Oftentimes a restoration project not only requires studying the principal materials and execution techniques inherent to the work, but is also an opportunity to research and test new operational methods in general. This, in turn, provides a better context within which we may conserve cultural heritages.The restoration work was carefully handled by a close and fruitful collaboration between the art historian, the scientific expert and the conservator.
Regarding the restoration of this Egyptian Polychrome Sarcophagus Lid, sponsored by the Archbishop of Seattle J. Peter Sartainthere, Patron of the North West Chapter were various problems that arose during the conservation process: the structure of the stone support, deciding which techniques to utilize, and distincely different levels of decay and deterioration which needed to be uniquely handled. The restorers carried out the appropriate and necessary steps to identify the adequate methods of intervention, and supported these with extensive scientific analysis.
The main issues faced during the restoration were those related to:
- Removing the substances used during the maintenance and/or previous restorations;
- Consolidating the stone support and the layers of paint;
- Reassembling and Grouting the fragmented parts of the piece, for its transfer and exhibit in the Vatican Museums.
The surface substances were removed using chemical materials. Restorers conducted studies and researched various supporting substances that could maintain the suspended solvent mixtures. They tested specific products which are not found in normal commercial availability. The results were first verified by comparing data from the microanalysis of induced fluorescence (polished sections, SEM-EDS, spettrofotometrie infrared, gas chromatography), and then appropriately documented in summary tables.
The surface substances were removed using laser ablation. Five different laser models were used to perfom 37 analyses in order to identify how best to match the different constituent pigments of the original paint layer. The blue and green Egyptian colors, especially, required the utmost attention. The efficiency of these machines has been regularly verified by measurements performed with a “Power Portable” meter, where each analysis is graphically shown on a general mapping. Restorers reported the parameters used in defining the characteristics of the ablation laser that was used on a specific operating table. The test of the results has been carried out by comparing data from colorimetric and microanalytical (polished sections) investigations.
The cohesion defects of the sandstone support were solved. Laboratory tests were executed on sandstone blocks in order to verify the effectiveness of four different consolidating products. Based on the obtained results, all borders and sections of unpainted decoration of the lid have been consolidated through repeated applications of nano-silica in different concentrations. The results were then verified through microanalytical surveys (petrography, SEM-EDS, mineralogical analysis).
The cohesion defects of the paint layer were repaired. Based on the results obtained from specific colorimetric investigations, restorers repeatedly applied a suitable consolidation product (Jan Funori) by using a spray gun. The restorers then injected a mixture of polymer, vinilbutirrate and nanosilica in order to consolidate the interfaces.
Different binding agents were tested in order to identify the most suitable product in order to create plaster similar in color and weight to the original stone, and which could be removed later if necessary. The final binding agent consists of a mixture of acrylic resin in solution and nanosilica.
Since the three subdivided sections of the lid required assembly, restorers considered it appropriate to design an assembly system. Using 3D scanning techniques, a perimeter frame was constructed to allow the work to be easily handled and exhibited within the Museums. This process is ongoing.
In addition, the Egyptian sarcophagus lid has been the subject of two discussions during last APLAR 5 Congress, on the use of laser ablation in the preservation of cultural heritage, which occurred September 18-20th at the Vatican Museums, demonstrated the further role advanced lasers can play in the world of art restoration. Special thanks to our California, D.C., Florida and International Chapters for their help in securing laser technology for the Vatican that is the envy of the museum community.
Two articles on this restoration project will be published in the Acts of the aforementioned conference and in the next Bulletin of the Vatican Museums. It is clear that the initial conservation project has been modified during the course of its work, involving additional operational modes, studies and research. This also means that there have been necessary time delays for the work but which also have allowed the emergency of results otherwise unattainable using more traditional methodologies.