Wall paintings studied using Raman spectroscopy: a comparative study between various assays of cross sections and external layers.
This work describes a comparative study between in situ applications of portable Raman spectroscopy and direct laboratory measurements using micro-Raman spectroscopy on the surface of small samples and of cross sections. The study was performed using wall paintings from different sites of the Alcazar of Seville. Little information was obtained using a portable Raman spectrometer due to the presence of an acrylic polymer, calcium oxalate, calcite and gypsum that was formed or deposited on the surface. The pigments responsible for different colours, except cinnabar, were not detected by the micro-Raman spectroscopy study of the surface of small samples taken from the wall paintings due to the presence of surface contaminants. The pigments and plaster were characterised using cross sections. The black colour consisted of carbon black. The red layers were formed by cinnabar and white lead or by iron oxides. The green and white colours were composed of green emerald or atacamite and calcite, respectively. Pb3O4 has also been characterised. The white layers (plaster) located under the colour layers consisted of calcite, quartz and feldspars. The fresco technique was used to create the wall paintings. A wall painting located on a gypsum layer was also studied. The Naples yellow in this wall painting was not characterised due to the presence of glue and oils. This study showed the advantage of studying cross sections to completely characterise the pigments and plaster in the studied wall paintings.
Materials Science Institute of Seville (CSIC-Seville University), Americo Vespucio 49, 41092 Seville, Spain. Electronic address: jlperez@icmse.csic.es.
Jose Luis
JL
Perez-Rodriguez
Technical Architecture Faculty University of Seville, Avda. Reina Mercedes s/n, 41012 Seville, Spain.
Maria Dolores
MD
Robador
Materials Science Institute of Seville (CSIC-Seville University), Americo Vespucio 49, 41092 Seville, Spain.
Miguel Angel
MA
Centeno
Materials Science Institute of Seville (CSIC-Seville University), Americo Vespucio 49, 41092 Seville, Spain.
Belinda
B
Siguenza
Department of Chemistry and Soil Sciences, School of Sciences, University of Navarra, Irunlarrea 1, 31008 Pamplona, Spain.
Adrian
A
Duran
D000818:Animals; D002119:Calcium Carbonate / Q000032:analysis / Q000266:history; D004396:Coloring Agents / Q000032:analysis* / Q000266:history*; D049668:History, 15th Century; D049669:History, 16th Century; D049670:History, 17th Century; D049671:History, 18th Century; D049672:History, 19th Century; D049691:History, Medieval; D006801:Humans; D010151:Paintings / Q000266:history*; D011791:Quartz / Q000032:analysis / Q000266:history; D013030:Spain; D013059:Spectrum Analysis, Raman / Q000379:methods*
D004396:Coloring Agents; D011791:Quartz; D002119:Calcium Carbonate
Pigments; Polychrome; Raman spectroscopy; Wall paintings