• artificial ageing
• curing
• ESI-q-ToF
• fatty acids
• HPLC-ESI-q-ToF
• hydrolysis
• modern oil paints
• oxidation
• TGA
• triglycerides

Modern oil paints, industrially produced since the early 19th century, show degradation phenomena which are different than the ones observed for traditional oil paints. Yellowing, surface cracking and efflorescences of metal soaps are some of the most common problems to face in oil paintings. The analysis of the composition of the original and degraded paint is fundamental to project conservation and restoration procedures.
Fresh and cured commercial oil paints have been studied in reverse-phase high-performance liquid chromatography coupled to electrospray ionization quadrupole time-of-flight mass spectrometry (RP-HPLC-ESI-q-ToF) and a chromatographic method has been developed to investigate the composition of the paint, in terms of fatty acids and glycerides, in a single chromatographic run. In order to improve the separation and resolution of fatty acids in HPLC-ESI-q-ToF, a derivatization procedure has been studied, in which the carboxylic moiety of fatty acids is transformed into a hydrazide group by the reaction with 2-hydrazinoquinoline. Derivatized fatty acids signals show improved resolution. The developed method was employed to study the degree of hydrolysis and oxidation of oil paint reconstructions.
Fresh commercial oil paints have been investigated via thermogravimetric analyses (oxygen uptake curves, TGAs) in order to study the capability of uptaking oxygen and the curing process of the paints. The influence of several treatments and additives, as well as that of different pigments dispersed in the same binding medium, has been investigated.
The influence of environmental moisture on the ageing process and on the hydrolysis degree of two sets of oil paint reconstructions has been investigated. One set of paint reconstructions was prepared in 2006 and naturally aged for ten years; another set of paint reconstructions was made in 2016 and cured for a few days before artificial ageing. The two sets of paint layers have been aged for 12 weeks in high and low relative humidity conditions at high temperature. The fatty acids and glycerides composition of the oil paints during ageing has been monitored by electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-q-ToF).