Identification of pigments used on late 17th century Albanian icons by total reflection X-ray fluorescence and Raman microscopy

Identification of pigments used on late 17th century Albanian icons bytotal reflection X-ray fluorescence and Raman microscopy

Nikolla Civici a, Ornela Demko a,b, Robin J.H. Clark b,*a Institute of Nuclear Physics, P.O. Box 85, Tirana, Albania

b Christopher Ingold Laboratories, University College London, 20 Gordon Street, London WC1H 0AJ, UK

Received 10 January 2005; accepted 18 January 2005

Abstract

The pigments identified on four beautiful icons painted by Constantin Ieromonachou during the late 17th century in churches of themedieval city of Voskopoja (Moschopolis) in south-east Albania have been identified. The analysis was carried out to establish whether thesame pigments were used on all the icons and whether this information could form a basis for future restorations. Total reflection X-rayfluorescence (TXRF) and Raman microscopy (RM) were both used to identify the pigments and the combination of techniques minimised thenumber and amount of samples which needed to be taken from each icon for the analyses. The main pigments identified were white lead,carbon black, indigo, gold, red ochre, red lead, ochre, gypsum, vermilion and a copper-based green.© 2005 Elsevier SAS. All rights reserved.

Keywords: Albanian icons; Constantin Ieromonachou; Pigment analysis; TXRF; Raman microscopy

1. Introduction

The study of the pigments on old icons, paintings or wallpaintings may provide information of great importance torestorers, museum curators and/or art historians, who needthis to select the best ways to restore works of art and to iden-tify the best preservation conditions. Art historians can thenbuild up a whole picture of the materials that make up a paint-ing [1].

Recently many instrumental techniques have been appliedto the study of works of art. Simple microchemical reactionspreviously used to identify pigments under a microscope [1,2]have in recent years largely been superseded by the use ofspectroscopic methods such as total reflection X-ray fluores-cence analysis (TXRF) and Raman microscopy (RM) for thispurpose [3–5]. The application of TXRF to pigment identifi-cation is based on the identification of one or more of theelemental constituents of a pigment. Having high sensitivityfor elements with atomic number greater than 18, TXRF isvery effective for the identification of most inorganic pig-

ments and, due to its high sensitivity, samples in the micro-gram range can be analysed. RM, being a technique that givesinformation about molecular structure, can be used to iden-tify both organic and inorganic pigments with comparableease [6]. A disadvantage of the technique is the possible pres-ence of broad-band fluorescence which may overwhelm theRaman signals, especially from varnished works of art suchas oil paintings or icons.

The results reported herein were obtained from the analy-sis of the pigments used on four beautiful icons painted byConstantin Ieromonachou during the period from the late 17thto the early 18th centuries; the icons are held in two churchesof the medieval city (now a village) of Voskopoja (Moschopo-lis), some 20 km north-west of Korcha in south-east Albania.The objectives were to establish whether the same pigmentswere used on all the icons and whether this information couldbe a basis for the future restoration of such icons. TXRF wasused to suggest the identities of the inorganic pigments presentand RM to confirm these and to identify any organic pig-ments present. This combination of techniques allowed thenumber and amount of samples taken from the icons for RManalysis to be minimised.* Corresponding author.

Journal of Cultural Heritage 6 (2005) 157–164

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2. The icons studied

Ieromonachou was one of the talented and productive ico-nographers of the period 1693–1726. His work is docu-mented for several icons in churches situated in central andsouth-east Albania, the icons being distinguished for theirmonumentality. It is believed that his main workshop was inVoskopoja and that, besides being a great master, he wouldhave been an authoritative personality among the clergy ofthe city [7].

The icons studied are painted as tempera on wood. Thoseentitled “St. John Vladimir” (133 cm × 67.5 cm, Fig. 1A) and“Noli me tangere (Do not touch me)” (54 cm × 35 cm, Fig. 1B)belong to the cathedral church of the “Dormition of the Vir-gin”, while those of “St. Demeter” (107 cm × 70 cm, Fig. 1C)and “Christ’s entry into Jerusalem” (54 cm × 37 cm, Fig. 1D)belong to the basilica of St. Nichola. The icon of “St. Deme-ter” is signed by Ieromonachou whereas the others are attrib-uted to him on the basis of stylistic evaluations. The icons arepreserved at the Department of Korcha of the Institute of

Fig. 1. Photos of the icons studied.

158 N. Civici et al. / Journal of Cultural Heritage 6 (2005) 157–164

Monuments of Culture, while pictures associated with thedescription of the icons are published by Kallamata [8].

