Hidden sketch revealed beneath Rembrandt’s The Night Watch

<span>Photograph: Peter de Jong/AP</span>
Photograph: Peter de Jong/AP

A hidden sketch by Rembrandt has been discovered beneath the thick paint of the Dutch master’s most famous work, The Night Watch, revealing for the first time the artist’s original vision for the vast canvas.

The preparatory drawing, made with beige paint with a high chalk content, was found as a result of a two-and-a-half-year investigation by restorers, data experts and art historians at the Rijksmuseum in Amsterdam.

The sketch reveals to researchers evidence of a series of changes Rembrandt van Rijn made to his arrangement of 34 different characters and the array of feathers, spears and swords around them, before the painting’s completion in 1642.

The Night Watch, depicting a militia under the command of Capt Frans Banninck Cocq, took three years to finish after being commissioned by Amsterdam’s civic guard for a banqueting hall at its Kloveniersdoelen headquarters.

Pieter Roelofs, the Rijksmuseum’s head of paintings, said it had been possible to make Rembrandt’s secret sketch visible through a “calcium map” of the work due to the artist’s use of a chalk-rich paint that could be picked up by the latest scanning technology.

He said: “We see straight lines and curves. With the curves he created an initial sketch for the architecture in the background. You may ask why is this so important? Well, it gives us the feeling we can peek over Rembrandt’s shoulder while he was working on The Night Watch.

“We always suspected that Rembrandt must have sketched it on the campus before starting this complex composition. But that was always an assumption.

“Now that we can see beneath the surface better than ever before, we now have the proof, this gives us real insight into Rembrandt’s creative process for the first time. It is fascinating to see how he’s searched for the right composition. We’ve discovered the origins of The Night Watch.”

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Since the summer of 2019, staff working on what they have called Operation Night Watch have been using the latest technology to seek out fresh insights into the painting ahead of its restoration.

Rembrandt used the impasto technique, involving the application of thick paint on the canvas to achieve a three-dimensional structure that reflects light.

Imaging methods were used to get beneath the layers. They found that Rembrandt originally painted feathers for the helmet of the militiaman Claes van Cruijsbergen, but later painted them over.

He sketched more spears than he painted, adjusted the leg position of sergeant Rombout Kemp and there are signs that there was an additional sword in the original between the captain and his lieutenant, Willem van Ruytenburch.

“Why did Rembrandt change his mind, you might ask?” said Roelofs. “We don’t know. But probably he removed the feathers, because they drew too much attention as Van Cruijsbergen is in the centre of the composition.”

The main purpose of the latest research into The Night Watch was to prepare for its first restoration in over 40 years.

Despite the painting having endured a tumultuous four centuries, including transportation into a bunker in coastal dunes at the start of the second world war, its condition is said to be very good despite evidence of abrasion, discoloration and paint loss over time.

The priority, Roelofs said, was to tackle the deformation of the canvas seen in particular in its top left-hand corner, which is believed to have been happened during its 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 will be taken from its current wooden stretcher, the framework to which the painting has been held by metal tacks since 1975, said Petria Noble, the museum’s head of painting conservation.

She said: “We strongly feel that the wooden stretcher is contributing to the problem because a wooden stretch actually reacts differently to the canvas. It will then be put on to a new strainer, a non-reactive material, that we feel will actually be much more stable for the painting. The deformations are then expected to relax and the painting they will assume a flatter, more even surface.

“One of the first things that you actually need to do is to remove very gently and systematically those tacks. And of course we have to use some gentle weight to actually coax those deformations, that we see along the left and the right edges, out.”

The process will start in January and is expected to take up to three months, after which further possible conservation techniques will be considered, including removal of several varnish layers on the surface of the work.