Vincent Cattersel

A differential expression analysis technology developed for linear modelling of gene expression data was used in combination with thermally assisted hydrolysis and methylation gas chromatography/mass spectrometry (THM-GC/MS) to support the analysis of lacquers and varnishes on historical objects. Exudates from tropical trees such as Manila copal, sandarac, South American copal and Congo copal, which were frequently used in finishing layers on decorative objects up to the early 20th century, were compared through this approach. Highly discriminating features indicate biomarkers that can help to identify copals in resinous lacquers. The approach allows new, more systematic ways for finding biomarkers in the analysis of lacquered objects of art and varnishes.

This study focuses on the very beginning of lacquerware production with chinoiserie decoration in Spa from the end of the seventeenth century to the third quarter of the eighteenth century. Through an interdisciplinary approach, the historical and material-technical context of this important historical lacquer production is elucidated. Archival research was conducted along with a stylistic study of thirty objects, mainly boxes. Furthermore, seventeen of the objects from this study group were chemically analysed for their organic ingredients, pigments and metal applications.

A set of 19th-century furniture in black lacquer, on papier-mâché or on turned wood, has been subjected to an in-depth observational, historical and chemical study. The results show four different technological approaches: two for the papier-mâché objects and two for the wooden chairs. The cyclic labour-intensive lacquering procedure of repeated stoving and polishing lacquer on papier-mâché with mother-of-pearl inclusions is reflected in the cross-sections. Pinaceae resin and heated oil are frequently found, conform with surviving recipes. A variant of ‘the old form of varnish’, as historically described, was likely used. In the two pairs of wooden chairs, the lacquer layers are thinner than on the papier-mâché items. They contain copal and show different stratigraphies. These observations can be the starting point to relate technological and chemical variations to different origins. New art historical findings on lacquer production and trade in England, France and Belgium, and the study of contemporary recipes, frame the analytical results in a historical context. GRAPHICAL ABSTRACT

A late 17 ^th century white European lacquered cabinet, attributed to the Gérard Dagly workshop and belonging to the Barbara Piert-Borgers private collection of Far-East and European lacquerware, has been investigated by means of terahertz time domain imaging (THz-TDI), giving new insights into its composition.

Direct identification of pigments in mediaeval illuminated manuscripts was one of the first applications of Raman spectroscopy in art and archaeology. In previous in situ analysis of handwritings, the equipment was typically provided with a single excitation source. In this work, a portable Raman spectrometer (EZRAMAN‐I‐DUAL Raman system) is introduced to characterise the pigments used in an important illuminated mediaeval manuscript, De Civitate Dei (Library in Bruges, Ms.106). Characteristics important for these in situ measurements were discussed. We introduce a set‐up that allows stable positioning of the equipment and point out the advantage of the availability of two lasers, which are part of the instrument. Good performance of the introduced Raman spectrometer, to allow pigment identification in a short time, is proved. Finally, pigments such as lead white (2PbCO₃ · Pb(OH)₂), lead–tin yellow type I (Pb₂SnO₄), malachite (Cu₂CO₃(OH)₂), mosaic gold (SnS₂), vermillion (HgS), carbon black (C), red lead (Pb₃O₄) and azurite (Cu₃(CO₃)₂(OH)₂) could be identified. These pigments were often used in mediaeval artworks and contribute to the enrichment of information of the materials used by the illuminator. Copyright © 2014 John Wiley & Sons, Ltd.