The secrets of Rembrandt’s painting technique on The Night Watch remain lost to time for now. But researchers tasked with solving the mystery believe they may at least have gleaned some clues as to the perfect recipe for wall filler.
Scientists at AkzoNobel, the Dutch owners of Dulux paints, have been working since 2019 with conservators at Amsterdam’s Rijksmuseum on the restoration of Rembrandt’s masterpiece, building a better picture of how the 17th-century painter worked.
A key objective for Gerard van Ewijk, AkzoNobel’s research and designer manager, has been to uncover the recipe used by Rembrandt in his impasto technique, where paint is layered thickly enough to stand out from the canvas.
The well-defined clothing of Lieutenant Willem Van Ruytenburch on the painting – the full title of which is The Night Watch militia under the command of Capt Frans Banninck Cocq – is one example of where Rembrandt achieved such an innovative 3D effect.
The conclusions of Van Ewijk’s investigations into the paint pose perhaps more questions than answers, however.
Previous studies of a “tiny square of paint, smaller than a crumble of paint” had discovered egg yolk in the impasto, said Katrien Keune, head of science at the Rijksmuseum. Yolk was believed to have been mixed with boiled linseed oil and lead oxide to create what Van Ewijk described as a “kind of mayonnaise”.
After intensive work in the laboratories at the Rijksmuseum and AkzoNobel’s facility on the outskirts of the Dutch capital, Van Ewijk discovered that there had not been any need for the egg yolk in order to create the same effect.
A 30:70 ratio of raw linseed oil and lead white creates the perfect impasto paint, raising a perfectly plausible alternative recipe to that previously assumed to have been used.
“We even questioned whether the previous analysis had been correct but we think the egg was definitely there,” he said. “There are multiple recipes he could have used … I think one of the outcomes is that you don’t actually need [the egg] so it is still a bit of a mystery why it is there”.
But all is not lost. The strenuous efforts of Van Ewijk and his team have not only offered insight into the potential range of approaches open to the artist but has also delivered advances in the creation of Polycell, Dulux’s brand of wall filler sold in the UK.
“Looking at how he got such structured paint is helping us understand wall filler in a slightly different way,” Van Ewijk said, citing the new techniques used by his laboratory to examine their efforts at replicating the impasto.
The main purpose of the extensive research into The Night Watch had been to prepare for its first restoration in over 40 years following a tumultuous four centuries during which it was even hidden in a bunker in coastal dunes at the start of the second world war.
The first step – ahead of a decision later this year on whether to remove multiple layers of varnish applied to the paint over the centuries – had been to correct deformation of the canvas seen in its top left-hand corner.
The damage is believed to have been sustained during the painting’s stay in the Philips wing of the Rijksmuseum during the main building’s renovation between 2003 and 2013.
The 3.63-metre by 4.37-metre painting has now been removed from a wooden stretcher to which it was attached by metal tacks since 1975 and fitted to a new one made of a non-reactive material. A decision on next steps is expected in December.
AkzoNobel has also been advising the Rijksmuseum on the future lighting of the painting and the way to best photograph its many shades of black.
Petria Noble, head of paintings conservation at the Rijksmuseum, said AkzoNobel’s experiments had ruled out “as nonsense” some previous theories that wax or paint scrapings had been used by Rembrandt to create the thick impasto paint.
“This is sort of a missing piece of information that has puzzled historians and researchers for a long, long time, so you have to take it [step by step], going in the right direction to figure out what is going on,” she said.