Minuscule samples of paint are taken in order to answer several questions about The Night Watch. For example, the researchers may want to discover the reason for the white haze that can be seen in the picture surface here and there. They may also want to see how the paint layers are built up, or whether the paint has altered in the course of time, and if so, how.
Do they just snip a piece of paint out of The Night Watch?
The researchers start by very closely examining where they want to take paint samples. They choose spots where they expect to get the most information from the samples. In that way they get all the relevant information from the fewest possible samples. The samples that are eventually taken measure roughly 200 micrometres. One micrometre is 0.000001 metres. So it cannot even be seen with the naked eye.
What can we learn from this?
The illustration below is of a paint sample that was taken in the 1970s. This minuscule sample comes from the cheek of one of the figures on the left in the painting. The sample reveals the different paint layers. You can see the ground layer, and above it a paint layer containing lead white, yellow ochre, and little bits of brown, white and red pigment depicting the man’s skin.
The first research question
The main research questions to be answered concern the white haze that can be seen here and there on the surface if the picture. Near the little dog, for instance, but elsewhere too.
These are the questions.
-Is the white haze the result of a chemical reaction in the paint? And how closely is it connected with the original paint?
-Or is it a paint layer that was added later?
Why is it important to know this?
If the white haze is closely associated with the original paint it cannot be removed safely. In theory, removal is an option if it is on the surface or a later addition.
How is a sample examined?
The paint sample is first embedded in a little block of resin. The block is then polished to create a paint cross-section. The cross-section is photographed and examined with various microscopic analysis techniques.