was a combine of Dry and Wet laser cleaning (classical technique) with F 1 to 2 J/cm2 Both Dry and Wet cleaning with F J/cm2 the laser interaction produced a change of colour turning its in orange-gold Complete cleaning with F 5 J/cm2 “very Wet” (Techniques n.3 + lens L1) Chianca sample The colour surface after cleaning was different from surround area, because of the typologies of these adsorbing stones, all the air pollution was adsorbed to surface darkening itself. Technique Daurelio n.2: F 2 J/cm2 water + absorbing coat Tufo sample Very Wet Cleaning Cleaning with Technique Daurelion.1 F 6 J/cm2 Dry cleaning Blackening Iron oxidation Dry cleaning F 2.4 J/cm2 Blackening Chianca sample Dry cleaning Blackening F 2.4J/cm2 Iron oxidation Very Wet F 2.4 J/cm2 Cleaning Conclusions The Nd:YAG Q-Switch laser had showed a satisfactory cleaning of different sample surfaces without any damage to the substrates. The “very Wet” condition mode and Technique Daurelio n. 2 had permitted the complete cleaning of the most fastest marker and pen graffiti. WET: increase colour tone
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