White marble has generally been considered a typical image of antiquity. However, the lack of colour has no relation to ancient aesthetics. In fact, antiquity cultivated a veritable wealth of colours, but after centuries of deterioration, very little paint remains on the artefacts giving rise to the mistaken notion of white marble as a classical ideal.
Polychromy comes from the Greek words poly (many) and chroma (colour) i.e. multi-coloured. Polychromy covers the use of many colours, e.g. in connection with paint applied onto architecture and sculpture. These colours were an important aspect of ancient artefacts. Due to disadvantageous conditions of preservation, the fragility of the paint, and, not least, to actual cleaning, the majority of the original colours have now disappeared.
Polychromy means “the state of being multi-coloured” and refers in the context of ancient sculpture to the – for many people still surprising – circumstance that the impressive white marble statues which we often associate with antiquity were originally painted. Polychromy research aims at uncovering and describing this circumstance and thus provides us with a greater understanding of the ancient Mediterranean cultures and their art. A fundamental part of this research consists of registering, documenting, and analysing the surviving traces of colour on ancient artefacts.
This work is complicated, particularly because of the typically microscopic size and fragile character of such traces of colour. Since colour traces gradually degrade and disappear due to factors such as climatic conditions, light/radiation etc. this documentation will in the course of time serve as the only evidence of the sculptures’ and other objects’ original paintwork, which was of such crucial importance for their aesthetic appearance in antiquity. Forming the basis for ongoing polychromy research as well as ensuring accessibility of ancient polychromy for research and educational purposes in the future, great requirements are expected from this documentation. Thus, polychromy research plays a key role in the Ny Carlsberg Glyptotek’s efforts to preserve our cultural heritage for posterity, something which is among the museum’s most important responsibilities.
When Humanities Meet the Natural Sciences
Although it has become a well-established fact that ancient sculpture and architecture were painted, there is still far more to explore in terms of research. New methods, particularly in the realm of the natural sciences, can contribute with new knowledge, for example of binding agents, painting techniques and provenance (origin), which will lead to a new understanding of ancient polychromy. By combining archaeological, historical, and linguistic studies with scientific methods of analysis it is thus possible to find answers to completely new research questions.
Polychromy research is an interdisciplinary undertaking and is dependent on contributions from many different academic fields in order to make progress in the widest sense. Neither the archaeologist nor the chemist can carry out polychromy research single-handedly. It is precisely in the dialogue between different specialists from the humanities and the natural sciences that new progress and advances happen.
Fig. 1. Etruscan antefix, NCG inv. no. HIN 69. To the right VIL image showing the presence of Egyptian blue (photos: Signe Buccarella Hedegaard).
Ancient Polychromy and Natural Scientific Analyses
One of the integral capabilities of the research project is photographic techniques such as visible-induced luminescence (VIL) imaging, a method developed at the British Museum in 2009, and ultraviolet fluorescence (UVF). The VIL method can identify the synthetic pigment Egyptian blue – even on the level of individual pigment grains. Whether or not the pigment is invisible even under a microscope, a VIL image can reveal its presence. In black/white pictures Egyptian blue appears chalk-white (Fig. 1). The method makes it possible, with great precision, to distinguish Egyptian blue from other pigments of the same shade and, not least, to confirm that ancient artworks were originally painted - even if no traces of colour are visible to the naked eye today.
UVF is useful to polychromy research because it helps to locate organic substances such as adhesives and surface coatings used for ancient polychromy as well as modern repairs. Furthermore, madder lake, made from the dye madder red which is obtained from the dried roots of the common madder Rubia tinctoria has a characteristic coral-red fluorescence which is easily detected. The UVF images of the Glyptotek’s Egyptian mummy portraits shown in Fig. 2 are clear examples of this.
Fig. 2. Mummy portrait from Fayum, Egypt. 2nd century CE. NCG inv. no. ÆIN 682. To the right: UV image showing the fluorescence of organic red lake (photos: Maria Louise Sargent).
The coral-red fluorescence is a strong indication of the presence of madder lake in the depicted garments.
