image/svg+xml143XII/2/2021INTERDISCIPLINARIA ARCHAEOLOGICANATURAL SCIENCES IN ARCHAEOLOGYhomepage: http://www.iansa.euOrientation Patterns Characteristic for the Structure of the Ceramic Body of Wheel-thrown PotteryRichard Thér1*, Petr Toms21Department of Archaeology, Philosophical Faculty, University of Hradec Králové, Rokitanského 62, 500 03 Hradec Králové, Czech Republic2Private researcher, Machovská Lhota 71, 549 63 Machov, Czech Republic1. IntroductionDuring the past decade, we have been developing a methodology based on quantifcation of the orientation and alignment of the components of a ceramic body as one of the principal features refecting pottery-forming techniques that are theoretically observable on every sherd (Thér, 2016; Thér et al., 2019; Thér and Toms, 2016). Many of the phenomena that occur on the surface of pottery fragments and can be related to pottery-forming practices are randomly preserved, and their interpretation is further complicated by the common practice of combining several techniques during the forming and fnishing of vessels. One diagnostic attribute can, at least theoretically, be observed on every ceramic sherd – the orientation of the structure of the ceramic body. The relationship between forming techniques and the orientation of the components of the ceramic material has long been recognised (Balfet, 1953; Bordet and Courtois, 1967; Felts, 1942; Giford, 1928; Linné, 1925, p.33; Shepard, 1956, pp.183–184). The application of physical force to the plastic clay during forming is the main factor afecting the alignment of the components. The resulting orientation and alignment are characteristic of each forming method, although some orientation patterns might result from more than one fabrication process (for an overview of the assumptions for particular techniques see Berg, 2008, Figure 1; Carr, 1990; Courty and Roux, 1995, Table 1; Livingstone Smith, 2007, pp.88–146; Middleton, 2005, Figure 4.8; Pierret, 1995, pp.46–50; Roux, 2019, Figure 3.20; Rye, 1981, pp.58–89; Thér, 2020, Figure 9; Whitbread, 1996).Measurement of the orientation refnes the analysis of preferred orientation by defning the exact intervals of orientation variability for the individual forming techniques and their combinations. For the measurements, we selected two basic sections: sections perpendicular to the wall surface in the plane parallel to the vessel height (hereinafter referred to as a radial section) and sections tangential to the vessel wall cut through a core zone of the wall (hereinafter referred to as a tangential section). Originally, we captured three transects approx. 6 mm wide in each thin section at a magnifcation of 40 times in plane-polarised light using a standard petrographic microscope. The resultant images have a resolution of 1.09 μm. Then inclusions and voids were extracted using object extraction and separation methods in Volume XII     ●     Issue 2/2021     ●     Pages 143–154*Corresponding author. E-mail: richard.ther@uhk.czARTICLE INFOArticle history:Received: 19thFebruary 2021Accepted: 6thOctober 2021DOI: words:orientation analysiswheel throwingpottery formingimage analysisthin section petrographyABSTRACTThe described analysis follows recent fndings related to the orientation of particles and voids in a ceramic body that is characteristic for wheel-made pottery. The analysis is focused on the potential variability within wheel-throwing method and is based on an experimental collection that combines the factors of the experience and motor habits of individual potters and the vessel shape. The orientation of the components of a ceramic body is calculated for two sections: radial and tangential. The sections are analysed using optical microscopy. The calculated orientation and alignment refect the throwing style of potters using the same forming method.
