Title
Exploiting external reflection FTIR spectroscopy for the in-situidentification of pigments and binders in illuminated manuscripts.Brochantite and posnjakite as a case study
Author
Chiara Zaffino, Vittoria Guglielmi, Silvio Faraone, Alessandro Vinaccia, Silvia Bruni
Year
2015
Journal
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy
Abstract
In the present work, the use of portable instrumentation allowing in-situ reflection FTIR analyses is
exploited to identify the coloring matters of northern-Italian illuminations dating to the XVI century.
In order to build a database of spectra, reference paint samples were prepared spreading the pigments
on parchment with two different binders, i.e. gum arabic and egg white, used in antiquity. Pigments
for the database were chosen considering their use in the Middle Ages and in the Renaissance and their
response in the mid- and near-IR region. The reflection FTIR spectra obtained resulted to be dominated by
the specular reflection component, allowing the use of the Kramers–Kronig transform to convert them to
the more conventional absorbance FTIR spectra. Several pigments could thus be identified in ancient
illuminations, even if some green details showed a spectral pattern different with respect to the most
common commercial green pigments of the database. Therefore, in addition, basic copper sulfates
brochantite and posnjakite were synthesized and characterized. In three green details, posnjakite was
identified, both as a pure compound and together with malachite.
Instrument
RMP100, V-570, FTIR 6100
Keywords
Fourier transform infrared spectroscopy, Reflection FTIR, In-situ analysis, Pigments, Illuminations, Basic copper sulfates