Scientific imagery at the Royal Institute for Cultural Heritage: a long tradition

The scientific examination of works of art at the Royal Institute for Cultural Heritage was pioneered by our founder, Paul Coremans. His seminal publication, L’agneau mystique au Laboratoire. Examen et traitement, Les Primitive Flamands, III, Contributions à l’étude des Primitifs flamands, 1953) on the study and conservation of Jan Van Eyck’s celebrated polpytych in the Cathedral of St Bavon in Ghent, transformed the way works of art were studied in this country and elsewhere. In addition to artistic style and iconography, Van Eyck’s altarpiece was investigated from the point of view of its techniques and materials. Not only did Coremans see this as interesting research in its own right, he stressed the importance of technical examination prior to undertaking any conservation-restoration treatment. Van Eyck’s altarpiece was examined with x-radiography, infrared photography, raking light, macro- and ultraviolet fluorescence photography, the binocular microscope and cross-sectional analysis.

Under Coremans’ leadership, radiography was established as an essential part of the examination and study of works of art. Numerous works of art of major importance have been recorded with this method in areas as diverse as paintings, polychrome wooden sculpture, metalwork and textiles. Examples include Rubens’ two masterpieces of panel painting, Descent from the Cross and Elevation of the Cross in the Cathedral of Our Lady in Antwerp, Rembrandt’s Night Watch in the Rijksmuseum and the Vieux Bon Dieu de Tancrémont, a thousand year old Rhino-mosan polychrome wooden sculpture from the Chapel of Tancrémont. scl11388dchssehuy_400_01

The film-based method used at IRPA has not changed fundamentally over the years, although strati-radiography (not used any more as too dangerous for the operator), stereo-radiography and large format radiography were introduced in the 1960’s and 1970’s. Recent advances in the field of computed radiography are also currently being tested.

Like radiography, infrared imaging was adopted in the early days of the Institute for the study of underdrawings, changes of composition and condition of paintings. For many years this consisted of infrared photography, using infrared film, giving high resolution images covering the 700-900 nm range of the electromagnetic spectrum. An early example of the use of infrared photography for the study of techniques following on from Van Eyck’s altarpiece is Dirk Bout’s Justice of Othon from the Royal Museums of Fine Arts in Brussels, published in the Institute’s first Bulletin in 1958.

In 1985, infrared photography was supplemented by infrared reflectography, using a Hamamatsu infrared vidicon, which extended the spectral range to about 2.2 µ. The vidicon enabled the visualisation of underlying drawing lines through a wider range of pigments than previously possible. The vidicon was replaced in 1999 by a platinum silicide focal plane array thermal imaging video camera with a spectral range of 1.1-2.5 µ, superior geometric properties, a much greater tonal range and improved clarity of image. In 2011, the Institute acquired a higher resolution thermal camera. It has an Ethernet interface and an indium gallium arsenide (InGaAs) captor, the new standard for infrared reflectography.