image/svg+xmlIANSA 2021 ● XII/2 ● 143–154Richard Thér, Petr Toms: Orientation Patterns Characteristic for the Structure of the Ceramic Body of Wheel-thrown Pottery144Table 1. Orientation analysis results for experimental samples taken in tangential and radial sections. MD – Mean direction, CSD – Circular standard deviation.SampleMin. thicknessMax. thicknessDif. in thicknessShapeAuthorWheelRadial sectionsTangential sectionsMDCSDMDCSD1379749101113BowlHenryMotorised7352836240485001953BowlHenryMotorised53319303394551251180BowlHenryMotorised33627384480658071001BowlHenryMotorised3352731548335617784BowlHenryMotorised3394123650225587565BowlHenryMotorised4353437738094265456BowlHenryMotorised4392231834924377885BowlHenryMotorised1363837936724415743BowlHenryMotorised43325341040804550470BowlHenryMotorised53351311140264318292BowlHenryMotorised73338351240434393350BowlHenryMotorised13542311338304021191BowlHenryMotorised13239381436723979307BowlHenryMotorised63142351537844373589BowlHenryMotorised73023301636164229613Conical v.HenryMotorised152821331733113742431Conical v.HenryMotorised192637341835104471961Conical v.HenryMotorised1427313519437256511279Conical v.HenryMotorised1434393820395651561200Conical v.HenryMotorised933453321404053291289Conical v.HenryMotorised133235352243954700305Conical v.HenryMotorised304218172339344593659Conical v.HenryMotorised243919212441974538341Conical v.HenryMotorised254019202544464970524Conical v.HenryMotorised132932312645495163614Conical v.HenryMotorised152843412744765379903Conical v.HenryMotorised1431433828321351751962Conical v.HenryMotorised173523242945545529975Conical v.HenryMotorised2232262230461759771360Conical v.HenryMotorised163326293126803270590BowlPeterMotorised5292933323150317727BowlPeterMotorised53216383331513617466BowlPeterMotorised83219343439714362391BowlPeterMotorised92937363532944134840BowlPeterMotorised83245403634173859442BowlPeterMotorised103047403737434146403BowlPeterMotorised03824283836584372714BowlPeterMotorised23238433936664086420BowlPeterMotorised83528304037384265527BowlPeterMotorised83318294135984154556BowlPeterMotorised113424334238714282411BowlPeterMotorised1231243243308742341147BowlPeterMotorised73820324436914187496BowlPeterMotorised93832254537274185458BowlPeterMotorised1134272646484959311082Conical v.PeterMotorised133721204748855,10E+03215Conical v.PeterMotorised122826244842275013786Conical v.PeterMotorised63035234940945015921Conical v.PeterMotorised123021305045505016466Conical v.PeterMotorised364521305146435404761Conical v.PeterMotorised8343227
image/svg+xmlIANSA 2021 ● XII/2 ● 143–154Richard Thér, Petr Toms: Orientation Patterns Characteristic for the Structure of the Ceramic Body of Wheel-thrown Pottery145SampleMin. thicknessMax. thicknessDif. in thicknessShapeAuthorWheelRadial sectionsTangential sectionsMDCSDMDCSD5246205395775Conical v.PeterMotorised263420215340384897859Conical v.PeterMotorised223013185444905162672Conical v.PeterMotorised184413265550616,15E+031091Conical v.PeterMotorised133822295646195163544Conical v.PeterMotorised52721215746015274673Conical v.PeterMotorised112521245838904120230Conical v.PeterMotorised184026275947165365649Conical v.PeterMotorised275127226047835099316Conical v.PeterMotorised73131206188249686862Conical v.PeterFlywheel213417356288329545713Conical v.PeterFlywheel193615286389819604623Conical v.PeterFlywheel22401828648493101591666Conical v.PeterFlywheel13364276578708400530Conical v.PeterFlywheel16351231668607110982491Conical v.PeterFlywheel1733173167396560192054BowlThomasMotorised103064168391654971581BowlThomasMotorised1234163969355455111957BowlThomasMotorised33453270421664512235BowlThomasMotorised935173471434964752126BowlThomasMotorised1833113272392658161890BowlThomasMotorised1635172873370271273425BowlThomasMotorised1440132874394766062659BowlThomasMotorised1537113275377163352564BowlThomasMotorised2336113276428252911009BowlThomasMotorised940193377425656581402BowlThomasMotorised1344133178436460781714BowlThomasMotorised1141202979327357422469BowlThomasMotorised83273680295457732819BowlThomasMotorised835113581354264772935BowlThomasMotorised113993582651381941681Conical v.ThomasMotorised134035398362197205986Conical v.ThomasMotorised2241183684647180631592Conical v.ThomasMotorised113610298567737352579Conical v.ThomasMotorised154017378667157233518Conical v.ThomasMotorised203724368771207343223Conical v.ThomasMotorised203716388871798131952Conical v.ThomasMotorised194011308975358166631Conical v.ThomasMotorised164129379073058214909Conical v.ThomasMotorised194225379167867729943Conical v.ThomasMotorised11398399267757370595Conical v.ThomasMotorised83616409369697340371Conical v.ThomasMotorised836183494792390601137Conical v.ThomasMotorised835142895747791141637Conical v.ThomasMotorised213322309684768922446Conical v.ThomasMotorised19331739Table 1. Orientation analysis results for experimental samples taken in tangential and radial sections. MD – Mean direction, CSD – Circular standard deviation. (Continuation)JMicroVision software (Roduit, 2014). Two basic measures were chosen to express the object orientation: (a) mean direction (MD) – average orientation of objects, and (b) circular standard deviation (CSD) – the dispersion of the values from the average (Fisher, 1993, pp.75–78; Mardia and Jupp, 2000, pp.15–19).In the frst experimental collection, we found several signifcant markers distinguishing wheel fnishing, 
