INTRODUCTION

The most striking difference about the present-day study of early Netherlandish painting as compared to the nineteenth century is the application of technical methods. These methods elucidate physical and technical aspects of paintings that, when analyzed in an art-historical context, can help in understanding the working methods of the painters.

Technical methods were first systematically employed in restoration laboratories to learn more about the physical condition of paintings and to detect overpainting. Starting in the 1920s, the use of X-rays, ultraviolet and infrared light was introduced in rapid succession. What these methods have in common is that they can reveal elements of a painting that are otherwise invisible. They all use radiation which cannot be perceived by the human eye: ultraviolet and X-rays have a shorter and infrared rays a longer wavelength than visible light. This radiation is converted into images we can see, which are subsequently recorded in the form of radiographs or reflectograms.

Art historians were initially somewhat hesitant about the application of these methods, and X-rays caused particular concern. Around 1930 there was a spate of rumors that X-radiography had caused serious damage to pictures, including the Rembrandts in the Gemaldegalerie in Kassel. Extensive checks carried out on ‘worthless’ paintings then proved conclusively that X-rays are not harmful to works of art. Once the panic had subsided the arsenal of scientific research methods gradually expanded.

Roughly two groups of methods can be distinguished: those for surface examination, whereby the painting need not be touched, and those for point investigation, which require minuscule samples of the paint. To the first group belong examination with the stereo-, or binocular microscope, ultraviolet, infrared and X-rays, to the second group methods for the analysis of paint samples. Dendrochronology, which falls into neither group, stands alone.

In order to grasp the value of the data yielded by the various methods, one must first understand the structure of a fifteenth-century painting made in the Low Countries. First of all there is the support on which the artist paints. The vast majority of the extant pictures of this period is painted on wood and the pictures are therefore usually called panels. The wooden support was first smoothed and then covered with several layers of warm animal glue so that the ground, applied later, would adhere better.