analytical study of coptic wall paintings in egypt, el...

An International Journal ofMINERALOGY CRYSTALLOGRAPHY GEOCHEMISTRYORE DEPOSITS PETROLOGY VOLCANOLOGYand applied topics on Environment Archaeometry and Cultural Heritage

DOI 1024512013PM0002Periodico di Mineralogia (2013) 82 1 25-40

PERIODICOdi MINERALOGIAestablished in 1930

Analytical study of Coptic wall paintings in Egypt El-Bagawat necropolisKharga Oasis a case study

Ahmed Abo El-Yamin1 Hussein Marey Mahmoud2 and Atef Brania2

1Ministry of State for Antiquities Affairs PO 11211 Cairo Egypt 2Department of Conservation Faculty of Archaeology Cairo University PO 12613 Giza Egypt

Corresponding author marai79hotmailcom

Abstract

The present study aims to analyze Coptic wall paintings dating back to the late thirdearlyfourth to the seventh century AD from El-Bagawat necropolis Kharga Oasis Egypt Theanalysis was carried out by means of optical microscopy (OM) scanning electron microscopy(SEM) equipped with an energy dispersive X-ray detector (EDS) X-ray diffraction analysis(XRD) Fourier transform infrared spectroscopy (FT-IR) and the petrographic examinationThe results allowed the identification of the stratigraphic analysis of the wall paintings theirchemical composition and the painting technique employed On the other hand the resultspermitted a comparison between the Coptic wall paintings and those from the PharaonicPtolemaic and Roman periods The obtained results will enrich our knowledge concerningsome painting materials from an important example of the Coptic art in Egypt

Key words Coptic Wall Paintings EL-Bagawat necropolis Kharga Oasis SEM-EDS XRDFT-IR Green earth

Introduction

The actual term ldquoCoptrdquo and accompanyingadjective ldquoCopticrdquo originate from the Arabicldquoqibtrdquo which itself is a corruption of the Greekterm ldquoΑιγύπτιοςrdquo (Aigyptios) for the people ofEgypt Today the term ldquoCopticrdquo refers to theChristian population of Egypt (Malaty 1992Middleton-Jones 2011) Christianity wasprobably introduced to the Kharga Oasis in the

latter half of the third century or the beginningof the fourth century The greater part of theCoptic monuments was built with mud brickMud-brick architecture was by no means the firstuse of earthen architecture in ancient Egypt(Emery 2011) Mud-brick continued to be usedfor the lining for burial chambers and for roofvaulting for the subterranean portions in tombsof the New Kingdom and in the PtolemaicRoman and even in Coptic tombs (Spencer

Mahmoud_periodico 300413 0817 Pagina 25

AA El-Yamin HM Mahmoud and A Brania26 Periodico di Mineralogia (2013) 82 1 25-40

1979 Fathy 1989 McHenry 1996 Kemp2000)

The early Christian necropolis of El-Bagawat(occupies a surface area of 10000 squares) islocated about 3 km from the centre of KhargaOasis The Kharga Oasis is located to the westof the Nile valley 550 kilometres to the South ofCairo El-Bagawat necropolis is perhaps theoldest major Christian cemetery in the world itconsists of a vast expanse of domed mud brickmausoleums and underground galleries datingback to the fourth century AD which were builtover the site of an earlier Egyptian necropolis ofpit graves (Fakhry 1951) The architectural styleof the 263 tomb-chapels varies from simple one-room structures to family mausoleums withornate faccedilades enhanced with faux columns andarches and domed roofs (see Figure 1) Althoughmany of the chapels at the necropolis wereundecorated and consisted simply of a singlechamber built over the tomb shaft some were

much more elaborate and contained plasteredwalls with painted biblical scenes in a strangemixture of styles while others have elementsreminiscent of earlier Egyptian architecture(Zibawi 2005) Two of the most outstanding andbest preserved of the decorated chapels arenamed lsquoChapel of the Exodusrsquo and lsquoChapel ofPeacersquo (Capuani 2002) Figure 2 shows generalview of El-Bagawat necropolis at El-KhargaOasis and an example of the individual chapelsin addition to patterns of the wall paintings foundin these chapels The main art form in the Copticmonasteries and churches was the wall paintings(Gabra 2000) The investigation of Coptic wallpaintings is among the most attractive targets tobe investigated because few published papersare available about the painting materials andtechniques used in the Coptic monuments

The analytical investigations of the ancientpainting materials bring us much information ondevelopments in ancient technologies and thepropagation of ancient cultures It is indispensableto determine the chemical and mineralogicalcomposition of the wall paintings before anyconservation and restoration projects All thematerials used in the construction of wallpaintings undergo degradation when exposed toaggressive environments The rate and symptomsof such process are influenced by number offactors including the properties of material itselfthe natural factors and human actions Thedeleterious effects of acids on historical andmodern structures are complex the reaction ofcarbonate stone or plasters based on calciumcarbonate with sulfuric acid causes the formationof gypsum Sulfation is the process of chemicalcorrosion of carbonate materials due to acidattack by H3O+ ions in the presence of sulfate ionsin aqueous solution and leads to the formation ofgypsum (Ausset et al 1999)

