Medieval Tuscan glasses from Miranduolo, Italy: A multi-disciplinary study

Abstract

Twenty transparent glass fragments from Miranduolo were analysed by Variable Pressure-Scanning Electron Microscopy-Energy Dispersive System (VP-SEM-EDS), Particle Induced X-Ray Emission and Particle Induced Gamma-Ray Emission (PIXE/PIGE) and Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS). The fragments are dated from mid-13th to mid-14th century CE, when the first Tuscan glass-making workshops emerged. Miranduolo did not have an in situ glass-making workshop. Hence, the aim was to determine the glass production technology and raw material provenance. All the glasses are of plant ash (PA) sodalime-silica (Na-Ca-Si) composition, with eighteen being made with Levantine plant ash (LPA), one with Barilla plant ash (BPA), and one Na-Ca-Si glass with high magnesium and low potassium (HMg-LK). The production of LPA glasses can be distinguished according to the use of different sand typologies as former. It seems probable that glasses were produced regionally from multiple Tuscan glass factories.

Evidencing Human Occupation of a Small Island Through Ancient Glass: The Case of Ustica (Palermo, Italy)

“…The Ustica glass fragments did not display significant visual signs of surface deterioration which tends to be a characteristic of soda glass as they are less prone to heavy deterioration than potassium-based (wood-ash) glasses (Orlando, Olmi, Vaggelli, & Bacci, 1996;Ortega-Feliu, Gómez-Tubío, Respaldiza, & Capel, 2011;De Bardi, Wiesinger, & Schreiner, 2013). The lack of degradation or its minimal impact (heterogeneity in occurrence and thickness) on soda glasses coming from archaeological contexts has been noted in previous studies (Genga, Siciliano, Famà, Filippo, Siciliano, Mangone, Traini, & Laganara, 2008;Posedi, 2016;Posedi, Kertész, Barrulas, Fronza, Schiavon, & (Gao et al, 2002) and results from the present study.…”

“…All these elements are considered to be impurities in the silica source and a positive correlation of iron and titanium, titanium and niobium, titanium and zirconium indicate the presence of columbite (FeNb 2 O 6 ) which is selectively deposited with Fe-Ti bearing oxide minerals (zircon and ilmenite) (Posedi et al 2019 and references therein). Columbite minerals are common in the areas where granitic rock outcrops can be found (Scott Ercit, 1994;Abdalla, Helba, Mohamed, 1998;Posedi et al 2019 and references therein).…”

Modeling of Bohemian and Moravian glass recipes from Gothic to Baroque periods

“…Glassmakers in the Renaissance and Baroque periods modified this recipe and developed new ones. When calculating the batches, it was necessary to manually adjust the values for sulfates (as SO 3 ) and chlorides (ac Cl) as they decompose and volatilize during melting [16]. We found out that setting the values for SO 3 and Cl at 0.3 wt % each fitted the best the chemical composition of finished glasses.…”

“…This is a surprising finding because there is no direct source proving the use of beech ash potash in Central Europe before the 17th century. In southern Europe however, the purification of halophytic plant ashes was a common process in the 14th century [15,16]. Due to the higher amount of iron, the favorable Fe/Mn equilibrium in the beech ash, and the reducing atmosphere in the furnace, Gothic glasses were colored green.…”

“…Historical sources suggest around 3.8 kg As 2 O 3 to 100 kg of sand [5,27]. As 2 O 3 acts as a refining agent and it also helps with glass decoloring [16].…”