People from Ghent University and Van Eyck: archaeometry

Ghent’s focus is on Van Eyck and the Ghent Altarpiece in 2020. Lots of people from Ghent University are also involved in this year of celebration. We have been putting a number of them in the spotlight. This week: Peter Vandenabeele.

In Ghent, it’s all about Van Eyck and the Ghent Altarpiece in 2020. One of the highlights is undoubtedly the return of the restored painting to St. Bavo’s cathedral. Years of research preceded the amazing renovation. Moreover, many people from Ghent University have contributed with new insights relating to the Ghent Altarpiece. You have already gained a glimpse into these insights over the past few weeks. Today it’s time for the last part: archaeometry with professor Peter Vandenabeele. "It was fantastic to be able to study the layers of paint from such close proximity. A little bird was actually no more than a simple spot of paint once you were so close to it. So clever."

What is the link between your area of expertise and research into the Ghent Altarpiece?

Peter Vandenabeele: "My area of expertise is quite a special one. I am a professor in Archaeology for the research domain archaeometry, as well as being associated with the Chemistry department. Archaeometry involves applying science (chemical) techniques in human science, for example in dating archaeological objects. I specialise in the chemical analysis of pigments. To do so, we use a number of techniques, such as Raman spectroscopy. This inspects the molecules present in the paint layers. We also use X-ray fluorescence, a technique for studying atoms. Both techniques were applied in the chemical analysis of pigments in the Ghent Altarpiece."

What insights were gained as a result of your research?

Peter Vandenabeele: "For the first time in history, pigment analysis on the outer panels revealed which materials were used for overpainting. Although we did struggle to convince those involved in the restauration. After all, they view things from their own perspective and are trained to interpret what they see in a different manner. Because of our results, colleagues from Antwerp were brought in to scan the outer panels. The scanned images of the overpainting confirmed our findings.

Using X-ray fluorescence we also discovered that there was silver in the frames. We knew they were the original frames due to the quatrain inscribed (link to article Max Martens), however, we had no idea what they looked like originally. The silver in the original frames was hidden by all the varnish and other overpainting on top. We now know that the frames were gilt, and featured a very fine layer of silver foil.

We were also able to identify the various pigments in the layers of paint. This led to some surprising discoveries as well. After all, in literature it always says that only two green pigments were used in the Middle Ages: malachite and verdigris. In fact, our analyses revealed the use of many more types of green pigment. Van Eyck also used blends - for example on the sibyl on the uppermost right outer panel - which are rarely mentioned in literature. Were other processes used to make them, were they familiar with other types of pigment after all? These are all questions that still need investigating.

We also used our 3-D microscope to make a digital study of the different paint layers. By measuring the thickness of the layers and the cracks. The microscope was also used a lot by those doing the restauration, for a detailed study of the panels."

Who from Ghent University was involved in this research?

Peter Vandenabeele: "Besides the doctoral students, I also worked in the Chemistry department with the research team under professor Laszlo Vincze, as specialists in X-ray fluorescence. Also with professor Luc Moens (Raman research team), with Maximiliaan Martens (Art) and with Hélène Dubois (head of the restauration team). The interdisciplinary approach was very interesting. Everyone looks from a different perspective at the mystic lamb, and each has their own interpretation. The comparison of such perspectives caused many exciting discussions."

Missed the previous articles?

Did you miss the previous articles’ No problem, here they are:

• People from Ghent University and Van Eyck: philosophy, ethics and religion
• People from Ghent University and Van Eyck: art sciences and social history
• People from Ghent University and Van Eyck: engineering