Conservation of the Byzantine Monastery of Jabal Haroun

Christina Danielli, Anna Karakoski, Sari Pouta

The team of conservators working on the ongoing excavation of the Byzantine Monastery on Jabal Haroun is composed by a senior conservator from Rome, Italy, and two Finnish conservators who have graduated in Conservation studies from the Espoo-Vantaa Institute of Technology. Each member of the team is specialized in different aspects of the field (stone, plaster, metal, glass), which helps in dealing with the variety of objects found during the excavation and the treatment 'in situ' of different materials.

Most of the conservation work carried out during the excavation regards the stabilization of the exposed architectural structures, which are chosen according to the importance of their integrity within the site and their condition. Objects and small architectural fragments (marble, painted plaster) are registered and packed for transportation. Most of the registered objects are cleaned, documented and transported straight to the Petra Museum. The objects in need of immediate stabilization are treated in situ and registered metal finds are transported to Finland for conservation.

Intervention on the architectural structures is recorded using graphic documentation. Digital images of the areas undergoing conservation are recorded before and after the treatment and printed. State of conservation and treatment plan are recorded on sheets of acetate superimposed on each digital image using an international code of symbols based on the Normal 1/88 Lexicon. The recorded data will be transferred into a software program in Helsinki.

Building techniques and treatment of the main church area.

The buildings and outer walls of the monastery were built with large blocks of local sandstone cemented with a thin layer of mud mortar mixed with local sand and fly-ash. During later phases some walls were rebuilt using a lime mortar mixed with sand. The interior walls and stone benches lining the perimeter of the inner church area were covered with a lime based plaster. In some areas the plaster was colored with an orange -yellow iron oxide pigment and some fragments of decoration and lettering were also found in Trench I and M. Most of the floors were paved with marble flagstones, fitted on a bedding of hydraulic (water-resistant) mortar.

Many areas of the site had been reused and rebuilt during later phases, thus creating some difficulty in the correct preservation of the structures. Due to the fact that the function of some of these structures has not yet been defined by the archaeologists, only small local repairs were carried out on the masonry. Most of the conservation work during the last two seasons concerned the consolidation of the marble floors and what remains of the plaster covering the walls and benches.

Masonry

The main problem concerning the masonry is the erosion due to exposure and weathering. Eroded sandstone blocks -which were very fragile and compromised the stability of the walls- were substituted by limestone ones. Although rainfall is scarce, the possibility of sudden downpours of rainwater is not infrequent, and would have devastating effects on the excavated masonry and plaster already weakened by erosion factors. To avoid water infiltration and the displacement of detritus and small stones which are loosely encased in the masonry, lime mortar repairs and pointing between the joints were carried out in the areas where the disruptive effect of running water would compromise the integrity of the structure.

Plaster

Small, fragmentary areas of plaster were present on almost every wall and bench of the main church area. The plaster was cleaned using soft brushes to loosen the soil accumulated on the surface. Roots and concretions were removed mechanically using a scalpel. Hydraulic mortar was injected in the gaps between the plaster and the masonry to secure the fragments. After this operation, lime mortar repairs were applied with small spatulas around the edges and in the cracks and fissures of the plaster fragments to avoid the infiltration of sand or water.

Numerous fragments of painted plaster were found while excavating in Trench I and the south Pastophorion. Small fragments were found loose in the soil while larger pieces were found still attached to collapsed blocks from the western wall of Trench I. The plaster consisted in a thin layer (5 to 8 mm.) of compact lime (Trench I) or gypsum (Trench M) with very little sand aggregate. The surface was painted with Greek lettering and decorative patters of foliage and geometric designs. A red iron oxide pigment was used for the lettering and the foliage, while other hues of green, red and yellow were used for the decorative patterns.

