Previous observations of the intaglios on quartz cylinder seals from Western Asia suggested that they had been engraved by one or more of four basic techniques, that is, micro-chipping, Jiling, drilling and wheel-cutting. In this paper we test our earlier observations and interpretations experimentally. Examination and comparison of experimentally engraved ,features with the seal intaglios was made directly with a binocular microscope and also by examination of impressions with a scanning electron microscope. Successful replication was achieved using tools of Pint, chalcedony, copper, bronze and iron together with quartz and emery abrasives.
Optical Coherence Tomography (OCT) is a non-invasive subsurface 3D imaging technique based on the Michelson interferometer. The non-invasive nature of OCT and its speed of acquisition makes it possible to image large volumes of intact objects to yield a complete overview of the microstructure. The production methods for ancient Egyptian faience were first investigated using scanning electron microscopy (SEM) imaging of the microstructure in polished sections and microprobe analysis of the composition of the glass phases. These studies were based on original Egyptian faience objects and laboratory reproductions of faience beads made using three different production methods. The microstructure of the same laboratory samples and the Egyptian faience objects from the British Museum Research Laboratory Collection are re-examined using OCT. It is found that OCT virtual cross-section images can be used to group ancient faience objects into three categories on the basis of the morphology of the surface glaze layer and the glaze-core interaction layer. The OCT images correspond well with SEM images of polished sections of ancient faience objects and laboratory reproductions. The virtual cross-sections produced by OCT are somewhat limited by the penetration depth, which is affected by the high absorption coefficient of the material and, therefore, cannot always provide information on the presence or absence of interparticle glass that binds together the quartz particles in the core. Nevertheless, the top two layers are well imaged and since OCT images can be obtained rapidly and without the necessity of removing a sample, the method can be applied to a very much wider range of ancient faience objects than is possible by SEM examination of polished crosssections. In summary, this paper examines to what extent OCT can assist the investigation of the production techniques of ancient Egyptian faience.
Cylinder seals, which were produced more or less continuously for about 3000 years in Western Asia, were worked with designs in intaglio. In this paper we report the results of an investigation into the techniques used to engrave seals composed of quartz. Our observations were made with a binocular microscope and supplemented by examination of impressions wifh a scanning electron microscope. A range offactors was considered, including shape in plan, topography, surface texture and orientation of features. In this way four basic techniques of engraving have been recognized. They have been tentatively interpreted as micro-chipping, $ling, wheel-cutting and drilling.
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