Pigment analysis of wall paintings and ceramics from Greece and Cyprus. The optimum use of x-ray spectrometry on specific archaeological issues

X-RAY SPECTROMETRYX-Ray Spectrom. 29, 18–24 (2000)

Pigment Analysis of Wall Paintings andCeramics from Greece and Cyprus. TheOptimum Use of X-Ray Spectrometry onSpecific Archaeological Issues

E. Aloupi,1 A. G. Karydas2 and T. Paradellis2*1 THETIS–Science and Techniques for Art History Conservation Ltd, 41 M. Moussourou Street, 116 36 Athens Greece2 Laboratory for Material Analysis, Institute of Nuclear Physics, NCSR Demokritos, 153 10 Aghia Paraskevi Attiki, Greece

This paper deals with archaeological issues which lend themselves to a simple but very effective treatmentby means of x-ray spectroscopy. The common feature of all the samples presented here is that they can bereduced to a simple spectroscopic question concerning the presence or absence of certain chemical elementsin the ancient pigments. Copyright 2000 John Wiley & Sons, Ltd.

INTRODUCTION

The identification and quantification of the elements thatcompose objects with an archaeological interest providesa first strong indication for the origin of the raw materialsand the technology applied in their production. In somecases (in metals or pottery materials) the concentrationof the minor and trace elements might also address thequestion of age and provenance of the objects. The strongrequirement by archaeologists and curators for the exclu-sive use of non-destructive analytical techniques duringthe examination of archaeological material makes x-rayanalytical techniques a unique tool in the understandingof the cultural heritage.1,2 The variety of the analyti-cal techniques that have been developed over the lastthree decades, employing different excitation probes (ionor x-ray beams) and instrumentation, have successfullyaddressed the above questions in a very effective way.For example, the external proton induced x-ray emission(PIXE) technique with variable incident proton energyallows the determination of the elemental depth concen-tration profile of pigments and thus the arrangement ofpaint materials in definite layers.3 In addition, when PIXEis combined with the Rutherford backscattering (RBS)technique, the characterization of the surface composi-tion relative to the bulk, e.g. slip versus fabric in potterymaterials, can be achieved.

However, x-ray techniques based on energy dispersion(PIXE, x-ray fluorescence) are suitable for determiningonly the elemental composition and not the chemical orgeochemical form of the materials analysed. This cer-tainly is a disadvantage, especially in pigment analysis.If archaeologists can provide some additional materialso that x-ray diffraction (XRD) techniques may also beapplied, the combination of the two methods is a powerful

* Correspondence to: T. Paradellis, Laboratory for Material Analysis,Institute of Nuclear Physics, NCSR Demokritos, 153 10 Aghia ParaskeviAttiki, Greece.

tool for the understanding of ancient pigment technol-ogy. If not, x-ray fluorescence alone may provide answersin cases where only well-defined questions have beenposed, whose answer relies on the resolution of a givendichotomy. In the case of Bronze Age wall paintings fromKnossos, Thera, Pylos, Tiryns and Mycenae, for instance,4

the blue pigments identified were either the natural glauco-phane, Na2.Mg,Fe/3Al 2Si8O22.OH/2, from the amphibolegroup, or the synthetic Egyptian blue, CaCuSi4O10. Thediagnostic elements in this case are Fe and Cu, respec-tively, and the question is whether glaucophane or Egyp-tian blue is spectroscopically translated to Fe or Cu.

A number of case studies dealing with similar questionswhich were undertaken by the authors during the last quar-ter of a century are presented chronologically, admittingsimple qualitative but definite answers, and are discussedin terms of their archaeological relevance.

1976; BRONZE AGE WALL PAINTINGS:GLAUCOPHANE OR EGYPTIAN BLUE?

In the course of a broad research project dealing withsystematic analyses of the inorganic pigments from thewall paintings discovered at Knossos, Thera, Pylos, Tirynsand Mycenae,4 – 6 the blue pigments presented an intrigu-ing chronological variation scheme in the case of Theraand Knossos (Fig. 1). The colour palette in the BronzeAge was mainly based on mineral pigments (i.e. goethite,limonite) and carbon for the red, yellow and black. Theblue was either the well known Egyptian blue, the syn-thetic pigment produced in Egypt and imported to Greeceas described in detail by Titeet al.,7 or glaucophane, ahydrous sodium magnesium aluminium silicate mineralrich in iron from the amphibole group. Different shadesand colour variations were obtained by mixing or over-painting the above basic colours.

