The works that have come down to us are precious and must be studied with the utmost care. For this reason, the use of chemical methods requiring sampling is becoming increasingly rare: removing material, even in very small quantities, is not acceptable on exceptional works. What's more, the sample is not always representative of the complete work, as it is often located on the edges of the painting or in already damaged areas, around gaps.
As a result, many new non-invasive analysis methods have been developed over the last twenty years. The AGLAE particle gas pedal at the Louvre has paved the way for this approach. Other technologies based on electron-laser interaction are also being developed. But it is above all the new portable instruments developed for in situ analysis that offer the greatest advantages for art research.
This lecture describes some of these techniques and considers their advantages and limitations. Various point analysis methods can be combined to provide maximum elemental (X-ray fluorescence spectrometry), molecular (UV-visible, near- and mid-infrared and Raman spectroscopies) and structural (X-ray diffraction) information. They can also be used to obtain chemical maps of the entire work, opening the way to a more global understanding of its creation at all scales: study of colors, repentirs, repaints, superimpositions, alterations..
