Infrared radiation (IR)

Infrared cameras provide a non-invasive method of looking under the surface of a painting.

This method reveals what is hiding beneath.

IR examination detects carbon-based materials such as graphite, charcoal and ink. As a result, it is most effectively used to detect under-drawing: the preparatory sketch, drawing or outline that the artist used as a guide for the painting. Looking at under-drawing can help scholars build up a picture of how an artist worked as well as revealing important information about who painted the picture.

As Infrared rays can pass through the layers of varnish that often coat paintings, it can also be used to show whether a painting has been restored or retouched. However, detecting under-drawing is the most useful function.

IR was used to analyse the under-drawing in the artwork Man in Oriental Costume, seen in Series 1 Episode 4: Rembrandt