Between mid-January and mid-March, visitors to the Rijksmuseum could only see the reverse of The Night Watch. During these two months the structural treatment of the painting took place, which was necessary to address deformations in the canvas and to optimize the tension in the painting.
New tensioning system
The painting was first laid face down on a worktable after which the tacks that held the canvas to the non-original wooden stretcher were removed. The stretcher was then lifted off the canvas and hung on the rear wall of the glass room for several weeks, until it was dismantled at the end of February. Despite the fact that the stretcher, which dates from 1975, is not original, it is an important part of the conservation history of The Night Watch and will be preserved as such. After this, the canvas lay free, and the reverse was now fully accessible.
Support canvas
The canvas that is currently visible is the support canvas, or lining canvas that was applied to the back of Rembrandt's original canvas during the last treatment in 1975 using a warm mixture of wax and resin. The lining canvas is larger than the original canvas, resulting in relatively wide edges of only the lining canvas along all four sides. These edges were considerably stiff due to the wax resin mixture and showed rigid creases caused by the folding of the canvas around the wooden stretcher. In preparation for the new tensioning system, the edges were flattened and the excess wax resin was removed from the canvas using warmth. This made the edges flexible enough to fold over and stitch, creating a casing, or tunnel as it were, through which a thin stainless steel rod (diameter 5 mm) was inserted, one on each side. Springs were then attached to the metal rods, which were then fixed to the new aluminium strainer.
Removing the deformations
Simultaneously with the work on the edges of the lining canvas, the undulations in the painting were treated. Laying it flat, removing the wooden stretcher and treating the edges already reduced these deformations considerably. The deformations were sufficiently flexible to be flattened just by the use of light weight. The new tensioning of the painting using a spring system ensures that the tension in the canvas will be evenly distributed at all times. The loading of the springs can be precisely adjusted, controlled and if necessary, adjusted.
From 16 March onwards The Night Watch can be seen upright again on its new strainer.