Looking beneath the paint
An original explanatory article about examining paintings with infrared imaging.
A finished painting can conceal earlier work. The surface shows the design which remained, while drawings or changes beneath it may be invisible to someone standing in the gallery. Conservators can investigate some of these hidden details without scraping away the picture.
One method uses infrared radiation, which lies beyond the wavelengths visible to human eyes. Equipment records how materials interact with it and produces an image which people can study. Some paint layers allow infrared radiation to pass through more readily than visible light, making certain features below them detectable.
Carbon-based drawing materials can absorb infrared strongly. An underlying drawing made with a suitable dark material against a lighter preparation may therefore become clearer in an infrared image. It can help researchers examine how the artist planned a figure or altered a design before completing the surface.
The method has limits. Different materials respond differently, so it does not produce an equally clear view through every painting. Failure to see a line does not automatically prove that the artist made no preparatory drawing. The materials or the method may limit what is recorded.
An infrared image is consequently another piece of evidence. Used alongside examination of the painting and other research, it can reveal aspects of making which the finished surface hides. The interest is not only in finding a dramatic secret picture: even a small adjustment can help explain a working process.
What can researchers learn from infrared examination of a painting, according to the article?