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XII/1/2021
INTERDISCIPLINARIA ARCHAEOLOGICA
NATURAL SCIENCES IN ARCHAEOLOGY
homepage: http://www.iansa.eu
Analysis of Middle Nubian Vessel-forming Technology Using
Refectance Transformation Imaging (RTI)
Aaron M. de Souza
1*
, Martina Trognitz
2
1
Austrian Archaeological Institute, Austrian Academy of Sciences, Franz Klein-Gasse 1, 1190 Vienna, Austria
2
Austrian Centre for Digital Humanities and Cultural Heritage, Austrian Academy of Sciences, Sonnenfelsgasse 19, 1010 Vienna, Austria
1. Introduction
According to the existing framework, the Nile Valley of
Lower and Upper Nubia (Figure 1) was populated by
three so-called Middle Nubian Cultures – the C-Group,
Kerma, and Pan-Grave cultures – during a period spanning
c. 1850–1500 BCE (Figure 2). Each of the three groups was
defned typologically, based on distinct material culture
traditions and patterns of distribution following a now
outdated culture-historical approach. The C-Group was
thought to be confned primarily to Lower Nubia (Bietak,
1968; Säve-Söderbergh, 1989), the Kerma tradition to Upper
Nubia (Edwards, 2004, pp.65–84), while the Pan-Grave
tradition comprised mobile or partially mobile groups spread
across a vast region from Middle Egypt up to the Fourth
Nile Cataract and the surrounding desert regions (Bietak,
1966; Säve-Söderbergh, 1989, pp.15–19; de Souza, 2019,
pp.140–143). For much of the 20
th
century, these three
archaeological cultures were viewed as bounded and distinct
entities, but recent research has demonstrated that these
divisions can no longer be supported. It is now understood
that the Nubian cultural landscape was highly complex and
interconnected (Edwards, 2004, pp.10–23; Raue, 2019,
pp.293–333), but the outdated divisions persist in scholarly
discourse. In the absence of any alternative descriptive
system, the labels C-Group, Pan-Grave, and Kerma will
be used in this paper for reasons of clarity, albeit with the
recognition that those labels need to be urgently revised.
In order to investigate these interconnections, the current
analysis uses the concept of
chaîne opératoire
(Gosselain,
2012, pp.244–246; Roux, 2016; D’Ercole
et al.
, 2017, p.554;
Gosselain, 2018) as a means for understanding the series of
choices made by ancient Nubian potters when making these
vessels. According to Gosselain (2012, p.246), the concept
is also an analytical tool for documenting and interpreting
those technological choices in a systematic way. This study
applies Refectance Transformation Imaging (RTI) to Middle
Nubian ceramics in order to identify and analyse physical
traces of the vessel-forming process that might otherwise
be invisible to the unaided eye or difcult to capture using
Volume XII ● Issue 1/2021 ● Pages 19–35
*Corresponding author. E-mail: aaron.desouza@oeaw.ac.at
ARTICLE INFO
Article history:
Received: 9
th
September 2020
Accepted: 14
th
April 2021
DOI: http://dx.doi.org/10.24916/iansa.2021.1.2
Key words:
Refectance Transformation Imaging (RTI)
documentation
pottery technology
second millennium BCE
technological heritage
material culture
Kerma
Pan-Grave
C-Group
ABSTRACT
Refectance Transformation Imaging (RTI) is a photographic technique used to generate digital
surrogates of surfaces that can be viewed using virtual lighting coming from interactively set directions,
enabling the close structural examination of objects under digital raking light.
In this study, RTI was applied to Middle Nubian pottery from sites near the Second Nile Cataract
that were excavated by the Scandinavian Joint Expedition to Sudanese Nubia in the early 1960s. The
ceramic traditions under investigation are currently known as C-Group, Pan-Grave and Kerma. An
overarching aim of the project is to assess the possibility of understanding the relationships between
these groups through detailed analyses of their material traditions. Based on the hypothesis that
technological traditions may be related to cultural heritage, RTI is applied in this study to observe
morphological traces of ceramic vessel forming processes.
Two technological groups were identifed, one consistent with paddle-forming, and another consistent
with hand-building on a mat-lined surface. These technological groups correspond very closely to
cemetery distributions, which suggests that the diferent techniques may be specifc to diferent pottery-
making traditions. It is suggested that vessel forming-technology in the so-called C-Group tradition is
distinct from that of the so-called Pan-Grave and Kerma traditions, and that the validity of the divisions
between Nubian cultural groups should thus be further interrogated.
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standard photographic processes (see chapter 4). It will
be shown that careful observation of the surface features
revealed by the RTI process can assist in identifying
similarities or diferences in pottery-making technologies
that may in turn be linked to cultural heritage and traditions.
