This study presents three different archaeological basketry fragments, but all part of objects made with the technique of diagonal twilling (confirmed by the presence of the endings of selvedges of the twilled surface), which consists of plaiting several strands to create an even twilled surface. The three basketry fragments are in different stages and modes of preservation. They were selected to represent poor, sufficient and very good preservation of their plant tissues, so the potential of the CT-scanning could be tested for different taphonomic environments. The first two fragments, subject to CT-scanning, came from a single object – a twin-handled woven sack (zembil) from the Late Minoan (circa 1450 BC) settlement of Akrotiri (Santorini, Greece), while the third one consists of a woven mat fragment from the Roman burial mound Kitova (1st c. BC – 2nd c. AD), located in South-east Bulgaria (Fig. 1).
The sack from Akrotiri (Inventory numbers 035, later 8860, 8862) is a published item, which comes from Pillar Shaft 68A (Beloyanni, 2007). It is made in diagonal twill, while the handles are coiled. The size of the item is 0.175 cm in height and 0.275 cm in diameter (ibid.). Another smaller basketry item was discovered inside vessel 035 together with its content – carbonised barley grains (ibid.; Sarpaki, 1992; Fig. 2.a). Object 035 is preserved in a charred mode, and its vegetal tissue is infiltrated with the fine particles of the volcanic tephra, following the Santorini eruption. Besides, at the time of its discovery, the item has been treated with a 10% solution of thermo-plastic resin (Paraloid B-72®), to preserve its structure as a whole. The two analysed fragments were sampled form the body weave of the object and near the base (Fig. 2.a, red arrow). Both fragments were initially evaluated with the application of Reflected Light optical microscopy (BF-DF, Olympus BX 51) and the first one consists of agglomerated plant parts of a monocotyledonous plant(s) and was considered poorly preserved (SCAN 1), while the second one was considered sufficiently preserved single plant part of a monocotyledonous plant (SCAN 2).
The mat from Kitova mound is an unpublished item, originating from the central burial of the mound (Grave 6), where a young female individual was covered with a woven mat, perhaps placed as a shroud. The mat was in contact with several large bronze vessels and a wooden box amongst the grave offerings. Based on the inventory the burial was dated between 1 century BC and 2nd century AD. The mat is preserved in desiccated mode and as an assemblage of numerous fragments with an approximate surface coverage in situ 0.5m x 0.7m. In terms of conservation, the mat was treated with a 10% solution of the acrylic resin Paraloid B-72®, but prior to its application, a fragment (2.4 cm x 1.2 cm) was sampled for the purposes of the archaeobotanical analysis (Fig. 2.b, red arrow). This fragment was also examined under Reflected Light microscopy and its preservation was evaluated as very good (SCAN 3).
The micro-CT scans were conducted with Phoenix v/tome/x M® industrial scanner and were performed at the Hounsfield Facility of the University of Nottingham, UK. The achieved resolution came to 8µ due to the relatively large sample sizes (circa 4mm in diameter), which determined the FOD (focus-to-object distance) of 818.6(7) µ and 32.74(9) µ, operating in magnification x24.9. The scans were analysed with Phoenix datos/x 2.0 CT® software, where three-dimensional images and videos were produced (Supplement). The imaging was oriented along the X and Y-axis of the specimen, where the horizontal view (X) consists of a virtual transversal plane (Fig. 3.a), while the vertical (Y) shows the virtual longitudinal plane (Fig. 3.b). The density of the scanned material is what the radiograph reflects: areas with low X-ray absorption and hence with lower material density are visualised with dark voxels (the volumetric pixel unit used in X-ray CT), while the areas with high X-ray absorption and denser material are visualised with brighter voxels (Beailieu & Dutilleul, 2019; Kozatsas et al. 2018; Mansbridge 2015). In addition, the standard radiograph view was combined with “Surface determination mode” (hereafter: SDM) in order to enhance the visibility of the density of the anatomical features of the observed vegetal tissues (as in Fig. 3 and Fig. 5). The anatomical descriptions of the monocotyledons followed Cuttler (1969), Evert (2006), Metcalfe (1960; 1971).