In Situ Unilateral 1H-NMR Studies of the Interaction Between Lead White Pigments and Collagen-Based Binders

Abstract

The lead white pigment, 2PbCO 3 ÁPb(OH) 2 , is thought to play a critical role in the degradation of paint in illuminated manuscripts. Cracking, flaking, and separation of paint films containing lead white on parchment and other works of art have been reported, and have been attributed to the interaction of the pigment with the binding media. A previous study by Fourier transform infrared spectroscopy showed lead white to induce a change in the state of hydration of protein-based binders, though the mechanism of this process is still not well understood. In this work, we apply in situ 1 H unilateral nuclear magnetic resonance (NMR) to explore the nature of the interaction between lead white and collagen-based binders while at the same time we evaluate the feasibility of applying unilateral 1 H-NMR to assess the condition of the paint in medieval-illuminated manuscripts and to follow up the effectiveness of consolidation treatments. Carr, Purcell, Meiboom, and Gill (CPMG) measurements reveal that the addition of lead white to binders derived from collagen, such as bone, rabbit skin or fish glues, increases the T 2eff relaxation constant of these binders. This effect is more pronounced at low relative humidity. The increase in T 2eff suggests that the pigment induces a change in the protein that leads

Nondestructive Testing of Objects from Cultural Heritage with NMR

“…The evaluation by mono-exponential fitting, inverse Laplace transformation, and multivariate data analysis consistently showed an increased T 2eff of the binder when lead white is present in the mixture due to a transition from an ordered secondary protein structure to a more mobile random coil state. These material changes are easily observed using NMR relaxation measurements and can be used as an indication for the change of the conservation state of the art materials [34].…”

A non‐invasive NMR relaxometric characterization of the cyclododecane–solvent system inside porous substrates

“…[12][13][14] Moreover the spin-spin and spin-lattice relaxations can also be affected by the interaction between the binder and pigment. [15] Finally, these two parameters can be used to describe plastic, polymer, rubber and gum, all very common materials in modern and contemporary art. [16,17] In this contribution, the longitudinal and transversal decays are useful in distinguishing between solution and solid CDD contributions.…”

Identification of complex structures of paintings on canvas by NMR: Correlation between NMR profile and stratigraphy

“…Moreover, the pigment can influence the relaxation properties, and studies about the interaction between lead white pigments and collagen-based binders have been performed. [38] Recently, NMR has been used to study painted canvas. In previous studies, [21,39,40] NMR profiling was used to monitor the moisture uptake in controlled relative humidity atmosphere and after the application of solvent-cleaning procedures.…”