2. Research objective
The goal of the analysis was to test hypotheses regarding
ceramic vessel-forming technologies among the Middle
Nubian cultures. It has previously been proposed that Nubian
pottery was formed using either the coiling or slab-building
method (Arnold, 1993, pp.33–36), or by using a percussive
process such as paddle forming (Arnold, 1993, pp.17–20).
Both of these methods have been cited as primary forming
processes (
i.e.
, the processes used to create the overall vessel
shape), and it is likely that both slab building and paddle
forming (see chapter 6.1) were employed for diferent types of
vessels and perhaps even in combination (Nordström, 1972,
pp.47–48; Williams, 1983, pp.29–36). RTI was employed
on a group of Middle Nubian vessels selected from the
Figure 1.
Map of Egypt and Nubia showing the locations of the SJE concession and the sites from which samples were taken. Map by A. de Souza.
0 200 km
0 5 km
0 5 km
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Scandinavian Joint Expedition (SJE) collection in order to
identify physical traces of vessel-forming technologies that
might otherwise be invisible to the unaided eye. These new
insights might also revise understandings of Middle Nubian
ceramic technologies and, by extension, critically reconsider
the existing Nubian cultural divisions.
3. Samples and sites
The samples for the analysis were all selected from objects
collected by the Scandinavian Joint Expedition to Sudanese
Nubia (the “SJE”), the bulk of which are now housed at the
Museum Gustavianum, Uppsala University, Sweden (Säve-
Söderbergh, 1970, pp.13–18). All objects were exported
from Sudan in accordance with the agreed division of fnds,
and full permission to document the objects using RTI was
granted by the curatorial staf of the Museum Gustavianum.
A total of 25 objects drawn from fve cemetery sites
were documented using RTI. The 15 objects that yielded
meaningful information are summarised in Table 1. The
remaining 10 objects that produced inconclusive results are
listed in Table 2.
As the aim of the analysis is to look for
technological variations between pottery-making traditions
according to their current defnitions, the sample selection
was limited to objects that could be attributed to one of the
existing cultural divisions with relative security. Attributions
were based on characteristics such as shape, ware and overall
style, as well as considerations of the archaeological contexts
in which the objects were found. Regarding chronology,
at present there is no absolute chronology for the Middle
Nubian traditions and, as such, only a relative sequence can
be given.
All of the samples are undecorated black-top wares with
a range of surface treatments including coated and uncoated,
burnished and unburnished. In order to capture as much of
the vessel surface as possible, complete or intact objects
were prioritised for selection. In cases where intact objects
were not available, the largest possible sherds that preserved
all or most of the vessel profle were selected for analysis.
Ten samples came from SJE Site 65, all of which could
be attributed to the so-called C-Group tradition based on
morphology, ware, and the character of their respective
contexts. SJE Site 65 as a whole may also be attributed to
the C-Group tradition and is broadly contemporary with the
late Middle Kingdom and Second Intermediate Period on the
Egyptian timeline (Säve-Söderbergh, 1989, pp.174–180).
All of the samples are black-topped bowls with red-coated
and burnished exteriors (Figures 5a, 5c, 5e and 6a, 6c, 6e).
Five samples were taken from SJE Site 170, which has
mostly been attributed to the so-called Pan-Grave cultural
horizon (de Souza, 2019, pp.150–153) with some evidence
for activity related to the Kerma tradition. The site is roughly
contemporary with the late Second Intermediate Period in
Egypt (Säve-Söderbergh, 1989, pp.192–199). Of the fve
samples from Site 170, three could be attributed to the Pan-
Grave ceramic tradition based on their overall style and
morphology (Table 1; Figures 7c, 7e, 8a). The fourth sample,
170/39:3 (Figure 9), is a small shallow bowl with a mat-
impressed exterior that strongly suggests a Kerma attribution
based on parallels with the same surface treatment from sites
in Upper Nubia (for parallels, see: Rufeux, 2012, fg. 28;
Figure 2.
Comparative timeline of ancient
Egypt and Nubia.
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Table 1.
List of RTI samples that yielded meaningful information.
Object No.TraditionPreservationSurface features noted in RTI
65/0:9C-GroupIntactParallel ripples from base to rim.
65/2:1C-Group
Sherd
Areas of fat zones, some elongated narrow depressions.
65/62A:1C-Group
Sherd
Large fat areas to exterior.
65/63:1C-Group
Sherd
Large fat areas to exterior.
65/107:2C-Group
Sherd
Flat marks toward base, some parallel grooves on max diameter.
65/239:4C-GroupCompleteFlat areas to exterior.
170/2:1Pan-GraveCompleteSmall circular dimples toward base; vertical burnishing and scrape marks to upper body.
