Which recipes did Rembrandt use to prepare his paints? How have his pigments aged over the centuries? Some pigments have even degraded, resulting in the formation of non-original materials? To answer these questions, scientists from the Rijksmuseum took precious minuscule paint samples from The Night Watch to a synchrotron facility.

A synchrotron is a large particle accelerator where a beam of high energy X-rays is generated. This beam is so focused that research can be carried out on a micro scale. The technique of X-ray diffraction is particularly suitable for identifying and mapping the inorganic materials in Rembrandt's paint layers.

Paint samples from different areas of the painting were investigated at the synchrotron. The small diameter of the beam and the high sensitivity make it possible to analyze the thin crusts that have formed on some parts of the surface of The Night Watch. Furthermore, we can discover the chemical composition of the lead soap protrusions.

The research at the synchrotron also allows us to better understand how Rembrandt made his famous quartz ground.

Operation Night Watch has collected a huge amount of data -- about 51 terabytes -- from all the different imaging techniques used to study the painting. Things have come a long way since the last major conservation treatment of The Night Watch was performed in 1975-1976. If we used 1976-era technology to store this much data it would require a stack of 8-inch floppy disks stretching more than 320 km tall!

The amount of data varies greatly per technique. The list below shows the amount of captures generated and the total file size per technique.

For some techniques, we collect a huge amount of information for each pixel even though we have comparatively fewer pixels. For example, for MA-XRF scanning, we collect 4096 channels of information per pixel (a finely resolved energy spectrum), which is then analyzed by computer to produce a map of a few dozen elements. Similarly, for reflectance imaging spectroscopy (RIS), we collect images at more than 500 different wavelengths to reconstruct the reflectance spectrum (an incredibly precise description of how the object interacts with visible and infrared light) for the whole painting.

For other techniques, such as 5 µm resolution visible-light photography, we collect less information per pixel, but the tiny size of each pixel (less than 1/10th the width of an average human hair!) means that we have an enormous number of pixels so the size still adds up.

Finally, the 15 µm resolution 3D structured-light photography has both a high resolution and a large amount of data per pixel (13 photos from each of 3 cameras for each location), so it generates a staggering amount of data in order to produce an elevation map for the whole painting.

By combining the latest imaging technology with the latest computer technology, we can gain much deeper insights into the painting than has ever been possible before.

• Daylight photography (20 µm): 528 captures, 317GB

• Daylight photography (5 µm): 8.439 captures, 5.063GB

• UV photography (20 µm): 528 captures, 317GB

• Macro X-ray fluorescence (500 µm & 250 µm): 56 captures, 1.008GB

• Reflectance imaging spectroscopy -VNIR (168 µm): 80 captures, 355GB

• Reflectance imaging spectroscopy -SWIR (168 µm): 127 captures, 1.130GB

• Optical coherence tomography: 66 captures, 1.500GB

• 3D scanning - Artec Spider (3D): 127 captures, 886GB

• 3D scanning (15 µm):135.346 captures, 40.604GB

Total size: 51.181GB