Pictured above are fragments of stone on the long, and numerous mastabas, or raised platforms found at Mut Temple and many other archaeological sites throughout Egypt. These mastabas provide safe areas to store fragmentary blocks away from the often very salty soil. Soluble salt, by dissolving and recrystalizing within the body of a fragment, can cause a great deal of damage to even very durable stones.
Khaled and I spend much of our time on site, joining fragments. The purpose of this is so that inscriptions are more easily read and frankly, so that these often small fragments do not become lost. In an outdoor environment, we need to use a durable adhesive. In this case, we use an epoxy with a barrier layer of a more reversable adhesive. Making joins that are perfect can be tough.
Often the surfaces are so eroded, there are not good clean areas to join. Also, getting the right balance, so that the pieces stay together while the adhesive cures can be a challenge. At least in Egypt, there is enough sand to make many sandboxes to assist in this effort.