170/30:1Pan-GraveIntactClusters of small dimples toward base.
170/31:2Pan-GraveIntactClusters of small dimples toward base.
170/38:2Pan-Grave?
Sherd
Parallel ripples from base to rim.
170/39:3Kerma?IntactMat impressed; covered with irregular rounded dimples.
266/B.1.2
Kerma
IntactMat impressed; entire exterior surface covered in rows of circular dimples.
332/33:2Pan-GraveIntactClusters of dimples toward base.
410/7:4
KermaSherd
Mat impressed; covered with impressions of herringbone weave.
410/21:2Pan-Grave
Sherd
Patches of small dimples and one large fat area.
Table 2.
List of RTI samples for which the results were inconclusive.
Object No.TraditionPreservationReason for exclusion
65/21:1(5)C-Group
Sherd
RTI taken of interior surface only. Comb scraped surface.
65/64:4(3)C-Group
Sherd
Sherd too small, no traces of forming processes observed.
65/246:1C-Group?
Sherds
No traces of forming processes observed.
65/311:2C-Group
Sherd
Sherd too small, no traces of forming processes observed.
170/05:1Pan-Grave?
Sherd
Sherd too small, no traces of forming processes observed.
170/37:2
Kerma
IntactKerma beaker; surface highly polished, no traces of forming processes observed.
170/37:3
Kerma
IntactKerma beaker; burnishing has erased traces of forming processes.
170/46:1Pan-Grave?IntactNo traces of forming processes observed.
410/20:1
Kerma
IncompleteKerma beaker; burnishing has erased traces of forming processes.
410/23:1
Kerma
IntactKerma beaker; burnishing has erased traces of forming processes.
Rose, 2012, pp.18–21, fg. 4–5; Budka, 2017, fg. 67).
The attribution of the ffth sample, 170/38:2, is uncertain,
but it has been tentatively assigned to the Pan-Grave ceramic
tradition by association and by its macroscopic characteristics
(Figure 8c). Four additional samples from this site yielded
inconclusive results (Table 2).
One vessel comes from grave 266B, which is an isolated
burial in the vicinity of a larger cemetery that was attributed
by the excavators to the C-Group (Säve-Söderbergh, 1989,
pp.239–240). The vessel is a large globular jar with a mat-
impressed exterior surface that is consistent with examples
known from the Kerma tradition.
A small black-topped bowl (332/33:2), came from
SJE Site 332, which was identifed by the excavators as
a “Middle Nubian (C-Group?) and Late Nubian cemetery”,
with some earlier elements (Säve-Söderbergh, 1989, p.246).
The character of the context is undetermined, but the bowl
itself could be attributed to the Pan-Grave tradition based on
its overall morphology.
Four samples were drawn from SJE Site 410, one of the
southernmost sites in the SJE concession located in the
vicinity of the second Nile Cataract. This site was described
by the excavators as a mixed Pan-Grave and Kerma cemetery
and most graves were identifed by loose stone rings at the
surface (Säve-Söderbergh, 1989, pp.251–254, pl. 158–159).
One sherd has an obviously mat-impressed surface consistent
with examples known from the Kerma tradition (Figure 4).
Another bowl with a defned black-top could be attributed
to the Pan-Grave tradition on stylistic grounds (Figure 8a).
In addition, two Classic Kerma beakers from this site (Säve-
Söderbergh, 1989, pl. 23) were documented using RTI, but
their highly polished surfaces produced unusable results
(Table 2).
Regarding chronology, all of the graves, and in particular
those from SJE Site 65, were at least partially disturbed and
easily dateable objects were almost entirely absent. Based on
the pottery forms, it was possible to devise a broad relative
sequence. The vessels attributed to the C-Group pottery
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tradition are all relatively shallow with tapered bases that are
characteristic of a relatively early date, most likely Bietak’s
Phase IB or IIA (Bietak, 1968, pp.96–105, Taf. 8; Säve-
Söderbergh, 1989, pp.7–9), which more or less corresponds
to the 12
th
Dynasty in Egypt, c. 2000–1800 BCE. The overall
style of the vessels attributed to the Pan-Grave and Kerma
traditions as well as their fnd contexts suggest a slightly
later date in the Second Intermediate Period in Egypt, c.
1650–1550 BCE. For samples attributed to the Pan-Grave
tradition, characteristics such as defned and applied black-
tops point to a date during the later phases for that tradition
(de Souza, 2019, pp.35–37, pp.119–122). For the mat-
impressed wares assigned to the Kerma tradition from SJE
Sites 170 and 410, well-dated parallels and the presence of
well-known beaker forms point towards a date in the Classic
Kerma period (c. 1700–1500 BCE). Overall, it would appear
that the C-Group samples from SJE Site 65 are earlier than
the Pan-Grave and Kerma samples, which are more or less
contemporary with one another.
