Madder lakes: how the synthesis’ conditions affect the lakes’ structure and degradation

Abstract

This thesis is part of an active collaboration between Ca’ Foscari University of Venice and the University of Antwerp (Belgium). The main aim of this thesis is to study how the synthesis’ conditions may affect the structure and degradation pattern of Madder lakes, precisely alizarin and purpurin. Lakes are well known to be sensitive to degradation factors such as light, humidity and temperature. Nevertheless, synthesis’ conditions could also affect the chemical reactivity and the degradation pathway of lakes. For this reason, alizarin and purpurin lakes were synthesised following different protocols, by varying the proportions of the reagents and the pH values. Samples were then exposed under different conditions (light and dark conditions) and investigated by Fourier-transform infrared (FTIR) spectroscopy and Spectrocolorimetry to monitor and understand their behaviour and stability over time. Next to this, to evaluate the influence of the protocols on the morphology, the structure and the composition of the lakes were studied in detail by FTIR and Spectrocolorimetry. In particular, the coordination of dyes with Al and the presence of different Al-based by-products would be explored depending on the synthesis conditions. These results will be extremely important for the analysis of historical artworks where madder lakes are present.