Gasanova et al. Herit Sci (2017) 5:33 DOI 10.1186/s40494-017-0145-2 RESEARCH ARTICLE Open Access Non‑invasive sub‑surface analysis of the male portrait underlying the Titian’s Studio Ecce Homo Svetlana Gasanova* , Nikolas Bakirtzis and Sorin Hermon Abstract The present study discusses new research on the analysis of a portrait of a male fgure discovered under the painting of Ecce Homo, attributed to the studio of Titian (ca. 1488–1576), with an estimated date in the 1550s. The portrait was examined with non-invasive methods: X-ray radiography (XRR), digital microscopy and micro-XRF. The examination of XRR images exposed the details of the painting’s underlying depiction, which according to the details preserved appears to be a completed or nearly fnished portrait of a standing man. The application of digital microscopy on the Ecce Homo painting’s cracks enabled the identifcation of the work’s stratigraphy. Micro-XRF performed on selected spots allowed to identify lead white, vermilion, red iron oxide, umber, carbon black and copper green in the underly- ing portrait. The described investigation methodology was guided by the close visual analysis of the Ecce Homo work and proved to be efective in the identifcation of the pigments of the hidden painting and the reconstruction of its colour palette. Keywords: Hidden painting, Micro-XRF, X-ray radiography, Digital microscopy, Titian, Ecce Homo Introduction the pictorial layers. However, the reading of XRR and IRR Te reuse and repainting of canvases was a common images might be complicated as the images result from practice in artists’ workshops. Artists often recycled overlap of all the pictorial layers. Te recently introduced these materials for various reasons such as unsuccess- terahertz (THz) imaging technique overcomes this obsta- ful compositions, unpaid commissioned paintings or cle by yielding a 3D structure. Being a complementary unsatisfed clients. Te number of discoveries related to technique to XRR and IR, in terms of pigment identifca- reused canvases hiding unknown preparatory drawings tion, THz imaging also allows the collection of data on or even fnished paintings under later applied composi- the thickness of various pictorial layers [8, 9]. Another tions is constantly growing [1–5]. Tis is mainly due to important method for the study of hidden paintings non-invasive imaging methods that are now at the dis- is neutron activation autoradiography (NAAR), which posal of scientists and are capable of reading the hidden allows the identifcation of a wide range of pigments compositions. Among these, X-ray radiography (XRR) [10]. Nonetheless, apart from the use of radioactive and infrared refectography (IRR) are the most con- sources, NAAR’s signifcant disadvantage is the absence ventional techniques for the identifcation and study of of portable devices requiring transportation of the ana- underlying paintings [6, 7]. Tese are fast and straight- lysed paintings to the dedicated laboratory. Providing forward methods able to image hidden compositions, additional research tools to address the challenges pre- provided that X-ray or IR opaque materials are present in sented in the study of paintings hidden under later picto- rial compositions, the scanner X-ray fuorescence (XRF) technique has the potential to not only reveal contours *Correspondence: [email protected] of underlying works, but also to yield maps of elemental The Science and Technology for Archaeology Research center (STARC), The Cyprus Institute, 20 Konstantinou Kavaf street, Aglantzia, distribution, thus, suggesting the presence of certain pig- 2121 Nicosia, Cyprus ments [11–16]. © The Author(s) 2017. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/ publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Gasanova et al. Herit Sci (2017) 5:33 Page 2 of 11 Te above described techniques are powerful tools, a gesture of self-exoneration that resonates with the bibli- which are rapidly developing and conquering the feld cal narrative of the depicted scene. To the right of Christ’s of the heritage science. However, there are only a few fgure stands a youth, presumably a boy. He is wearing a laboratories, which are able to aford and support the bright blue headscarf, while a bright red earing adorns his development of such advanced infrastructure. Tus, the right ear. Te youth is holding the rope bounding Christ’s technical examination of works of art and hidden paint- hands. Behind this fgure and over Christ’s right shoulder ings in particular, has become a challenge for laboratories is the head of another participant, seemingly a man hold- with limited