4. The RTI method
Refectance Transformation Imaging (RTI) is a photographic
technique used to generate digital surrogates of surfaces
that can be viewed with light coming from an interactively
set direction, enabling the examination of objects under
digital raking light. The method involves taking multiple
photographs (the “image stack”) of an object with a camera
positioned perpendicularly to it, with a moving light source,
i.e.
, the object and camera remain stationary, but the light
source is moved around the object and comes from a
diferent angle in each picture. Digital relighting is enabled
by the use of Polynomial Texture Maps (PTM), a digital
image format that does not store a fxed colour value for each
pixel, but instead uses a refectance function to calculate the
luminosity of the surface, which infuences how a surface
is visually perceived: bright, dark, refective or dim. Simply
put, the colour is computed depending on the view settings
(
e.g.
incident light angle) and the surface geometry,
i.e.
, the
surface normals, of the captured object (Malzbender
et al.
,
2001, p.521; Trognitz, 2016). Surface normals represent
points on a three-dimensional object where a normal can be
determined along which, according to the law of refection,
extant light is refected in the same angle as incident light
(Figure 3). The refectance function allows for an accurate
representation of the three-dimensional surface’s shape in
a two-dimensional PTM.
In order to calculate the PTM from the image stack, the
position of the light source in each image must be known.
This can be achieved in one of two ways: by using a dome-
shaped device with fxed mounted lights that surrounds
the object (Malzbender
et al.
, 2001, pp.520–521) or by
using a hand-held light source for which the origin can be
calculated by using refective spheres placed in the image
frame (Mudge
et al.
, 2006). The latter method, known as
Highlight RTI (H-RTI), is detailed by CHI (Web CHI b)
and Historic England (2018, pp.7–23) and was employed
for the present analysis. With H-RTI, a virtual “dome” of
light around the object is created by manually positioning the
light source along imaginary arcs. The current recommended
H-RTI workfow, software for building and viewing an RTI
fle, and further related methods were developed by Cultural
Heritage Imaging (CHI), who openly and freely provide their
materials and also ofer in-depth, hands-on training classes.
The inherently curved surfaces of the vessels in this analysis
required certain considerations in capturing the images. In
order to compensate for the curvature, the camera was set
to capture an increased depth-of-feld using a wide aperture
(F18–22) and prolonged exposure time (up to 2 seconds) to
ensure that the entirety of the vessel surface was in focus. The
prolonged exposure time in turn dictated that a continuous
light source was required, in this case, a hand-held LED
torch, rather than a conventional fash. A string attached to
the light source assisted in maintaining a consistent distance
to the object. The torch was moved along a series of twelve
imaginary arcs, each of which comprised four individual
images. With three additional images in which the light source
was held further away from the object, each object was thus
captured with a total of 51 photographs. The last three images
were optional and used only if additional flling light was
required to brighten the fnal image.
The captured image stacks were computed into an RTI
fle with the RTIBuilder software developed by Cultural
Heritage Imaging (CHI) (Web CHI a). The fnished RTI fles
can only be viewed with specialised software, in this case,
the RTIViewer developed by CHI (Web CHI d) was used.
RTIViewer Version 1.1 ofers a range of rendering modes,
each with further sub modes and settings (Malzbender
et al.
,
2000; Malzbender
et al.
, 2001, pp.525–526; Palma
et al.
,
Figure 3.
On a three-dimensional surface
the surface normals (red dashed) point
into diferent directions. The incident light
(yellow) is refected (green) along the
surface normal. A PTM (Polynomial Texture
Map) stores the surface normals and the
incident light angle and can visually provide
an accurate representation of the three-
dimensional surface in a two-dimensional
fle. (CC-BY 4.0 M. Trognitz)
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2010, pp.6:5–6:7; CHI, 2013, pp.13–23; Schroer, 2014).
These rendering algorithms help in enhancing the visual
perception of shape and surface detail by, for example,
changing material properties of objects or enhancing
shape cues provided by shading (Malzbender
et al.
, 2000).
Figure 4 serves as an example of the efects that diferent
rendering algorithms have on the perception of the object’s
shape and surface textures for sample SJE 410/7:4. Of all
of the available viewing modes, specular enhancement
proved most useful for the current analysis in that it best
Figure 4.
Sample SJE 410/7:4 rendered using diferent visualisation modes under the same lighting conditions. Each mode enhances the visual perception
of shape and surface detail in diferent ways.
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aided in the visualisation of often very subtle manufacturing
traces preserved on the surface of the vessels (Figure 4h;
Malzbender
et al.
