Blackening of Pompeian cinnabar paintings: X-ray microspectroscopy analysis
Red Pompeian paintings, very famous for their deep intensity, are currently suffering from darkening. The origins of this darkening degradation are not clearly identified yet and remain a major issue for curators. In the specific case of cinnabar (HgS)-based red pigment, a photoinduced conversion in...
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| Veröffentlicht in: | Analytical chemistry (Washington) Jg. 78; H. 21; S. 7484 |
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| Hauptverfasser: | , , , , , , |
| Format: | Journal Article |
| Sprache: | Englisch |
| Veröffentlicht: |
United States
01.11.2006
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| ISSN: | 0003-2700 |
| Online-Zugang: | Weitere Angaben |
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| Zusammenfassung: | Red Pompeian paintings, very famous for their deep intensity, are currently suffering from darkening. The origins of this darkening degradation are not clearly identified yet and remain a major issue for curators. In the specific case of cinnabar (HgS)-based red pigment, a photoinduced conversion into black metacinnabar is usually suspected. This work is focused on the blackening of red cinnabar paintings coated on a sparry calcite mortar. Different samples exhibiting different levels of degradation were selected upon visual observations and analyzed by synchrotron-based microanalytical techniques. Atomic and molecular compositions of the different debased regions revealed two possible degradation mechanisms. On one hand, micro X-ray fluorescence elemental maps show peculiar distributions of chlorine and sulfur. On the other hand, X-ray absorption spectroscopy performed at both Cl and S K-edges confirms the presence of characteristic degradation products: (i) Hg-Cl compounds (e.g., corderoite, calomel, and terlinguaite), which may result from the reaction with exogenous NaCl, in gray areas; (ii) gypsum, produced by the calcite sulfation, in black coatings. Metacinnabar is never detected. Finally, a cross section was analyzed to map the in-depth alteration gradient. Reduced and oxidized sulfur distributions reveal that the sulfated black coating consists of a approximately 5-mum-thick layer covering intact cinnabar. |
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| Bibliographie: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
| ISSN: | 0003-2700 |
| DOI: | 10.1021/ac0612224 |