article_snippet: X-ray fluorescence (XRF) is a non-destructive technique, which can identify the presence of certain pigments.
article_snippet: X-ray fluorescence (XRF) was first used in the 1940s and applied to paintings in the 1950s.
article_snippet: a non-destructive technique, which can identify the presence of certain pigments involves bombarding the artwork   with x-rays so powerful that the artwork   cause atoms in the picture’s layers to emit ‘florescent’ x-rays of the artwork   own.
article_snippet: XRF can be used to identify the colours of hidden paintings or to see earlier versions of famous pieces. 
article_snippet: By mapping the x-rays of copper, for blue and green, iron, for yellow, orange and brown, and mercury, for red, scientists can see full-colour 'maps' of previous versions.