Cleaning of metallic artworks using eco-friendly gels amended with microorganisms.

The HELIX project, developed at the Haute Ecole Arc Conservation-Restauration, in collaboration with the University of Neuchâtel, the University of Bologna and Arc’ Antique conservation and research laboratory, aims to develop green formulations to clean altered and tarnished surfaces from copper, iron and silver artworks. The goal is to propose a sustainable method that is conscious of the challenges in the conservation field, while limiting the risks for the artwork itself, the operator and the environment.           

While exploiting the ability of some microorganisms (fungi, bacteria) and green solvents as well as the assets of the use of gels in the field of conservation, corrosion products and/or old and defective organic coatings will be removed from tarnished metallic surfaces. Mechanisms and performances induced by the microorganisms will be evaluated for their ability to remove corrosion and/or organic coatings from previous intervention. When possible, only metabolites extracted from microorganisms will be used in order to avoid the manipulation of living cells by end-users. This project gives birth to two PhD thesis, focused respectively on the use of hydrogels and bio-based organogels.  

Microorganisms will be selected and incorporated into hydrogels, derived from biological sources (agar from seaweed, Gellan gum from bacteria). In parallel, non-aqueous solvents (e.g. Deep Eutectic solvents – DES) and green thickening agents (e.g. poly β-hydroxybutyrate – PHB) will be chosen and employed to prepare bio-based organogels. The stability, the texture and the application of such formulations as well as relative removal methods will be studied. Then, gels efficiency will be assessed on metal coupons prepared preliminarily. The performances of our new gels will be compared to commonly used methods in conservation, such as gels containing chemical chelating agents (e.g. EDTA) or mechanical methods. Mock-ups will be analysed before and after ageing treatments, thanks to various analytical techniques (SEM-EDS, FTIR and Raman spectroscopy, gas chromatography, XRD etc.).

Finally, selected gels will be tested on real artworks, representative of targeted degradation features, in close interaction with conservators-restorers.

This project is supervised by Prof. Edith Joseph (Haute Ecole Arc Conservation-Restauration and Laboratory of Technologies for Heritage Materials, University of Neuchâtel), Prof. Stephan von Reuss (Laboratory of Bioanalytic Chemistry, University of Neuchâtel) and Dr. Elodie Guilminot (Laboratoire Arc’ Antique, Nantes, France) for the thesis on hydrogels and Dr. Giorgia Sciutto (University of Bologna, Italy) for the one related to organogels.



Edith Joseph, assistant professor


Monica Albini, PhD


Lidia Mathys-Paganuzzi, lab technician


Coralie Montavon, master student