Applied Physics A

, Volume 121, Issue 3, pp 915–938

Cinnabar alteration in archaeological wall paintings: an experimental and theoretical approach

  • Madeleine Kegelman Neiman
  • Magdalena Balonis
  • Ioanna Kakoulli
Invited Paper

DOI: 10.1007/s00339-015-9456-x

Cite this article as:
Neiman, M.K., Balonis, M. & Kakoulli, I. Appl. Phys. A (2015) 121: 915. doi:10.1007/s00339-015-9456-x

Abstract

The red mineral pigment known as cinnabar (HgS) was commonly employed in Roman fresco wall paintings. Fresco artists of the period favored this pigment for its striking red color. However, upon excavation and exposure to air and light, cinnabar-pigmented surfaces recovered from archaeological contexts often proved to be unstable. Mural paintings colored with cinnabar that have been exposed in the open air frequently demonstrate a disfiguring, irreversible darkening of the surface. Traditionally, scholars have attributed this alteration to a light-induced phase change from red α-cinnabar to black β-cinnabar (meta-cinnabar). While this transformation has not been totally excluded, the prevailing view among conservation scientists is that chlorine plays a key role in the darkening process through the formation of light-sensitive mercury chloride compounds, or as a catalyst in the photochemical redox of Hg(II)S into Hg(0) and S(0). Using laboratory-based experiments and thermodynamic modeling, this paper attempts to further clarify the mechanism(s) and kinetics of cinnabar alteration in fresco applications, especially the role of light, humidity, and chlorine ions. Additionally, it explores possible pathways and preventive as well as remedial conservation treatments during or immediately following excavation, to inhibit or retard darkening of cinnabar-pigmented fresco surfaces.

Copyright information

© Springer-Verlag Berlin Heidelberg 2015

Authors and Affiliations

  • Madeleine Kegelman Neiman
    • 1
  • Magdalena Balonis
    • 2
    • 3
  • Ioanna Kakoulli
    • 4
    • 5
  1. 1.UCLA-Getty Conservation ProgramUniversity of CaliforniaLos AngelesUSA
  2. 2.Department of Materials Science and EngineeringUniversity of CaliforniaLos AngelesUSA
  3. 3.Institute for Technology AdvancementUniversity of CaliforniaLos AngelesUSA
  4. 4.Department of Materials Science and EngineeringUniversity of CaliforniaLos AngelesUSA
  5. 5.UCLA/Getty Conservation Program and Cotsen Institute of ArchaeologyUniversity of California Los AngelesLos AngelesUSA

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