1. 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