Principles of the present interventions

    A general principle of the works is to carry them out on the basis of decisions taken as objectively as possible, with transparency in all phases. These goals are achieved primarily by means of an interdisciplinary approach to the interventions during the phases of study and application, the publication of general and specialized studies for the restoration of the monuments prior to the actual interventions, their submission as top-level studies to a procedure of multiple assessment and then the final publication of the works.

    The International Conferences of specialists held at regular intervals for exchange of opinion about the various proposals for interventions on the monuments and other special subjects, comprise a particularly important feature of the works. The interventions, in themselves, are conducted in the spirit of the Venice Charter (1964), the internationally accepted framework of principles codifying the requirements for the restoration of monuments. The following principles were formulated particularly for the monuments of ancient Greek architecture, and stem from the actual building system of the monuments of the classical period.

• The principle of reversibility of the interventions. This means the possibility of returning the monument to its condition prior to the intervention.

• Respect for the authentic material, retention of the structural autonomy of the architectural members and their original structural function.

Compliance with the above theoretical principles leads to specific choices in planning structural interventions on the Acropolis monuments, which can be summarized as follows:

• Interventions are restricted to those parts of the monuments that have been damaged in earlier restorations or show structural deficiencies.

• The materials used in restoration must be harmless and compatible with the authentic materials.

• For joining fragments, the titanium rods required by the structural study, should be used as sparingly as possible and the holes for titanium reinforcements be as few as possible, so as to avoid damaging the ancient material.

• To the extent possible, the existing ancient cuttings are used for joining the members. The basic criterion for calculating the reinforcements is that in a near-limit situation the reinforcements should fail rather than the ancient material.

• In the joining of ancient fragments, only pieces that come from the same architectural member are joined together.

• In restoration supplements of new marble are limited. The decision is always made on the basis of the structural and aesthetic autonomy of the member involved and the integrity of the area being restored.

The method of the interventions

    In cases of severe damage the area of the monument affected is dismantled. The process of dismantling includes the removal of rusted reinforcements and filling material.

    After the members are removed, they are structurally restored in the laboratory. New Pentelic marble is used wherever supplements are necessary. To make the supplements, a cast is first made of the missing parts, and using a pointing device the points marked are transferred from the cast to the new marble. After completion, the supplement is joined to the ancient marble with titanium reinforcements and white cement mortar. Diameter and depth of the titanium rods are determined on the basis of structural efficiency. The sockets for the titanium reinforcements never penetrate the outer surface of the members.

    After they have been restored, the architectural members are reset in their original locations and joined by means of titanium clamps and dowels. In this resetting of the members, geometrical distortions in the area being reassembled are removed, so that the original appearance of the building is attained to the extent possible.

    In addition to dismantled architectural members, scattered ancient members that have been recognized as belonging are also reset in their original or a corresponding position. In a few cases, for reasons of stability, it may be preferable to set a few architectural members made entirely of new marble rather than using ancient members restored with new marble that are preserved in fragmentary condition.