Research aimsIn general few studies have been undertaken

to analyze Coptic wall paintings in Egypt (Ali

Figure 1 A map of Egypt the location of KhargaOasis is highlighted with a red circle (afterhttpwwwmapscom)


1995 Helmi and Ali 1995 Bolman 2002Lyster 2008 Moussa et al 2009 Ali et al2011 Marey Mahmoud and Papadopoulou2012) Many questions were raised at the

beginning of this analytical research concerningmainly the technical development of paintingmaterials and techniques used during the Copticage in Egypt Moreover although their historical

27Analytical study of Coptic wall paintings in Periodico di Mineralogia (2013) 82 1 25-40

Figure 2 a) General view of chapels of the El-Bagawat necropolis b) An individual chapel shows one of thepatterns found in the necropolis c d) Plastered fault and paintings of the chapel (No 25) at the necropolis e)An example of the wall decorations at the chapel (No 210) at the necropolis f) The state of conservation of thewall paintings at the necropolis


and artistic importance there is a paucity ofinformation concerning the Coptic wall paintingsof El-Bagawat necropolis at Kharga Oasis Forthis the mean research task of the present workwas devoted to analyze samples of wall paintingscollected from some selected chapels at thenecropolis (chapels No 25 amp 210) according tothe registration numbers of the chapels providedby the Egyptian supreme council of antiquities(SCA)

The sample characterization was performedusing optical microscopy (OM) scanningelectron microscopy (SEM) equipped with anenergy dispersive X-ray detector (EDS) X-raydiffraction analysis (XRD) Fourier transforminfrared spectroscopy (FT-IR) and thepetrographic examination The results of thisstudy bring us useful information on paintingmaterials and techniques used in an importantexample of Coptic wall paintings in EgyptMoreover the obtained data permit comparisonbetween the Coptic wall paintings and thosefrom the Pharaonic Ptolemaic and Roman agesin respect to their structure the chromatic paletteand the painting technique Furthermore theresults will help in establishing a conservation-restoration plan for the wall paintings atEl-Bagawat necropolis

Materials and methods

SamplesThe wall paintings of the studied chapels show

several deterioration forms such as crackingblistering and detachment of the painted layersAs a result of the state of preservation of themurals fifteen (15) tiny samples of the detachedpainted plasters were carefully collected andchosen for analysis In addition five (5)representative mud brick samples were collectedin order to determine their chemical andmineralogical composition Table 1 showscodes description and location of the studiedsamples

The analytical methodologyIn this work the analytical techniques utilized

to study the wall paintings samples were SEM-EDS XRD FT-IR and the petrographicexamination In order to identify the stratigraphicstructure of the paint layers some cross-sectionswere examined by a stereomicroscope

Optical microscopy The stratigraphic structure of the paint layers

was examined using a Zeiss (stemi DV4)stereomicroscope with a Sony camera (DSC-S85) The examination was carried out onfractured surfaces of the raw samples and alsosome tiny samples were embedded in epoxyresin (EpoFix) in order to prepare polished cross-sections

Scanning electron microscopy with an EDXmicroanalysis detector (SEM-EDS)

The microstructure and the morphologicalcharacteristics were determined by a Quanta 3D200i scanning electron microscope made by FEIThe microanalysis was carried out using anenergy dispersive X-ray analysis (EDAXPegasus XM4) The accelerating voltage wasbetween 15-20 kV Highly polished cross-sections prepared on the studied samples wereexamined using SEM The investigation wascarried out in the backscattered electrons mode(BSE)

X-ray diffraction analysis (XRD)In order to determine the mineralogical

composition of the plaster layers the collectedsamples were ground into powder in an agatemortar PXRD data were collected using aPhilips XrsquoPert PW3290 diffractometer with Ni-filtered CuKα radiation on randomly orientedsamples The counting statistics of the X-raydiffraction method were as follows step size001deg 2θ start angle 3deg end angle 63deg and scanspeed 002deg 2θsec The XrsquoPert HighScoreSoftware 2006 was used for the semi-

28 AA El-Yamin HM Mahmoud and A BraniaPeriodico di Mineralogia (2013) 82 1 25-40



quantitative determination of the mineral phasesThe detection limit was plusmn 2 ww

Infrared spectroscopySmall amounts of the paint samples were

removed and mixed with a KBr powder (~ 150mg) After grinding the mixture was pressed inan evacuated die in order to produce a pellet FT-IR spectra were collected using a Jasco 4100FT-IR Spectrometer in transmittance mode overa wave number range of 4000 to 400 cm-1 at aresolution of 4 cm-1

Petrographic examinationThe prepared thin-sections of the plaster

samples were examined by a Nikon EclipseE600 microscope with photographic attachmentsinclude PixeLINK PL-A623 digital camera