scientifc facilities. In the present study, we ing a pole with a lighting device in the form of a brazier propose a multi-technique approach based on the inte- containing bright red coals. gration of XRR as the frst step in the delineation of the Prior to its acquisition by the current owner, the paint- contours of hidden compositions, digital microscopy ing underwent preliminary XRR, which revealed an for the examination of painting stratigraphy and micro- underpainting depicting the portrait of a standing man. XRF for pigment identifcation. Te aim of the study is Tis work was overpainted with the Ecce Homo at a 180° to reveal the potential of the proposed approach in the angle. No further art historical information was available identifcation of the compositional elements and the pig- on the initial painting in regards to its subject, colour or ments of hidden paintings. pigment composition. Te present study is part of a com- Te analysed case study is the painting of Ecce Homo plex technical examination of the Ecce Homo painting, (Fig. 1a, oil on canvas, 94 × 107.5 cm), attributed to Tit- involving the analysis of the preparation layers, canvas ian’s studio with a suggested date in the 1550s [17]. Te treatment, pigments, binding media, varnish, conserva- work depicts the theme of Ecce Homo (“behold the tion state and history of restorations. man”), a topic explored by Titian in the later phase of his artistic career in a series of paintings [18, 19]; at least fve Methods other known works are now kept in Saint Louis, Dresden, X-ray radiography Te Prado, Munich and Hampton Court. Te work, also Te digital XRR was performed at the radiology depart- identifed as “Christ mocked”, provides a close up view of ment of the Mediterranean Hospital of Limassol. Images the meeting of Pontius Pilate and Christ, a compositional were obtained in transmission mode from a Cu X-ray perspective that departs from other versions of the topic tube operated at 30 kV, 500 µA. Te acquisition time was featuring more distant views of the event such as his 1543 set to 20 ms. Te painting was positioned facing the digi- work, now at the Kunsthistorisches Museum in Vienna. tal detector (DX-D 40G, Agfa, 35 × 45 cm) with the dis- In the examined work, the central fgure of Christ is tance between the X-ray source and the detector of 1.2 m. depicted naked, bound and crowned with a wreath of Fifteen (15) images were taken in total, in order to cover thorns. Standing along his left side is Pilate, dressed in the roughly 1 m2 of the canvas and its wooden frame. a lavish costume and wearing an elaborate turban-like Tese were frst processed with an X-ray medical imaging headpiece. He is raising his left hand with an open palm, software (eFilm Workstation) and then exported into an Fig. 1 The Ecce Homo painting: a visible image, b X-ray radiography image and c X-ray radiography image rotated at 180° revealing the hidden portrait Gasanova et al. Herit Sci (2017) 5:33 Page 3 of 11 image processing software (Adobe Photoshop 2015) for XRR and microscopy observations) and pigment com- fnal alignment and detection of features’ contours. position between the upper and the lower paintings were analyzed. To achieve this step of the process, the visible Digital microscopy image was compared with the XRR image in every spot Te surface of the upper painting was photographed with analyzed. For example, the area of man’s left cuf exe- a Hirox KH-8700 digital microscope at various magnif- cuted with a white (based on microscopy observations) cations (35×−2500×) according to the target, using the pigment corresponds to a dark brown background of Ecce dual illumination revolver zoom lenses. Tis test allowed Homo, which allows to suggest the presence of diferent to check the presence of underlying layers, their color as pigments in the upper and the lower paintings. Addition- well as to study the pigment particles. ally, we predominantly chose areas of the lower painting, which correspond to homogeneous areas of Ecce Homo. XRF Tis allowed to assume the equal contribution of the XRF conditions upper painting signal in the resulting XRF spectra within Te XRF spectra were recorded with an ARTAX- the area of interest. For example, spectra from all spots 200 μ-XRF spectrometer (Bruker), equipped with a in the area of man’s left hand (lower painting) have equal molybdenum X-ray tube, an integrated CCD camera with contribution from the corresponding homogeneous area sample illumination and laser spot, a silicon drift detector of Ecce Homo. Tus, the diference in spectra from spots with a resolution of <150 eV and a 0.65 mm collimator.