The 50 samples of blue pigments selected were anal-ysed by the x-ray fluorescence technique. A few mil-ligrams of the pigment were placed on a thin Mylar sheet

CCC 0049–8246/2000/010018–07 $17.50 Received 9th June 1999Copyright 2000 John Wiley & Sons, Ltd. Accepted 10th August 1999

PIGMENT ANALYSIS OF WALL PAINTINGS AND CERAMICS 19

Figure 1. Map of Greece and Cyprus showing the places referredto in this paper.

and analysed. The elemental concentrations were esti-mated on a semiquantitative basis by normalizing all peakintensities to the strongest one.

According to the XRF data,4 the samples were dividedinto three types. type A [Fig. 2(a)]: the dominant elementis copper with significant Ca content. Pb, As, Sr, Snas trace elements and Fe of the order of a few percentnormalized to Cu were also detected. Type B [Fig. 2(b)]:the dominant element is iron with traces of Ti, Mn Rb,Cr, Ni, Y. The total absence of Cu is characteristic of thistype. Type C: iron is the prominent element with varyingamounts of copper.

The above analyses were complemented by x-raydiffraction and petrographic examination4,8 that correlatedtype A with the presence of pure Egyptian blue, type Bwith glucophane and type C with a mixture of glauco-phane with Egyptian blue. As shown in Table 1, Egyp-tian blue was used at all five sites. The samples fromthe palaces of Mycenae, Tiryns and Pylos (Mainland in

Table 1) dated after 1400BC and the samples from Knos-sos after 1500BC show exclusive use of pure Egyptianblue (type A). For dates earlier than 1500BC the Knossospigments indicate use of the Egyptian blue as early as ca3000BC. The glaucophane was identified only in Middleand Late Bronze Age samples dated earlier than 1700BCand not later than 1500BC and in most Theran samplesfrom the destruction level of Akrotiri due to the volcanoeruption are dated before 1500BC. In both Knossos andThera, type C blue, i.e. mixtures of the two pigments, isassociated with Late Minoan I period and the late partof Middle Bronze Age. Although glaucophane occurs asa mineral in both Thera and Crete, its presence has notbeen established in the geographic area from Knossos.The introduction of glaucophane in the colour palette ofMinoan wall paintings was attributed to Theran artisansand in view of the extended relationship between the twosettlements its presence in the wall paintings from Knos-sos was explained as an import from Thera. This claimis further supported by its abandonment after¾1500 BCor rather after the end of Late Minoan IA defined bythe eruption of the volcano in Thera which destroyed theisland. The discussion above is not affected by the abso-lute chronology of the Thera eruption. A recent analysisof well documented specimens from the wall paintings ofthe Xesti 3 (basically rooms 3 and 15, but also from thestaircase of room 5), the House of the Benches and someother parts of the excavation area at Akrotiri (Sectors A,B and C),9 verified the scheme of the parallel use of bothpigments in Thera, included in Table 1. This last publica-tion allowed a more precise identification of the mineral inthe form of riebeckite Na2.Fe2C,Mg,Fe3C/3Si8O22.OH/2,which like glaucophane belongs to the group of amphi-boles. Also the presence of exactly the same mineralogicalphase in the ‘glaucophane’ blue pigments from Knossospointed decisively to the Theran origin of the pigment.8

Another interesting result of the work by Filippakiset al.4 was the identification of Egyptian blue in Knossos

Figure 2. Typical XRF spectra of blue pigments based on (a) Egyptian and (b) glaucophane blue.

Copyright 2000 John Wiley & Sons, Ltd. X-Ray Spectrom. 29, 18–24 (2000)

20 E. ALOUPI, A. G. KARYDAS AND T. PARADELLIS

Table 1. Overview of the blue pigment distribution as a function of provenanceand chronology (ž = Egyptian blue (presence of Cu);� = amphiboles(glaucophane, presence of Fe);N = mixture of both (presence of bothCu and Fe))

as early as the 3rd milleniumBC that coincides withthe first appearance of the pigment in Egypt during the4th Dynasty. This observation which contradicts earlierassertions by Sir Arthur Evans10 led the authors to raiseinteresting archaeological questions introducing the ideaof a simultaneous local production of the synthetic bluepigment in early Minon Crete, which still remain to beaddressed.

