Uncovering the van Eycks' original masterpiece
Conservators from Antwerp and the Netherlands have discovered that layers of overpainting have been added to the Ghent Altarpiece, one of Europe's greatest masterpieces
Underneath the varnish
The conservation team currently working on the physical investigation, cleaning and restoration of Jan van Eyck’s “The Adoration of the Mystic Lamb”, also known as the Ghent Altarpiece, have announced an important discovery. After removing yellowed layers of varnish, conservators were able to determine that large areas of the painted surface are in fact overpaint or retouching, added perhaps hundreds of years after Van Eyck.
The treatment of the Ghent Altarpiece began in October 2012 and is being carried out in stages. Currently, the back panels of the two side wings, designed to be visible when the altarpiece is closed, are undergoing analysis and cleaning at a special conservation laboratory at the Museum of Fine Arts in Ghent. A glass window (pictured below) allows visitors to watch the conservators in action. The remaining panels continue to be on view at Sint-Baaf’s Cathedral.
The overpaint affects large areas of all six panels and covers the garments of the depicted donors, the robes of the Archangel Gabriel and of the Virgin Mary, architectural elements in the background, and the grisaille depictions of Saint John the Evangelist and Saint John the Baptist. The repainted areas were difficult to distinguish from the original paint layer with the naked eye, especially when they were covered with thick, discoloured varnish.
The conservation team was able to determine with great certainty which areas have been repainted, using technology developed by scientists at the University of Antwerp and Delft University in the Netherlands. They created a mobile scanner that lets investigators know exactly what non-organic materials make up the different layers of paint covering a two-dimensional surface. The device has also been used to examine paintings by Van Gogh, Rubens, Rembrandt, Hans Memling and Jackson Pollock.
X-ray fluorescence, or XRF, has been used for years to analyse the chemical compounds present in each layer of paint. Art historians and conservators use this data to make determinations about when and how different pigments were used. But until recently, this type of investigation was hampered by the fact that it could only be performed in situ using a small, focused X-ray device. Single points of the painted surface could be analysed, but this method yielded only fragmentary data about the work as a whole.
Large-scale XRF can be performed by a scientific device called a synchrotron, which is a type of particle accelerator the size of a warehouse. There are only a handful of these facilities in the world, and bringing fragile paintings to them for analysis can be risky.
The Macro-XRF scanner invented by professor Koen Janssens of the University of Antwerp and professor Joris Dik of Delft University, on the other hand, allows the entire painting to be scanned at once, one tiny area at a time, and the resulting data can be mapped over the surface as a whole. In this way, separate pigment maps can be created for each element and superimposed on the original work, yielding information about the artist’s methods as well as later interventions and damage to the paint surface.
The Macro-XRF device is also portable, allowing it to be brought to works of art wherever they are. There are currently two such devices built by the Flemish-Dutch team; in addition to the one used on the Ghent Altarpiece, another has been traveling in the United States, on loan to institutions such as the Getty Museum in Los Angeles.
The data obtained from the XRF scan of the van Eyck panels confirmed conservators’ observations about later overpainting to the altarpiece. In the case of the portrait of female donor Elisabeth Borluut, there seemed to be a second layer of red paint covering her original gown. Chemical analysis of a microscopic paint sample confirmed that the upper layer incorporates the pigment azurite, which contains copper.
The copper distribution map created by the Macro-XRF scanner showed that a small test area, cleaned of the upper paint layer, contains no copper. Thus, it is possible to clearly differentiate between Van Eyck’s painting and the later overpainting. The original painting revealed beneath the cleaned area shows a more delicate and nuanced handling of texture and shadows consistent with other works by Van Eyck.
Pigment analysis of the crimson overpaint layer also revealed the presence of kermes, an organic dye derived from dried insects and widely used in the middle ages. In the 1600s, cochineal from the New World replaced kermes as the source of crimson dye in Europe, so conservators are confident that the overpainting can be dated to before the middle of the 17th century.
Last autumn, the Ghent conservation team convened a panel of international experts to present their preliminary findings from the cleaning and analysis of the altarpiece. Art historians, paintings conservators and museum curators responded enthusiastically to the new data and agreed that the overpainting should be removed. The next phase of the treatment process will reveal even more of van Eyck’s original masterpiece.
An exhibition about the restoration of “The Adoration of the Mystic Lamb” is on at the Caermersklooster cultural centre in Ghent. In addition, a website allows users to zoom in on high-resolution images of each panel and see the results of the original conservation assessment. The restoration is expected to be finished in 2017.