Another extremely important analytical method in polychromy research is X-ray fluorescence (XRF) which can be carried out with handheld apparatus. The method is also non-invasive and thus does not damage the objects examined. XRF is used to identify elements and it is particularly suited to the analysis of inorganic pigments and glazes (Fig. 3). In addition to these non-invasive methods of analysis, the research project makes use of a range of other natural scientific methods in order to advance new knowledge about the polychromy of antiquity.
Fig. 3. Investigations with handheld XRF of a relief from the processional way in ancient Babylon (photo: Ana Cecilia Gonzáles)
GC-MS and LC-MS/MS
Paint consists primarily of pigment, which provides the colour, and a binding agent, which binds the grains of pigment together. Hitherto it has been the inorganic pigments which have received by far the greatest attention in research. This is partly because the pigments are crucial for the colour of the paint, and partly that they are most often significantly better preserved than organic binding agents, which perish easily and have typically decomposed beyond recognition or completely disappeared. The study of ancient binding agents constitutes a major challenge, but is rendered possible by ever more sensitive methods of analysis. The binding agents are of considerable significance for, for instance, the precise shade of colour, the degree of saturation and sheen. There can, therefore, be a great difference in the paint’s “expression”, depending on whether, for instance, egg, oil, or wax is used. Comparative studies of painting techniques can also give us insight into how they were developed and spread geographically. Finally, a characteristic of binding agents can help us evaluate to what degree the objects are actually ancient or not, as well as forming the basis for adopting the most appropriate conservation procedure.
The Glyptotek has initiated collaborations with various research institutions in order to identify the organic binding agents used in the painting of ancient artefacts in the museum’s collections. Among the methods employed is gas chromatography coupled with mass spectrometry (GC-MS), a procedure which can be used to identify lipids, carbohydrates and proteins. The British Museum and the University of Pisa have carried out GC-MS analyses of selected objects: one result of which has been the identification of proteins from egg, beeswax and animal glue (an adhesive created by prolonged boiling of animal connective tissue).
In addition, a collaboration has been established with the ERC-financed project TEMPERA (Teaching Emerging Methods in Palaeoproteomics for the European Research Area) at the Danish National Research Foundation’s Centre for GeoGenetics in Copenhagen. This research focuses on so-called proteomics – a term which covers the study of all the proteins which are identified in, for example an archaeological sample. One of the new methods being tried out on artefacts from the Glyptotek is liquid chromatography coupled with mass spectrometry (LC-MS/MS) which makes possible the identification of species from even quite small samples. LC-MS/MS analysis has led to the identification of glue extracted from cattle of the species Bos taurus in the painting of a number of architectural fragments from Egypt in the museum’s collections (Fig. 4).
Fig. 4. Sampling of binding media for LC-MS/MS analyses. The architectural fragments belong to the so-called Palace of Apries in Memphis, Lower Egypt, ca. 589-568 BC (photo: Luise Ørsted Brandt).
Lead and copper isotope analysis
The identification of ancient pigments leads to new questions. Among the most challenging of these is: where, in geographical terms, do the pigments actually come from? Precisely this aspect has considerable influence on our understanding of the significance of polychromy, artisan traditions, and – not least – ancient trade routes and circumstances. Here geochemistry can provide us with numerous leads in the investigation of the mining areas from which the valuable raw materials were extracted. Lead and copper isotopes can, for instance, contribute to establishing the geological origin of such raw materials.
In close collaboration with international researchers from the University of Padua and the German Mining Museum in Bochum, the Glyptotek has therefore carried out research into the geological origin of the metals used to produce ancient glazes and pigments. Lead and copper isotope analysis has made it possible to pinpoint the places of extraction of the copper used to produce Egyptian blue on a selection of ancient artefacts from the Mediterranean. Isotope analysis has likewise been used to locate geological sources of the glazes on coloured tiles which decorated the magnificent Ishtar Gate and Processional Way of the palace in Babylon, built from 605 to 562 BC.
