A exploração de enzimas na limpeza da pintura milagre da bilocação de Santo António

Abstract

Enzymes are biological molecules of a protein nature that act as catalysts for chemical reactions. In the field of conservation and restoration, they have been used for cleaning dirt and removing altered protective layers, achieving highly positive results. From this perspective, the viability of applying a “green” methodology to clean a painting was investigated. The artwork used as the basis for this research is a 17th century oil painting on canvas titled “St. Anthony saving the father from the gallows”, one of the saints’ bilocation miracles. Of unknown authorship, the painting presents pathologies aligned with case studies where the use of enzymes shown promising results. Part of this investigation involved examining the painting’s history and provenance. It was originally located in a private chapel in Torre de Moncorvo and Vitor Serrão believes it may have come from the now-defunct Convent of St. Francis in the same town. On the reverse side of the painting, an inscription and drawing of charcoal were identified and thoroughly analysed. The painting entered the Douro Museum in 2023 as part of the project “Identify to Conserve”, which aims to preserve cultural heritage at risk in the Douro Demarcated Region. The painting exhibited numerous overpainted areas and two heavily altered protective layers applied at different times. The most recent layer covered remnants of an older one, which likely had not been fully removed due to the challenges involved. FTIR analyses revealed complex mixtures in these layers, suggesting the presence of natural resin in the older varnish and a combination of acrylic resin and wax in the more recent one. The green paint layers were completely overpainted with oil paint, and an incomplete cleaning attempt had left these areas heavily stained and uneven. The aim of the project was to test enzymes for removing these layers and explore their use in combination with PVA-B hydrogels. Various formulations of enzymatic solutions were tested, including enzyme kits, enzymatic soap, and buffered gelled solutions. A specific protocol was developed to evaluate the effectiveness of cleaning, aiming to understand the mechanisms of interaction between the enzymes and the different tested media, assessing their functionality, efficiency, and limitations. This approach allowed for a systematic and replicable comparison. Different formulations of PVA-B combined with solvents were tested to address issues that could not be resolved with enzymes alone, such as the removal of overpaints and restoring the readability of all areas with green paint layers.

Date of Award	25 Mar 2025
Original language	Portuguese
Awarding Institution	Universidade Católica Portuguesa
Supervisor	Maria Aguiar (Supervisor) & Carlos Filipe Nunes Mota (Co-Supervisor)