Often, scientific analysis of archaeological artefacts allows for deep insights into their past uses. Is it possible to find out more about life in ancient Egypt by taking a look inside these artefacts without damaging or unsealing them? Development of non-invasive and non-destructive methods of analysis are crucial to answering this question; specifically, a variety of neutron techniques can help. Before we delve into these techniques, let us find out a bit about the owners of these grave goods…
Kha and his wife, Merit, were considered wealthy in the time known as the New Kingdom in Egypt (1550-1069 BCE). Kha was an architect and director of work at Deir el-Medina in Luxor, and he would have managed the planning and construction of his own tomb. Merit sadly predeceased him and was buried in the coffin planned for Kha’s use. Their tomb is considered one of the richest non-royal burials ever discovered and dates from between 1425 and 1353 BCE. Neutron and gamma techniques were used to understand just two of the many grave goods buried with Kha and Merit – an alabaster vase and a metallic situla.
Neutron techniques are routinely used in the field of cultural heritage and were employed here to investigate the contents of the sealed vase. Neutrons interact with the nucleus of an atom, and the neutron penetration depth depends on the elemental composition of the material. Different atoms interact with the neutrons to different extents. Atoms such as carbon, hydrogen, and oxygen interact more with the neutron, producing darker areas in the radiograph, whereas the neutron can penetrate metallic areas more easily so appear lighter in the radiograph. Neutron techniques differ from the more common x-ray techniques as x-rays interact with the electrons in the atom, not the nucleus, and often have a strong dependency on the atomic number of the element and the density of the material. X-rays are better for studying heavier elements, and if you would like to find out more about how they are employed in heritage science, take a look at these blog posts. Figure 1 shows a photograph of a sealed vase from the tomb and its corresponding neutron radiograph. The radiograph of the vase in figure 1b shows a plug covered with linen to seal in a homogeneous, organic material, which is represented by the darker area in the radiograph.
Neutron techniques were able to differentiate the material of the outer walls of the vase, the plug, its linen covering, and its inner contents. Neutron tomography is a way of acquiring 3D information for the artefacts, where many radiographs are taken at a variety of angles and pieced together computationally. This method was chosen so the inner morphology of the object could be studied without opening the vase! A linear attenuation coefficient can help determine the type of material present; it defines the fraction of the neutron beam that is scattered or absorbed by the sample (after taking sample thickness into consideration). By comparing the value experimentally obtained for the plug area to a theoretically calculated value for alabaster, it can be concluded that the plug is made of alabaster just like the walls of the vase. Linear attenuation coefficients were also calculated for the contents of the vase, showing that it contains a mixture of oils and wax. This vase was found in a chest containing 6 other similar vases, and since it contains oil, it has been suggested that these vases could contain the seven sacred oils used during the burial ritual.
To determine the elemental composition of the oil and the alabaster vase non-destructively, prompt gamma-ray activation analysis (PGAA) was used. The nuclei of the elements in the sample capture neutrons from the neutron beam and emit gamma-rays characteristic of that specific element. In the sealed vase, magnesium, calcium, and sulfur were attributed to the alabaster, and carbon and oxygen were assigned to its organic contents. For the bronze-based metallic situla, PGAA showed nickel, vanadium, and nitrogen indicating bitumen covering part of the artefact, as shown below with its neutron radiograph in figure 2. These results agree with previous archaeological studies, which suggested that the stitula was likely to be covered with bitumen. Further neutron diffraction studies showed that the situla was composed of a bronze alloy.
Further analysis is currently taking place on the alabaster, wood, and textile artefacts discovered in this burial assemblage, so we can eagerly anticipate more interesting insights into these fascinating grave goods. In the meantime, if you are interested in life in ancient Egypt, search online to explore work from the archaeological site at Deir el-Medina and to find out more about Kha and Merit and their tomb!
All figures adapted with permission from John Wiley and Sons, Inc.