, 2000; 2001, pp.525). This viewing mode
also enables the image to be desaturated and hence brings
focus to the structure of the object without the distraction of
colour.
For archaeological purposes, the RTI process is a versatile,
mobile, and relatively low-cost method of documenting
objects for detailed digital analysis both in the feld and
in a museum or laboratory setting. The mobile equipment
enables working in a variety of indoor and outdoor settings,
including remote areas and even underwater settings
(Historic England, 2018, pp.52–54). Virtually any material
can be captured (Earl
et al.
, 2010; Earl
et al.
, 2011), with
object sizes ranging from the microscopic (Historic England,
2018, pp.45–48) up to larger objects or even to complete sites
(Historic England, 2018, pp.49–51). The samples of the RTI
Systems for Ancient Documentary Artefacts project (AHRC
RTISAD) include materials such as ceramic, wood, metal,
stone or bone (Earl
et al.
, 2011, pp.151) with surface fnishes
ranging from matte to shiny. The diferent rendering methods
provide extended tools for analysis beyond what is visible
with the unaided eye or difcult to capture using traditional
photographic methods, while still clearly representing 3D
shape characteristics. Finally, RTI-fles provide a perfectly
lit and location-independent means for the study of an
object’s surface, thus providing “access to colour and texture
in a way hitherto largely restricted to those in direct contact
with the material culture” (Earl
et al.
, 2010, pp.2049). For
its application to Nubian-style pottery specifcally, RTI has
also been used to analyse pottery that combines Nubian and
Egyptian technologies at the sites of Wadi el-Hudi (Brand,
2018, pp.36–37, fg. 9–10) and at Tell Edfu (de Souza, 2020,
p.316, fg. 6).
Like every documentation method, besides its advantages,
RTI also has disadvantages that may limit its applicability to
archaeology, largely dictated by the shape, size, or location
of the object to be documented.
Ideally, the surface being photographed should be as
fat as possible. Curved objects, for example, the interior
of a vessel, can be difcult or impossible to photograph
using RTI due to extensive self-shadowing. Objects with
a less pronounced curvature might still be viable for RTI
if the camera’s depth of feld can be adjusted accordingly,
as was the case for this analysis. Curved objects or objects
with multiple sides can be documented, but photographing
the entire object requires multiple image stacks taken from
diferent angles. 3D scanning may be a more viable option
for these kinds of objects.
Although the process is portable, sufcient space around
the object being documented is needed. The object should
be positioned in the centre of the real or virtual dome, which
itself should have a radius of at least two times the diameter
of the object. Therefore, particularly large objects require an
accordingly large surrounding space. The viability of RTI
can also be limited in confned spaces such as a tomb, a cave,
or a museum storeroom. The equipment itself can also pose
challenges, for example, the legs of a tripod, which can cast
shadows over the object when using the H-RTI method.
Ambient light and especially daylight must also be
considered, as the artifcial light source should ideally be
the only light source in the captured images. However, it
is possible to conduct RTI outdoors in a shaded location
provided that the light conditions are consistent and the
exposure time and aperture are adjusted to reduce natural
ambient light in the digital images.
5. Results
The results relating to the 15 samples that yielded meaningful
information are summarised in Table 1. The RTI fles and
data are accessible via ARCHE (A Resource Centre for the
HumanitiEs): http://hdl.handle.net/21.11115/0000-000D-
FEA5-B.
All but one of the samples from Site 65 displayed large
fattened facets on their exterior surfaces, especially towards
the base (Figures 5 and 6). Sample 65/2:1 (Figures 5a–b)
also displays elongated depressions. Sample 65/0:9 does
not have any obvious fattened facets at the base but does
display parallel ripples running from the base to the rim
(Figures 5e–f).
Of the fve samples from Site 170, three specimens
(Table 1; Figures 7c/e, 8a) each display clusters of small
rounded dimples towards the base that have been partially
diminished by the burnishing process (Figure 7d/f, 8b).
The dimples are approximately 5–7 mm in diameter. The
mat-impressed surface of the shallow bowl assigned to the
Kerma ceramic tradition, (170/39:3, Figure 9), can be easily
discerned with the unaided eye, and while RTI signifcantly
enhances the visualisation of the surface texture, the weave
pattern of the mat could not be easily discerned. It appears to
have been tightly woven with small rounded loops, similar
to the three aforementioned samples. The cultural attribution
of a fourth sample from the site, 170/38:2, is uncertain, but
it has been tentatively attributed to the Pan-Grave ceramic
tradition based on its context (Figure 8c). This sherd does
not display the clusters of dimples but rather shows parallel
ripples running vertically between the base and the now-
missing rim (Figure 8d).
