Il Silenzio: The First Renaissance Oil Painting on Canvas from the Uffizi Museum Restored with a Safe, Green Antimicrobial Emulsion Based on Citrus aurantium var. amara Hydrolate and Cinnamomum zeylanicum Essential Oil.

Debora Minotti,Maria Grazia Bellardi,Paola Mattarelli,Francesca Bugli,Luigia Sabatini,Stefania Garzoli,Alice Peduzzi,Lara Vergari,Lorenzo Barbanti,Roberto Rosato,Maria Rita Proto,Maura Di Vito,Maurizio Sanguinetti,Daphne De Luca

doi:10.3390/jof8020140

Abstract

Preserving artworks from the attacks of biodeteriogens is a primary duty of humanity. Nowadays, restorers use chemicals potentially dangerous for both artworks and human health. The purpose of this work was to find a green and safe formulation based on natural substances with fungicidal activity to restore ancient oil paintings, particularly “Il Silenzio” (by Jacopo Zucchi) preserved at the Uffizi Museum in Florence, Italy. The study was divided into two phases. First phase (in vitro study): three essential oils (EOs) and four hydrolates (Hys) were analysed by GC-mass spectrometry and in vitro tested against six ATCC strains of molds. An emulsion based on the more active natural compounds was tested on aged and unaged canvases samples to evaluate both their fungicidal activity and the impact on chemical-physical parameters. Finally, an in vivo toxicity test performed on the Galleria mellonella model assessed the safety for health. Second phase (in situ application): the emulsion was sprayed on the back of the painting and left to act for 24 h. Biodeteriogens present on the “Il Silenzio” painting were microbiologically identified before and after the treatment. The emulsion formulated with C. zeylanicum EO and C. aurantium var. amara Hy showed the best antifungal activity both in vitro and in situ without altering the chemical-physical characteristics of paintings. Furthermore, no in vivo toxicity was shown. For the first time, a green antimicrobial emulsion based on Hy and EO, safe for operators, was used to decontaminate an artwork colonised by fungi before the restoration practices.

Highlights

All microbial agents that affect artwork will cause irreversible damage
The chemical composition of the C. zeylanicum essential oils (EOs) was characterised by cinnamaldehyde (66.0%) as a major compound followed by β-caryophyllene (5.8%), (E)-cinnamyl acetate
The chemical compositions of other EOs and Hys have already been analysed by our group [23,24,25]

Summary

Introduction

All microbial agents that affect artwork will cause irreversible damage. it is essential to monitor these contaminations in order to avoid damage such as increased fragility, disconnection, change of colour, or complete destruction of the canvas painting [1].The biodeterioration control of cultural heritage materials involves measures to stop the degradation caused by both microorganisms and organisms and, whenever possible, to delay its reappearance. Vegetable/animal fibres, wood, and painted artworks are mainly attacked by fungi due to their cellulose content, while stone colonisation follows a precise pattern: fungi prior to algae, mosses, and lichens and common organisms (from cryptogams to higher plants). Fungi represent both a serious danger to artefacts and a risk to human health. In addition to the prevention practices, those of disinfection are carried out before any other manipulation to avoid the spreading of spores, which are potentially dangerous for both artworks and human health. The most used products in the restoration of paintings are Preventol® RI80/RI50, Biotin R, and Biotin T.

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