Identification, stability and ageing phenomena of colorants used in modern inks in archive documents, prints, caricatures and other written heritage objects

The project is dedicated to the problem of fading and the analysis of modern colourants that occur, for example, in printing inks but also in various other colours or inks of the 20th century that were used by renowned artists such as M. Deix and E. Sokol in their caricatures and drawings. The high light sensitivity of some colourants makes it sometimes impossible for museums, archives, etc. to exhibit some of their objects. By identifying the problematic colour components, the appropriate precautions can be taken and recommendations made.

Therefore, the aim of the project is to develop an analytical protocol for the identification and characterization of the stability/ageing phenomena of colorants used in modern inks even by direct analysis of micro-samples and non-invasive analysis on the objects or documents itself.

Therefore, the MeV SIMS (Secondary Ion Mass Spectrometry using primary ions in MeV range) and the newly available combined XRF-Reflectance Spectroscopy imaging (RSI) in the VIS-NIR-SWIR range (380 - 2500 nm) will be applied. As already reported, MeV SIMS is a novel method still under development in the field of cultural heritage applications which enables the exact identification of synthetic organic colorants due to their low fragmentation and the detection of molecular ions during the measurement. Furthermore, this method is highly surface sensitive and no chemical pre-treatment or separation of the ink colorants in the mixtures often found in modern inks is necessary. The MeV SIMS works as direct analysis on solid ink micro-samples placed onto the surface of the metal indium drops. Combined XRF/RS imaging using portable instrument will be explored for non-invasive examination of the ink colorants directly on objects. It will be tested if fingerprints of colorants (and their ageing products) in the VIS-NIR-SWIR range can be determined leading to the exact identification of the ink colorants.

For the characterization of the stability and ageing phenomena of the colorants in modern inks, mock-up samples will be prepared with selected colorants. These samples will be aged using microfading as well as by applying an ageing study in accordance with lighting conditions in archives and museum collections of supporting partners. Furthermore, microfading will also be used for testing stability of inks on selected real objects. Analytical methods mentioned above will be applied before, at different ageing stages and after ageing in order to describe the ageing phenomena. In selected cases GC/MS will be employed as Heart Cut-Evolved Gas Analysis (HC/EGA/GCMS) in order to analyse volatile organic compounds (VOCs) and providing further information on the degradation processes of inks used.