image/svg+xmlIANSA 2021 ● XII/2 ● 143–154Richard Thér, Petr Toms: Orientation Patterns Characteristic for the Structure of the Ceramic Body of Wheel-thrown Pottery146wheel shaping, and wheel throwing as basic levels of the contribution of rotational movement in pottery forming1, especially in the mean directions in core areas of radial sections, in CSD in core areas of radial sections or the mean direction in tangential sections (Thér, 2016).In the second experimental dataset, we focused directly on the distinctions among diferent uses of the potter’s 1There are two basic ways to classify variants of the application of rotational movement in the pottery-forming sequence. The frst approach classifes individual combinations of the techniques applied at diferent stages of the forming. The forming methods are then referred to as, for example, wheel coiling or wheel moulding (Berg, 2009; Roux, 2019; 2017; Rückl and Jacobs, 2016; Thér and Toms, 2016). Analternative approach is to separately defne the variants of the use of rotational movement and defne them independently of the other techniques (Berg, 2008; 2007; Choleva, 2012; Courty and Roux, 1995; Henrickson, 1991; Roux, 2003; Roux and Courty, 1998; Thér, 2016; Thér et al., 2017; Thér and Toms, 2016). The diferences in the contribution of rotational movement to the whole forming sequence are the main criterion in this classifcation:(a) Wheel fnishing. The vessel is formed by some hand-building technique and subsequently the rotational movement is used for surface modifcations and minor shape corrections, i.e. only in the fnishing stage.(b) Wheel shaping. A roughout of the vessel is formed by some hand-building technique and subsequently rotational kinetic energy (RKE) is used to shape and thin the vessel walls. This technique can be used in assembling and fnishing the vessel.(c) Wheel throwing. The entire forming sequence is performed using RKE.The main interest of the orientation analysis is to defne the relation between the contribution of rotational movement in forming and orientation patterns: thus, we use the second approach to classifcation.wheel. In this dataset, we evaluated the efect of the degree of transformation of the clay mass, the shape of the vessel, the velocity of rotation or the individual experience and skills of the potter. The principal fnding of the analysis of the second experimental collection was that the specifc characteristics of the orientation of wheel-thrown samples are developed especially in the lower parts of the vessels. The signifcant diference between the results obtained from lower and upper parts of the experimental vessels can be seen especially in the tangential sections. The diference is due to the fact that the lower part of the vessel undergoes a strong transformation when the potter creates a basic form prepared for lifting. While she/he lifts the clay mass upward, the rest of the clay is lifted above the fngers but is not afected by their movement (Thér and Toms, 2016, pp.38–39).The analysis of the second experimental series also confrmed the observation made in the frst experimental series, namely that the upper ends of the objects in the marginal zones of wheel-thrownpottery incline inwards towards the core of the wall (Figure 1). We called this phenomenon “imbricate pattern” and suggested that this pattern is caused by shear stress induced by upward movements of the fngers during wheel throwing. The clay mass in the margins moves more quickly during lifting than the mass in the core of the wall. Therefore, marginal zones can be seen as shear zones with a predominance of shear stress. The comparison of internal and external areas shows that the inclination of the inclusions and voids inwards is more strongly developed in the external area. We explained this phenomenon by the disproportion of the forces required on the interior and exterior of the vessel, which causes larger shear deformation on the exterior area of the vessel wall and subsequently a more pronounced imbricate pattern in this area (Thér and Toms, 2016, p.38).In the third experimental series described in this study, we focused solely on the orientation patterns resulting from wheel throwing and especially on those variables whose signifcant efect became the subject of hypotheses after evaluating the previous series.a) Above all, the shape of the vessel is important. The analysis suggested that the shape signifcantly infuences the orientation parameters. Samples taken from the oblate ellipsoid fashioned in the second experimental series showed below-average CSD values in radial sections from the lower parts of the vessels but, more importantly, a signifcant increase in CSD and lesser deviation from the horizontal axis in tangential sections (Thér and Toms, 2016, Figures 5 and 7). The distortion from typical wheel-throwing values for conical shapes could be hypothetically proportional to the degree of transformation that is required to fnish the shape of the vessel extra to the lifting of the clay.b) The second experimental series also showed that the orientation patterns refect the equilibrium established between the potter´s actions and tools she/he uses during forming. If the potters use an unfamiliar clay or rotational device or throw an unusual shape, they disturb the equilibrium gained by experience and thus also the alignment typical for the Figure 1.Imbricate pattern – orientation pattern typical for wheel throwing observed in radial sections. The upper ends of the objects in the marginal zones of wheel-thrown pottery incline inwards towards the core of the wall.
