Identification of bird taxa species in ancient Egyptian mummies: Part 2, A qualitative evaluation of the utility of CT scanning and 3D printing

Ancient Egyptians believed that objects created in the image of a god, in either animal or hybrid form, from artificial or organic materials could act as a communication device, effectively enabling a dialogue between the devotee and the deity. The mummified remains of animals concealed within linen wrappings were popular votive offerings. These mummies are now investigated using non-destructive techniques such as three-dimensional Computed Tomography (CT). Using techniques developed in medicine it is possible to generate three-dimensional computer models of the bones within animal mummies from CT data. These models can be used to produce visualisations of the bones but can also be physically reproduced by 3D Printing. There are a number of parameters and decisions that can be made at both the scanning and 3D printing stages that can affect the quality of the final physical artefacts and how closely they resemble the real bones. This study aimed to explore the effects of different CT scanning Field of View, 3D printing processes and materials and qualitatively evaluate the extent to which the resulting 3D Printed replica bones accurately reproduced the identifiable features of real bones. Two different CT scanning sessions were conducted and 30 3D printed replica bones produced using three different processes, material extrusion, stereolithography and PolyJet modelling. Different materials were used to investigate the effects of colour and transparency. The replicas were provided to five experts in bird anatomy who were asked to evaluate the replicas and comment on their utility for species identification by the bone-in-hand method. The results showed that transparent materials were less useful than those with a uniform neutral colour. Replicas made with thinner layers were preferred due to their smoother surface. Overall, the PolyJet modelling replicas were ranked highest. The replicas made from higher resolution CT data (a smaller Field of View) produced superior replicas. This study provides a rigorous evaluation of the practice of producing 3D Printed replicas of animal anatomy from archaeological remains and has shown the utility of the practice for species identification.