Rodrigues et al. Herit Sci (2021) 9:22 https://doi.org/10.1186/s40494-021-00480-w RESEARCH ARTICLE Open Access A transparent dialogue between iconography and chemical characterisation: a set of foreign stained glasses in Portugal Alexandra Rodrigues1* , Mathilda Coutinho1,2, Andreia Machado1, Bruno A. Martinho3, Luís Cerqueira Alves4, Maria Filomena Macedo1,5 and Márcia Vilarigues1,5 Abstract This work presents the frst results of the iconographic study and analytical characterisation of a set of four stained- glass panels that are part of the collection of National Palace of Pena (Sintra, Portugal). These panels were collected by the King Ferdinand II in the mid-nineteenth century, for his main residence the Palace of Necessidades (Lisbon, Por- tugal), and only frst presented to the general public in 2011. This study contributes with the knowledge of Technical Art History and Heritage Science to a better and deeper understanding of their history, materials and techniques used in the production, where an art-historical and a scientifc approach are applied to attribute their origins. Based on the analysis of the formal and stylistic characteristic of the panels, it is proposed that the drawings used for the production of three of these panels may be based on the design and painting being carried out in the same workshop, and that the four panels have the same provenance (Germany). The composition of the glass and grisaille was determined and colourising elements were identifed. Through this approach, conclusive correlation between the analysed glasses was possible: all are calcium rich or calcium–potassium rich types, and the results also suggest that the same source of silica was used for their production. A typical mixture of glass and lead oxide was found in the grisaille applied on the painted panels. However, less usual was the use of a copper oxide pigment for the black grisaille. All these fndings support the proposals made regarding provenance and production period (ffteenth century). Keywords: Stained glass, Iconography, Chemical composition, µ-EDXRF, UV–vis spectroscopy, PCA Introduction social and cultural innovations. In the Middle Ages, Te art of stained glass has always sought to interact with stained glass gained an important role with the construc- the surrounding space by creating architectural planes tion of cathedrals, reaching its peak in the ffteenth cen- that allowed illumination while transforming the experi- tury with Gothic architecture. During the Renaissance ence of light into one specifc and meaningful to the pur- period, single glass sheet panels and roundels showing pose of a building [1]. From the beginning, production themes of family and local interest brought stained glass of stained glass developed side by side with economic, into a more intimate and domestic setting with highly personalised imagery. From the eighteenth century onwards, medieval and later stained-glass panels were *Correspondence: [email protected]; [email protected] 1 VICARTE, Research Unit Vidro e Cerâmica para as Artes, Hangar III, collected in order to decorate private houses and chapels FCT‑NOVA, campus da Caparica, 2829‑516 Caparica, Portugal [1–3], often bought in the art market and/or through an Full list of author information is available at the end of the article intricate network of dealers which grew throughout the Alexandra Rodrigues developed the research for this article fully as a member of VICARTE Research Unit. nineteenth century [4]. Tis was the case with Ferdinand © The Author(s) 2021. 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The Creative Commons Public Domain Dedication waiver (http://creat​iveco​mmons​.org/publi​cdoma​in/ zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. Rodrigues et al. Herit Sci (2021) 9:22 Page 2 of 16 II’s stained-glass collection, housed today at the Pena stained glass panels was restored and displayed [6]. Te National Palace (PNP) [5]. Tese stained-glass panels— collection’s main group currently consists of thirty-seven produced in Central and Western Europe (namely, in panels, to which ninety Fernsterbierscheiben (window the territories of modern Germany, Switzerland and the beer panels, i.e. small rectangular glass pieces painted Netherlands)—had been originally installed in churches, to celebrate the opening of a house or an important monasteries, manor houses, and artisans’ workshops, family event, such as a wedding) have been added. Tis prior to their installation in the Portuguese Palaces, is a highly diverse set of stained-glass panels, produced which is merely a short chapter in their long history [5]. between the fourteenth and eighteenth centuries, which Te history of this unique stained-glass collection were randomly grouped together [7]. begins with King Ferdinand II (1816–1885)—born and Tis study aims to contribute to the knowledge of the raised in Vienna, married to Queen Maria II (1819– history, materials, and techniques used in the produc- 1843) since 1836, and King of Portugal since 1837 [6]—, tion of a group of four panels within this collection. In who dedicated part of his life to collecting and fnanc- the present work, a relation between the stylistic, formal ing works of art, and his vast collection of glassware and and iconographic studies, and the chemical characterisa- stained glass was a source of pride for him [5]. tion of some of the glass fragments allowed us to attrib- Ferdinand II kept the greater part of the objects ute the set to the same origins, highlighting the ability of acquired in Portugal and overseas—collections of paint- already widely recognised and here employed scientifc ings, armour, sculptures, porcelain and others—in his heritage studies to resolve complex historical questions royal residence, the Palace of Necessidades (located in (e.g. [9, 10]). Combining the tools and procedures from Lisbon). Tese collecting activities included a group of the felds of Art-History and Archaeometry (Techni- stained-glass panels of diferent origins and sizes, with cal Art History) as was done here, is increasingly prov- which he decorated the windows of the Palace’s dining ing to be an indispensable methodology when studying room, very much in the style of the other Saxe-Coburgs’ medieval stained-glass. Micro Energy Dispersive X-Ray castles [5, 6]. Later in his life, he lived in the old cloister Fluorescence ( µ-EDXRF) was used in order to obtain a of Pena (restored and turned into a Palace), where he non-destructive characterisation of the composition also ordered to be mounted another group of stained- the glass and grisaille used in the production of three glass panels in the windows of the Great Hall [6]. Te of the panels (Virgin of the Apocalypse, Saint Ambrose, choice for the use of stained-glass windows in the open- Saint Gregory). Tis information was, in turn, used to ings of the main rooms of residences refected a central help establish the origins, art schools and artistic trends and northern European tradition [6]. It is known that the involved in the manufacture of the panels, as well as its King bought a large number of stained-glass panels on recently established relation with the fourth element (Sig- the German art market between 1850 and 1860, in order mund von Schönfels coat of arms). to decorate his summer palace in Sintra [7, 8], but as recent investigations suggests, the mainly foreign stained Materials and methods glasses arriving during that period have likely been set Visual observation and art‑historical approach on display at the Palace of Necessudades due to the early Te four panels under study are currently held by PNP death of the Queen [8]. (acc. nrs. PNP2809, PNP2810, PNP2821 and PNP2822) Unlike the windows installed in the main hall of Pena (Figs. 1 to 2). Tese stained glasses were observed with Palace’s, the stained-glass windows frst located in Palace the aim of understanding their production technology of Necessidades remained unknown to the general pub- and evaluating their state of conservation. An icono- lic until very recently. As such, the transference of the graphic analysis (an art historical analysis) was also made, panels to PNP is a story in and of itself [6]. Te stained- interpreting what could be seen in the glassworks under glass windows were transferred by 1949, since during study. On the basis of these observations, the objects the Republic (after 1910), the Palace of Necessidades were related to other primary sources (images and texts). was handed over to the Ministry of Foreign Afairs and Tis art historical interpretation is published elsewhere its contents were stored and gradually dispersed. It was [11], and it will herein be used as single reference, provid- in 1949 that, after being requested by the conservator ing it is an authoritative secondary source. of PNP, the ‘eight wooden frames with stained-glass win- dows’ arrived at this Palace. Unfortunately, their poor Chemical analyses and statistical methods state of preservation required an intervention before Energy dispersive X‑ray fuorescence they could be installed, and so they were to lie forgotten Concerning the chemical characterisation, several frag- in the storeroom for the next sixty years [6].