Results

Optical and petrographic examinationThe optical examination on fragments of the

plaster layers showed their stratigraphic sequenceprofile Figure 3a shows photomicrographobtained on a fraction of the plaster sample Itwas clear that the paint layer is well adhered tothe underlying preparation layer Below it a fineplaster ‛intonacorsquo with thickness ranges from 150to 200 microm is clearly observed In Figure 3b thethick coarse plaster ‛arricciorsquo is clearly observedThe thickness of this layer ranges from 300 micromto 15 mm The coarse plaster is rich in siliceousaggregates mainly of local sands and the matrixbinder is mainly of lime The petrographicanalysis carried out on thin sections of the fineplaster layer (Figure 3c d) shows that the plasterlayer is texturally heterogeneous The matrix is

No Colour Label of sample Description Location

1 Green Gr1 Painted fragment Chapel No 25

2 Olive-green Gr2 Powder Chapel No 210

3 Light green Gr3 Paint flake Chapel No 210

4 Dark green Gr4 Painted fragment Chapel No 210

5 Red-brown R1 Painted fragment Chapel No 210

6 Red R2 Coloured grains Chapel No 25

7 Pink R3 Painted fragment Chapel No 25

8 Light red R4 Paint flake Chapel No 25

9 Yellow Y1 Tiny piece Chapel No 210

10 Yellow Y2 Powder Chapel No 25

11 Dark yellow Y3 Painted fragment Chapel No 25

12 Light yellow Y4 Paint flake Chapel No 25

13 White W1 Painted fragment Chapel No 25

14 White W2 Paint flake Chapel No 25


Table 1 Codes description and location of the studied samples



based mainly on fine-grained calcium carbonateSlightly large siliceous and calcareous aggregatesare observed in the matrix The coloured patches

(mainly with light brown hues) are attributed toiron oxides associated in the plasters Somesilicate minerals (such as muscovite

Figure 3 a) Stereomicroscopic image of polished cross-section of the plaster layer showing the stratigraphy ofthe different layers b) Stereomicroscopic image showing details of the outer surface of the ground layer c d) Optical photomicrograph of thin sections prepared on the fine plaster layers under cross polarized light e f) Optical photomicrograph of thin sections prepared on the coarse plaster layers under cross polarized light


Analytical study of Coptic wall paintings in 31Periodico di Mineralogia (2013) 82 1 25-40

KAl2Si3AlO10(OH)2) with different coloursranges between yellow to reddish-brown hues arealso noticeable The microscopic imagesobtained on thin sections of the coarse plasterlayer (Figure 3e f) show aggregates of largesharp grains of quartz (SiO2) and limestonefragments are clearly observed embedded in thecarbonated matrix

Mineralogical characterizationTable 2 shows the mineralogical composition

of the studied samples The XRD analysis onpowder sample of the mud brick (Figure 4a)shows major component of quartz Otherminerals of calcite (CaCO3) plagioclase (albiteNaAlSi3O8) potassium feldspar (microclineKAlSi3O8) and clay minerals (kaoliniteAl2Si2O5OH4 and illite KAlSi3AlO10OH2) werealso measured The XRD analysis of the fineplaster indicates that calcite is the majorcomponent in the sample Traces of gypsum

(CaSO42H2O) quartz and kaolinite were alsomeasured The XRD analysis of the coarseplaster (Figure 4b) shows that the sampleconsists mainly of quartz and calcite In somesamples traces of kaolinite potassium feldspar(microcline) plagioclase (albite) were alsofound The render samples show majorcomponents of calcite with traces of quartz andgypsum Concerning pigment samples XRDanalysis showed that the green pigment (sampleGr1) consists of quartz calcite glauconitegypsum and clay minerals The red pigment(sample R2) consists of quartz calcite hematite(α-Fe2O3) potassium feldspar plagioclasegypsum and clay minerals The yellow pigment(sample Y2) consists of calcite quartz goethite(α-FeOOH) potassium feldspar plagioclase andclay minerals The white pigment (sample W1)contains calcite as major component with minoramounts of gypsum while traces of quartz werealso found

SampleComponent Q C Kf Pl Gy He Go Gl Cl

Mud brick +++ + + + minus minus minus ++ ++

Coarse plaster +++ + + + minus minus minus minus minus

Fine plaster + +++ + minus + minus minus minus +

Render + +++ minus minus + minus minus minus +

Green pigment +++ + + + + minus minus + +

Red pigment +++ + + + + + minus minus +

Yellow pigment +++ ++ + + minus minus + minus +

White pigment + +++ minus minus ++ minus minus minus minus

Q = quartz C = calcite Kf = K-feldspar Pl = plagioclase Gy = gypsum He = hematite Go = goethite Gl = glauconite Cl = clay minerals ndash = not determined + = traces ++ = minor constituent +++ = major constituent