Communicating Ancient Colours
One important aspect of polychromy research is the communication of it to other research milieux and to the broad public. Besides various printed publications, reconstructions are useful tools for this purpose – nothing communicates colours better than the colours themselves. Thus, research into ancient polychromy has always been linked with colour reproductions for documentation, dissemination and research purposes. Reconstructions encompass watercolours, coloured prints, painted copies in plaster and marble as well as digital reconstructions in 2D and 3D. Each format has its advantages and disadvantages: each of which, it goes without saying, should be evaluated in relation to whether the communication of it takes the form of a publication or an exhibition.
It is of paramount importance to stress that all attempts to reconstruct archaeological artefacts involve a degree of speculation and uncertainty. The reliability of any reconstructive endeavour depends on the particulars of the data obtainable. The inclusion of scientific data as a basis for a reconstruction does by no means eliminate the element of subjectivity; every single step of the way from idea to end product is still based on countless subjective interpretations and decisions influenced by aesthetic criteria, preconceptions, skills, and interests. However, there is a huge difference between data-based interpretation and mere speculation introduced to join up the dots where no data are available.
The Ny Carlsberg Glyptotek has experimented with reconstructions in different formats. Although there are many advantages of one to one experimental reconstructions, they are very expensive and time-consuming to produce as these are best executed in marble and painted with the correct pigments and binding agents. The digital reconstructions are, on the other hand, quicker to produce and adjust both during and after their production and can easily be copied and shared without affecting their expression. In addition, the various interpretations of the surviving traces of colour are easy to communicate through reproduction of several versions side by side. Most recently, the research team has accordingly focused on digital reconstructions. An example is the digital 2D reconstruction of one of the museum’s Etruscan architectural terracottas (Fig. 5). Another experiment, carried out in the museum in collaboration with Rigsters 3D, involves photogrammetry.
Fig. 5. Etruscan antefix from c. 400 BCE, discovered in Orvieto, NCG inv. no. HIN 453 (photo: Ole Haupt). On the right: A reconstruction by Lars Hummelshøj.
First, the artefact is photographed in great detail. The photographs form the basis for a 3D model to which the VIL recordings are added. The film shows four 3D versions incl. a monochrome model, a model in colour, a model showing the distribution of VIL, and a model in colour with the luminescence patterns added in blue (Fig. 6).
Ancient art and the senses
No matter how beautiful the sculptures may appear without paint, their present expression is far from representative of their ancient appearance. The notion of antiquity as clad in white marble is, however, beginning to fade into the background in favour of a new, more accurate interpretation which takes its point of departure in the original polychromy. Nevertheless, we still have a tendency to forget that the art of antiquity had additional dimensions, of which there were additional ones which are likewise invisible to the observer of today.
In relation to polychromy, it is relevant to include the effect of light. Light played a functional, spiritual, as well as a social role in ancient societies and obviously had an impact on how the colours were experienced. In order to understand the original experience of ancient sculptures, it is therefore necessary to understand the relation between light, object surfaces, colours, and the contrasts this creates, as this relationship constructs a visual atmosphere that affects our perception of the individual artefact. Furthermore, light is also significant to our knowledge and understanding of conservation and painting techniques. A further aspect is the original context versus the museological context and the fact that we today take artificial light for granted. This is of great importance to our interpretation of the polychromy, especially in the context of reconstructions, digital as well as physical, as the light affects our perception of the ancient sculptures and their polychromy.
In addition to being painted, some sculptures, particularly cult images and acrolithic statues, could be adorned with or even clothed in textiles. This was also the case for architecture. The addition of textiles would potentially transform their appearance drastically. Thus, neither the marble nor the polychromy is sufficient to comprehend the original appearance and expression of many artworks, which makes the involvement of textiles essential for the study of ancient art and architecture.
Henceforth, therefore, there should also be a focus on other, at first glance inaccessible dimensions of antiquity, such as light, in order to achieve a new, more inclusive, holistic understanding of the art of antiquity, starting in the collections of the Ny Carlsberg Glyptotek. The objective is to develop innovative, interdisciplinary approaches to the study of ancient sculpture – a subject in which both the material and the written source material are fragmentary and difficult to access.