St. John Vladimir is still a very popular Saint, veneratedby the Orthodox, Catholic and Muslim peoples alike in theregions of the ex-Archbishopric of Ohrid. St. John was a 10thcentury Serbo-Christian prince from Kraja, north of Shko-dra, who married the daughter of the Bulgarian King Samueland later was beheaded in Ohrid by his brother-in-law, KingVladislav. St. John was buried at a church near Elbasan (cen-tral Albania), which he had built after a vision he had hadduring a hunting ride. His wife built a house near the churchand lived there until she died, following which the monasteryin his name was founded. In this icon the Saint is depictedfull-length, dressed in princely vestments and mitre, holdinga cross in the right hand and his decapitated head in the left.A detail in the bottom right shows this monastery.

The icon “Do not touch me (Noli me tangere)” shows theappearance of Christ to Mary from Magdala and Mary themother of Jacob, after his resurrection. The women are kneel-ing symmetrically on either side of Christ; he is depicted fromthe front wearing a gold himation and at a greater size thanthe women, whom he is blessing. The main figures are setbetween two symmetrical hills, luxuriant with vegetation, withthe image of the city of Jerusalem in heaven depicted at thetop.

The icon dedicated to “St. Demeter” shows the scene inwhich the Saint is killing the gladiator. St. Demeter, the pro-tective saint of Thessaloniki, is shown in decorated militarydress mounted on a red horse. Particularly interesting is thedepiction on the right of the towering city of Thessalonikisurrounded by two fortified circular white walls. Houses out-side the walls show the extension of the city. A prismaticmountain and hills with sparse foliage form the landscapearound the bay, on which sailing warships are shown.

The icon “Christ’s entry into Jerusalem” shows Christmounted on a donkey entering into the city of Jerusalem. Infront and to the right of its walls, is depicted a crowd of peoplewaiting to greet Him. His disciples on the left are followingtheir Master, the whole atmosphere being festive. The elon-gated mass of the city walls of Jerusalem on the right is bal-anced by a tall hill on the left. This event is celebrated on theSunday before Easter (Palm Sunday).

3. Experimental

3.1. Sample collection

For TXRF analysis the pigment micro-samples were col-lected according to the method proposed by Klockenkamperet al. [3,4]. A small amount of material is rubbed off thepainted object within a restricted area by means of a dry cot-ton bud (a Q-tip). This method is almost non-destructive as itleaves no visible damage, and is effective if the painted areais not covered by varnish. However due to the protective layerof varnish on the surface of each icon, two Q-tips were used

at each point sampled. The first was wetted with an organicsolvent such as alcohol or acetone and used to remove thevarnish; the second, used dry, was then used to collect thepigment sample. On completion of the analysis all the smallexposed areas were again covered with varnish. Ten to fifteenmicro-samples covering the main colours and their hues werecollected from each icon. The sampling points are indicatedby numbers inserted on each of Figs. 1A–D. Finally a smallamount of sample was transferred from a Q-tip to a glasscarrier and analysed by TXRF.

The samples for RM were collected by removing smallpieces of pigment and ground from near to areas already dam-aged, special attention being paid to avoid further damage.Only a few samples of this kind were collected from the iconsof “St. John Vladimir” and “St. Demeter”. These samplescould be analysed directly on the spectrometer.

3.2. Instrumentation

The TXRF analysis system is composed of a tube excita-tion system, a total reflection module, an X-ray spectrometerand spectrum acquisition system together with quantificationsoftware. A Philips PW 1729 X-ray generator (50 kV, 50 mA)and a Mo anode fine focus X-ray tube (Philips PW 2215/20)were used for excitation. The total reflection module designedat the Vienna Atominstitute [9] and provided by the Interna-tional Atomic Energy Agency was attached to the X-ray tube.In order to reduce the background, a tungsten/carbon multi-layer monochromator (Osmic Inc., USA.) was used insteadof a cut-off reflector for monochromatisation of the primaryradiation from the tube. The incident angle of the primaryX-ray beam on the multilayer is adjusted to the diffractionangle of Mo Ka radiation, which should be about 0.51° forthis multilayer [10]. After adjustment of the total reflectionangle on the sample carrier, a spectrum with low backgroundis achieved. The X-ray spectrometer consisted of a Si(Li)detector (PGT, 30 mm2, 3 mm sensitive depth) with a resolu-tion of about 165 eV at 5.9 keV, the spectrum acquisitionsystem (Canberra) of a Mod 2024 fast spectroscopy ampli-fier, a Mod 8076 ADC, a Mod 3105 high voltage power sup-ply and a Genie 2000 MCA.

During the measurements the generator was operated at40 kV and 40 mA, the samples being measured for times vary-ing from 200 to 1000 s. The program AXIL [11] was used foranalysing the spectra. The internal standard method was uti-lised for the quantification of data via the program ’Regres-sion of Count Rates vs. Concentration’ from the QXAS soft-ware package [12] distributed by the International AtomicEnergy Agency. Lead, which was found in most of the pig-ment samples, was usually used as internal standard; where itwas absent, the element with the highest intensity was usedas internal standard. The relative concentrations were laternormalised to 100% and the final values represent the con-centrations relative to the total of all elements detected.

