Comparative chromatographic and mass-spectrometric studies of triterpenoid varnishes: Fresh material and aged samples from paintings
The triterpenoid resins dammar and mastic are frequently used as varnishes for paintings. Unfortunately, these varnishes degrade in the course of time. A large number of aged yellowed varnishes taken from paintings from several museum collections were analyzed by gas chromatography/mass spectrometry (GCMS) to identify oxidized triterpenoids, which are formed during natural aging processes. Discrimination between the different types of aged varnishes was achieved by direct temperature-resolved mass spectrometry (DTMS). GCMS further showed that the triterpenoid fraction strongly decreases during aging. It is likely that a higher molecular weight fraction is being formed.
van der Doelen, G. A, van den Berg, K.-J, & Boon, J. J. (1998). Comparative chromatographic and mass-spectrometric studies of triterpenoid varnishes: Fresh material and aged samples from paintings. Stud. Conserv., 43, 249–264.