A secret varnish: restoration photographs of The Night Watch from 1911

As part of Operation Night Watch, the large-scale research project into the condition of The Night Watch currently underway at the Rijksmuseum, paintings conservator Esther van Duijn is looking into the restoration history of Rembrandt's great masterpiece. In the RKD archives she found a series of remarkable glass negatives, showing the restorer Albertus Hesterman applying a secret varnish to The Night Watch with the help of his sons, at the beginning of the twentieth century.

Attack with a cobbler's knife

In 1911 Rembrandt's Night Watch was attacked in the Rijksmuseum with a cobbler's knife. Luckily only the varnish was damaged. In order to repair the scratched varnish, the museum enlisted the services of the restorer Albertus Johannes Hesterman (1848-1916) and his sons, Frederik Coenraad (1873-1932) and Albertus Johannes (1877-1955). On the day after the incident the scratches were removed using a small brush and some alcohol. But the story does not end there. At the time, The Night Watch was covered with a thick, multi-layered coat of varnish; shortly after the attack a journalist described the varnish as being 'as thick as a dime'. Undoubtedly this thick coat had provided good protection against the knife attack. However, the varnish layers had yellowed strongly with age, becoming increasingly opaque as microscopically thin cracks developed in these layers. In those days, people were less averse to yellowing – it was a natural part of the 'patina' of a seventeenth-century painting, something that was in fact considered fitting to a painting by Rembrandt. The opaque quality of the varnish on the other hand was an old problem, and there had been several attempts since 1889 to restore the varnish.

Photograph of The Night Watch in 1911, showing the damage inflicted with the cobbler's knife, collection Noord-Hollands Archief, Haarlem

Varnish based on a secret recipe

When the local treatment of the knife scratches rendered the varnish distinctly clearer in those specific places, it was soon realised that the entire paint surface needed treatment. The Hesterman family had been working for the Rijksmuseum since 1896 and it seemed an obvious choice to ask them to carry out the task, especially since they claimed to have a varnish that preserved the transparency of aged varnish layers longer than previous treatments. They refused to divulge the ingredients, however, on the grounds that it was a trade secret. The City of Amsterdam, the owner of The Night Watch, could not agree to this. The Committee of Supervision and Advise for Paintings of the City of Amsterdam (Commissie van Toezicht en Advies voor de Schilderijen der Gemeente Amsterdam) refused to have the great work varnished with an unknown substance. Barthold van Riemsdijk, the then director of the Rijksmuseum, stepped in as an intermediary and suggested calling on the help of a chemist, who would be able to assess the safety of the ingredients – naturally in strict confidence – and act as an independent arbitrator. That idea was rejected but in May 1911 the Hestermans finally agreed to share the composition of their varnish with the committee secretary. Without revealing the secret information to his fellow committee members, the secretary told them that all of the ingredients were commonly used in restoration practice at the time and thus safe to use.

Hesterman and his two sons at work during the final phase of the restoration, glass negatives from 1911, collection RKD, Hesterman Archive

Photographs of the treatment

The Hestermans worked on The Night Watch for several weeks starting in the last week of November 1911. Unfortunately there is no written report describing the treatment they applied. This makes the recent find of eight glass negatives in the Hesterman archive at the RKD all the more valuable. Three of these records show Hesterman and his two sons at work during the final phase of the restoration. Each of them is holding a small bottle, presumably containing the contested varnish, as well as a cloth. Little by little they treat the varnish, having first rubbed (or powdered) it, rendering it nearly opaque. The photos clearly show the change in the whitish varnish, which after the treatment has completely regained its translucency. In addition the archive also contains five photographs of just the painting, without restorers, during and after the treatment. The restoration was hailed by the press but sadly the result was short-lived. One year later the varnish of The Night Watch was already beginning to degrade again. Or, as the committee secretary remarked to his colleagues when they had discussed the Hesterman varnish: "There are 'secret solutions' that owe their mystery purely to the fact that they are secret."