Colour and Space in Cultural Heritage (COSCH) fosters international collaboration in the area of documentation of material cultural heritage. The main objective is to enhance methods of recording objects – for conservation and study – through applications of digital, optical, spatial and spectral technologies. Researchers participating in COSCH seek to develop solutions to questions that have not been fully resolved, such as simultaneous measurement of colour and shape or the wider use of specialist technologies. This issue is primarily devoted to techniques that support examination, documentation and display of historic paintings. A number of non-invasive, electronic imaging methods are covered, including open-source solutions and portable technologies that can be brought to the object, thus minimising transportation of works of art.
The way experts look at pictures is different from that of non-specialists. The former have the added benefit of, on the one hand, handling them, looking close-up and all round. On the other, they support examination and documentation of art with applications of science and a range of digital technologies. A reverse of a picture is rarely shown to the public, yet it often holds important hidden information about the materials and history of the painting. One can normally immediately tell whether the canvas, or other support, was man or machine made. Inscriptions, labels, stamps and seals, if present, may, for instance, refer to the maker(s) and also record changes in ownership and loans. In this issue Taylor Bennett describes an interesting investigation of the reverse of an oil painting. An inscription on a label attached to the stretcher identifies the subject of the painting as a view of Venice and states it is an original by J. M. W. Turner. Such labels are never taken for granted by art experts: a painting is attributed to an artist and dated through technical examination, as well as stylistic and historical research. The subject of Bennett's investigation is not the attribution of the painting to Turner. The Author is interested in stamped labels that are not visible: they are on the original canvas and are obscured by a later lining. The Author describes the application of transmitted infrared imaging and other examination techniques in considerable detail. Details of the equipment and software used — the setup and modifications to a camera; the steps in the imaging process, from capture to editing — are provided. Future research has been suggested. The reader will be able to find out what has been revealed and why these new insights are important to the history of the painting, and more broadly to the history of suppliers of artists' materials. The investigation into a view of Venice leads to streets of London. The description of Bennett's scientific investigation will be of considerable value to future projects seeking to reveal similar features hidden to the eyes, without invading the historic fabric of the object. The article is exemplary in its clarity and quality of the illustrations (in the 11MB PDF, one of two PDFs available).
Andrea Casini, Costanza Cucci, Marcello Picollo, Lorenzo Stefani and Tatiana Vitorino, the co-authors of a paper on red lake pigments, also note how essential — for the conservators of historic objects — is the knowledge of the original materials and production methods. Identification of pigments, for instance, supports authentication and dating of paintings and polychromed objects. The Authors made paints based on some 15th- and 19th-century recipes. (Worth noting is the availability of a major resource, Colour ConText. A Database on Colour Practice and Knowledge, which gives online access to thousands of historic artisanal recipes and associated information.) The Authors describe their analyses of red lakes through non-invasive applications of hyper-spectral imaging to determine characteristic reflectance spectra, and Fibre Optic Reflectance Spectroscopy to validate the findings. The Authors argue that the determined spectra may be usefully recorded in a database, and records of further red lake pigments added, for reference when examining historic materials. Understandably, there are limitations to the techniques used, which require more research.
Case studies conducted by COSCH researchers include an in-depth analysis and recording of the late medieval wall paintings in the Château de Germolles in Burgundy, France. In the 19th century the decoration was plastered over only to be rediscovered in the 1940s. The technique of the original paintings and its iconography pose many questions and challenges for art historians, conservators and heritage scientists. The study is investigating some of these questions, using a number of the latest imaging technologies, alongside more traditional examination methods and historical research. The study may help to answer the puzzling question why the Germolles court paid for materials that are listed in contemporary records, but are not present in actual paintings. Christian Degrigny reports.
COSCH is primarily concerned with data captured through advanced optical technologies for the purposes of recording and conservation of material cultural heritage. The originators of imaging projects should envisage as wide future use of high quality images as it is feasible, including their integration within collection records, but also within possible multisensory multimedia systems. The condition and significance of the object are criteria used by museums when deciding what should be digitised. Significance is assessed not solely in terms of material and artistic values. Other factors also play a part: historical and social significance of artefacts, past and present, and the use of captured data for interpretation and visitor experience. The underlying meaning of art tends to differ from one audience to another. Jule Rubi's paper illustrates what this complexity means for museum practice. The Author considers use of digital images specially captured to serve virtual reunification of several 17th-century paintings. The paintings are by the Flemish artist Denys Van Alsloot. They show the Ommeganck procession in Brussels in 1615. Originally conceived as a series, the pictures are scattered between collections in different countries. Until recently none was accessible to the public; one of the original paintings has survived in two parts. The logistics of such digitisation involving international interdisciplinary collaboration with several partners — the Department of Theatre and Performance of the Victoria & Albert Museum in London, the Prado Museum in Madrid and the Advanced Imaging Technology Laboratory of the University of Kyoto — are also considered. The paper reads like an educator's wish list for an engaging museum experience and a wide range of expectations of electronic imaging.
The project confirms the significance of electronic documentation for preservation of material heritage, but also for interpretation and communication of intangible heritage, in this case of an old Belgian tradition of ceremonial processions. This particular project involved infrared and high-resolution RGB imaging, envisaging an immersive public display of reunited virtual surrogates of the original paintings. This practice is well established in historical visualisation, often combining accurate 3D visual records of extant objects with virtual surrogates of their lost parts; some virtual reunification attempt representation of the original context and later modifications. Such work is relevant to the COSCH Working Group 5, concerned with visualisation, and more broadly to the consideration of how images of cultural heritage objects are being used. The COSCH meetings and Think Tank for early-stage researchers, to be held in Neuchâtel in the autumn 2015, will be devoted to this subject.