Environmental effects on surface lead–calcium apatite formation on Roman wall paintings
Abstract The formation of lead apatites in heritage objects is increasingly recognized as a recurrent phenomenon, however their origins and formation mechanisms remain poorly understood. This study explores the process behind the darkening and surface clouding in Roman fresco paintings, providing no...
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Nature Portfolio
2025-05-01
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| Series: | Scientific Reports |
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| Online Access: | https://doi.org/10.1038/s41598-025-03620-5 |
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| author | Francesc Albert-Tortosa Núria Jiménez Trinitat Pradell Salvador Butí Victoria Beltran Lídia Font Nati Salvadó |
| author_facet | Francesc Albert-Tortosa Núria Jiménez Trinitat Pradell Salvador Butí Victoria Beltran Lídia Font Nati Salvadó |
| author_sort | Francesc Albert-Tortosa |
| collection | DOAJ |
| description | Abstract The formation of lead apatites in heritage objects is increasingly recognized as a recurrent phenomenon, however their origins and formation mechanisms remain poorly understood. This study explores the process behind the darkening and surface clouding in Roman fresco paintings, providing novel insights into the formation of lead-calcium phosphates, PbxCa(5−x)(PO4)3Cly(OH)(1−y), and plattnerite, β-PbO2, from the pigment minium, Pb3O4, linked to interactions with environmental factors and dust deposition. A combination of microanalytical techniques was used, including optical microscopy, scanning electron microscopy and elemental analysis, synchrotron-based X-ray diffraction and Raman and FTIR spectroscopy. The results show that slightly acidic rainwater or atmospheric moisture reacts with the minium and the calcium carbonate present in the wall painting’s binder, resulting in the formation of plattnerite and the release of Pb2+ and Ca2+ ions, while the environment supplies chloride and phosphate ions, present in the infiltrating water. This process culminates in the precipitation of the lead-calcium apatite, due to its high stability. This apatite acts as a cement that incorporates dust and organic residues, forming a layer several tens of micrometres thick that tends to expand outwards. These findings contribute to a better understanding of pigment degradation mechanisms and will help inform conservation strategies. |
| format | Article |
| id | doaj-art-3fec36292bbf44beb1828dd5d7f5193a |
| institution | DOAJ |
| issn | 2045-2322 |
| language | English |
| publishDate | 2025-05-01 |
| publisher | Nature Portfolio |
| record_format | Article |
| series | Scientific Reports |
| spelling | doaj-art-3fec36292bbf44beb1828dd5d7f5193a2025-08-20T03:16:51ZengNature PortfolioScientific Reports2045-23222025-05-0115111310.1038/s41598-025-03620-5Environmental effects on surface lead–calcium apatite formation on Roman wall paintingsFrancesc Albert-Tortosa0Núria Jiménez1Trinitat Pradell2Salvador Butí3Victoria Beltran4Lídia Font5Nati Salvadó6Departament d’Enginyeria Química, Universitat Politècnica de Catalunya·BarcelonaTech (UPC). EPSEVGDepartament d’Enginyeria Química, Universitat Politècnica de Catalunya·BarcelonaTech (UPC). EPSEVGDepartament de Física, Centre de Recerca en Ciència i Enginyeria Multiescala de Barcelona, Universitat Politècnica de Catalunya·BarcelonaTech (UPC)Departament d’Enginyeria Química, Universitat Politècnica de Catalunya·BarcelonaTech (UPC). EPSEVGA-sense lab, University of AntwerpMuseu d’Història de Barcelona MUHBA, Institut de Cultura, Ajuntament de BarcelonaDepartament d’Enginyeria Química, Universitat Politècnica de Catalunya·BarcelonaTech (UPC). EPSEVGAbstract The formation of lead apatites in heritage objects is increasingly recognized as a recurrent phenomenon, however their origins and formation mechanisms remain poorly understood. This study explores the process behind the darkening and surface clouding in Roman fresco paintings, providing novel insights into the formation of lead-calcium phosphates, PbxCa(5−x)(PO4)3Cly(OH)(1−y), and plattnerite, β-PbO2, from the pigment minium, Pb3O4, linked to interactions with environmental factors and dust deposition. A combination of microanalytical techniques was used, including optical microscopy, scanning electron microscopy and elemental analysis, synchrotron-based X-ray diffraction and Raman and FTIR spectroscopy. The results show that slightly acidic rainwater or atmospheric moisture reacts with the minium and the calcium carbonate present in the wall painting’s binder, resulting in the formation of plattnerite and the release of Pb2+ and Ca2+ ions, while the environment supplies chloride and phosphate ions, present in the infiltrating water. This process culminates in the precipitation of the lead-calcium apatite, due to its high stability. This apatite acts as a cement that incorporates dust and organic residues, forming a layer several tens of micrometres thick that tends to expand outwards. These findings contribute to a better understanding of pigment degradation mechanisms and will help inform conservation strategies.https://doi.org/10.1038/s41598-025-03620-5Lead calcium apatitePlattneriteWall paintingLead pigmentsSynchrotron-based X-ray diffractionScanning electron microscopy |
| spellingShingle | Francesc Albert-Tortosa Núria Jiménez Trinitat Pradell Salvador Butí Victoria Beltran Lídia Font Nati Salvadó Environmental effects on surface lead–calcium apatite formation on Roman wall paintings Scientific Reports Lead calcium apatite Plattnerite Wall painting Lead pigments Synchrotron-based X-ray diffraction Scanning electron microscopy |
| title | Environmental effects on surface lead–calcium apatite formation on Roman wall paintings |
| title_full | Environmental effects on surface lead–calcium apatite formation on Roman wall paintings |
| title_fullStr | Environmental effects on surface lead–calcium apatite formation on Roman wall paintings |
| title_full_unstemmed | Environmental effects on surface lead–calcium apatite formation on Roman wall paintings |
| title_short | Environmental effects on surface lead–calcium apatite formation on Roman wall paintings |
| title_sort | environmental effects on surface lead calcium apatite formation on roman wall paintings |
| topic | Lead calcium apatite Plattnerite Wall painting Lead pigments Synchrotron-based X-ray diffraction Scanning electron microscopy |
| url | https://doi.org/10.1038/s41598-025-03620-5 |
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