Gianluca Poldi

Multi-technique characterization of dyes in ancient Kaitag textiles from Caucasus

Kaitag textiles, named after the Kaitag district of Southwest Daghestan, Russia, where it is being manufactured, are a unique embroidered textile art form. They were used by families on special occasions such as the birth, marriage or death of one of their members and were thus passed down from generation to generation as family heirlooms. Today, only a few hundred of these precious antique specimens can still be found, and surviving examples are mostly from the seventeenth and eighteenth centuries. In this article, an extensive work for the scientific analysis of Kaitag textiles is presented as the logical continuance and updating of the investigations performed by thin layer chromatography almost two decades ago. A multi-technique approach involving the combined use of micro-invasive and nondestructive techniques suitable for in situ analyses was used, aiming to identify the colourants of Kaitag textiles and the inks employed for the underlying drawing. Analyses were performed by high-performance liquid chromatography, surface-enhanced Raman spectroscopy, scanning electron microscopy combined with energy dispersive X-ray analysis, as well as visible reflectance spectroscopy and X-ray fluorescence. In addition, infrared reflectography and ultraviolet fluorescence were employed to visualise underlying drawings and possible restorations. Corrosion phenomena observed in brown- and black-dyed areas were also investigated.

Lorenzo Lotto's painting materials: an integrated diagnostic approach.

This paper presents the results of a comprehensive diagnostic investigation carried out on five paintings (three wood panels and two paintings on canvas) by Lorenzo Lotto, one of the most significant artists of the Italian Renaissance in the first half of 16th century. The paintings considered belong to 1508-1522 period, corresponding to the most significant years of Lottos evolution. A wide array of non-invasive (reflectance spectrometry and X-ray fluorescence) and micro-invasive analytical techniques (optical microscopy, scanning electron microscopy with energy dispersive spectroscopy, micro-FTIR spectroscopy, micro-Raman spectroscopy, gas chromatography coupled with mass spectrometry and high performance liquid chromatography coupled with photodiode array detection and mass spectrometry) were applied in order to provide a large set of significant data, limiting as much as possible the sampling. This study has proved that Lottos painting palette was typical of Venetian practice of that period, but some significant peculiarities emerged: the use of two kinds of red lakes, the addition of calcium carbonate and colourless powdered glass, the latter frequently found in pictorial and ground layers. Moreover, the integrated investigation showed that Lottos technique was sometimes characterized by the use of coloured priming and multi-layer sequences with complex mixtures. Chromatographic analyses allowed to identify in all specimens: azelaic, palmitic and stearic acids, generally referring to the presence of drying oils. The extension of additional non-invasive examination to about 50 paintings by the same author, spanning from 1505 to around 1556, helped to verify the evolution in the use of some pigments, such as the yellow ones, where Pb-Sb yellow was used alongside Pb-Sn yellow.

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.