Evolution of past enamel technology and metal conservation issues: the case of two Byzantine style bindings

The results of a Raman spectroscopic study of the cloisonne' and basse-taille enamels, which beautify two Byzantine style bindings from the Marciana Library (Venice), namely the Lat. III, 111 and the MsGR.I.53 codexes, are presented in this work. The first binding dates back to the 13th century and was subject to an early restoration work in the 14th century, when new enamels substituted four originals. The second binding, from the 15th century, shows a lower number of enamels, all originals, and with a larger color palette. The white and yellow enamels of both codexes were successfully characterized and the red ones, where hematite was not used. Interestingly the white and yellow color of the 13th century enamels of the Lat. III, 111 codex has been obtained by an ancient technique of the glass technology, which was already obsolete in the 13th century, and is based on the use of calcium antimonate and Naples yellow. The white color in the other binding's enamels have been instead obtained by using cassiterite, according to the tradition of the time. Cassiterite was also mixed to Naples yellow in the enamels of the MsGR.I.53 codex, to change the yellow hue. The identification of agents determining some colors is instead uncertain or not feasible by Raman spectroscopy. The transparency of the 14th century enamels of the Lat. III, 111 codex has allowed the comparison of metal degradation below the enamels and in regions exposed to the atmosphere. Copyright (C) 2012 John Wiley & Sons, Ltd.