Our knowledge on the composition of the Swabian denarii in the Kingdom of Sicily (1194-1266) is still based on A. Sambon's determination performed at the beginning of 20th century and it is limited to reign of Frederick II. No analyses were carried out for Henry VI's coinage or for those of the three last Swabian kings (Conrad I, Conrad II [Corradino] and Manfredi). As Henry VI's imperial denarius equalled ½ milanese denarius (mezzano), which had a weight of 1 gram and an alloy of 500‰ Ag, it was assumed that a one-gram Sicilian denarius should have an alloy of 250‰ Ag. No data on the three last Swabian kings are available; it has been assumed that the denarii's alloy equaled Frederick's last emission of 1249. This study aims at determining the composition of the denarius alloy and its devaluations, by comparing two different analytical methods in order to guarantee reliable results. Two different techniques were used for the measurements: Laser-Induced Breakdown Spectroscopy (LIBS) and X-Ray Fluorescence (XRF). LIBS is a microdestructive superficial technique which at certain condition can be used to obtain volumetric data by exploiting the ablation effect which each laser pulse produces on the object surface. The X-Ray fluorescence, on the other hand, a non-destructive volumetric technique, which is however largely influenced by compositional inhomogeneity between the surface and the volume of the object. After a first set of measurements, the results obtained with the micro-LIBS at the University of Bari were compared with those obtained with Portable XRF at the CNR Pisa. The LIBS measurements were optimized so that the size of the micro-crater produced by the laser on the surface of the coins was minimised. The results were compared and showed good degree of similarity in the silver concentration determined by the two instruments. This outcome allowed to continue the analysis with XRF only, which has the advantage of being a non-destructive tool. This will discuss the results obtained on the whole collection and will demonstrate that the techniques employed to determine the denarii's silver content are not influenced by the surface enriched layer, which is typical of coins dating back to that historical period.
Alloy composition of the swabian denarii in the kingdom of Sicily (1194-1266). Comparison of analysis techniques, Part I
Gioacchino Tempesta
;
2017-01-01
Abstract
Our knowledge on the composition of the Swabian denarii in the Kingdom of Sicily (1194-1266) is still based on A. Sambon's determination performed at the beginning of 20th century and it is limited to reign of Frederick II. No analyses were carried out for Henry VI's coinage or for those of the three last Swabian kings (Conrad I, Conrad II [Corradino] and Manfredi). As Henry VI's imperial denarius equalled ½ milanese denarius (mezzano), which had a weight of 1 gram and an alloy of 500‰ Ag, it was assumed that a one-gram Sicilian denarius should have an alloy of 250‰ Ag. No data on the three last Swabian kings are available; it has been assumed that the denarii's alloy equaled Frederick's last emission of 1249. This study aims at determining the composition of the denarius alloy and its devaluations, by comparing two different analytical methods in order to guarantee reliable results. Two different techniques were used for the measurements: Laser-Induced Breakdown Spectroscopy (LIBS) and X-Ray Fluorescence (XRF). LIBS is a microdestructive superficial technique which at certain condition can be used to obtain volumetric data by exploiting the ablation effect which each laser pulse produces on the object surface. The X-Ray fluorescence, on the other hand, a non-destructive volumetric technique, which is however largely influenced by compositional inhomogeneity between the surface and the volume of the object. After a first set of measurements, the results obtained with the micro-LIBS at the University of Bari were compared with those obtained with Portable XRF at the CNR Pisa. The LIBS measurements were optimized so that the size of the micro-crater produced by the laser on the surface of the coins was minimised. The results were compared and showed good degree of similarity in the silver concentration determined by the two instruments. This outcome allowed to continue the analysis with XRF only, which has the advantage of being a non-destructive tool. This will discuss the results obtained on the whole collection and will demonstrate that the techniques employed to determine the denarii's silver content are not influenced by the surface enriched layer, which is typical of coins dating back to that historical period.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
