Search

The studies on the finishing technique of the stone monuments in Persepolis (Iran) are part of the archaeological project jointly launched in 2008 by Iran and Italy, named 'From Palace to Town'. The first experimental results, obtained on a very limited number of samples, revealed that the Achaemenid builders and sculptors used a white pigment, a kind of bone white, calcium fluorapatite, obtained by burning animal bones, to hide the dark grey colour of the stone. In order to verify these unexpected results, a new campaign was implemented to analyse a much larger number of samples. XRF spectrometry, a non‐destructive technique, was used and the experimental results were further elaborated by PCA. The presence of a white superficial layer was confirmed, and the use of fluorapatite was confirmed as well, but only on monuments attributed to the Xerxes period or later, while in the earlier monuments the white layer was obtained using gypsum. [ABSTRACT FROM AUTHOR]

One of the aims of the 5-year Iranian/Italian project for Persepolis, called ' From Palace to Town' was to contribute to the conservation of the stone monuments of the imperial site. As part of the activities dedicated to this purpose, a diagnostic study was carried out. Various aspects were considered: petrographic characterization of the stone, forms and factors of decay, and in situ testing of suitable conservation treatments. The present paper reports on the unexpected results of the study on the finishing of architectural surfaces. The results obtained on a limited, but nevertheless significant, number of samples collected from the monuments of the imperial Terrace, allow us to state that the dark grey limestone used for several (or many?) monuments was covered on purpose with a thin, fine whitish layer containing fluorapatite, as major component, and calcite. It is highly probable that the fluorapatite was obtained from calcined animal bones and that slaked lime was used as a binder. Further evidence for this is the discovery of a kiln with the remains of calcined bones and, nearby, a waste pit with animal bones containing fluorapatite. A second white layer, obtained with barium sulphate, was detected in one of the samples beneath the external, earthy encrustation. It could be perhaps interpreted as the remnants of a polychrome finishing. [ABSTRACT FROM AUTHOR]