One of Amsterdam's most iconic art and history museums, the Rijksmuseum, is using Raman spectroscopy to study and improve the preservation of ancient paintings, sculptures, and other historical objects.
The Rijksmuseum in Amsterdam, The Netherlands, was the most visited museum in the country in 2013 and 2014. It offers a representative overview of Dutch art and history, from the Middle Ages to the 20th century, and of major aspects of European and Asian art. The Rijksmuseum not only keeps artwork and precious artefacts, but also conserves, restores, researches, prepares and presents them, both on its own premises and elsewhere.
Raman spectroscopy allows researchers to obtain answers to vital questions relating to the restoration of artefacts, such as: Which pigments did the painter use? What is the corrosion product in the damaged part of the enamel? Does the treatment of this bronze object leave residues on the surface? From where does the clay in the ceramic object originate?
The Conservation Department at the Rijksmuseum is using a Renishaw InVia confocal Raman microscope equipped with a polarised light microscope and 785nm and 532nm lasers. The polarised light microscope is essential for this work as cross sections of paint layers, which typically consist of multiple coloured pigment grains, are impossible to visualise in reflected light with bright field illumination only. By using Raman spectroscopy in combination with other analytical techniques, researchers are able to identify relationships between contemporary artists' use of paint materials. This includes, for example, discovering whether artists worked in the same workshop or shared their knowledge or materials.
Raman spectroscopy is also being employed by other research institutions as a means to better study and preserve ancient works of art. In April, scientists from the UK’s Science and Technology Facilities Council (STFC) and Italy's Institute for the Conservation and Valorisation of Cultural Heritage (ICVBC), tested a new technique, micro-Spatially Offset Raman Spectroscopy (micro-SORS), on artwork dating back several centuries. Tiny flakes of paint were analysed from religious murals and sculptures housed in devotional chapels in Northern Italy.
Similar to the Renishaw instrument, the micro technique combines SORS with microscopy concepts, allowing scientists to analyse the chemical composition of artwork at a greater depth than has been possible before. Laser light is used to probe through the surface layers, and a small number of photons will scatter back with changed colour, according to the different paint components they represent.
According to the researchers, the technology would have a major impact on the conservation of artwork and other historical objects in the future.