Terahertz analysis of stratified wall plaster at buildings of cultural importance across Europe

Terahertz (THz) radiation is being developed as a tool for the analysis of cultural heritage, and due to recent advances in technology is now available commercially in systems which can be deployed for field analysis. The radiation is capable of penetrating up to one centimetre of wall plaster and is delivered in ultrafast pulses which are reflected from layers within this region. The technique is non-contact, non-invasive and non-destructive. While sub-surface radar is able to penetrate over a metre of wall plaster, producing details of internal structures, infrared and ultraviolet techniques produce information about the surface layers of wall plaster. THz radiation is able to provide information about the interim region of up to approximately one centimetre into the wall surface. Data from Chartres Cathedral, France, Riga Dome Cathedral, Latvia, and Chartreuse du Val de Bénédiction, France is presented each with different research questions. The presence of sub-surface paint layers was expected from documentary evidence, dating to the 13th Century, at Chartres Cathedral. In contrast, at the Riga Dome Cathedral surface painting had been obscured as recently as 1941 during the Russian occupation of Latvia using white lead-based paint. In the 13th Century, wall paintings at the Chapel of the Frescos, Chartreuse du Val de Benediction in Villeneuve les Avignon were constructed using sinopia under-painting on plaster covering uneven stonework.. This paper compares and contrasts the ability of THz radiation to provide information about sub-surface features in churches and Cathedrals across Europe by analysing depth based profiles gained from the reflected signal. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

A reappraisal of Baskerville's Greek types

Ιn the eighteenth century the printing of Greek texts continued to be central to scholarship and discourse. The typography of Greek texts could be characterised as a continuation of French models from the sixteenth century, with a gradual dilution of the complexity of ligatures and abbreviations, mostly through printers in the Low Countries. In Britain, Greek printing was dominated by the university presses, which reproduced conservatively the continental models – exemplified by Oxford's Fell types, which were Dutch adaptations of earlier French models. Hindsight allows us to identify a meaningful development in the Greek types cut by Alexander Wilson for the Foulis Press in Glasgow, but we can argue that in the middle of the eighteenth century Baskerville was considering Greek printing the typographic environment was ripe for a new style of Greek types. The opportunity to cut the types for a New Testament (in an twin edition that included a generous octavo and a large quarto version) would seem perfect for showcasing Baskerville's capacity for innovation. His Greek type maintained the cursive ductus of earlier models, but abandoned complex ligatures and any hint of scribal flourish. He homogenised the modulation of the letter strokes and the treatment of terminals, and normalised the horizontal alignments of all letters. Although the strokes are in some letters too delicate, the narrow set of the style composes a consistent, uniform texture that is a clean break from contemporaneous models. The argument is made that this is the first Greek typeface that can be described as fully typographic in the context of the technology of the time. It sets a pattern that was to be followed, without acknowledgement, by Richard Porson nearly a century and a half later. The typeface received little praise by typographic historians, and was condemned by Victor Scholderer in his retrospective of Greek typography. A survey of typeface reviews in the surrounding decades establishes that the commentators were mostly reproducing the views of an arbitrary typographic orthodoxy, for which only types with direct references to Renaissance models were acceptable. In these comments we detect a bias against someone considered an arriviste in the scholarly printing establishment, as well as a conservative attitude to typographic innovation.