The surviving buildings at Amarna are predominantly made from sun-dried mud bricks. They include the palaces and the enclosure walls and pylons of the two main temples. After the city was abandoned the walls either fell down in sections or began to crumble away. In both cases the rubble formed embankments at the base of the walls and so helped to protect them. Eventually, with the addition of fresh sand blown in by the wind, the site as a whole stabilised, the positions of walls and buildings marked by slight swellings in a relatively smooth though undulating surface. Excavation removes the protective embankments and so exposes what is left at the bottom of the walls to fresh erosion.
The natural forces that bring about erosion are wind and rain. Every year strong winds blow from the north in the winter and from the south in the summer, in both cases driving dust and sand across the desert surface. Where they hit ancient walls they erode the face, often to the greatest extent close to the ground, so undermining the wall. Although rainfall is low, when it does occur it penetrates the surface of mud bricks and loosens the bonding of the particles. When the bricks dry out, the damp layer becomes dust, which rapidly blows away. Often the mud was originally mixed with pebbles rather than with straw. The pebbles fall out as the dust blows away. Eventually only the pebbles remain to mark the line of the wall.
The best way to preserve excavated structures is to rebury them in sand. Some buildings are so large that this is not feasible, and in any case some of them are of major public interest. Since 1988 the EES expedition has included within its annual programme of work repairs to the ancient brickwork at two major sites, the Small Aten Temple (in the Central City) and the North Palace. The North Palace was dug in 1923 and 1924 and was the subject of many photographs at the time. On comparing them with the appearance of the building more than seventy years later it can be seen that something like half of the brickwork has been lost to erosion.
After a series of experiments carried out in the late 1980s by structural engineer Richard Hughes it was decided not to use chemical treatment. Cost was one reason but another is the ability of the mud of the bricks to act as a filter and to separate the chemical from the solvent. The result is the formation of a hard crust, which in time separates from the more loosely consolidated core of the brick and falls away, so hastening erosion. Instead, the work has concentrated on the making of new mud bricks to a relatively resistant formula and to use them to cap walls where a loose upper surface has developed, to patch the sides of walls especially where weathering is undermining them, and to lay fresh, bonded lines of bricks to mark the outlines of ancient walls where little or nothing of the original survives. In general our policy is to leave as much as possible of the original brickwork visible.
For the first ten years the work was supervised by architect Michael Mallinson. Since then architect Suresh Dhargalkar (who for many years was employed to supervise building conservation on some of the royal palaces in the United Kingdom) has been responsible. They have worked alongside construction specialists from the Supreme Council of Antiquities of Egypt. The builders and workmen who carry out the repairs are local men who have developed years of experience.