Table 2 The mineralogical composition of the studied samples



Microstructure and microanalysisFigure 5 shows BSE and SEM images

obtained on some paint layers The BSE imageobtained on a polished cross section of the greenpaint layer (Figure 5a) shows coarse aggregatesof the pigment material The elemental analysis

obtained by the EDS detector (Figure 5b)showed that potassium aluminium silicon andiron were detected Among mineral pigmentsonly green earth contains the above elementsMoreover the existence of sodium detected inthe EDS spectrum of the sample suggests that

Figure 4 Representative XRD patterns of a) mud brick sample b) coarse plaster layer


Analytical study of Coptic wall paintings in 33

glauconite was used to obtain the green colourThe detection of sulphur is probably due to thepresence of calcium sulphates (gypsum)resulting from the chemical transformation ofcalcium carbonates in the render layer

The SEM investigation obtained on the outersurface of the yellow pigment sample (Figure 5c)shows a heterogeneous distribution of large andsmall crystals of ochre and quartz The EDSmicroanalysis of the sample (Figure 5d) showsthat the peak of iron is present which indicatesthe existence of iron oxide The contribution ofsilicon and aluminium suggests possibleexistence of an aluminosilicate material(probably the kaolinite) The BSE image

obtained on the red pigment sample showsslightly fine grains of the red ochre The EDSmicroanalysis of the sample affirms the presenceof the beak of iron which suggests the use of ironoxides of red ochre Minor amounts of siliconand aluminium were found together with tracesof sodium iron and sodium were also detectedThese elements probably refer to aluminosilicatematerials (eg clays) and plagioclase (albite)The investigation of the white pigment showsfine grains of calcium carbonate The EDSmicroanalysis shows high concentration ofcalcium in the sample For mud brick samplesthe EDS microanalysis shows major amounts ofsilicon with minor amounts of calcium

Periodico di Mineralogia (2013) 82 1 25-40

Figure 5 a) BSE image of a polished cross-section of the green paint layer (sample Gr 1) and the EDS spectrumb) obtained on the same sample c) SEM image of the outer surface of the yellow paint layer (sample Y1) andthe EDS spectrum d) obtained on the same sample


AA El-Yamin HM Mahmoud and A Brania34

aluminium and iron Other elements of sulphurpotassium magnesium sodium and titaniumwere also detected The fine plaster layers showelemental composition with concentrations ofCaO ranging from 6554 to 7499 The coarseplaster layers show elemental composition withconcentrations of CaO ranging from to 335 to4611 The EDS microanalysis of the rendsamples show high concentration of calcium withtraces of sulphur and silicon The SEM-EDSresults obtained on the studied samples are givenin Table 3

FT-IR resultsFigure 6 displays FT-IR spectra obtained on

the yellow and green paint layers (samples Gr1and Y1) In Figure 6a the characteristic bandsat 1419 867 782 and 708 cm-1 are all of calciumcarbonate These bands are come from theunderlying ground layer The band at 549 cm-1

indicates the presence of iron oxide The outerOH groups at 3747 and 3693 cm-1 are attributedto amounts of kaolinite The band at 1653 cm-1

is attributed to (νC = O amide I) together withthe bands at 2988 and 2896 cm-1 attributed to

methylene groups (vasym and vsymCH2) arebelieved to belong to a proteinaceous materialThe bands at 3000-3750 cm-1 indicate hydroxylgroup The bands at 400-475 cm-1 indicate thepresence of amorphous silicates The band at1044 cm-1 is attributed to in-plane Si-Ostretching modes In the FT-IR spectrum of thegreen pigment (Figure 6b) glauconite wascharacterized by the small band at 664 cm-1 withbroad peaks in the 1110-950 cm-1 region Theselast bands are mainly at 970 and 1055 cm-1 Inthe region 3400-3700 cm-1 three narrow bandsat 3420 3690 and 3747 cm-1 are present suchbands are characteristic of the stretching ofhydroxyl (O-H stretching) groups depending onthe nature of the cations (Moretto et al 2011)

The bands at 913-849 cm-1 are attributed to Si-O stretching bands and the bands at 1000-1100cm-1 are for asymmetric Si-O-Si stretchingbands The bands at 2989 and 2896 cm-1 are formethylenic groups 1646 cm-1 (amide I) and at1529 cm-1 (δN-H amide II) for a proteinaceousmaterial The presence of oil was concluded onthe basis of characteristic bands at 1737 and1247 cm-1 (stretch C-O-C) The plaster layers


