A NEW HORIZON FOR ATOMIC OXYGEN IN SUSTAINABLE HERITAGE CONSERVATION: GREEN TECHNOLOGY FOR CONTACTLESS CLEANING OF THE WORKS OF ART

The cultural heritage conservation profession is increasingly aware of climate change, scrutinizes unsustainable approaches, and seeks alternatives to environmentally hazardous and waste- generating methods. Mainstream cleaning methods frequently require mechanical action and physical contact with water or solvents, which can damage many sensitive art materials, and conservators now encounter fragile and untreatable surfaces where soot from smoke or fire, and diverse organic contaminants cannot be removed at all with conventional means. In the context of sustainability, the paper will discuss a radically different green approach to the cleaning of artworks based on extremely short-lived oxygen atoms -atomic oxygen (AO), which could provide a breakthrough solution to safely remove problematic contaminants from a broad range of surfaces in a non-contact manner, without health or environmental concerns or waste, which resonates with the sustainability ethos and the needs of the field today. AO is naturally present in Low Earth Orbit at 96%, but not on the ground, where it is extremely short-lived and self-reactive and must be produced and used instantaneously. Therefore, its practical application requires a generation system tailored for conservation, which will be discussed in the context of past research since B. Banks tested the AO method at NASA in the 1990s. We will discuss the design and working principle of the AO proof-of-concept system working at atmospheric pressure to achieve O fluencies around 1021m-3 by flowing gaseous mixture O2 in He (0.1-10 v.% O2), using radiofrequency (RF, 13.56 MHz) field, pulsed modulated RF field at the frequency range 2-100 MHz, as well as recent atomic oxygen cleaning experiments at the European Space Agency’s LEOX facility. Directed to the artwork’s surface, the AO beam ablates carbon-based contaminants by converting them mainly into CO, CO2, and H2O vapors. AO is a short-lived active species (a few milliseconds in room conditions) and has the second-highest electronegativity of all reactive elements. Thanks to these qualities, AO interacts readily with a broad range of contaminants, eliminating soiling through ablation at the atomic scale. Since the atomic surface area of contact with the fluid is much more intense than with a volatile species, AO is expected to prove a superior alternative or supplementary means for enhanced safety and efficiency of mainstream methods. The discussion on practical cleaning applications will be supported with experimental testing and characterization of AO on 39 samples of archetypal sensitive and porous art materials, such as plaster, alabaster, gouache, acrylic, and oil paint, carried out in the ESA’s LEOX facility. Preliminary testing shows that AO technology could fill the critical gap in green cleaning methodology for cultural heritage materials considered untreatable by other means. The paper discusses future research and development plans for AO technology in cultural heritage conservation under the Research Foundation Flanders FWO funded PLASMART (2022-2026) project for fundamental science and the European MOXY project (2022- 2026), funded under the Horizon Europe call Green Technologies for Cultural Heritage.