An EPSRC-funded gas chromatography mass spectrometer (GC-MS) has helped specialists in the National Gallery’s scientific department study the organic chemistry of Old Master paintings to understand how they were made and how they have changed over time.
GC-MS is the core means of microanalysing paint samples, and the analysis techniques were first developed in the National Gallery laboratory, which remains a world leader in the study of the materials and techniques of Old Master paintings.
In painstaking investigations, the scientists used the GC-MS to study the characterisation and composition of paint-binding media, additions to paint media such as resins and the composition of old varnishes.
The results of their work have raised complex questions of disputed authorship and authenticity and shed light on the original colour balance of paintings.
One example is a painting known as The Virgin and Child with an Angel, which was originally attributed to Renaissance painter-goldsmith Francesco Francia and dated about 1490. The painting’s authenticity was queried in 1954 when another version appeared on the market and years of uncertainty ensued.
Finally, in 2009, a renewed campaign of scientific examination and comparative testing, including GC-MS testing on the paint media and varnish, proved that the gallery’s painting was indeed a fake that was painted in the 19th century.
Discussing the GC-MS technique, Ashok Roy, director of science at the National Gallery, said: ’Only tiny quantities of material are available for analysis as samples and the organic content can be very complex. In addition, the materials have generally changed over time so that analysis may be of degraded materials and the results [from the analysis] have to be translated into assessments of the original chemical composition when the painting was first produced.’