1989; LATE BRONZE AGE WALL PAINTINGSFROM THERA: EARTHEN OR MARINEPURPLE?

Contrary to the previous study, the question to beanswered here concerns a single sample of a purplematerial found in 1969 in Akrotiri, Thera. The materialwas sampled for comparison with the pigments of Theranwall paintings within the framework of a larger pigmentanalysis study as a follow-up of the work described above.The visual examination of the material was compatiblewith a ferruginous nature (i.e. ochre). However, the

non-destructive XRF analysis of about 50 mg of this verylight and powdered material (Fig. 3) revealed a calciticmatrix (Ca 34%) with a low Fe content (1.5%) combinedwith very high Br concentration (5300 ppm). Traces ofMn (2300 ppm), Cu (600 ppm) and Zn (600 ppm) werealso detected. In general, bromine offers a very powerfuldiscriminating criterion between marine and terrestrialenvironments. Br occurs in the hydrosphere as solublebromide salts. Its concentration in seawater is 65–70 ppmwhereas in the earth’s crust and streams are only 4.0and 0.02 ppm, respectively. This is further accentuatedbetween the marine and terrestrial biosphere (seaweed,sponges, shells, plants, etc.) owing to the formation oforganic bromine compounds. The use of bromine and itscompounds as a tracer of the contact between seawaterand sea-salt with ceramic and lithic artifacts is the subjectof an on-going research project.11

In the case of the purple Theran material, the highBr concentration strongly indicates a Br-enrichmentmechanism which naturally led to the possible presenceof an organic dye. More specifically it pointedto the precious ‘royal’ or ‘Tyrian’ purple, basedon 6,6-dibromoindigotin, C16H8N2O2Br2, derived from



Figure 3. XRF spectrum of the purple material from Akrotiri, Thera (inset photograph), showing high Br concentration.

murex shells (Murex brandaris and trunculus) andrelated species (Purpura haemastoma), which wasidentified by Friendlander in the beginning of thecentury.12

The organic nature of the dye was confirmed by dis-solving a small quantity in HCI and treating the solutionwith CHCl3 and observing the purple colouring in thephase of the solvent. A stoichiometric calculation of Brcontent in the molecule of 6,6-dibromoindigotin leadsto 1.5% (w/w) for the dye compound contained in thesample.

XRD analysis of the bulk material indicated the abun-dant presence of aragonite and calcite. The presence ofaragonite, which is the characteristic phase of CaCO3, insea-shells combined with the high Br concentration ledto the conclusion that the material in question originatedfrom crushed and pulverized live molluscs possibly fol-lowed by sieving, thus leading to a concentrated dye. Theoriginal study13 suggests a cosmetic use of the materialalthough its use as a wall painting pigment cannot beexcluded, especially in view of a recent identification ofthe material in Minoan wall- paintings from the MinoanPalace at Malia,14 Crete (Fig. 1). Subsequent analysisof pigments from Theran wall paintings9 based on theuse of analytical scanning electron microscopy–electronprobe microanalysis (SEM–EPMA) would not have beenable to detect Br. We therefore believe that all futureanalyses of wall paintings, Theran or Minoan, shouldinclude XRF-based Br detection. This becomes partic-ularly relevant following the advent of portable XRFsystems.

Tyrian purple in a calcitic matrix, referred to as‘purpurissum,’15 had been also identified in most of thepurple pigments contained in the ceramic bowls foundin Pompeii.16 It is widely known that Tyrian purple wasamongst the most expensive of antiquity’s goods, reservedfor kings, emperors and the upper classes of society. It isalso known that Phoenicians dominated the trade of theprecious dye in the Mediterranean basin during the his-toric period. It therefore becomes clear that the evidenceof its use in Crete and the Aegean, prior to its introductionby Phoenicians, is obviously important for the prehistoryof the Aegean.17,18

1994–96; CYPRIOT TERRACOTTA FIGURINES:CINNABAR OR OCHRE-BASED RED?

