THE SECTILIA PANELS OF FARAGOLA (ASCOLI SATRIANO,SOUTHERN ITALY): A MULTI‐ANALYTICAL STUDY OF THE RED,ORANGE AND YELLOW GLASS SLABS*

SEM–EDS, EMPA, ICP–MS and ICP–OES were applied to the study of three sectilia panels made of red, orange and yellow glass slabs. In order to determine the chemical state of Cu, XAS was also performed. The results indicate that, with the exception of the red samples, all slabs were made by mixing a siliceous sand with natron. The red slabs show significant compositional differences with respect to K₂O and MgO contents, probably linked to the use of plant ashes as a source of alkali. The red, orange and yellow slabs are coloured by metallic copper, cuprite and Pb antimonates, respectively. The comparison between the chemical composition of the Faragola samples and several glass reference groups did not provide conclusive evidence of provenance.     

RELIABILITY AND REPEATABILITY IN DENDROCHRONOLOGICAL ANALYSIS: TESTS USING THE FLETCHER ARCHIVE OF PANEL-PAINTING DATA

Research into the dates of timber used for art-historical objects has provided a large data set on which to test standard dendrochronological techniques. Some 177 sets of tree-ring measurements, originally analysed by the late Dr J. M. Fletcher at Oxford University, have been re-examined independently in the tree-ring laboratories at the University of Sheffield and the Museum of London Archaeology Service. The results show a high level of agreement between the laboratories. In contrast, many of the dates produced by Dr Fletcher for the paintings are not confirmed. The two different approaches described here also resulted in remarkably similar internal groupings of the dated material. These groupings probably reflect the provenance of the timbers and suggest that two different areas of the eastern Baltic supplied the bulk of the material with smaller quantities of panels originating in Britain and central Europe.     

THE SECTILIA PANELS OF FARAGOLA (ASCOLI SATRIANO,SOUTHERN ITALY): A MULTI‐ANALYTICAL STUDY OF THE GREEN,MARBLED (GREEN AND YELLOW), BLUE AND BLACKISH GLASS SLABS

Analyses at the Cu–K, Fe–K and Mn–K edge were performed to study the green, marbled (green and yellow), blue and blackish (deep greyish olive green) glass slabs decorating three sectilia panels from the archaeological site of Faragola. Results indicate that all slabs were made by mixing siliceous sand with natron, sometimes probably mixed with small percentages of plant ash. Cu²⁺ and Pb antimonates should be responsible for the opaque green colours. The dark green and yellow portions of the marbled slabs are respectively comparable to the slabs comprising only one of these colours. Cu²⁺ together with Ca antimonates probably produced light blue slabs, whereas cobalt was used to produce dark blue slabs. We consider it possible that the abundance ratio of Fe²⁺/Fe³⁺ and the complex Fe³⁺S^2? would have an effect on the blackish slabs. The contribution of Mn cannot be ascertained even if it could have played a role in darkening glass colour. The comparison between the chemical composition of Faragola samples and several glass reference groups provided no conclusive evidence of provenance; whereas, the presence of a secondary local workshop can be hypothesized.