Implementation, Monitoring, & Maintenance
Execution of the work, including preventive measures and remedial treatments and the development and implementation of monitoring and maintenance programs.
Preventive conservation measures
In order to slow deterioration in the cave, measures to reduce the infiltration of exterior air into the cave will be implemented, including keeping the door closed at all times, except when visited, and better sealing of the exterior door. Also to be instituted is a policy that closes the cave to visitors during periods of rain and high relative humidity.
Remedial treatment, including the development of methods of application
The implementation phase developed safe and appropriate methods of treatment application based on the existing condition of the paintings and the cave, and provided training in all aspects of treatment to Dunhuang Academy conservation team members.
In a salt-laden environment, the use of water-based treatments can lead to damaging deliquescence and crystallization of salts on or below the painting surface. All treatment materials selected included water, and this therefore needed to be taken into account. Several general principles were followed:
- Minimum amounts of water were used.
- Presses with highly absorbent layers were applied to the surface of the paintings after all treatments so that salts could be absorbed. The absorbent layers were monitored and changed when damp. The press covered and maintained contact with the surface of the painting until the treated area was completely dry.
- Surfaces of treated areas were examined post-treatment for evidence of salt crystallization. In high salt areas, an ultrasonic humidifier (i.e., a Preservation Pencil) was used to reduce salt on the surface after treatment.
- Treated areas will be monitored for salts and salt-related deterioration.
Specific application methods of treatment can also be altered to suit a particular condition or area. Grouting was carried out with syringes, combined with either needles and catheter tubes, depending on the size of the void and ease of access. Areas to be treated were studied and evaluated to plan the required sequence of treatments.
Consideration was also given during the implementation for a conservation approach that favors minimal intervention and future retreatability. In grouting of the wall paintings, the goal was not to fill every void but instead to do enough to anchor the paintings to the conglomerate by grouting key locations. This reduces the overall weight behind the paintings, a serious consideration for ceiling slope areas, and allows for future retreatability.
Final digital photographic documentation of the cave will be carried out by the Dunhuang Academy in late 2005.
Post-treatment condition monitoring program
Post-treatment condition monitoring is critical for preservation of the paintings over the long term. Regular inspection of selected monitoring areas for changes in condition is imperative as the causes of deterioration, soluble salts, are still present, and mitigation of deterioration depends on environmental control. High resolution post-treatment documentation photographs, detailed photographs in incident and raking light, post-treatment graphic documentation, and written notes of fixed monitoring areas provide the basis for assessing change. The fixed monitoring areas included representative examples of all recorded deterioration phenomena, and both treated and untreated areas. Given the difficulty of assessing painting condition, training of personnel is a critical component of the monitoring program.