Evaluation of the effectiveness of coatings for the protection of outdoor terracotta artworks through artificial ageing tests

Bibliographic Data

ID4675976
AuthorsSpadavecchia, S Spadavecchia (University of Bologna), Cristina Chiavari (0000-0001-7774-5228, University of Bologna, corresponding author), Francesca Ospitali (0000-0003-2382-2050, University of Bologna), Sabrina Gualtieri (0000-0002-2021-0078, Institute of Science and Technology for Ceramics), A C Hillar (University of Bologna), E Bernardi (0000-0002-0063-4594, University of Bologna)
Year2024
Volume70
Pages213-222
Publication date2024-11-01
Peer ReviewedYes
Open AccessYes
TypeARTICLE
VenueJournal of Cultural Heritage (JOURNAL)
Journal identifiersISSN: 1296-2074 • E-ISSN: 1778-3674
PublisherElsevier BV (PUBLISHER)
DOI10.1016/j.culher.2024.09.008
OpenAlexW4403176997
LanguageEN
Citations received3
References cited33

Outdoor terracotta weathering simulated under representative environmental conditions. • Four commercial protective coatings evaluated in term of effectiveness and durability. • Fluorinated coating does not limit water penetration in the terracotta substrate. • Silica nano-coating (followed by alkylpolysiloxane emulsion) suitable for terracotta. Historical-artistic heritage, when located outdoor, is heavily targeted by deterioration phenomena such as weathering and air pollution. This is especially true for terracotta artefacts, as the medium porosity which characterizes them makes their damaging easier. Nevertheless, there is limited academic research on conservation strategies with regards to coatings. Consequently, the restoration of the carbonate terracotta sculpture known as “Muro del vento” (Wind Wall) by Domenico Matteucci has become the starting point for an experimental investigation carried out in order to evaluate the effectiveness and durability - for outdoor terracotta artworks - of an array of protective coatings. In this paper, four commercial protective coatings, recommended both for natural and artificial stones, were evaluated: a vinylidene-fluoride-hexafluoropropene copolymer at 3 % in acetone, an aqueous emulsion of alkylpolysiloxane, an aqueous dispersion of functionalized silica nanoparticles, and a nanostructured and functionalized silica gel in hydroalcoholic solution. Coated and uncoated representative calcium-rich terracotta specimens were subjected to two different accelerated ageing procedures: rain runoff test and climatic chamber exposure. Concurrently, a long-term outdoor exposure was set up. The characterization of the specimens and the evaluation of the coating's performances were carried out through color, contact angles, water absorption and mass variation measurements, 3D digital microscopy, scanning electron microscopy, X-Ray diffraction, Raman micro-Spectroscopy and atomic absorption spectroscopy in order to quantify calcium release in rain. Overall, the proposed accelerated ageing procedures proved to be successful for evaluating effectiveness and durability of protective treatments on ceramic materials. Silicon-based coatings, especially nanostructured and functionalized silica gel, followed by alkylpolysiloxane emulsion, have been shown to be the most suitable coatings for outdoor terracotta artefacts, while the fluorinated coating did not provide adequate protection as it was not able to limit water absorption under runoff conditions

Archaeology · Architectural engineering · Forensic engineering · Terracotta · Building materials and conservation · Conservation Techniques and Studies · Cultural Heritage Materials Analysis · Engineering · History

Tools

Open DOIOpen Access