Characterization by ftir of the effect of lead white on some properties of proteinaceous binding media

Cracking, flaking, and separation of paint films containing lead white from the substrate on medieval parchment manuscripts and other works of art have been frequently reported by conservators. In this study, Fourier transform infrared spectroscopy (FTIR) was used to follow up the changes induced by the pigment on some properties of proteinaceous binding media commonly mentioned in medieval treatises. Evidence of the removal of water molecules from the vicinity of the peptide linkage groups C=O and CNH, with a small change in the protein's secondary structure due to aggregation, was obtained. The properties of the lead white-binder samples were compared to those of massicot-containing mixtures. Massicot was also found to promote aggregation of the binders, though it induces a smaller change than does lead white in the hydrogen-bonding characteristics of the peptide CNH group.