A new research study on the two pots (‘grapen’) discovered in 1997 in the cesspit in Rembrandt’s former house – now the Rembrandt House Museum has revealed the master’s secret, the Museum said in a press release.

The museum has mounted a new exhibition Rembrandt Laboratory: Rembrandt’s Technique Unravelled to present this discovery to the members of the public.

In 1997 an archaeological survey was undertaken in the cesspit in the inner courtyard of the Rembrandt House Museum. Two cooking pots were found during the excavations, one with a white layer on the inside and one with a beige layer. These layers were subjected to chemical analysis. The white layer in one pot proved to be a chalky substance that painters used to prepare wooden panels. The only thing that the beige layer told the researchers was that it contained some lead. Recent research into the one-handled pot with the beige layer, however, has produced more results: aside from the presence of tiny traces of lead, there is a mixture of ground quartz (sand), which contains some earth pigments and chalk and is said to be only used by Rembrandt used to prepare his canvases before he started to paint.

An archaeologist finds a tankard in Rembrandt’s cesspit (Spring 1997)

This combination matches the quartz ground which Karin Groen (one of the senior Rembrandt researchers at the then Centraal Laboratorium) discovered in Rembrandt’s paintings. Her research shows that Rembrandt only started to use a quartz ground for his paintings on canvas during the time that he lived and worked in Jodenbreestraat, in the present-day Rembrandt House Museum. This ground layer was not used by other painters in the seventeenth century; it was only used in Rembrandt’s workshop.

‘This is really fantastic news. We can now regard the pots as Rembrandt’s. This makes them true relics. Rembrandt started to use a quartz ground as soon as he moved into the present-day Rembrandt House Museum, and as far as we know he was the only one who did. Financially and practically he probably found a mixture of quartz and clay convenient. As a rule, painters prepared their canvases with two layers of paint: first a layer of red ochre to even out the texture of the canvas, followed by a layer of grey paint containing lead white. The pigments needed for this made it an expensive process, and it took a long time before everything was dry. Quartz was not only more affordable and could be used as the ground for a painting in one layer, a quartz ground also kept the canvas flexible. Extremely useful for large sizes.’ said Leonore van Sloten, Curator, The Rembrandt House Museum in a statement.

Pigments at Rembrandt’s House. ©️ Flickr

Six cases showcased in the exhibition Rembrandt Laboratory: Rembrandt’s Technique Unravelled will highlight new insights into Rembrandt’s paintings, discoveries from his cesspit, and his prints and drawings. In the exhibition visitors will step into the scientists’ shoes. How did Rembrandt make his paintings, etchings and drawings? And how do we research that today? Think about the dilemmas faced by researchers and restorers in the place where Rembrandt made his works of art almost four hundred years ago.

The Rembrandt Laboratory: Rembrandt’s Technique Unravelled runs from 21 September 2019 to 16 February 2020 in the Rembrandt House Museum, Amsterdam.