Two techniques were used in the Department of Geology to analyze the composition of the early restorer's materials and the original clay body and slip: X-ray diffraction (XRD) and scanning electron microscopy with energy-dispersive X-ray spectrometry (SEM with EDX).
X-ray diffraction requires destructive sampling. Chips of material are ground into a fine powder using an agate mortar and pestle and then loaded into sample holders. XRD yields mineral compounds by measuring diffraction patterns of X-rays bouncing off crystalline layers in the sample.
Scanning electron microscopy reveals surface topography at a higher
resolution and depth of field than a low-powered optical microscope.
When equipped with the EDX analyzer, the technique gives concentrations
for the major elements present.
The combined results of these analyses indicate that the restorer used two fillers and a resinous adhesive. First, he replaced large areas of loss with pieces of fired ceramic, identified by their characteristic, platey structure and composition as clay . Smaller areas of loss and irregular joins were covered with pink -tinted calcite (calcium carbonate). Finally, the restorer finished his recreation with his own birds in layers of paint and shellac.
