Fourier Transform Infrared spectroscopy (FTIR) is the most commonly used analytical technique for the characterization of molecular structures. The molecular bonds are excited by the absorption of light in the field of infrared wavelengths (usually of 4000-400 cm^-1). The functional groups of different compounds (amorphous, crystalline, mineral or organic) can be analyzed with a limit of detection of about 5%. Characteristic vibrational bands can be associated with each compound. This technique has the advantage of allowing an analysis of the overall sample, without having to separate the mineral phase to the organic phase. Infrared spectroscopy is widely used among other things for the identification of organic, mineral substances, pigments, corrosion and degradation products, etc... Particles of the order of 30 micrometers can be analyzed in non- or micro-destructive way using a spectrometer Nicolet iS5 FTIR equipped with an ATR accessory (ATR diamond crystal), available on demand at the Institue of Chemistry of the UniNE (contact: Prof. Edith Joseph, LATHEMA)