Rare Biogeochemical Phenomenon Associated to Manganese Patinas on Mural Painting and Granite Ashlars

Abstract

This article discloses a rare and outstanding type of Mn-rich black-blue patina found on mural painting and granite ashlars located in the church of Sta. Marinha, north of Portugal, and conjectures the phenomenon associated to the appearance of such patinas in different surface materials. This Mn-patina reported on mural painting and their origin is probably assigned to manganese leaching from building materials (i.e., granite and phyllites). Stained mural painting and granite examined by XPS and SEM have showed patinas enriched with manganese (IV) oxide, potentially catalysed by a microbiota, like fungi, observed in SEM micrographs. The pigments used to depict mural painting and groundwater were also analysed by micro-Raman and ICP-MS, respectively, indicating that they are unlikely manganese sources. Unstained building materials, such as granite ashlars, historic joints, mortars and phyllite rocks, were also analysed by ICP-MS showing that historic joints and mortars present significant concentrations of manganese, possibly associated to their absorbing feature. The main materials with potential to impart manganese to Mn-rich patinas are granite ashlars and phyllites. The aim of this investigation is to reveal and ascertain the hypothetical sources and the phenomenon responsible for the Mn-rich black-blue patina appearance, both on mural painting and granite ashlars.

Proto-Early Renaissance Depictions, Iconographic Analysis and Computerised Facial Similarity Assessment Connections: The 16th Century Mural Paintings of St. Leocadia Church (Chaves, North of Portugal)

“…Creating a comprehensive database of various analytical techniques is crucial when selecting the most appropriate solutions for restoring mural paintings. The investigation methodology concerning works of art involves identifying and resolving stylistic problems, as well as understanding the tools and techniques required to reconstruct damaged or missing components [1][2][3][4][5][6]. The facial resemblance in portraits provides valuable information for questions related to the identity of the portrayed individuals and their historic-artistic significance.…”

Mural Paintings Characterisation Using X-ray Fluorescence and Raman Spectroscopy—A Case Study: Nossa Senhora das Neves Chapel, Vilar de Perdizes, Galicia—North Portugal Euroregion

“…Mural paintings from other churches in the Vila Real district are also attributed to the Marão workshops of the 15th and 16th centuries. The following churches, among others, have examples of mural paintings: Santa Marinha, Vila Marim, 15th and 16th centuries [17]; Santa Maria, Covas do Barroso, 15th and 16th centuries; Nossa Senhora da Azinheira, Outeiro Seco, 16th century [18]; São João Baptista, Cimo de Vila da Castanheira, 16th century; Santa Leocadia, Chaves, 16th century; São Miguel, Três Minas, 16th century; Nossa Senhora de Guadalupe, Mouçós, 16th century, [19]; São Brás Chapel, Vila Real, 16th century; São Tiago, Folhadela, 15th and 16th centuries, [20]. The appreciation of these mural paintings will mean a revitalisation of this area with a low population density and a need to attract cultural tourism.…”