Sampleoxide Na2O MgO A12O3 SiO2 SO3 K2O CaO Fe2O3 TiO2

Mud brick 176 187 2465 4832 449 354 643 376 109

Coarse plaster 778 221 121 3082 145 076 4611 097 ndash

Fine plaster 281 180 376 556 736 228 7499 150 105

Render 165 ndash ndash 165 187 ndash 8954 ndash ndash

Green pigment ndash 702 643 5182 ndash 487 1554 1432 ndash

Red pigment ndash ndash 277 349 1005 198 631 7421 134

Yellow pigment ndash 176 498 2349 2086 163 2148 2496 ndash

White pigment ndash ndash ndash 267 579 ndash 9154 ndash ndash

Table 3 SEM-EDS analysis (wt) of the studied samples



Figure 6 FT-IR (KBr) spectra recorded on some paint layers a) The yellow paint layer (sample Y1) b) Thegreen paint layer (sample Gr1)



showed characteristic bands of calciumcarbonates (mainly of calcite) at 1430 878 and713 cm-1 and the band at 468 cm-1 is due toquartz The bands at 3440 1639 and 600 cm-1

are attributed to calcium sulphates (gypsum) Formud brick samples quartz kaolinite and illitewere identified on the basis of the characteristicbands at Si-O stretching in the 1300-400 cm-1

range the bands at 3696 cm-1 (Al---O-H str)3622 and 914 cm-1 (Al---O-H inter-octahedral)3450 and 1633 cm-1 (H-O-H str) 1033 cm-1 (Si-O-Si Si-O str) 790 cm-1 (Si-O str Si-O-Al str)[(Al Mg)---O-H] 693 and 468 cm-1 (Si-O str)Table 4 summarises the results obtained from theapplication of analytical techniques on thestudied samples

Discussion

Paintings supportThe main building material used in the

necropolis is the mud brick The XRD analysis ofmud brick samples showed that quartz is themajor component of the samples Other mineralsof potassium feldspar (microcline) calcite andclay minerals (kaolinite and illite) were alsomeasured Mud bricks should contain at leastthree of the following ingredients coarse sand forstrength fine sand to lock the coarse sand in placesilt and clay as binders and a plastic medium(Kemp 2000) Also mud brick contains organicmaterials like straw which added to prevent theshrinkage of the brick (Nicolini et al 2010) Clayminerals form an important group of thephyllosilicate or sheet silicate family of mineralswhich are distinguished by layered structurescomposed of polymeric sheets of SiO4 tetrahedralinked to sheets of (Al Mg Fe)(O OH)6octahedra Clay minerals have very fine particlesize usually lt 2 mm They are classified by thedifferences in their layered structures (Nayak andSingh 2007) There are several classes of clayssuch as smectites (montmorillonite saponite)mica (illite) kaolinite serpentine pylophyllite

(talc) vermiculite and sepiolite (Grim 1968) Ifone tetrahedral and one octahedral sheet arebonded together the structure is called 11 layersilicate structure Within the 11 family differentspecies of dioctahedral (eg kaolinite dickite) andtrioctahedral (eg chrysotile) minerals exist(Madejovaacute 2003)

Plasters and preparation layersThe stratigraphic analysis of the plaster layers

has shown that two layers are clearlydistinguishable XRD and FT-IR analysesrevealed the contentious detection of calciumcarbonate as the main constituent of the plastersboth as binder (lime) and filler The first plasterlayer is made up of lime wash with fine grainsof local silica sand The second layer is slightlythick and prepared from lime and large grains ofsilica sand Moreover the semi quantitativeSEM-EDS analysis performed on the plastersamples revealed concentrations of CaO SiO2Al2O3 MgO Fe2O3 and K2O which suggeststhat a non-hydraulic lime with low hydrauliccompounds was used to prepare the plasterlayers

Organic fibres of straw were used in the plasterlayers These fibres have traditionally been usedto improve the tensile strength (Elsen 2006) Aliet al (2011) reported that quartz calciumsulphate (gypsum) and calcium carbonate wereused to make the ground layer of wall paintingscoming from the monastery of St Jeremiah inSaqqara and preserved now in the Copticmuseum in Cairo (no 7953) In their study ofCoptic plasters from the Monastery of StSimeon (Deir Anba Hatre) Aswan Upper EgyptMarey Mahmoud and Papadopoulou (2012)showed that the ground layer consists ofaragonite and calcite with traces of gypsumquartz and clay minerals Non-hydraulic or aeriallime so-called since the phenomenon ofcrystallization can take place only in thepresence of air (hence the slowness to set and thepossibility of storing large quantities of slaked



Sample XRD SEM-EDS FT-IR

Mud brick Quartz calciteplagioclasepotassium feldsparkaolinite and illite

Si Ca Al K Fe TiMg Na S

Quartz kaolinite and illite showcharacteristic bands at Si-Ostretching in the 1300-400 cm-1

range the bands at 3696 cm-1 (Al---O-H str) 3622 and 914 cm-1

(Al---O-H inter-octahedral) 3450and 1633 cm-1 (H-O-H str) 1033cm-1 (Si-O-Si Si-O str) 790 cm-1

(Si-O str Si-O-Al str) (Al Mg)---O-H) 693 and 468 cm-1 (Si-O str)

Coarse plaster Quartz and calciteTraces of kaolinitepotassium feldspar(microcline)plagioclase (albite)

