Student Class Projects Focus on Technical Examinations of Cultural Materials

In the fall of 2009, the UCLA/Getty Conservation Program offered the course “Introduction to Archaeological Materials Science: Scientific Techniques, Methodologies and Interpretation” (CAEM M210) that focused on basic scientific techniques employed for the examination of archaeological and cultural artifacts to answer questions of anthropological significance and their state of preservation. Among the techniques covered were UV/VIS/NIR spectrophotometry, X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS), and Fourier Transform Infrared Spectroscopy (FTIR). Students were assigned small research projects in which they would apply these techniques, in addition to others discussed in this and other courses, to the investigation of various materials to answer questions about technology and condition.

The four groups of artifacts studied were:

• samples of a Byzantine wall painting from St. Neophytos, Cyprus
• samples of fibers associated with a mummy bundle excavated by the Tarapaca Valley Archaeological Project in Chile
• glazed ceramic sherds from the American Southwest
• 2 Balinese paintings on canvas belonging to the Fowler Museum at UCLA

At the end of the term, the students presented their poster, which was displayed at the Cotsen Institute of Archaeology. Below are two of the posters produced as the final project for the class.

Make sure to stay tuned to this blog for upcoming posts on the other posters presented, as well as future student projects.

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Investigation of Pigment Alteration in the Wall Paintings at the Enkleistra of St. Neophytos, Paphos, Cyprus
Steven Brightup, Sara Kiani, Nicole Ledoux, James Ma, Saurabh Sharma

Project Summary
A series of 5 blue and 5 red pigment samples from the Enkleistra of St. Neophytos, the place of reclusion, in Paphos, Cyprus were analyzed to determine the pigments identity and possible alteration products. Fourier Transform Infrared Spectroscopy (FTIR), Variable Pressure Scanning Electron Microscopy – Energy Dispersive X-ray Spectroscopy (VPSEM-EDS), Polarized Light Microscope (PLM), and Binocular (stereo) Microscope (BM) were used to analyze the samples and due to the limitations of the techniques, only inconclusive assignments can be made on the pigments’ identity.

From elemental analysis it is suspected that the blue pigment is lapis lazuli and that there are two different red pigments which are cinnabar HgS and red lead (Pb₃O₄). However, without phase analysis of these samples, a positive identification cannot be made. Alteration of red to black and dark blue to light blue were observed for the samples analyzed. A possible alteration of Cinnabar is to metacinnabar. Documented alteration products of red lead are to plattnerite [β-PbO₂] and anglesite [PbSO₄]. Fading of lapis lazuli has been attributed to the breakdown of the Al-O-Si in the literature. However, it was not possible to verify if these are the alteration products with the available tools.

The Identification of Fibers from a Mummy Bundle, Tarapaca Valley, Chile
Tessa de Alarcon, Elizabeth Drolet, Robin O’Hern and Cindy Lee Scott

Abstract
Fiber samples from a formative period mummy bundle from Tarapaca 40 in the Atacama desert of Chile were examined in an attempt to identify
them. Standards of human hair and alpaca were used for comparison. Fourier transform infrared spectroscopy (FT-IR) spectra were collected on the samples and standards. The morphology of the fibers and standards were examined using polarized light microscopy (PLM), scale casts and cross-sections. The spectra from the FT-IR analysis could not be used to differentiation between human and alpaca hair. Based on morphology, three samples were identified as camelid and two were tentatively identified as human.

Project News: Research and treatment of flaking arsenic containing paint layers on a Ptolemaic mummy cartonnage

The work described in this poster was conducted as part of a Master’s thesis project for the UCLA/Getty Conservation Program and presented at the Annual Conference of the Association of North American Graduate Programs in Conservation (ANAGPIC), Buffalo State College, April 24-25, 2009.

A Ptolemaic mummy cartonnage, belonging to the Robert V. Fullerton Museum at California State University, San Bernardino, seemed to be suffering from an alteration of the paint layers found on the object. The pigments used to decorate the mask had darkened and several areas, primarily those a dull yellow in color, displayed severe flaking. The flaking yellow pigment was found on alternating squares of the checkerboard pattern on the head, on the double headed cobra on the back, on the areas of the wig, above and below the headband, and on the face of the standing figure on the PL side of the mask. The aims of this project were to identify the cause of the flaking and treat the cartonnage.

In order to determine the causes of alteration to the dull yellow pigment, a technical study was conducted to identify the materials used in the manufacture of the mask, focusing on the pigments and binders applied to the areas now flaking. X-ray fluorescence (XRF), x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), polarized light microscopy (PLM), gas chromatography-mass spectroscopy (GC-MS) and ultraviolet (UV)-fluorescence were employed to characterize the cartonnage. The ground was found to be made primarily of calcite (CaCO₃) and the binder used for the pigments was a gum. Fatty acids identified in a brown material covering areas of the surface were thought to possibly be from the embalming material used for the mummy. The flaking paint was composed of the arsenic-containing pigment orpiment (As₂S₃), in addition to possible altered forms of the pigment such as arsenolite (As₂O₃) and pararealgar (AsS). Comparison of the flaking yellow squares on the head to the non-flaking yellow squares showed they both contained arsenic, but the quantity of arsenic in the flaking squares was higher.

Though the preliminary results of this research have helped to identify the materials used in the decoration of the cartonnage, no clear answer has been found to explain why some areas painted with arsenic-containing pigments are flaking while others are not. Further analysis will be undertaken to try and determine the cause of the flaking and whether the differences in the amount of arsenic in the yellow paint may be influencing the condition of the pigment in those areas. Treatment will also be conducted on the cartonnage to reduce the glossy material found on the surface, identified as Paraloid B-72 (an acrylic co-polymer resin), and to consolidate the areas of flaking paint.

Egyptian cartonnage images courtesy of Robert V. Fullerton Art Museum, gift of the Harer Family Trust, 2001