DETAILED DOCUMENTATION AND IN SITU CONSERVATION ACCORDING TO MORTAR CHARACTERISATION OF OPUS SECTILE UNCOVERED IN THE SAINT PHILIP CHURCH OF HIERAPOLIS (PAMUKKALE-TURKEY)

Abstract

During the archaeological excavations carried out in the ancient city of Hierapolis (Pamukkale-Turkey) in 2011-2012, a colourful opus sectile (ancient stone-art) dating back to the Middle Byzantine Period was revealed at the pavement of the Saint Philip Church. As the opus sectile was badly damaged, it was decided to preserve the opus sectile with the minimum of intervention. Before in situ conservation activities were initiated, a sam-ple was taken from bedding mortar of the opus sectile and the following analyses were carried out: loss on ignition, deal with acid and particle size distribution analysis, petrographic analysis (thin and thick sections, Stereo and Polarizing Microscope observations), as well as Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy (SEM-EDX). According to results of the analyses, a mortar closely resembling the original mortar was produced and applied to a total of 14 opus sectile panels.

The conservation treatments carried out during the 2012-2014 seasons included documentation of the opus sectile by detailed photography, drawings in the scales of 1:1 and 1:20 with the Auto-CAD program and 3D documentation with the Agisoft program, as well as aerial photos at the end of activities. Conservation treatments included mechanical and chemical cleaning, reinforcing the opus sectile panels and edges, filling the missing parts with lime mortar according to the results of the analyses, and finally the reburial of the opus sectile with Geotextile and a mixture of clay/sand/gravel (treated with herbicide to prevent plant intrusion) in different aggregate sizes.

The inter-disciplinary collaboration on this excavation enabled us to determine that all the materials used in the creation of the opus sectile pavement were derived from local materials. In addition, we succeeded in providing a detailed documentation from the beginning of the project to the end, including the materials used and all the interventions carried out. As a result, the detailed documented data that was gathered will also be used in monitoring the condition and state of preservation of the opus sectile for future conservation projects.