The mat-impressed surface of the large jar 266/B.1.2
(Figure 10) was visible with the unaided eye, but enhancement
through the RTI process revealed a weave pattern comprising
parallel rows of small circular impressions. The size of the
impressions (approx. 5 mm diameter) is consistent with
those observed on the samples from SJE Site 170.
Sample 332/33:2 is a small bowl attributed to the Pan-Grave
ceramic tradition based on its overall morphology (Figure 7a–
b). This bowl displayed the same clusters of small circular
dimples as those observed the examples from Site 170.
Clusters of larger dimples were observed on the base of
SJE 410/21:2, a small Pan-Grave style bowl (Figure 8e–f).
No informative surface details were observed on the
10 samples that have been excluded in ensuing discussions
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Figure 5.
Samples from SJE Site 65:
(a) 65/2:1 photograph (b) 65/2:1 RTI in specular enhancement mode; (c) 65/107:2 photograph (d) 65/107:2 RTI in
specular enhancement mode; (e) 65/0:9 photograph (f) 65/0:9 RTI in specular enhancement mode.
0 10 cm
0 10 cm
0 10 cm
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Figure 6.
Samples from SJE Site 65:
(a) 65/62A:1 photograph (b) 65/62:1 RTI in specular enhancement mode; (c) 65/63:1 photograph (d) 65/63:1 RTI in
specular enhancement mode; (e) 65/239:4 photograph (f) 65/239:4 RTI in specular enhancement mode.
0 10 cm
0 10 cm
0 10 cm
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Figure 7.
Samples of Pan-Grave style vessels showing possible matting impressions: (a) 332/33:2 photograph (b) 332/33:2 RTI in specular enhancement
mode; (c) 170/30:1 photograph (d) 170/30:1 RTI in specular enhancement mode; (e) 170/31:1 photograph (f) 170/31:1 RTI in specular enhancement mode.
0 10 cm
0 10 cm
0 10 cm
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Figure 8.
Samples of Pan-Grave style vessels showing possible matting impressions: (a) 170/2:1 photograph (b) 170/2:1 RTI in specular enhancement
mode (dimples marked by red arrows; (c) 170/38:2 photograph (d) 170/38:2 RTI in specular enhancement mode; (e) 410/21:2 photograph (f) 410/21:2 RTI
in specular enhancement mode.
0 10 cm
0 10 cm
0 10 cm
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(Table 2). In all of these cases, the surfaces of the vessels
appeared entirely smooth.
6. Discussion and conclusions
Based on the traces observed on the vessel surfaces, the
analysed samples could be divided into two technological
groups, namely paddle-forming and building on a mat,
which will be discussed in detail below. These technological
groups correspond very closely to the cemetery groups and,
by extension, it is suggested that they correspond also to
pottery-making traditions and potentially also to cultural
traditions.
6.1 Paddle forming
The frst technological group displays fattened facets on
the vessel exterior, which were observed exclusively on the
samples from SJE Site 65 (Figures 5 and 6). This type of
facetting is hypothesised as being consistent with the paddle-
and-anvil process, whereby a vessel is formed by beating the
clay into shape using a fat implement (a “paddle”) with or
without a supporting device on the interior side (an “anvil”).
The clay may also be beaten over a mould (Arnold, 1993,
pp.17–20; Shepard, 1954, pp.59–60). In order to confrm that
these facets are products of the paddling process, RTI was
applied to a modern experimental vessel produced by Georgia
Kordatzaki (Figure 11). Although the resulting vessel is not
Nubian in style, it presented a useful opportunity to observe
and document the physical traces left on a vessel’s surface by
the paddle-forming process. G. Kordatzaki’s vessel was built
using two processes. Coiling was employed as the primary
shaping process to build the body of the vessel. The vessel was
subsequently refned by paddling as the secondary shaping
process, which involved gently beating the vessel into its
fnal shape from the exterior using a fat wooden tool (the
“paddle”). As a fnal step, the vessel exterior was burnished
with a polished stone. The RTI process clearly captured the
fattened facets on the exterior of the experimental jug left
by the paddling process, and which remained visible even
after the burnishing process. These fattened marks were
analogous to the marks observed on the vessels from SJE
Site 65, strongly suggesting that they are also traces of the
paddle-forming process.
The analysed vessels from SJE Site 65 correspond
morphologically with the C-Group ceramic tradition according
to current defnitions (Säve-Söderbergh, 1989, pp.44–52,
pl. 16–19), and it is therefore suggested that these vessels
from this site were built using paddling as either a primary
or secondary-forming process, possibly in combination with
coil- or slab-building. Coil-building was likely to have been
practiced by Middle Nubian potters as it was already applied
in much earlier times (D’Ercole
et al.
, 2017, pp.560–61).
