Graffiti, as an act of vandalism, is a major danger to stone Cultural Heritage and a risk for the preservation of historical or modern buildings and monuments. Graffiti paints may damage architectural materials, accelerating their decay and leading to important loss in value and significance. Spray paints and felt-tip markers are the most widespread materials used for graphic vandalism. The preventive use of antigraffiti coatings that hinder the diffusion of the paints into the substrate may ease the recovery intervention but, on the other hand, many surfaces of historical value still remain vulnerable not having such protection at all, whose protection just became less effective or whose peculiar characteristics exclude such treatments. In this case, the interventions to remove graffiti most frequently rely on chemical products or mechanical tools. However, the most appropriate cleaning procedure should be chosen according to the chemical composition of vandalic paints and to the chemical-morphological characteristics of the substrate, in order to selectively remove the paints without damaging the support. The outcomes of recent laboratory research performed on painted marble are presented here, based on laser and low-toxicity chemical cleaning performed both as standalone methods and in combination. The advantage of the combined approach is based on the preliminary thinning of the superficial paint layer by pulsed laser radiation (physical approach) so as to optimize the action of the chemical cleaning performed in the second step. In addition, the risk of further colorant diffusion into the internal stone structure caused by the solvent-based cleaning is minimized. After the preliminary chemical characterization of the chosen paints, the different approaches were evaluated on both sound and aged marble through scientific examination of surfaces and cross-sections. Spectroscopic analyses and observation with optical microscopy, as well as with laser-scanner microprofilometry, were performed to check the presence of visible or hidden residues, possible damage of the marble structure, penetration depth and extraction efficiency of the paint.
I graffiti, intesi come atto vandalico, costituiscono un grave pericolo per il Patrimonio Culturale in pietra ed un rischio per la conservazione degli edifici e monumenti storici e moderni. Le vernici usate per i graffiti possono danneggiare i materiali architettonici, accelerandone il degrado e causando importanti perdite di valore e leggibilità. Le vernici spray e i pennarelli sono i materiali più usati per il vandalismo grafico. L'applicazione preventiva di antigraffiti che impediscono la diffusione della vernice nel substrato può agevolare l'intervento di recupero, ma molte superfici di valore storico restano ancora vulnerabili poiché non hanno tale protezione o questa, se c'è, ha perduto la propria efficacia. In questo caso, gli interventi per la rimozione dei graffiti si basano frequentemente su prodotti chimici o metodi meccanici, ma la procedura più appropriata per la rimozione dovrebbe essere scelta in base alla composizione chimica della pittura vandalica e alle caratteristiche chimico-morfologiche del substrato, al fine di rimuovere selettivamente la vernice rispettando al contempo il supporto lapideo. Vengono qui presentati i risultati di alcune recenti ricerche effettuate in laboratorio su provini che simulano superfici deturpate da graffiti. Sono stati confrontati diversi approcci basati sull'impiego di metodologie laser, su prodotti chimici a bassa tossicità e combinazioni dei due metodi. Il vantaggio del metodo combinato risiede nell'assottigliamento preliminare dello strato superficiale di vernice tramite laser (approccio fisico), che consente di ottimizzare l'azione della pulitura chimica effettuata in un secondo step. Inoltre, il rischio di un'ulteriore diffusione del colorante nel materiale lapideo ad opera della pulitura con prodotto a solvente è minimizzato. Dopo la caratterizzazione chimica preliminare delle vernici scelte, i diversi approcci sono stati valutati su marmo sia sano che invecchiato, mediante indagini scientifiche sulle superfici e in sezione trasversale. Analisi spettroscopiche e osservazioni con microscopia ottica, così come con microprofilometria laser-scanner, sono state effettuate per verificare la presenza di residui visibili o occulti, possibili danni alla struttura del marmo, profondità di penetrazione ed efficienza di estrazione della pittura.
Graffiti removal from historical buildings
Barbara Salvadori
2017
Abstract
Graffiti, as an act of vandalism, is a major danger to stone Cultural Heritage and a risk for the preservation of historical or modern buildings and monuments. Graffiti paints may damage architectural materials, accelerating their decay and leading to important loss in value and significance. Spray paints and felt-tip markers are the most widespread materials used for graphic vandalism. The preventive use of antigraffiti coatings that hinder the diffusion of the paints into the substrate may ease the recovery intervention but, on the other hand, many surfaces of historical value still remain vulnerable not having such protection at all, whose protection just became less effective or whose peculiar characteristics exclude such treatments. In this case, the interventions to remove graffiti most frequently rely on chemical products or mechanical tools. However, the most appropriate cleaning procedure should be chosen according to the chemical composition of vandalic paints and to the chemical-morphological characteristics of the substrate, in order to selectively remove the paints without damaging the support. The outcomes of recent laboratory research performed on painted marble are presented here, based on laser and low-toxicity chemical cleaning performed both as standalone methods and in combination. The advantage of the combined approach is based on the preliminary thinning of the superficial paint layer by pulsed laser radiation (physical approach) so as to optimize the action of the chemical cleaning performed in the second step. In addition, the risk of further colorant diffusion into the internal stone structure caused by the solvent-based cleaning is minimized. After the preliminary chemical characterization of the chosen paints, the different approaches were evaluated on both sound and aged marble through scientific examination of surfaces and cross-sections. Spectroscopic analyses and observation with optical microscopy, as well as with laser-scanner microprofilometry, were performed to check the presence of visible or hidden residues, possible damage of the marble structure, penetration depth and extraction efficiency of the paint.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