Raman spectra were recorded using a Renishaw System1000 Raman spectrometer, configured with an external Olym-

159N. Civici et al. / Journal of Cultural Heritage 6 (2005) 157–164

pus BH-2 confocal microscope, an air-cooled 21 mW Ar-ionlaser light source (514.5 nm), an air-cooled 20 mW He–Nelaser light source (632.8 nm) and an air-cooled CCD detectoroperating at –70 °C. In this instrument, neutral density filterswere used to set the laser power at the sample surface to avalue of between 0.5 and 6.0 mW. In order to avoid the unde-sirable Rayleigh scattering, two 100 cm–1 notch filters wereused. Wavenumber calibration was achieved by superposi-tion of neon emission lines on the spectrum recorded for eachpigment. It is expected that all band wavenumbers quoted areaccurate to ± 1 cm–1.

The spectra were collected using a He–Ne laser operatingat 632.8 nm. Due to the high fluorescence of the samples onlya short collection time was used and only a few scans weretaken. Data were collected via a PC, and the software pack-age GRAMS/32 (Galactic Industries, Salem, USA) was usedfor spectral analysis. The identification of the pigments wasperformed by comparing the measured spectra with the datain Raman libraries [5,13].

4. Results and discussions

For a better comparison of the pigments used on differenticons, the results obtained by TXRF analysis of the samplesare grouped into charts according to the colour of each pig-ment (Figs. 2-6). The results obtained by RM are also dis-cussed and some spectra presented (Fig. 7).

Ten samples, seven greys and one each of white, black andblue, were analysed by TXRF (Fig. 2). The common charac-teristic of these samples is that the major element detectedby TXRF is lead, together with small amounts of Ca, Feand Au in some cases. This suggests that white lead(2PbCO3·Pb(OH)2) was used as the white pigment on all ofthe icons and that probably at least some of the other pig-ments were applied over a layer of white lead, giving more

lightness to the overlayer. The application of a cochinealpurple lacquer over a layer of white lead has been detectedon an 18th century Greek icon [14]. The presence of lead inthe black sample may then arise from upward movement ofwhite lead from this layer. Carbon black was detected by RMas the main constituent of one black and two grey samples,while indigo was detected, also by RM, in one blue sample(Fig. 7). It seems that high broad-band fluorescence pre-vented the detection of white lead in the Raman spectra ofeither sample. The presence of carbon associated with a lowpercentage of Ca and Fe in the black sample indicates that amineral black pigment, probably charcoal/carbon black, wasused. Thus white lead was used as the white pigment andcarbon black as the black one. The grey and blue colours wereobtained by mixing the white pigment with carbon black andindigo, respectively.

Eight yellow samples were collected from the icons, andthe TXRF results on these are presented in Fig. 3. The mainelement detected in the first three samples, representing thebackground of the icons of “St. Demeter”, “St. JohnVladimir”and “Noli me tangere”, is gold which seems to have beenapplied as pure gold powder. Gold is also found in the samplecollected from the background of the icon “Christ’s entry intoJerusalem”, but here it seems to be mixed with other pig-ments containing Ca, Fe and Pb. Probably the gold was mixedwith yellow ochre (FeOOH), gypsum (calcium white,CaSO4·2H2O) or white lead. This kind of mixture, in differ-ent proportions, seems also to have been also used in the otheryellow samples collected from this icon, with hues rangingfrom pale to dark yellow.

Seven samples with colours ranging from ochre to darkbrown were collected from the icons “Noli me tangere” and“Christ’s entry into Jerusalem” and analysed by TXRF. Themain elements detected were Pb and Fe, associated some-times with smaller amounts of Ca, Au or Hg (Fig. 4). Thiskind of composition suggests a mixture of varying propor-

Fig. 2. The relative composition of black, grey, white and blue samples.


tions of red ochre (Fe2O3) with white lead. In this group isincluded the sample taken from Christ’s hair (point 10) onthe icon “Noli me tangere”, although this proved to be car-bon black.

Ten red samples, a colour which is widely used on all theicons, were collected from different points. The results of theTXRF analyses (Fig. 5) show that two kinds of red pigment,red lead (Pb3O4) and vermilion (HgS), were used, these pig-ments being identified by their key elements Pb for red leadand Hg for vermilion. Only red lead was detected on the iconof “St. John Vladimir”, whereas both red pigments were iden-tified on the others. In some of the samples based on vermil-ion, other pigments such as red ochre or calcium white andeven gold seem to have been added. Since by TXRF it is notpossible to determine whether the presence of lead in the redsamples implies the presence of red lead or white lead mixedin with the vermilion, two red samples were also studied by

RM. Only the main constituents, red lead and vermilion, couldbe detected in the Raman spectra (Fig. 7).

