Medieval Nubian Wall Paintings
The papers in this volume are the results of an extensive programme of research based on investigations of samples of Nubian mural paintings from the Middle Nile Valley dating from the 6th to the 14th century AD. Many of these samples came from paintings which are now in the National Museum, Khartoum and the National Museum in Warsaw. Others came from current archaeological excavations in Sudan. The composition of plasters, pigments and binders and lime washes are reported in detail together with an overview of previous and present conservation and transfer procedures. The data collected show the changes in painting methods and materials over time and the possible associated implications in terms of patronage, trading links, economy etc.
The papers in this volume are the results of an extensive programme of research based on investigations of samples of Nubian mural paintings from the Middle Nile Valley dating from the 6th to the 14th century AD. Many of these samples came from paintings which are now in the National Museum, Khartoum and the National Museum in Warsaw. Others came from current archaeological excavations in Sudan.
The composition of plasters, pigments and binders and lime washes are reported in detail together with an overview of previous and present conservation and transfer procedures. The data collected show the changes in painting methods and materials over time and the possible associated implications in terms of patronage, trading links, economy etc.
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MEDIEVAL NUBIAN WALL PAINTINGS<br />
Figure 6.5 Microphotograph of sample D_CB.III_14 with organic fibres highlighted.<br />
Figure 6.6 Large fibres of vegetal origin separated from the<br />
lower layer of sample D_CB.III_17.<br />
Figure 6.8 Cross-section of Banganarti plaster sample B_U_9.<br />
Figure 6.7 Locations for micromechanical testing.<br />
Besides binder and aggregates, the lower layer of<br />
sample D_CB.III_14 also contains organic fibres (Fig.<br />
6.5). It was possible to separate and measure some<br />
larger fragments (Fig. 6.6): their widths vary between<br />
0.4 and 1.3 mm and lengths between 5.3 and 2.8 mm.<br />
Their taxonomy was not determined but the fibres<br />
were probably from a member of the Poaceae family<br />
(grasses). The use of plant fibres in lime mortar, particularly<br />
flax, is known from the Byzantine technique<br />
of wall painting and was described by Dionysius of<br />
Fourna (1981) in his manual. Lucas (1934) mentions<br />
the use of straw in clay plasters in ancient Egypt. The<br />
presence of organic matter in the sample motivated<br />
60
CHARACTERISTICS OF NUBIAN PLASTERS<br />
Figure 6.9 SEM-EDS mapping of B_U_9 plaster.<br />
an attempt to analyse the proteins in the material<br />
(lower layer of sample D_CB.III_14) by mass spectrometry.<br />
Vegetal proteins from barley seeds (Hordeum<br />
vulgare) were found with the aid of two independent<br />
databases (Swissprot and NCBInr-viridiplantae).<br />
The main functions of the identified proteins relate<br />
to the provision or storage of the seed nutrition and<br />
as a defence mechanism against bacteria and fungus.<br />
The identified proteins included B3-hordein (developing<br />
endosperm), barwin (defence mechanism),<br />
61
MEDIEVAL NUBIAN WALL PAINTINGS<br />
Figure 8.8 Abd el-Gadir: a traveller’s name scratched on the wall painting. (Photo: Cristobal Calaforra-Rzepka, SNM 24325,<br />
courtesy of the Sudan National Museum, Khartoum.)<br />
Figure 8.9 Faras Cathedral, Nativity scene: oil stains and soot residues. (Photo: Cristobal Calaforra-Rzepka, SNM 24365,<br />
courtesy of the Sudan National Museum, Khartoum.)<br />
98
CONSERVATION OF NUBIAN MURALS<br />
Figure 8.10 Banganarti: intentional damage to a figure of a saint (iconoclasm). (Photo: Bogdan<br />
Żurawski, courtesy of the Institute of Mediterranean and Oriental Cultures, Polish Academy of<br />
Sciences.)<br />
mud-based bricks, renderings and powdered paint<br />
layer. Long-term action may result in the disintegration<br />
of plaster and mortar joints between bricks.<br />
Excavation affects the static properties of buildings,<br />
causing them to become unstable. This poses a<br />
threat to murals, especially in combination with the<br />
environmental changes that immediately follow the<br />
uncovering of decorated spaces. In non-homogeneous<br />
