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.