Thus, a two-stage forming process is highly probable. It is
worth noting that the facets left by the paddling process remain
visible using RTI even after the vessels were burnished, which
was also evident on the experimental vessel.
The parallel ripples seen on the exterior of three vessels
from Site 65 are likely a result of scraping the vessel with
a toothed implement to refne and thin the vessel walls. The
same marks were observed on the interior of vessels from the
same site, and it is possible that the scraping process would
have removed traces of coiling. The ripples observed on
exteriors of burnished vessels from Site 65 suggest that the
scraping marks were diminished by the burnishing process
to a point that they only became visible using RTI. The
possibility of combining processes was raised by Nordström,
who suggested that the C-Group potters combined coiling
and paddling (Nordström, 1972, pp.47–48), which is the
same process used for the experimental jug described above.
6.2 Building on a mat
The second technological group comprises pottery that
displays traces of having been built on a mat-lined surface
that leaves distinct impressions on the vessel exterior. The
interiors of these vessels are almost invariably smooth and
compacted, but not burnished. The mat-impressions on
the exterior and the smooth, compacted interior surfaces
strongly suggest that the wet clay mass was placed on a
mat-lined surface and the pressure used to form the vessel
was applied from the interior side. This type of technology
appears to be absent from SJE Site 65, but was observed at
Figure 9.
SJE 170/39:3. (a) photograph; (b) RTI image of vessel base
showing matting impressions in specular enhancement mode.
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Figure 10.
SJE 266/1.B.2 (a) photograph; (b) RTI image in specular
enhancement mode (zoom 1.5×); (c) RTI image in specular enhancement
Mode (zoom 1.8×).
Figure 11.
Experimental jug with cutaway neck, made by Dr. G. Kordatzaki.
Top: Photograph of the vessel by A. de Souza. Bottom: RTI images of base
(left) and shoulder (right) in specular enhancement mode showing fattened
areas resulting from the paddling process.
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0 10 cm
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all of the other sites in this study. The mat-impressions occur
as a herringbone weave (Figure 4) or as rows and clusters
of small rounded dimples across the vessel surface. Dense
coverings of such dimples are easily discerned on sample
170/39:3 (Figure 9) and the large jar 266/1.B.2 (Figure 10),
both of which can be attributed to the Kerma ceramic tradition
based on their style and available parallels. In these cases,
the mat-impressions have been left almost entirely unaltered,
and no coating or slip has been applied to the exterior. The
frequency with which mat-impressions occur indicates that
it was a conscious choice by the potter and hence it can be
identifed as a surface treatment in its own right.
Clusters of circular impressions towards the vessel base
were revealed by RTI on vessels 170/30:1 (Figure 7c–d),
170/31:1 (Figure 7e–f), 170/2:1 (Figure 8a–b), and also
on 332/33:2 (Figure 7a–b), all of which can be attributed
morphologically to the Pan-Grave tradition according
to current defnitions. It is suggested that these marks are
remnants of mat-impressions based on their resemblance
to the marks observed on the Kerma-style vessels 170/39:3
and 266/1.B.2. Both of those vessels are uncoated and
unburnished, but on the Pan-Grave style examples, the
mat-impressions have been mostly diminished by a red slip
coating and intensive burnishing. The dimples were faintly
evident to the touch, but became easily visible through RTI.
It is therefore suggested that the vessels in this second
technological group can be further divided into two
subgroups, one in which the matting impressions were
deliberately left as a surface treatment in their own right, and
one in which the marks were diminished through subsequent
surface treatment processes,
e.g.
, coating, burnishing. The
former subgroup correlates well with the pottery assigned
to the Kerma ceramic tradition, and the latter with that
attributed to the Pan-Grave ceramic tradition.
6.3
Chaînes opératoires
and cultural heritage
Percussive processes such as the paddle-and-anvil method
were likely known to ancient Nubian potters. An ostracon
now in Berlin has been interpreted as showing two female
Nubian potters making a large jar using this process
(Brunner-Traut, 1956, pp.58–9, pl. 50–51; Arnold, 1993,
fg. 15A). Arnold tentatively interprets the depiction, which
was presumably created by an Egyptian, as an indication
that this method of making pottery may have been perceived
as an unusual Nubian (
i.e.
, not Egyptian) activity and was
hence worthy of documentation, even if only informally
(Arnold, 1993, pp.17–20). Whilst there are some clear and
problematic assumptions about ethnicity in the interpretation
of this ostracon, it nevertheless demonstrates that this vessel-
forming technique was not unknown in the ancient Nile
Valley. The process of beating clay into shape was also
postulated by Williams (1983) in his analysis of the Nubian
pottery from Adindan (Figure 12), for which he suggests that
clay was pounded into shape from the inside on either the fat
Figure 12.
