A look inside Studio Rubens: the research behind the restoration

Since September 2023, the restoration of two monumental altarpieces has been taking place in the Rubens Gallery at the KMSKA. While the first two years were devoted entirely to Rubens’ Enthroned Madonna Adored by Saints, since September 2025 attention has shifted to his The Adoration of the Magi. The in-depth conservation treatment of the paintings — including cleaning, retouching and revarnishing — not only offers an excellent opportunity for scientific research; the two processes actually go hand in hand in a constructive interplay. Speaking on this subject is Lowie Vercruysse, who is currently examining The Adoration of the Magi as part of his PhD research.

What exactly are you researching as part of your PhD project?

“My research focuses on Rubens’ altarpieces, including The Enthroned Madonna and The Adoration of the Magi, as well as several others held in museum collections elsewhere. The works at the KMSKA are, both literally and figuratively, the largest case studies.

The Adoration of the Magi is the first Rubens painting on this scale to be scanned in its entirety using Macro-XRF. This places the project alongside major restorations such as Van Eyck’s Ghent Altarpiece and Rembrandt’s Night Watch. Based on these scans, we hope, on the one hand, to gain a better understanding of Rubens’ materials and painting techniques. How did his studio operate? Which pigments did he use? And how can this information help us determine whether he made changes to the composition?

This last question is also linked to our understanding of his transfer methods. We know that Rubens prepared his altarpieces through smaller preliminary versions. He would present these so-called modelli to his patrons before work on the final painting began. In the case of The Madonna Enthroned with Saints, differences emerged between these preparatory versions and the finished painting. What we are now trying to determine is whether this working method was applied consistently, and whether the changes occurred during the transfer process itself or afterwards.

Finally, the research also assists the conservators, who can use the results to better identify areas of damage or overpainting.”

You’re talking about Macro-XRF scans — what exactly does that involve?

“The abbreviation Macro-XRF stands for Macro X-ray Fluorescence. The device works like an X-ray scanner for paintings. A scanner directs a very fine beam of X-rays onto the surface of the painting. These rays interact with the different paint layers and subsequently send a signal back to the machine.

What makes this technique so special is that every chemical element present in the paint — such as lead, copper or mercury — emits its own distinctive signal. This allows the computer to generate a separate greyscale image for each individual element, revealing precisely where certain pigments are located within the painting.

The major advantage of Macro-XRF is that the X-rays can also retrieve information from underlying paint layers. This enables researchers to uncover details that are invisible to the naked eye. For example, the technique can reveal hidden sketches, overpainted details or compositional changes.”

So the pigments themselves are key to the research?

“Rubens used pigments containing various elements, such as lead, iron, tin and copper. By analysing the distribution of these detected elements, we can determine whether alterations were made, or identify areas that were previously restored or overpainted. The pigments reveal a great deal about the painting’s origins and history.”

And does the technique work flawlessly?

“One limitation of Macro-XRF is that three-dimensional information is translated into a two-dimensional image. Although we obtain information from the various superimposed paint layers, the results are ultimately displayed as a flat image. As a result, we do not always know precisely where a particular pigment is located or exactly how the paint layers are structured.

Conservators naturally benefit from the information provided by this technology. At the same time, however, they also contribute to the research by taking physical samples, which provide further insight into the stratigraphy and chronology of The Adoration of the Magi.”

What makes the works at the KMSKA so special?

“Both The Enthroned Madonna Adored by Saints and The Adoration of the Magi are altarpieces dating from the late 1620s and were in urgent need of thorough conservation and restoration. The Studio Rubens project made this possible, and we eagerly seized this rare opportunity for our research. After all, it takes several months to examine and scan paintings of this scale in depth, something that is not possible in every museum.

A veil of mystery has surrounded Rubens’ oeuvre for centuries, continuing to make him such a fascinating figure today. With a body of work comprising more than 1,400 paintings — including monumental altarpieces of this kind — and a highly efficient studio under his direction, questions remain as to how many works, and which parts of them, were executed by Rubens himself.

It is traditionally assumed that Rubens conceived the compositions himself in the aforementioned modelli, after which his studio transferred them onto large-scale canvases. Any adjustments or corrections, however, are believed to have been carried out by Rubens personally. Yet we cannot know this with absolute certainty.

Added to this is the long-standing tradition that Rubens painted The Adoration of the Magi entirely by his own hand. Naturally, we hope this research will shed further light on the matter. By revealing fewer corrections or compositional changes than might otherwise be expected, for example.”

Did you also have any particular expectations regarding The Adoration?

“I had no specific expectations; I feel like that’s the best approach to take. I do, however, hope to see certain techniques or practices that caught my attention while studying The Enthroned Madonna reappear here as well. Perhaps this may help us identify a broader pattern.

One example is the pigment recycling that Rubens appears to have practised: reusing residual pigments of various colours by mixing them together to create a kind of brown or grey tone. This becomes apparent through the unusually high number of elemental signals detected in such passages of brown paint, compared to ordinary brown pigments, which generally contain only iron (and/or manganese).

At the same time, the most exciting discoveries are often the ones you did not expect to find.”

And can you give us a sneak preview of any further findings?

“One of the discoveries resulting from the Macro-XRF scans of The Adoration of the Magi is the presence of underlying haloes. These are most clearly visible around the figure of the Virgin, but were most likely also used around Joseph, the standing figure on the right. The haloes are linked to Rubens’ painting technique and reveal more about the way he constructed the composition.

Rather than beginning with the background, as one might expect, Rubens started by painting the figures’ faces. Before working out a face in detail, he first applied a coloured area to indicate where the head would appear. This technique was crucial for achieving the desired lighting and colour harmony within the composition.

A face can appear very different depending on the colours surrounding it: against a dark background, a flesh tone may easily seem too pale or, conversely, too pink. By applying these coloured areas first, Rubens was able to calibrate the brightness and tonality of the faces in relation to their intended surroundings, even before the final background had been painted.

The scans reveal that the background around the faces was only completed at a later stage. After painting the faces, Rubens finished the figures and gradually worked from the foreground towards the background.”

“In addition, the scans also reveal several minor adjustments to the composition, although these are far more subtle than those identified in The Enthroned Madonna. For example, Balthazar’s eyes were altered, a hand resting on a staff was repositioned, and the plume on a hat was shifted slightly to the left.

These are relatively small changes with little impact on the overall composition, yet they remain visible through Macro-XRF analysis. They demonstrate that the painting process was not a static exercise in merely filling in details, but rather an ongoing search for balance and dynamism.

This research has been made possible in part through a collaboration with the University of Antwerp. The project is supervised by Professor Geert Van der Snickt and Professor Koen Janssens, together with the ARCHES/AXIS research group, the Research Foundation – Flanders (FWO), and KMSKA curator and Rubens specialist Dr Koen Bulckens.”