structures, such as Faras Cathedral, the decay process<br />
may vary in certain areas. For example, the painting<br />
representing St John and St Peter was executed on a<br />
wall built from two different materials: the lower part<br />
of the wall was made of stone, while the upper part<br />
comprised red brick. The lower part had suffered<br />
more damage than the rest of the painting (Fig. 8.11):<br />
the plaster layer was better preserved on the brick wall<br />
than on the lower stone wall. Delamination was also<br />
apparent on mud-brick pillars introduced in the later<br />
phases of the church (Cathedrals of Petros and Late).<br />
Transferred paintings: threats and risks<br />
The major risk is the decision to transfer the painting:<br />
there is always the possibility that the whole<br />
operation will fail, which may lead to total or partial<br />
99
MEDIEVAL NUBIAN WALL PAINTINGS<br />
Figure 8.46 Truss with a triangular lattice built of fibreboard<br />
according to Jędrzejewska’s method. (Photo: Hanna<br />
Jędrzejewska and Edward Jędrzejewski, courtesy of the<br />
National Museum in Warsaw.)<br />
Figure 8.48 Attaching a support structure to a transferred<br />
painting according to Jędrzejewska’s method. (Photo: Hanna<br />
Jędrzejewska and Edward Jędrzejewski, courtesy of the<br />
National Museum in Warsaw.)<br />
Figure 8.47 Faras Cathedral: support structure for the niche<br />
with the representation of the Virgin and Child. (Photo:<br />
Hanna Jędrzejewska and Edward Jędrzejewski, courtesy of<br />
the National Museum in Warsaw.)<br />
formed directly on the backs of the paintings (reinforced<br />
with aluminium mesh). The structures were<br />
not only poorly attached to the original, but they<br />
were also unstable and very heavy. In the end, this<br />
method was abandoned and most paintings treated<br />
under Hanna Jędrzejewska’s direction received a<br />
rigid support structure resistant to deformation.<br />
Supports developed in the National Museum in<br />
Warsaw by Hanna Jędrzejewska<br />
Hanna Jędrzejewska devised new supports for the<br />
Faras wall paintings in the National Museum in<br />
Warsaw. These were developed according to the state<br />
of knowledge and materials available at the time.<br />
Some of the early solutions were later replaced using<br />
more sophisticated, lighter materials. The artificial<br />
support, intended to be removable, also had to allow<br />
for the setting of original fragments slightly above<br />
the background level (Jędrzejewska 1965a: 230–31).<br />
Its design benefited from consultations with specialists<br />
and numerous tests (Jędrzejewska 1966a: 85–9;<br />
1966b: 205–6; 1992: 204–5).<br />
The gypsum supports were removed, a layer of<br />
fibreglass-reinforced mortar was applied to the back<br />
of each painting, and a new support was constructed<br />
consisting of two fibreboards joined with brass<br />
bolts. The inner board was attached to the back of<br />
the original, while the outer layer constituted a lattice<br />
structure that could be removed at any time<br />
(Jędrzejewska 1965b: 243–4). After completing the<br />
first two paintings, the method was modified and<br />
most of the paintings were completed using this new<br />
method.<br />
Jędrzejewska used earlier prepared structures<br />
consisting of only two perforated fibreboards fixed to<br />
an internal truss with a triangular (Fig. 8.46) or rectangular<br />
lattice built of fibreboard – or, in the case of<br />
larger paintings, of wooden slats attached using PVA<br />
or polyester resin as adhesive. The support achieved<br />
was a honeycomb structure, 3–5 cm thick, loadbearing,<br />
rigid but at the same time fairly lightweight,<br />
attached to the back of the painting using a thick<br />
mixture of polyvinyl acetate dispersion, chalk and<br />
sand, and left to dry under pressure. The adhesive<br />
penetrated the perforations, additionally reinforcing<br />
the join. Openings in the boards also functioned as<br />
ventilation holes (Fig. 8.47).<br />
The structures were larger than the original paintings,<br />
leaving a margin to be filled with background<br />
120
CONSERVATION OF NUBIAN MURALS<br />
Figure 8.49 Representation of St Amone attached to a support before application of the<br />
external background. (Photo: Hanna Jędrzejewska and Edward Jędrzejewski, courtesy of the<br />
National Museum in Warsaw.)<br />
121