Schematic diagrams showing
the process of shaping a pot by beating the
clay from the inside into a depression on the
ground. (After Williams, 1983, fgs. 4–6).
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ground or in a shallow depression, which may or may not be
lined with a mat (Williams, 1983, pp.29–36, fgs. 4–6). The
same process of building pottery on a mat-lined surface was
observed by Reisner at modern Kerma (Reisner, 1966), where
he also recorded mats with a closely-spaced rounded weave
pattern from ancient Kerma burials (Reisner, 1923, pl. 69.1).
Despite the small sample size in this analysis, the
technological diferences observed between the samples
from each of the sites point towards diferent material
traditions that might, in turn, correspond with diferent
cultural traditions. At least three diferent
chaînes opératoires
could be identifed based on the forming technologies, which
are illustrated in Figure 13. The process is broken down
into three manufacturing stages as defned by Roux (2016,
pp.5–6), namely roughout, preform, and fnishing.
The samples from SJE Site 65, attributed to the C-Group
tradition and characterised by the use of the paddling
technique, utilise all three of these stages. The roughout
stage involves the initial forming of the vessel, most likely
using coiling and/or pinching. During the preform stage,
the rough form was refned by scraping to thin the walls,
and then by paddling of the
exterior
surface. Both of those
processes were done whilst the clay was still wet. When the
vessel was leather hard, the fnishing processes of coating
and burnishing were executed in that order.
Vessels attributed to the Pan-Grave ceramic tradition seem
to have followed only a two-stage process. The RTI results
support the roughout being made by pressing or beating the
wet clay mass into shape from the
interior
on a mat-lined
surface. When the vessel was leather hard, it was fnished
by coating and burnishing, in that order. The preform stage
seems to have been omitted.
Mat-impressed vessels attributed to the Kerma ceramic
tradition were apparently subjected to only one stage in the
vessel-forming process, namely the roughout stage. The RTI
results strongly suggest that the wet clay mass was beaten
into shape from the
interior
on a mat-lined surface. The
vessels do not appear to have been further processed in any
way, and in all cases, they are uncoated and unburnished.
It therefore appears that the vessels attributed to the
C-Group ceramic tradition are technologically distinct from
those attributed to Pan-Grave and Kerma traditions, while
the latter two appear to have certain features in common.
The most fundamental diference is based on the methods
by which the wet clay was shaped into the vessel. While
the primary shaping processes employed in the C-Group
tradition remain unclear, the RTI analysis strongly suggests
that paddle forming was used at least as a secondary process.
By contrast, the mat-impressed exteriors of pottery attributed
to the Pan-Grave and Kerma traditions indicate that the clay
was shaped by applying pressure from the interior. The
mat-impressed wares attributed to the Kerma tradition are
distinct from others in the analysis in that they are not coated
or burnished and their uneven surfaces have not been treated
by any preforming or fnishing processes. Nevertheless, the
traces left by forming the vessels on a mat are analogous to
the marks observed on vessels from the Pan-Grave tradition,
but are entirely absent from the C-Group vessels in this
analysis. It is possible that chronological diferences may
be a factor (see chapter 3), and of course a sample of this
size should not be taken as being wholly representative,
but the consistency of the results suggests the possibility of
fundamentally diferent technological traditions.
This RTI analysis has provided evidence that the Pan-
Grave and Kerma pottery traditions are technologically more
closely related to one another than they are to the C-Group
tradition. That being said, caution must be exercised when
attempting to link this to “cultural” relatedness as our
Figure 13.
Châine opératoire
fow-chart showing the main technological steps for each of the forming techniques identifed in the analysis.
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understanding of ancient Nubian groups is in a state of fux.
The in-depth study of material technologies, in this case
by using RTI, has revealed distinct diferences between
assemblages, but also showed common features that connect
groups that were hitherto treated as separate cultural units.
This observation lends weight to the push for an overhaul
of the existing culture-historical framework for ancient
Nubia, and encourages more detailed analyses of material
technologies on the full range of available evidence, of
which ceramics is just one aspect.
Acknowledgements
This research was conducted as part of the frst author’s
InBetween
project, which has received funding from the
European Union’s Horizon 2020 research and innovation
programme under the Marie Skłodowska-Curie grant
agreement no. 796050. Thank you to the curatorial staf
of the Museum Gustavianum, Uppsala University for
their permission to work with and publish these objects.
Thanks also go to Georgia Kordatzaki (experimental
archaeologist & ceramic petrographer) for permission to
use her experimental jug as part of this analysis (facebook.
com/JasperHandmadeCeramics) and to Adam Grubner for
his photographic assistance. The application of RTI would
not have been possible without the materials provided by
Cultural Heritage Imaging (http://culturalheritageimaging.
org).
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