The study of six Cypriot–Archaic polychrome terracottafigurines (750–475BC) of the Louvre Collection19 byusing the proton induced x-ray emission (PIXE) non-destructive technique of the AGLAE accelerator facility20

of the Laboratoire de Recherches des Musees de Francerevealed the presence of cinnabar (mercury sulphide, HgS)in the red pigment of one figurine representing a horse-rider (Fig. 4, left). Interestingly, the blue-green pigment onthe same figurine was identified as a zinc-based material,which was initially related to the natural zinc carbonate(smisthonite). These observations provided a contrast withthe most frequent use of ochre for the red and greenearth (celadonite) for the green, detected in the rest ofthe figurines which have been analysed. The latter twominerals (i.e. iron hydroxides and green earth) are abun-dant in Cyprus, whereas cinnabar and smisthonite are notknown to be present in the island. A plausible explana-tion was that the use of such pigments, probably importedfrom Anatolia or even Spain, characterizes the produc-tion of a distinct ceramic workshop. The consolidationand interpretation of this suggestive evidence could onlybe achieved through a large-scale systematic study, whichwas undertaken during a wider project referring to thediachronic investigation of ceramic decoration techniquesin ancient Cyprus.

As a follow-up of the above study, all figurines of theNicosia Museum collection on which the red paint wasstill preserved (43 pieces in total) were analysedin situusing a portable XRF system. The system was built at theInstitute of Nuclear Physics, NCSR Demokritos and con-sisted of a109Cd source, a Peltier-cooled Si(PIN) detectorand portable data acquisition and analysis systems.

A typical example of these terracotta figurines that rep-resent singers and musicians, riders and horses, chariots,animals and birds is given in Fig. 5. As shown in a typ-ical x-ray spectrum in Fig. 6(a), the red pigment is aniron-rich material obviously derived by the use of ochrewithout signs of mercury in their XRF spectra. In view ofthese results it was then safe to conclude that the pres-ence of mercury sulphide (i.e. cinnabar) in the single



Figure 4. Cypriot terracotta figurines representing a complex of a horse and a rider (Cypriot-Archaic I, ca 750–600 BC), Musee duLouvre. The one on the left (No. AM 235, height 12.3 cm) revealed the unusual presence of cinnabar for the red and a zinc-basedmaterial for the green (photograph provided by D. Bagualt).

Figure 5. Cyproarchaic terracotta figurines (750–475 BC) from the collection of the Nicosia Museum analysed in situ with a portableXRF system.

figurine in the Louvre Museum must be attributed to post-excavation retouching having taken place in the period1870–80 when the above terracotta collection was boughtby the Louvre Museum. The date coincides with the firstintroduction of synthetic cinnabar, commonly known asvermilion. As for the blue–green Zn-based pigment, giventhe restriction of performing exclusively non-destructiveanalyses, PIXE results alone could not allow the drawing

of any reliable conclusion on the nature of this pig-ment. We note, however, the introduction of a syntheticblue–green pigment known as Rinmann’s green whichwas based on ZnO with varying CoO content21 by theend of 19th century.

The collection of 43 figurines was examined in less than2 h. This illustrates the power of new technology in a casewhere the archaeological question is very specific.



Figure 6. Typical XRF spectra of (a) Fe-rich red pigments and(b) Fe-rich and Mn-rich black pigments on Cypriot ceramicsfrom the Nicosia Museum. The spectra were obtained in situ atthe Nicosia Museum with a portable XRF system consisting ofa Peltier-cooled x-ray detector (XR-100T, 240 eV resolution atMn K˛ and a 109Cd radioactive x-ray source (20 mCi).

A recent analysis of similar terracotta figurines fromthe Cesnola Collection of the Metropolitan Museum ofFine Arts in New York by the SEM–EPMA techniqueverified the presence of iron-based red pigment in allfigurines examined. The analysis was undertaken in thecourse of the conservation procedure,22 as part of thereinstallation of the Metropolitan Museum of the Cypriotgalleries scheduled for the spring of 2000. The 230Cypriot–Archaic figurines of the Cesnola collection con-stitute one of the most significant collections of theseobjects and this will be their first exhibition since 1873,when they were brought to New York from Cyprus.

1996; CERAMIC DECORATION TECHNIQUES INCYPRUS: Fe- OR Mn-BASED BLACK?

Ceramic artifacts provide excellent material against whichcultural interactions can be studied since they containmulti-dimensional information with respect to the shape,the style of decoration (incised, painted, plastic), the fab-ric, the raw materials used, the manufacturing techniques,etc. It is now widely recognized that the investigation ofancient ceramic technology, which was usually based onthe analysis of the ceramic body in the past, can be com-plemented through the analysis of the pigments used forthe surface decoration.

