A team of more than twenty Rijksmuseum conservators, curators, scientists and photographers collaborates in Operation Night Watch in order to gain insight into the changes Rembrandt’s masterpiece, which he completed in 1642, has undergone. This will allow for the painting’s current condition to be better understood and for it to be preserved for future generations in the best possible way. To the visiting public, the project moreover has an added dimension: a glass chamber has been placed around the painting, so that museum visitors can take a look at the ongoing research and conservation process.

Rembrandt from a distance

Despite the coronavirus situation, the team kept up their hard work; work could not continue within the glass chamber between mid-March and 1 June, during which time the museum was closed to both staff and visitors, but there were enough sub-studies they could proceed with. Erma Hermens conducts technical art-historical research within Operation Night Watch and explains how the museum’s closure affected her work. ‘All of us suddenly had to work from home. Our weekly discussions soon continued again – now fully online – and, fortunately, our scientists could proceed with the data they had already gathered. As a technical art historian, however, you would ideally want to be face to face with the painting itself.’

Part of the research she was able to carry on with while the museum was closed is aimed at Rembrandt’s use of pigments, Hermens says. ‘Where did the pigments come from? Did Rembrandt buy different qualities of, for instance, the blue pigment smalt, or of white lead? To investigate this, we were able to use sources such as recipe books that were available online, albeit in a limited capacity. A large amount of literature and archive data has fortunately also been digitised.’

Meanwhile, the researchers have been working on-site with masks on while maintaining social distancing for some time already, but the project has incurred delays. The second phase – the conservation phase, which was supposed to begin after the summer of 2020 – has had to be postponed due to the coronavirus situation. Hermens: ‘The project’s schedule has been adjusted and is being organised as efficiently as possible. Lots of action is happening right now: high-resolution photography, 3D scanning of the paint surface, and extensive testing with regard to the potential future removal of varnish are now taking place. The Night Watch is a complex painting and everything is carefully researched and considered, both when it comes to Rembrandt’s technique as well as to the condition the painting is in.’

The production of smalt

‘At the moment, I am investigating the production of smalt, which is essentially a pigment made of blue glass; the colour is created by adding cobalt oxide to the glass. We know that Rembrandt used smalt in large quantities and in a number of different ways. To me, as a technical art historian, this is one of the most interesting discoveries in this project so far,’ Hermens explains. ‘His contemporaries also used it regularly. I would love to get to know more about the production of Dutch smalt, which is often praised for its quality.’

‘Only little is known about it, which makes doing research in archives and studying old recipes crucial when it comes to pinning down the production process and the composition of the smalt, the producers, the locations at which it was made, as well as potential import that may have taken place. Right now, I am working on this together with Paul van Laar, a Master’s student of the UvA’s Technical Art History programme, and Dr. Annelies van Loon, who is a scientist at the Rijksmuseum. Of course, the whole Operation Night Watch team is involved, too. Together with researchers from the UMC, we are moreover working on the application of Optical Coherence Tomography (OCT), with which we are trying to map how a glass-like pigment such as smalt behaves in a paint layer – very new and exciting.’

The man and the painting

Hermens also emphasises the small yet interesting changes in the composition of the painting the team has been able to track down. These changes can tell you something about Rembrandt’s creative process. ‘What I am most curious about is the way in which Rembrandt thought and how he made artistic decisions during his creative process. This allows you to better understand the painting, its many traces of ageing and the changes that have left their mark on the canvas and, thus, what the painting must originally have looked like.’

This knowledge subsequently ensures the painting can be conserved in a better way – a result that will be the product of the collaboration between the various disciplines that are contributing to the project. According to Hermens, the interdisciplinary working environment is highly stimulating: ‘The same interests and level of motivation underlie the work of everyone involved in this project. By combining expertise, responding to questions from other disciplines and brainstorming together, a sort of research arena is created in which everything converges – the teamwork within this project in inspiring, challenging, and leads to more than the sum of its parts.’

Conservation and Restoration at the UvA

The UvA programme in Conservation and Restoration is prominently represented in Operation Night Watch. Besides Erma Hermens, paintings conservators Susan Smelt, Lisette Vos, Nienke Woltman and Laura Raven, and technical art historian Ilse Steeman, all alumni of the Conservation and Restoration programme, are involved with the project, as is Robert Erdmann (Rijksmuseum Professor of Conservation and Restoration), who is responsible for data science and computational imaging within the project’s technical research.