Raman spectroscopic analysis of azurite blackening
Author(s)
Date Issued
February 2008
Type
Article
Abstract
Azurite is a basic copper carbonate pigment largely employed in painting realization. The areas painted with azurite are easily alterable and are often less resistant than the other parts of artworks. The azurite
alteration in a black pigment, the copper oxide (tenorite), has been studied by micro-Raman spectroscopy. The blackening can be due to thermal or chemical alterations: in the second case the alterations being due
to the presence of alkaline conditions. Laser-induced degradation of azurite has been studied as a function of the grain size. The results show that the temperature of the grains decreases as the size increases, and azurite degrades into tenorite only below the critical value of 25 μm. To study the chemical alteration of
azurite, the pigment has been applied on the plaster of terracotta samples and analyzed at different pH values by micro-Raman spectroscopy. As opposed to most part of the analytical techniques, it can detect
the presence of both azurite and tenorite molecules in the same micro areas, and provides a valuable tool to determine azurite degradation.
Citation
E. Mattei, G. de Vivo, A. De Santis, C. Gaetani, C. Pelosi, U. Santamaria, Raman spectroscopic analysis of azurite blackening, Journal of Raman Spectroscopy, Vol. 39, Issue 2, February 2008, pp. 302-306.
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