The ceramics in the Cyprus Museum in Nicosia providea complete and comprehensive archaeological collection

for the study, which spans more than 40 centuries fromNeolithic to Hellenistic times (5000–325BC). Owing tothe nature and wealth of the material, the first step of theproject consisted of anin situ survey using non-destructiveXRF analysis and examination under a stereoscope, inconjuction with digital recording of visual information(digital camera, 3-D image recording system).23

The XRF analysis of 75 ceramic artifacts revealed avery clear chronological pattern in the nature of the ubiq-uitous black or dark colour [Fig. 6(b)]. Essentially all darkdecorations in Cypriot pottery from the Neolithic to theMiddle Bronze Age (5000–1625BC) are based on the useof iron-rich materials. As is well known, iron-rich clays(Fe2O3 ¾9–18%) with low CaO (<3%) and relativelyhigh K2O content (¾3.5–6%) produce dark-coloured pig-ments when fired in a reducing atmosphere and for thisreason the technique is mostly known as ‘the iron reduc-tion technique.’ From the end of the Late Bronze Ageonwards (1050–325BC), the dark colours were achievedthrough the use of Mn ores (umbrae). These materials withvarying Mn3O4 (2.5–15%) and Fe2O3 (20–65%) contentsproduce black or brown easily with firing without anyspecial requirements in kiln atmosphere. Figure 7 summa-rize the XRF results and shows clearly that the transitionbetween the two dark-colour techniques occurs during theLate Bronze Age (1625–1050BC) on the so-called WhiteSlip Pottery (WSI and WSII shreds in Fig. 7).

The alternative use of Mn-rich and Fe-based black indi-cates the use of both different raw materials and firingprocesses, which consequently point to different tech-nological traditions.24 – 26 The latter, seen in the contextof the different ethnic origins of the various pottersin Cyprus (native Cypriots, Cretans, Mycenaeans, Syro-Palestinians, Phoenicians) during several periods wasinitially attributed27 either to the introduction of newproduction techniques or the resistance of local tradi-tion to external influence. Recent detailed analyses on awell documented sequence of this characteristic Cypriotpottery28 revealed that the change from Fe-black, in WSI,to Mn-black, in WSII monochrome ware was introducedthrough the bichrome WSI wares in order to facilitate thesimultaneous production of red and black on the sameobject. Whereas the ancient craftsmen were able to pro-duce black and red, separately, using iron-based pigments,when called upon to produce a bichrome effect they foundit more convenient to use Mn for the black. This is under-standable if we consider the difficulties of the fine tuningbetween firing atmosphere and temperature required toproduce a bichrome effect based on Fe only.29 It canthen be argued that given the availability of all requiredraw materials in Cyprus, the subsequent adoption of amore convenient technique for the production of darkmonochrome wares [see proto White Painted I (pWPI)and White Painted I (WPI) samples in Fig. 7] and its sub-sequent spread over the whole island was not surprising.

CONCLUSIONS

It is clear that the use of x-ray-based analytical techniquesprovide archaeologists with extremely important clues andinformation about our ancestors’ technology, commercialand cultural contacts. In return, physicists who employ



Figure 7. Chronological distribution of Fe- and Mn-based pigments produced by non-destructive in situ XRF analysis of 75 Cypriotceramic artifacts from the collection of the Nicosia Museum. The time-scale focuses on Late Bronze Age objects bearing monochromedark decoration.

these techniques do share with them the excitement of thesediscoveries and the joy of a significant participation in theprocess of understanding our history. Today, all EuropeanUnion research-funding agencies give significant priority to

the understanding and conservation of cultural heritage. Weare confident that in this framework, x-ray-based analyticaltechniques developed so far and the significant expertiseaccumulated will prove relevant to these projects.

REFERENCES

1. C. P. Swann, Nucl. Instrum. Methods B, 130, 289 (1997).2. M. F. Guerra, X-Ray Spectrom. 27, 73 (1998).3. C. Neelmeijer, W. Wagner and H. P. Schramm, Nucl. Instrum.

Methods B, 118, 338 (1996).4. S. E. Filippakis, B. Perdikatsis and T. Paradellis, Stud.