image/svg+xmlIANSA 2021 ● XII/2 ● 143–154Richard Thér, Petr Toms: Orientation Patterns Characteristic for the Structure of the Ceramic Body of Wheel-thrown Pottery147technique. This especially applies to the beginner for whom all the components of the technique are new (Thér and Toms, 2016, Figure 7). In this current, third experimental series we compared three professional potters who routinely produce pottery, to see whether the results are comparable when the potters have (a) a similar, high level of skill, (b) create shapes that do not difer signifcantly from what they are used to forming on a wheel, and (c) use familiar tools, i.e.potters are in equilibrium with their working environment.2. Materials and methodThe third experimental collection is focused on the variability of orientation patterns within the wheel-throwing method. So far, one principal experienced potter with 23 years of experience in wheel throwing, Peter Toms, was employed in our experiments. Along with Petr Toms (hereinafter referred to as Peter) we included two other professional potters: Jiří Lang (hereinafter referred to as Henry) and Tomáš Macek (hereinafter referred to as Thomas).Two diferent vessel shapes were replicated: a simple conical vessel 180 mm in height and 200 mm in diameter at the top and an S-shaped bowl 85 mm in height and 200 mm in diameter at the top (depicted in Figure 2). The S-shaped bowl was chosen because, in our application of the methodology, we are dealing mainly with Late Iron Age pottery in Central Europe, and this is the most common shape of wheel-made pottery in this context.Each potter formed 15 slightly conical pots and 15 S-shaped bowls. The target wall thickness for all the containers was 5 mm. No other parameters of the forming method were specifed in order not to force the potters to employ motions that are not “natural” for them. All the potters used their wheels (motor-driven) and the same fne-grained commercial clay – Witgert 10. The experimental collection was created during one session in one pottery workshop after the potters became acquainted with the selected pottery shapes. The speed of the wheels was measured by a laser tachometer.The dataset was complemented by six conical vessels thrown by Peter on a replica of a fywheel made of a wooden-spoked wheel. The device is located in the Archaeological park of prehistory in Všestary (Czech Republic). Peter does not work on this wheel on a regular basis and there was a minor technical problem related to ftting the wheel socket in the axis which caused vibrations of the wheel when a certain speed was reached.Two oriented thin sections were cut from the lower body of each experimental vessel: tangential and radial (Figure 2). The entire area of each thin section was recorded at a magnifcation of 200× using a Keyence VHX6000 digital microscope. The resultant images have a resolution of 1.11 μm. The analysis followed the published methodology (Thér, 2016; Thér and Toms, 2016), except for the software treatment. The components of the ceramic materials were extracted using automatic area measurement tools available in the Keyence VHX6000 measurement software. The range of threshold values chosen to separate inclusion and void representations was based primarily on colour saturation, which shows the best results for the thin sections with uneven thickness (resulting in uneven brightness of the captured image).The extracted objects in the radial sections were analysed only in the external zones of the section (one-third of the thickness adjacent to the outer edge). The focus on the external area follows the results of the analysis of the