The Importance of the Carlsberg Foundation for the Research Project
For more than a decade, outstanding research on ancient polychromy has been carried out at the Ny Carlsberg Glyptotek with grants from the Carlsberg Foundation. Thus, the museum has compiled extensive expertise within this line of research gaining a leading position internationally. About the grant, Cecilie Brøns says:
“The grant from the Carlsberg Foundation provides us with a fantastic opportunity to continue the research already undertaken, consolidating it and pursuing it into new fields of research – something I am very exited to do.”
She further states:
“The grant from the Carlsberg Foundation makes it possible for us to dare to experiment and to test new ideas and seize opportunities by implementing science-based methods from the fields of geology, geochemistry, physics, chemistry, and digital media to a far higher degree than previously. Thus, the project crosses disciplines by combining the humanities and natural sciences, which makes it possible to break new ground and draw new conclusions of great importance for our understanding of ancient art and architecture.”
The Carlsberg Foundation plays a key role for archaeological excavations as well as museum collections. Thankfully, the Carlsberg Foundation understand that archaeological research is based not only on newly excavated finds since new knowledge and methods - and particularly innovative thinking - create ground for achieving primary research results based on artefacts that have been discovered decades or even centuries ago and are now housed in museum collections. Hence, the museums are essential generators of ground-breaking, fundamental research.”
Selected Publications
Brøns, C., Hedegaard, S.B. & Rasmussen, K.L. “The real thing? Studies of polychromy and Authenticity of Etruscan Pinakes at the Ny Carlsberg Glyptotek”. Studi Etruschi LXXIX - MMXIV, 195-223.
Brøns, C. et al. 2018. Antikkens Farver. Sfinx.
Brøns, C. “Sensing the ancient world: The multiple dimensions of ancient Graeco-Roman art.”
CHS Research Bulletin. A publication of the Harvard Center for Hellenic Studies, 2018.
Brøns, C., Rasmussen, K.L., Lluveras, A., Melchiorre di Crescenzo, M. & Stacey, R. 2018. “Painting the Palace of Apries I: Binding media and coatings”. Heritage Science 6.6, 2018: https://link.springer.com/article/10.1186/s40494-018-0170-9
Brøns, C. & Skovmøller, A. 2017. “Colour-coding the Roman toga: The materiality of textiles represented in sculpture”. Antike Kunst 60, 55-79.
Brøns, C., Hedegaard, S.S. & M.-L. Sargent, M.-L. 2016. “Painted Faces. Investigations of the Polychromy of Etruscan Antefixes in the Ny Carlsberg Glyptotek”. Etruscan Studies 19.1, 23-67.
Brøns, C. (in press). “Pigments and Dyes: The use of colourants for the depiction of garments on Egyptian mummy portraits in the Ny Carlsberg Glyptotek.“ In Gleba, M., Busana, M.S., & Meo, F. (eds.), Purpureae Vestes VI. Textiles and dyes in the Mediterranean economy and society.
Rodler, A., Klein, S., Artioli, G. & Brøns, C. (in press). ”Provenancing Glaze Colourants: Polychrome Faunal Reliefs from the Ishtar Gate and Processional Way of Ancient Babylon”. Archaeometry.
Rodler, A., Artioli, G., Klein, S. Klein, Fink-Jensen, P. & Brøns, C. 2017. ”Provenancing Ancient Pigments: Lead Isotope Analyses of the Copper Compound of Egyptian Blue Pigments from Ancient Mediterranean Artefacts”. Journal of Archaeological Science: Reports 16, 1-18.
Skovmøller, A., Brøns, C. & Sargent, M.-L. 2016. “Egyptian Blue. Ancient myths, modern realities”. Journal of Roman Archaeology 29.1, 371-387.
Fig. 4. Gottfried Semper: the entablature of the Parthenon. Akvarel, Anwendungen der Farben in der Architektur und Plastik, 1836, pl. 5.