Number

296-EN

Section

General Section

Use

Abstract

This case story presents the use of Pseudomonas stutzeri for the biocleaning of mural paintings, for the purpose of eliminating remains of organic material from old restorations or insoluble saline efflorescence. Traditional techniques used in cleaning involve: solvents, spirits, alkalis, acids and soaps, as well as simple mechanical actions (ex. scraping with a scalpel).

Substituted substances

Reliability of information

Evidence of implementation: there is evidence that the solution was implemented and in use at time of publication

Reason substitution

other toxic effects

Other type of alternative

Bacterial suspension

Hazard Assessment

Substances to be substituted: The restoration agent is a mixture containing substituted substances: EDTA (ethylenediaminetetraacetic acid) is not listed in the SUBSPORTplus Database. Potassium hydroxide is not listed in the SUBSPORTplus Database. Ammonium carbonate is not listed in the SUBSPORTplus Database and has no harmonised classification according to Annex VI of Regulation (EC) No 1272/2008 (CLP Regulation). Alternative substances: The bacterial suspensions show usually no chemical hazards.

Description of Substitution

The frescoes in the Church of Santos Juanes in Valencia, Spain, were damaged by fire in 1936 and improperly restored in the 1960s and from salt blooms (a side effect of pigeon nests). Researchers at the Institute of Heritage Restoration and the Centre for Advanced Food Microbiology from the Polytechnic University of Valencia (Spain) had an idea to use the harmless Pseudomonas bacteria to clean the works instead of toxic chemicals. Pseudomonas stutzeri bacteria were developed by a team of biologists, who taught the group that cleaned the Campo Santo di Pisa in Italy from practical knowledge. Effectively trained to eat salt and glue, the bacteria are brushed onto the frescoes and covered with a gel that, when heated with lights, creates perfect conditions and aids clean-up. Just 90 minutes later, the targeted area of the fresco is washed clean with water and dried, killing the bacteria and leaving behind a shiny clean section to admire. In the past, to remove foreign materials encrusted on ancient artworks restorers used reactive chemicals that are non-selective and toxic. Or they tried to wear away the crust by mechanical means, which is time consuming and can damage the paint. In this way, about one third of the frescoes decorating the walls of the baroque and gothic Church, whose original structure dates back to the 13^th century, have been restored to date.

Case/substitution evaluation

The alkaline agents for restoration of old frescoes can be substituted by non-chemical alternative. It is a bacterial suspension and contains leaving microorganisms. They are selected for these processes and are not sporulating and non-pathogenic, so they do not generate a risk to workers. According to the research publication from Pilar Bosch Roig the biocleaning is favourable from a health and environmental point of view. The SUBSPORT team is not aware of potential disadvantages with the method described.

State of implementation

In use

Date and place of implementation

2011 in Spain

Availability ofAlternative

on the market

Producer/Provider

See: Contact: Information supplier

Type of information supplier

Research

Contact

Polytechnic University of Valencia (Spain)

Publication source: author, company, institute, year

National Geographic (2012) Kleine Helfer in der Kirche. 1 (2012), S. 29

Date, reviewed

November 26, 2021