Radiation Physics and Chemistry 61 (2001) 717–719

Analysis of fresco paintings by X-ray fluorescence method

T. $Cech!aka,*, J. Gerndta, L. Mus!ıleka, I. Kopeck!ab

aCTU Prague, Faculty of Nuclear Science and Physical Engineering, B$rehov !a 7, 115 19 Praha 1, Czech RepublicbState Institute for Preservation of Historic Monuments, Vald$stejnsk !e n !am $est!ı 1, 110 00 Praha 1, Czech Republic

Abstract

An XRF technique was used for the analysis of fresco paintings. The analysis of paintings makes it possible toexamine pigmented materials. An application of the method is used to illustrate the technique.r 2001 Elsevier Science

Ltd. All rights reserved.

Keywords: X-ray fluorescence analysis; Fresco paintings; Si(Li) detector

1. Introduction

Nuclear techniques represent invaluable tools in non-destructive diagnostics which is applied to archaeologi-cal findings and objects of arts, mainly for dating anddetermining the composition of materials used in the

production of artefacts (Bonizzioni, 1998). In this workwe present the application of X-ray fluorescence analysis(XRFA) in examining fresco paintings from Karlstejn

castle and Zirovnice castle.

2. Present investigation

The X-ray fluorescence apparatus built and operatedby the Laboratory of Quantitative Methods in Researchof Ancient Monuments (FNSPE, TU Prague) was used

for the purpose of inspecting fresco paintings. The X-raysources (radionuclides) generate characteristic X-rayphotons from the sample. The Si(Li) detector measures

the numbers and energies of the photons emitted fromthe specimen. The energy and number of photonsdetected determine each element and the amount of

measured atoms respectively. These results give data forqualitative and quantitative analysis of the samples.XRFA is a relatively simple and non-destructive

method. The capability for in-situ measurement is one

of the big advantages of this method. Appropriateradionuclide source for the exciting of XRF radiation

were used (e.g. 55Fe enables excitation of elements withZ up to 23, 238Pu is used for elements in the interval 20–39, etc.). A Si(Li) semiconductor detector with a 5 lDewar vessel and portable spectroscopy system was

used to allow in situ measurement. Narrow collimationof the exciting beam makes it possible to select a givenarea of the fresco painting.

Fig. 1 shows the spectrum of green pigment in a frescofrom the Zirovnice castle. Cu-malachite (Cu-CO3 �Cu(OH)2) has been found mostly on wall paintingsfrom the 7th to the 18th century, while other copperbased pigments, for example: mountain-green, sea-greenor Sheel’s-green were not considered since in the yearsduring which the painting was being completed. Copper-

green (Cu(CH3COO)2.Cu(OH)2.nH2O) was not beingused for wall paintings. In addition, detection has beenmade of Cl as an additive of malachite, available in

Czech lands from mineral chlorite and of Fe as anadditive to earth-green (a mixture of indefinite composi-tion of hydro-silicates, containing glaukonite or selado-

nite, in which the coloring element was Fe2+). Use wasnot restricted to any particular historical time.Pb has also been found, being an additive of lead-

cinite yellow (Pb2SnO2 or Pb2Sn2SiO7)Fused from the13th to the 17th century and in lead-white (2PbCO3 �Pb(OH)2) used with no time restriction. The measuringequipment did not allow estimates of additives of Sn or

As which were normally accompanying elements in*Corresponding author. Fax: +420-2-2320861.

E-mail address: cechak@br.fjfi.cvut.cz (T. $Cech!ak).

0969-806X/01/$ - see front matter r 2001 Elsevier Science Ltd. All rights reserved.

PII: S 0 9 6 9 - 8 0 6 X ( 0 1 ) 0 0 3 8 5 - 1

natural sources of lead-white. The other possible sourceof lead is massikote known as lead-yellow (PbO) the

latter being used in Europe from the 15th century.Fig. 2 shows the spectrum of blue pigment in the

fresco from the Zirovnice castle. (Cu)-azurite (CuCO3.-

Cu(OH)2) was used in Europe from the 15th to the 16thcentury (other blue pigments containing Cu includingmountain blue or Egyptian-blue, are not consideredbecause of the date of the painting). Fe is possibly an

impurity contained in azurite, or might otherwise have

come from later retouching (restoration in the 1960s)

that may have used Prussian-blue (Fe4(Fe(CN)6)).XRF techniques also make it possible to have simple

determination of fresco parts which was restored. See

for example Fig. 3.

3. Conclusion

The valuable fresco paintings from the Karlstejncastle and Zirovnice castle were investigated using

XRFA. The measurements were carried out in colla-boration with the Analytical Laboratory of the StateInstitute for the Preservation of Historic Monuments.

Suitable analysis of paintings makes it possible to detectthe types of colours and to evaluate changes in the

Fig. 1. Green pigment malachite in a fresco from the Zirovnice

castle (15th century).

Fig. 2. Blue pigment azurite in a fresco from Zirovnice castle

(15th century).

Fig. 3. Comparison of red pigments in the fresco from the

Karlstejn castle, 14th century (above) and 19th century after

restoration (below).

T. $Cech !ak et al. / Radiation Physics and Chemistry 61 (2001) 717–719718

surface colour of paintings and suggest useful and timelyprocedures for their conservation and restoration.

Acknowledgements

This work was supported by the Research ProjectJO4/98:210000019 and grant VS 96052 of the Ministryof Education, Youth and Sports of the Czech Republic.

References

Bonizzioni, L., et al., 1998. TXRF analysis applied to

environment monitoring and archeometry. Proceedings of

the European Conference on Energy Dispersive X-Ray

Spectrometry, Bologna.

T. $Cech !ak et al. / Radiation Physics and Chemistry 61 (2001) 717–719 719