Pb and Cu were the main elements detected by TXRFon green samples from the icons “Noli me tangere”,“St. John Vladimir” and “St. Demeter” (Fig. 6). This sug-gests that a mixture of white lead with a copper-basedpigment, malachite (CuCO3·Cu(OH)2) or verdigris(Cu(CH3COO)2·nCu(OH)2), was used on these icons. Themain element detected in green samples from the icon“Christ’s entry into Jerusalem” was arsenic (Fig. 6), suggest-ing that this colour may arise from a mixture of the yellowpigment orpiment (As2S3) and a blue pigment such as indigo.Indigo was indeed detected in the Raman spectrum of one ofthese samples (Fig. 7), although it did not prove possible todetect any orpiment in this way. Mixtures of yellow and bluepigments (chrome yellow and ultramarine blue, respectively)

Fig. 3. The composition of yellow samples.

Fig. 4. The composition of ochre and brown samples.


have been identified previously on 19th/20th century over-paintings of Greek icons [15].

The ground layer of the samples collected for RM wasanalysed by TXRF. The main elements detected in all the spec-tra were Ca and S associated with traces of Sr, Fe and Pb. Thepresence of Ca and S suggests that the ground layer consistedessentially of gypsum. Strontium and iron could be impuri-ties in the natural gypsum, while lead probably arises fromthe thin layer of white lead presumed to have been applied atleast partly over the ground layer.

5. Conclusion

The main pigments used on the four icons painted by Iero-monachou at the end of the 17th century in two churches ofthe medieval city of Voskopoja have been identified by a com-

bination of TXRF and RM techniques. The results show thatonly a limited number of pigments were used for the differ-ent colours on the icons, a summary being given in Table 1.

The main white pigment used was white lead, while cal-cium white was identified mainly in some mixtures. Carbonblack seems to have been used as the black pigment and thegrey colour was obtained by mixing this material with whitelead. A mixture of white lead and indigo was used for theblue colour in the icon “St. Demeter”. Gold was used to deco-rate the background of the icons. A more complex mixture ofgold with yellow ochre and a white pigment was used for theyellow colour on the icon “Christ’s entry into Jerusalem”.Three red pigments were identified: red lead and vermilionwere used alone or in admixture, while red ochre mixed withwhite or red pigments, depending on the hue, was used forthe ochre or brown colour. A copper-based green pigmentsuch as malachite or verdigris was used for the green colour

Fig. 5. The composition of red samples.

Fig. 6. The relative composition of green samples.


on the icons “St. John Vladimir”, “St. Demeter” and “Nolime tangere”, while the green colour on the icon “Christ’sentry into Jerusalem” was obtained with a mixture oforpiment with indigo. The analytical results indicate that gyp-sum was used for the ground (preparation) layer of the iconsand that it was probably covered with a thin layer of whitelead.

The palette of the four Albanian icons studied appears tobe similar to, but slightly more diverse than, that of a 15thcentury Greek icon and a little less diverse than that of four18th century Greek icons recently studied [16].

References

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Fig. 7. The measured Raman spectra.

Table 1Summary of the main pigments identified

Colour St. John Vladimir Noli me tangere St. Demeter The Entering into JerusalemWhite White leadBlack Carbon blackGrey White lead +

carbon blackWhite lead +carbon black

White lead +carbon black

White lead +carbon black

Blue White lead +indigo

Yellow Gold Gold Gold Gold + yellow ochre +calcium or lead white

Ochre and brown Red ochre +white lead

Red ochre + white lead

Red Red lead Red lead, vermilion +red or white lead

Red lead + vermilion Vermilion + red or white lead

Green Malachite or verdigris Malachite or verdigris Malachite or verdigris Orpiment + indigo


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[14] D. Bikiaris, S. Daniilia, I. Papaggelos, Y. Chryssoulakis, in:K. Paraskevopoulos (Ed.), Non-destructive characterization of thepainting materials through micro-Raman and micro-ATR-FTIR spec-troscopic measurements: two case studies from the post-Byzantineiconography, in Physics in Culture, Aristotle University Publication,Thessaloniki, 2000, pp. 73–90.

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[16] L. Burgio, R.J.H. Clark, K. Theodoraki, Raman microscopy of Greekicons: identification of unusual pigments, Spectrochim. Acta A Mol.Biomol. Spectrosc. 59 (2003) 2371–2389.


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Identification of pigments used on late 17th century Albanian icons by total reflection X-ray fluorescence and Raman microscopy