Si Ca Al K Fe MgNa

Characteristic bands of calciumcarbonates at 1430 878 and 713 cm-1

and the band at 468 cm-1 is due toquartz The bands at 3440 1639 and600 cm-1 are attributed to calciumsulphates (gypsum)

Fine plaster Calcite traces ofgypsum quartz andkaolinite

Ca Si S Al K FeMg Na Ti

Render Calcite with traces ofquartz and gypsum

Ca Si S Na

Green pigment Quartz calciteglauconite gypsumand clay minerals

Si Al K Fe Ca MgK

Glauconite was characterized by thesmall band at 664 cm-1 with broadpeaks in the 1110-950 cm-1 regionThese last bands are mainly at 970and 1055 cm-1

Red pigment Quartz calcitehematite potassiumfeldspar plagioclasegypsum and clayminerals

Si Al Fe S K Ti Red ochre presented bands at 690and 555 cm-1 are attributed to ironoxide the bands at 3696 and 3622cm-1 are due to kaolinite

Yellow pigment Calcite quartzgoethite potassiumfeldspar plagioclaseand clay minerals

Si Al Fe S K MgTi

Yellow ochre showed bands at 549cm-1 indicates the presence of ironoxide The outer OH groups at 3747and 3693 cm-1 are attributed toamounts of kaolinite

White pigment Calcite gypsum withtraces of quartz

Ca Si S Characteristic bands of calciumcarbonates at 1407 and 872 cm-1

Table 4 Summary of the results obtained from analytical methods applied on the studied samples



lime) (Adam 1994 Toprak 2007) The detectionof sulphur in the samples suggests thetransformation of calcium carbonates in theplaster layers to gypsum (CaSO4H2O) asconfirmed by XRD analysis The materials usedin old restoration interventions of the wallpaintings at the necropolis probably helped in theoccurrence of this process

Green pigmentPapers have been published on the

characterization of Coptic wall paintings all ofwhich suggest that earth pigments are the maincomponents of the chromatic palette used in thesemurals The XRD EDS and FT-IR analysesconfirmed the green pigment as green earth andspecifically of glauconite Indeed in the celadonitecomposition the percentage of aluminium islower (0-02) with respect to glauconite (03-08) (Moretto et al 2011) Glauconite chemicalcomposition is approximately (K Na) (Fe3+ AlMg)2 (Si Al)4O10(OH)2 similar to celadonitebut with a great content of aluminium due to apartial substitution of Al3+ for Si4+ in thetetrahedrally coordinated layer (Aliatis et al2008) Other greenish clayey minerals can beincorporated into pigments labelled and includedin ldquogreen earthsrdquo pigments eg greenishsmectites chlorites serpentines and pyroxeneswith accessory minerals (eg quartz calcitegoethite and feldspars) (Hradil et al 2003Aliatis et al 2008)

Red pigmentThe red pigment was identified as red ochre

The EDS microanalysis showed highconcentrations of iron are present A smallcontribution of silicon and aluminium mayindicate the presence of aluminosilicate materials(eg clays) The various shades of ochre aredetermined by several factors the average size ofcrystallites the corresponding dispersion theirproportion with respect to the presence of otherchemical components such as aluminosilicate

materials and other minor components (calcitegypsum etc) (Ramos et al 2008) Moussa et al(2006) in their study of Coptic wall paintings inAl Qurna and Wadi El Natrun-Egypt reportedthat the red pigment is hematite and the brownpigment is hematite of Aswan

Yellow pigmentThe FT-IR and XRD analyses revealed that the

yellow pigment was identified as yellow ochreThe hue of goethite is affected by its crystallinityand elemental purity Ali et al (2011) showedthat manganese was added in the form of MnOto obtain dark yellow colour in wall paintings atthe Coptic museum in Cairo

White pigmentFrom the XRD and FT-IR analyses the white

pigment was identified as calcite EDS analysisshowed high concentration of calcium in all thestudied samples Traces of gypsum were alsofound in some samples

Painting techniqueFrom the FT-IR analysis the use of a

proteinaceous binder (probably of animal glue)was recorded In some cases the content ofanimal glue was not confirmed because theamide I and II bands are masked by the broadbands of calcium sulphate oxalate andcarbonate That suggests that al secco techniquewas used as painting technique Al seccotechnique is used for painting on dry plaster withpigments mixed with different types of organicbinders (Hein et al 2009)

Conclusions

Different analytical techniques such as OMSEM-EDS XRD FT-IR and the petrographicexamination were applied to answer somequestions concerning materials and techniquesused in Coptic wall paintings from El-Bagawatnecropolis Kharga Oasis Egypt The results



showed that the main building material in thenecropolis is the mud brick The mud bricksamples consist mainly of quartz with otherminerals of calcite plagioclase (albite)potassium feldspar (microcline) and clayminerals (kaolinite and illite) were alsomeasured Concerning the plaster layers theresults showed that the plaster layers used in theexamined wall paintings are based mainly onlime The results indicated that calcite is thepredominant phase found in the fine plasterlsquointonacorsquo with traces of quartz and kaoliniteThe coarse plaster lsquoarricciorsquo consists mainly ofsilica sand with minor amounts of calcite Tracesof kaolinite potassium feldspar (microcline)plagioclase (albite) were also found The rendersamples show major components of calcite withtraces of quartz and gypsum

