Biocleaning to Remove Graffiti: A Real Possibility? Advances towards a Complete Protocol of Action

Abstract

The first academic studies on the use of microorganisms in cleaning procedures appeared in the late 1980s/early 1990s. In the past thirty years, most of such studies have addressed the removal of nitrate and sulphate salts and organic matter from surfaces by using non-pathogenic anaerobic microorganisms, mainly sulphate-reducing bacteria. The successful use of microbes in the removal of graffiti paint remains, however, a work in progress. Biocleaning surfaces to remove graffiti is not a simple task, because of the complex chemical composition of graffiti paints. This study looks at ways of improving the bioremoval of graffiti and presents the latest findings regarding different methodological aspects of cleaning natural and man-made stone. Granite and concrete substrates were coated with silver and black graffiti spray paints for comparison of the efficacy of the biocleaning method on these different materials. Visual and microscopic examination along with colour and infrared measurements made after application of the bacterial strains tested (previously shown to be suitable candidates for bioremoval of graffiti) revealed remarkably successful results. The findings presented thus represent progress in the development of a biocleaning protocol applicable to the in-situ removal of graffiti. Important improvements have been made regarding the time of treatment, which has been reduced by up to 20 days, and the use of a culture medium enriched with powdered graffiti, which facilitates and accelerates the adaptation of the microorganisms to the target surface.

The Potential Use of Microorganisms as Restorative Agents: An Update

“…Biocleaning approach has recently been evaluated also for the removal of graffiti paint, a very common cause of disfigurement of monuments, buildings and other urban structures. Sanmartin et al investigate an efficient biocleaning protocol for in situ application, reducing time of treatment and using a specific culture medium for the adaptation of bacteria to target substrate [82][83][84].…”

The Bad and the Good—Microorganisms in Cultural Heritage Environments—An Update on Biodeterioration and Biotreatment Approaches

“…Successful application of bacteria for biotreatment of different materials ( Table 2 ), was shown i.e., for Thiobacillus denitrificans for FeS and mineral sulfur transformation for historical wood treatment [ 131 ] or Pseudomonas stutzeri , Aerobacter aerogenes , Comamonas sp. for graffiti cleaning [ 132 ]. Animal glues were often used in paper manufacturing and reparation of ancient paper artworks, but aged glue can create distortions, tensions, cockling and discoloration of paper materials.…”

Dry biocleaning of artwork: an innovative methodology for Cultural Heritage recovery?

“…Microorganisms become virtuous when used for the removal of harmful compounds from CH [14][15][16][17][18][19][20][21][22][23][24][25][26][27]. In the last two decades, many applied studies have shown that biocleaning of altered CH surfaces has some advantages over the traditional cleaning methods; indeed, chemical treatments are not always sufficiently selective consequently damaging stone surfaces [28][29][30][31].…”