Die HD-Mikroskopie zeigt Details einer emaillierten und vergoldeten Circusszene auf einer römischen Kugelbauchflasche aus Glas. Foto: J. Vogel, LVR-LandesMuseum Bonn
Regarding archaeological excavations there is often disappointingly little to look at to the eye of the unskilled viewer. In particular, this applies with respect to the found objects.
Having been in the ground for so long, the old objects have undergone strong changes, and depending on the material, may have even been destroyed. Whereas ceramic objects are mostly well preserved, organic materials such as textiles, wood, bones, and leather are considerably decomposed and only come down to us preserved under special case conditions. In addition to these organic materials, also glass and especially metals are subject to decay processes if they have been in the ground a long time. Metal objects in particular are often not identifiable as fresh ground findings. Objects made of iron, for example, look like lumps of rust, having been completely deformed by corrosive materials in the ground. Over the course of centuries, a hard corrosive layer forms that is made up of a mixture of rust, sand, and gravel. A special way of retrieving objects through excavating is the so-called block excavation. For this, one or several found objects are removed from the ground together with the earth surrounding it, underlaid with a stable support, and laterally secured with plaster casts. After finding and retrieving the objects, an arduous process of restoration and conservation measures must follow in order to prepare the findings for further scientific treatment, and subsequent presentation in exhibitions and museums. These works are carried out in the restoration and conservation workshop especially equipped for this, whereby all of the working steps on the object are documented. The x-ray examination, particularly for block excavations and metal objects, constitutes the first part of these measures. This process functions without causing damage to the findings. It is indispensable for all further working steps having to do with the object. With the aid of the x-ray image, the object is documented in its condition close to the actual finding. For metals, the various material densities are relatively easy to show in the x-ray image with regards to the surrounding earth, corrosive layer and the actual object so that in this early stage, it is already possible to look inside the block of earth and identify the found object beneath its corroded layer. In doing this, the objects contained in the block of earth are not only shown in their original positions to one another, the external form of the individual objects and other further details which contain important information are also revealed. The x-ray image allows for drawing conclusions with respect to joining techniques, adornments, and inlays that were accomplished using other metals, thus providing hints to the object's original appearance and production techniques. Moreover, the x-ray can tell us something about the object's state of preservation. Thus, it will be very useful for further restoration work and the subsequent scientific evaluation of the objects. The evaluation of the x-ray image often decides which objects are worth restoring at all. It often happens that archaeologists unearth metal fragments that do not belong to the layer of culture being examined. Often, heavily rusted bomb fragments from WWII may not be differentiated from Roman knife blades in the ground, for example. Also in the case of Roman nails found in large quantities, often an evaluation of the x-ray images suffices for determining the further scientific treatment. To restore each individual nail would be disproportionate in terms of the work efforts required and the result expected. However, it is not only possible to examine metals, but also other materials such as ceramics, glass, and organic materials. Depending on what the issue is, the x-ray provides answers to questions concerning production techniques, technical features and in the case of closed vessels, their contents. In addition, x-ray examinations are not only suitable for archaeological objects. Since the method functions without destroying anything, all works of art from collections and museum holdings may be subjected to it. Here as well, the x-ray image provides answers to even the most varying questions. With respect to the paintings, overpaintings, fill-ins with putty, and retouchings may be evidenced. For sculptures, it is possible to determine how the piece was built and joined together. Many works of art that have been in collections for a long time have their own restoration histories. In such cases, an x-ray examination makes it possible to prove the traces of previous work, repairs, and rarely, even forgeries.
LVR-LandesMuseum Bonn, Colmantstr. 14-16, 53115 Bonn
Tel. +49 (0) 228 / 2070 - 0, Fax +49 (0) 228 / 2070 - 299
TUE - FRI, SON 11 a.m. - 6 p.m., SAT 1 p.m. - 6 p.m., MON closed
Guided tours for school groups available from 10 a.m.
MON - FRI 8 a.m. - 4 p.m.