Did You Know ...

... why van Gogh's Sunflowers shine?

Scientific examinations are a key requirement for the conservation of great works of art. Such investigations combine various disciplines such as art history, restoration and microscopy. For example, paint pigments in paintings are characterized by attributes such as chemical composition, morphology, degree of crystallinity and particle size. The materials used can be identified by analyzing these features. Experts examine the morphology of pigments with the aid of optical and scanning electron microscopy. They also use microscopy with polarized light to determine the minerals contained in the pigments.

A research team at the University of Queensland in Brisbane (Australia) is using this method to analyze cross sections of pinprick-sized paint samples from Vincent van Gogh's famous Sunflowers. The samples were taken from the edge of the canvas or along cracks in the painting. In a process known as serial block-face imaging, scientists copy series of paint sections from one sample block using a ZEISS Sigma VP field emission microscope. The microscope contains a microtome with a diamond blade. This high-precision blade produces thousands of serial sectional images – all originating from just one real block. This process culminates in the generation of a three-dimensional image. The aim is a type of mapping of the various layers of paint. This method provides scientists with a better understanding of the aging process of such famous paintings. The system, which is usually used for biological samples, is being used to examine pigments for the first time.

The insights gained are also vital if a painting is to be restored or cleaned. In this case, the porosity must be determined precisely, so as to decide which solvents can be used and how deeply they will seep into the painting. The pigment attribute data obtained through the microscope analysis enables the scientists to model the microporosity, thus laying the foundations for the gentle and successful restoration and therefore the conservation of this work of art.

10 July 2015