Conserv. 21, 143 (1976).5. S. Profi, L. Weier and S. E. Filippakis, Stud. Conserv. 19, 105

(1974).6. S. Profi, L. Weier and S. E. Filippakis, Stud. Conserv. 21, 34

(1976).7. M. S. Tite, M. Bimson and M. R. Cowell, in Archaeological

Chemistry III, edited by J. B. Lambert, Advances in Chem-istry Series, Vol. 205, p. 215. American Chemical Society,Washington, DC (1984).

8. V. Perdikatsis, in La Couleur dans la Peinture et l’Emaillagede l’Egypte Ancienne, edited by S. Colinart and M. Menu,Vol. 4, p. 103. Centro Universitario Europeo per i BeniCulturali, Ravello (1998).

9. V. Perdikatsis, V. Kilikoglou, S. Sotiropoulou and E. Chrys-sikopoulou, in The Wall Paintings of Thera, Vol. I, edited byS. Sherratt, Thera Foundation Petros M. Nomikos and TheraFoundation, Athens, in press.

10. A. Evans, The Palace of Minos at Knossos, I. Macmillan,London (1921).

11. E. Aloupi, A. Karydas, T. Paradellis and I. Siotis, paper pre-sented at the 31st International Symposium of Archaeome-try, Budapest, April–May 1998.

12. P. Friendlander, Ber. Dtsch. Chem. Ges. 42, 765 (1909).13. E. Aloupi, Y. Maniatis, T. Paradellis and L. Karali-Yanna-

copoulou, in Thera and the Aegean World III, editedby D. A. Hardy, C. G. Doumas, J. A. Sakellarakis andP. M. Warren, Vol. I, p. 488. Thera Foundation, London (1990).

14. Ch. Boulotis, Glaas III: the Frescoes. Archaeological Society,Athens, to be published.

15. S. Augusti, I Colori Pompeiani, pp. 73–76 De Luca, Rome(1967).

16. A. Donati, Romana Pictura, pp. 95, 203. Electa Milan. (1998).17. D. S. Reese, Annu. Br. Sch. Athens 82, 201 (1987).18. R. R. Stieglitz, Bibl. Archaeol. 57, 46 (1987).19. E. Aloupi and D. Mc Arthur, in The Coroplastic Art of

Ancient Cyprus, IV, edited by V. Karageorghis, Vol. IV, p. 145.A. G. Leventis Foundation, Nicosia (1995).

20. M. Menu, Nucl. Instrum. Methods B, 45, 597 (1990).21. R. J. Gettens and G. L. Stout, Painting Materials. Dover, New

York (1966).22. L. Barnes and E. Salzman, in Glass, Ceramics and Related

Materials, edited by A. B. Paterakis, p. 71. EVTEK Instituteof Arts and Design, Department of Conservation Studies,Vantaa, Finland (1998).

23. E. Aloupi, A. Karydas, P. Kokkinias, D. Loukas, T. Paradellis,A. Lekka and V. Karageorghis, in Proceedings of the3rd Symposium on Archaeometry of the Greek Societyfor Archaeometry, Athens, 1999, edited by Y. Bassiakos,E. Aloupi and G. Fakorellis, in press.

24. W. Noll, Ber. Dtsch. Keram. Ges. 59, 3 (1982).25. R. E. Jones, in Greek and Cypriot Pottery, The British School at

Athens, Athens, Fitch Laboratory Occasional Papers 1 (1986).26. E. Aloupi and Y. Maniatis, in Thera and the Aegean World

III, edited by D. A. Hardy, C. G. Doumas, J. A. Sakellarakisand P. M. Warren, Vol. I, p. 459. Thera Foundation, London,(1990).

27. V. Karageorghis, N. Kourou and E. Aloupi, in OpticalTechnologies in the Humanities, OWLS IV, edited byD. Dirksen and G. von Bally, p. 3. Springer Berlin (1997).

28. E. Aloupi, V. Perdikatsis and A. Lekka, in White Slip Ware,edited by V. Karageorghis. A. G. Leventis Foundation,Nicosia, not yet published, in press.

29. M. Tite, M. Bimson and I. C. Freestone, Archaeometry 25, 17(1983).


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Pigment analysis of wall paintings and ceramics from Greece and Cyprus. The optimum use of x-ray spectrometry on specific archaeological issues