In comparison with the Pharaonic plasters thestratigraphy of the studied Coptic wall paintingsis almost the same and in all cases it dependsmainly on the quality of the painting supportThe walls of the chapels at the necropolis aredecorated with a chromatic palette based mainlyon earth pigments The results revealed the greenpigment as green earth (specifically ofglauconite) the red pigment as red ochre(hematite α-Fe2O3) the yellow pigment asyellow ochre (goethite α-FeOOH) and the whitepigment as calcite with minor amounts ofgypsum The XRD and FT-IR analyses showedthe continuous detection of calcium carbonatesin all the examined samples Moreover anindication of a proteinaceous binder (probably ofanimal glue) was found which suggests that alsecco technique was applied in the studied wallpaintings The results will be used in theconservation-restoration interventions of thesewall paintings In conclusion the investigationof additional samples will be of importance toimprove our knowledge of the materials used inthe Coptic wall paintings in Egypt

Acknowledgements

The authors are grateful to the archaeologistsand conservators at the ministry of state forantiquities affairs of Egypt (El-Kharga office) fortheir collaboration during collection of thesamples The constructive anonymous reviewand the editorial handling are kindly thanked

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Capuani M (2002) - Christian Egypt Coptic Art andMonuments through Two Millennia The LiturgicalPress

Elsen J (2006) - Microscopy of historic mortars - areview Cement and Concrete Research 36 1416 -1424

Emery VL (2011) - Mud-Brick Architecture InUCLA Encyclopedia of Egyptology Willeke W(Ed) Los Angeles httpdigital2libraryuclaeduviewItemdoark=21198zz0026w9hb

Fakhry A (1951) - The Necropolis of El-Bagawat inKharga Oasis Government Press Cairo




Fathy H (1989) - Architecture for the poor Anexperiment in rural Egypt American University inCairo Press

Gabra G (2000) - New discoveries of Copticmonuments problems of their preservation andpublication In Coptic studies on the threshold of anew millennium In Immerzeel M and Van derVliet J (Eds) Proceedings of the SeventhInternational Congress of Coptic Studies Vol IILeiden 1069-1078

Grim RE (1968) - Clay mineralogy New YorkMcGraw Hill Book Co

Hein A Karatasios I and Mourelatos D (2009) -Byzantine wall paintings from Mani (Greece)microanalytical investigation of pigments andplasters Analytical Bioanalytical Chemistry 3952061-2071

Helmi F and Ali M (1995) - Study of Coptic MuralNiche in Mari-Gergis Church Cairo- Egypt InPancella R (Hrsg) Proceedings of the LCPCongress ldquoPreservation and restoration of culturalheritagerdquo Montreux 24-29 September Lausanne729-736

Hradil D Grygar T and Hradilova J (2003) - Clayand Iron Oxides Pigments in the History ofPainting Applied Clay Science 22 223-236

Kemp B (2000) - Soil (including mud-brickarchitecture) In Ancient Egyptian materials andtechnology Nicholson PT and Shaw I (Eds)Cambridge Cambridge University Press 78-103

Lyster W (2008) - Cave Church of Paul the Hermitthe Monastery of St Paul in Egypt Yale UniversityPress

Madejovaacute J (2003) - FTIR techniques in clay mineralstudies review Vibrational Spectroscopy 31 1-10

Malaty TY (1992) - Dictionary of church TermsAlexandria Egypt

Marey Mahmoud HH and Papadopoulou L (2012) -Characterization of Coptic Plasters from theMonastery of St Simeon (Deir Anba Hatre)Aswan Upper Egypt Restoration of Buildings andMonuments 18 (2) 81-92

McHenry P (1996) - The adobe story A globaltreasure Albuquerque NM (Ed) University ofNew Mexico Press

Middleton-Jones H (2011) - An Introduction to TheCoptic Period in Egypt The Early Christian era 1st

Century AD - 7th Century AD Egyptological 3Moretto LM Orsega EF and Mazzocchin GA

(2011) - Spectroscopic methods for the analysis ofceladonite and glauconite in Roman green wallpaintings Journal of Cultural Heritage 12 (4) 384-391

Moussa A Kantiranis K Voudouris KS Stratis JAAli MF and Christaras V (2009) - Diagnosis ofweathered Coptic wall paintings in the Wadi ElNatrun region Egypt Journal of Cultural Heritage10 (1) 152-157

Nayak PS and Singh BK (2007) - Instrumentalcharacterization of clay by XRF XRD and FTIRBulletin of Materials Science 30 (3) 235-238