Painted plaster has a high deterioration rate and the pigments can discolor in a very short period of time if left exposed to sunlight. A temporary shelter was created to keep the fragments in a cool dry place, while the most fragile pieces were fixed using a gauze bandage imbibed with acrylic resin and packed in boxes. Due to the fragility of the plaster and the high risk of deterioration if left on the site it was decided to detach the larger fragments from the blocks with 'Stacco' technique and carry them to Finland for further conservation work and study.

Marble

The floors of the main church area were paved with large slabs of proconnesian marble, probably a re-employment of roman quarried elements. Most of these slabs were broken and cracked in many places, a damage possibly caused by earthquakes during the time of occupation or later. As sand carried by strong winds is deposited daily on the floor surface, it penetrates into the fissures of the marble, creating further cleavage. Although the amount of rainfall is scarce, the enlargement of these fissures creates a dangerous opportunity for water infiltration and plant life, which would increase the damage and finally dismember the fragments. Since the marble is lying on a bedding of hydraulic mortar which is in good condition, it was decided not to interfere with the original setting by fixing only the surface cracks with a lime based mortar containing fly-ash to better integrate the repairs with the color of the marble. The slabs were first cleaned with water and the sand and debris removed from the cracks with soft brushes, after which the mortar was applied on the wet surface.

The principal materials used for the treatments were:

• Hydrated lime, local clay and sand for mortar repairs.
• Hydraulic lime for grouting and re-adhesion of plaster surfaces to the masonry.
• Acrylic Resin (Paraloid B72) for the temporary fixing of ceramic vessels and painted plaster.
• Silica based compounds (ethyl silicate) for the consolidation of masonry blocks and bedding layers.

Due to the difficulty of ordering and transporting chemical products and lime from abroad, preference was given to local products and traditional techniques.

The arid climate and the rapid change in temperature and relative humidity on the site, as well as its elevation (1250 meters above sea level) demanded particular care in the choice of the treatments and in their timing. Traditional conservation procedures and proportions had to be slightly altered and carried out at particular hours of the day. Due to the elevated temperatures (circa 40°) at midday, all chemical treatments had to be minimal and applied during the late hours of the afternoon. Mortar repairs were applied under a protective shelter, which provided lower temperature and avoided direct sunlight. Metal finds and glass were treated (if necessary) and packed immediately after excavation to prevent further corrosion.

Small Finds

Small finds consisted mostly of metal, glass, stone and pottery, but there were also a few objects made of bone, coral and mother-of-pearl. During the excavation, all finds were documented, cleaned and carefully packed before transportation to the Petra Museum. The finds were cleaned mostly mechanically, and water or solvents were used when needed. Also first aid conservation was carried out in the field by consolidating very fragile objects. In some cases broken marble or ceramic pieces were glued with acrylic resins. Registered finds and some other objects were transported to Finland for further conservation in proper facilities at the University of Helsinki. In order to avoid any damages caused by transportation or changes in humidity and temperature, the objects were packed with acid free tissue paper and placed into specially prepared carton boxes or perforated plastic bags. Metals were packed in sealed boxes with silica gel, to keep the humidity level low. In Finland, the objects were cleaned properly using microscopic magnification, and the stabilization treatments were carried out to avoid further deterioration. After the conservation and documentation, the objects were repacked for the transportation back to Petra.

As conservation work carried out during an archaeological excavation becomes part of the history of the site, the choice of intervention should be considered carefully. Before starting to work on treatments at the Jabal Haroun excavation site, the building techniques and constituent materials were identified and documented. A mapping of the different levels and quality of deterioration was carried out in view of future conservation work and long-term preservation projects. The Byzantine complex of Jabal Haroun may one day become a site open to visitors and scholars interested in understanding and viewing the physical evidence of monastic life in the Middle East. It is thus extremely important that in this initial phase the historical authenticity of the site be preserved, by limiting intervention to a minimum while assuring a proper maintenance.The close collaboration with all the members of the FJHP, as well as frequent exchange of opinions was essential for the successful application of these important principles.