The conservation of the architectural surfaces in the tablinum of the House of the Bicentenary at the ancient Roman site of Herculaneum is a collaborative project of the Getty Conservation Institute, the Herculaneum Conservation Project and the Soprintendenza Pompeii. As part of this project, a study was undertaken by a multi-disciplinary team comprised of conservators and conservation scientists to understand the effects of the catastrophic 79 CE eruption of Mt. Vesuivus on the wall paintings at Herculaneum. Due to the eruption, Herculaneum was destroyed as a living city, and yet preserved nearly intact for two millennia, buried under twenty meters of volcanic material. Discovered in 1709, and excavated as an open-air site in the early to mid-twentieth century, Herculaneum preserved a wealth of Roman cultural heritage, including the exquisitely painted walls of the tablinum of the House of the Bicentenary. The decorative scheme of the tablinum is composed of red, yellow and black monochrome backgrounds with decorative borders and floral and architectural elements. In the center of each wall are figurative scenes emulating portable paintings. As a result of the eruption, the wall paintings suffered severe damage and alteration, notably in large swaths of yellow monochrome background converted to red when exposed to the heat generated by hot mud and ash from the volcano. This color shift significantly changed the appearance of the decorative scheme. The objective of this study was to distinguish the fields of original red monochrome background from the fields of red, which had converted from yellow due to heat from the eruption. The methodology followed for the study consisted of preliminary background research, a stylistic study of similar wall painting schemes in the region, and materials analysis to identify original and altered yellows and reds in the tablinum. Based on the background research, conservators and scientists worked together to develop an approach to analyze the monochrome fields of original and altered red paint in the tablinum in order to characterize their pigment compositions and differentiate between them. Portable X-ray fluorescence spectroscopy (XRF) was used in situ to map the monochrome backgrounds. Laboratory analysis, using optical and electron microscopy, x-ray diffraction, and micro-Raman spectroscopy, was conducted on representative samples collected from areas retaining original yellow color; areas thought to be originally red; and areas thought to be originally yellow, now appearing red. These analyses suggested that the paints were not made with pure ochre pigments, but contained admixtures of secondary materials in small amounts, which appeared to be different in the yellow and red fields. This paper will present the results of the research showing that the compositions of the original and altered reds were sufficiently different to be distinguished from one another. The results of the study have contributed to a better understanding of the original decorative scheme of the room, and the implications for conservation and interpretation. Moreover, the methods developed here can be used to better understand Roman painting technology and potentially identify original and converted pigments at other sites in the Vesuvian region.
Speakers are Leslie Rainer and Kiernan Graves; co-authors are Gilberto Artioli, Arlen Heginbotham, Francesca Piqué, and Michele Secco