Nicolini I Meucci C and Pettiti I (2010) -Characterization of Archeological mud bricks fromSudan Diagnostica per lrsquoArte 3 1-7

Ramos PM Ruisaacutenchez I and Andrikopoulos KS(2008) - Micro Raman and X-ray fluorescencespectroscopy data fusion for the classification ofochre pigments Talanta 75 (4) 926-936

Spencer AJ (1979) - Brick architecture in ancientEgypt Warminster Aris amp Phillips

Toprak G (2007) - Characteristics of limes producedfrom marbles and limestones Msc Thesis theGraduate School of Engineering and Science ofİzmir Institute of Technology Turkey

Zibawi M (2005) - Bagawat Peintures paleacuteochreacutetiennesdrsquoEgypte Editions AampJ Picard

Submitted August 2012 - Accepted December 2012




1979 Fathy 1989 McHenry 1996 Kemp2000)

The early Christian necropolis of El-Bagawat(occupies a surface area of 10000 squares) islocated about 3 km from the centre of KhargaOasis The Kharga Oasis is located to the westof the Nile valley 550 kilometres to the South ofCairo El-Bagawat necropolis is perhaps theoldest major Christian cemetery in the world itconsists of a vast expanse of domed mud brickmausoleums and underground galleries datingback to the fourth century AD which were builtover the site of an earlier Egyptian necropolis ofpit graves (Fakhry 1951) The architectural styleof the 263 tomb-chapels varies from simple one-room structures to family mausoleums withornate faccedilades enhanced with faux columns andarches and domed roofs (see Figure 1) Althoughmany of the chapels at the necropolis wereundecorated and consisted simply of a singlechamber built over the tomb shaft some were

much more elaborate and contained plasteredwalls with painted biblical scenes in a strangemixture of styles while others have elementsreminiscent of earlier Egyptian architecture(Zibawi 2005) Two of the most outstanding andbest preserved of the decorated chapels arenamed lsquoChapel of the Exodusrsquo and lsquoChapel ofPeacersquo (Capuani 2002) Figure 2 shows generalview of El-Bagawat necropolis at El-KhargaOasis and an example of the individual chapelsin addition to patterns of the wall paintings foundin these chapels The main art form in the Copticmonasteries and churches was the wall paintings(Gabra 2000) The investigation of Coptic wallpaintings is among the most attractive targets tobe investigated because few published papersare available about the painting materials andtechniques used in the Coptic monuments

The analytical investigations of the ancientpainting materials bring us much information ondevelopments in ancient technologies and thepropagation of ancient cultures It is indispensableto determine the chemical and mineralogicalcomposition of the wall paintings before anyconservation and restoration projects All thematerials used in the construction of wallpaintings undergo degradation when exposed toaggressive environments The rate and symptomsof such process are influenced by number offactors including the properties of material itselfthe natural factors and human actions Thedeleterious effects of acids on historical andmodern structures are complex the reaction ofcarbonate stone or plasters based on calciumcarbonate with sulfuric acid causes the formationof gypsum Sulfation is the process of chemicalcorrosion of carbonate materials due to acidattack by H3O+ ions in the presence of sulfate ionsin aqueous solution and leads to the formation ofgypsum (Ausset et al 1999)

Research aimsIn general few studies have been undertaken

to analyze Coptic wall paintings in Egypt (Ali

Figure 1 A map of Egypt the location of KhargaOasis is highlighted with a red circle (afterhttpwwwmapscom)




























Results


































































Mud brick 176 187 2465 4832 449 354 643 376 109


Fine plaster 281 180 376 556 736 228 7499 150 105















Discussion

















Si Ca Al K Fe MgNa






Ca Si S Na


Si Al K Fe Ca MgK





Si Al Fe S K MgTi



















Conclusions






Acknowledgements


References

































































Results


































































Mud brick 176 187 2465 4832 449 354 643 376 109


Fine plaster 281 180 376 556 736 228 7499 150 105















Discussion

















Si Ca Al K Fe MgNa






Ca Si S Na


Si Al K Fe Ca MgK





Si Al Fe S K MgTi



















Conclusions






Acknowledgements


References




















































































Mud brick 176 187 2465 4832 449 354 643 376 109


Fine plaster 281 180 376 556 736 228 7499 150 105















Discussion

















Si Ca Al K Fe MgNa






Ca Si S Na


Si Al K Fe Ca MgK





Si Al Fe S K MgTi



















Conclusions






Acknowledgements


References














































Discussion

















Si Ca Al K Fe MgNa






Ca Si S Na


Si Al K Fe Ca MgK





Si Al Fe S K MgTi



















Conclusions






Acknowledgements


References
















































Si Ca Al K Fe MgNa






Ca Si S Na


Si Al K Fe Ca MgK





Si Al Fe S K MgTi



















Conclusions






Acknowledgements


References




















































Conclusions






Acknowledgements


References










































Acknowledgements


References







































analytical study of coptic wall paintings in egypt, el...

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