Chiara Zaffino

Exploiting external reflection FTIR spectroscopy for the in-situ identification of pigments and binders in illuminated manuscripts. Brochantite and posnjakite as a case study

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.

Multi-technique investigation of historical Chinese dyestuffs used in Ningxia carpets

In this article, an extensive work is presented concerning the characterization with both chromatographic (high-performance liquid chromatography) and spectroscopic (surface-enhanced Raman spectroscopy and visible reflectance spectroscopy) techniques of historical Chinese dyestuffs in several carpets, mostly coming from the Ningxia region in Northern China and dating to the seventeenth–nineteenth centuries. Notably, the color of the background of these fine artifacts has been an object of debate since, while being depicted as bright red in the ancient iconography, nowadays it appears as orange/yellow. Therefore, in addition to the identification of all the colorants used in the carpets, the present study investigated the reasons of this apparent inconsistency, pointing out an explanation based on the joined use of the yellow dye obtained from the pagoda tree and a “fugitive” dye obtained from brazilwood.