Identification of colourants in icons of the Cretan School of iconography using Raman spectroscopy and liquid chromatography

Ioannis Karapanagiotis, Dimitrios Lampakis, Alexander Konstantas, Helen Farmakalidis

Journal of Archaeological Science 40 (2013) 1471-1478

The stratigraphies of twenty-five (25) samples removed from twenty (20) icons of the Cretan School of iconography are studied using Optical Microscopy and micro-Raman spectroscopy. The objects are dated in 15the17th c. and belong to the collection of the Benaki Museum, Athens, Greece. Cinnabar, red ochre, minium, yellow ochre, azurite, malachite, lapis lazuli, lead white, carbon black, and indigo are identified in the cross-sections of the icon samples using Raman spectroscopy.

**Fig. 1.** (a) The Birth of St. John the Baptist, unknown, 43 x 32 x 1.5 cm (icon 3732) and (b) St. Luke painting the Virgin, signed by Domenicos Theotokopoulos, 41 x 33 x 2 cm (icon 11296), Benaki Museum, Athens, Greece.

For four (4) icons no data were available from previous investigations regarding the identity of the red organic colourants. Microsamples were extracted from these icons and analysed using High-Performance Liquid Chromatography coupled to a Diode Array Detector (HPLCeDAD). The HPLCeDAD results provide support to recently published reports which showed that kermes used in Cretan icons of the early period was replaced by cochineal after the discovery of the New World. The study of the cross-sections of the icon samples with Optical Microscopy revealed the combinations of the various inorganic and organic colourants.

**Fig. 2.** Icon 22251; sample of orange light. Sample’s cross-section in (a) reflected and (b) UV light are shown. Four Raman spectra which lead to the identifications of pigments in the sample’s cross sections are included as examples. In particular the following identifications are shown: (c) red ochre, (d) lead white. The complete stratigraphy (a, b) is as follows: (1) gesso ground; (2) imprimatura: red ochre, lead white and grains of carbon black and yellow ochre (3) underlay: organic lake and grains of lead white; (4) light: cinnabar and grains of lead white and yellow ochre; (5) varnish.

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