A XANES study of chromophores in archaeological glass

Abstract

Abstract:We applied X-ray Absorption Near Edge Spectroscopy (XANES) to obtain information on the origin of glass color of several archaeological samples and on the oxidation conditions employed during their production. We studied a series of selected glass fragments mainly from excavated primary and secondary production centers and dated to the first millennium AD containing iron and manganese in a wide compositional range. In most of the studied samples iron is rather oxidized, while Mn K-edge XANES data show that, in all the studied glass, Mn is mainly present in its reduced form (predominantly 2+), with the possible subordinate presence of Mn3+. The most oxidized samples are the HIMT (High Iron Manganese Titanium) glasses, while the less oxidized belong to the primary natron glass series from the early Islamic tank furnaces at Bet Eliezer (Israel), and to the series coming from a Roman glass workshop excavated in Basinghall Street, London. In these glasses, iron is approximately equally distributed over the 2+ and 3+ oxidation states. The XANES analyses of two glass which had been deliberately decolorized using Sb-and Mnbased decolorizers, demonstrate that Sb is more effective than Mn as oxidant.Response to Reviewers: Torino 04/10/12Dear Editor please find enclosed the revised version of the manuscript APYA-D-12-00685 "A XANES study of chromophores in archaeological glass." by Rossella Arletti, Simona Quartieri and Ian Freestone, modified after the reviewers' comments. All the points raised by the reviewers are commented in the following. Editor:The manuscript may look just as "another paper reporting the study of ancient glasses from other provenances" once the novelty eventually contained in the submitted manuscript is not dully emphasized. Beyond complementing the reported chemical data, a more detailed physical discussion of XANES results would help support the submission of the manuscript to Applied Physics A, Materials Science & Processing.-A table with the whole chemical analyses of all the samples was provided -some more details have been added to the description of the method adopted for the determination of Fe oxidation state. Powered by Editorial Manager® and Preprint Manager® from Aries Systems CorporationReviewer #1: Page 2, line 57-58: It would benefit the readers to include a reference of using arsenic to control the color due to Fe oxidation state as I found it is less common than antimony and manganese for the same role.-As far as we are aware, arsenic was not used regularly as a decolorant in glass until the eighteenth century AD in Bohemia. It was used on a regular basis in the nineteenth century (see Dungworth D, 2011. The Value of Historic Window Glass. The Historic Environment 2, 21-48). This reference has been added to the manuscript.Page 3, line 26: Please delete a space before the last bracket.-The text was corrected according to the referee suggestion Page 3, line 30: Please use a comma between 20 and 21.-The text was corrected according to the referee suggestion Page 4, line 13: The...

Spectroscopic Investigation of the Coloration and Fabrication Conditions of Medieval Blue Glasses

“…Data from this study 13‐1: ◯; 13‐2: ▵; 13‐3: ◇; 13‐4: ◻ as original (black plain symbols). Data from previous studies are reported: ❋, ×, ⧖, ▽, black symbols: blue and blue‐green glasses, gray symbols: other colors. Three domains (i), (ii) and (iii) are distinguished (see discussion).…”

“…The quantification of the redox ratio from the centroid position of the pre‐edge is complex because of the overlapping contributions of Fe 2+ and Fe 3+ and the dependence of the intensity of each contribution on the chemical composition. The redox ratios presented in this study were estimated from the edge energy position at a normalized absorbance of 0.5 and using two reference soda‐lime glasses (respectively 95 mol% and 10 mol% Fe 2+ evaluated by wet‐chemistry) . We estimated the Cu + concentration from the intensity of the feature at 8984 eV after subtracting the main edge contribution and using one reference soda‐lime glass (containing 45 mol% of Cu 2+ ).…”

“…The redox ratios presented in this study were estimated from the edge energy position at a normalized absorbance of 0.5 and using two reference soda-lime glasses (respectively 95 mol% and 10 mol% Fe 2+ evaluated by wet-chemistry). [26][27][28] We estimated the Cu + concentration from the intensity of the feature at 8984 eV after subtracting the main edge contribution and using one reference soda-lime glass (containing 45 mol% of Cu 2+ ). Redox ratios are estimated from XANES results with an error of AE5%.…”

Browning Phenomenon of Medieval Stained Glass Windows

“…Although Mn-bearing crystalline compounds have already been studied at the Mn K-edge using Si(111), [28][29][30][31][32] Si(220) [33][34][35][36] or even Si(511) monochromator crystals, 37 only few studies present measurements performed using a Si(311) monochromator. 38,39 A set of Mn-bearing crystalline compounds (Table 2) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 …”

To be purple or not to be purple? How different production parameters influence colour and redox in manganese containing glass

“…For example, Gliozzo (2017) recently drew an inventory of a large quantity of Roman decoloured glasses and calculated based on 104 samples that manganesedecoloured glass contains on average 1.10 ± 0.63 wt% of MnO with a maximum of 2.43 wt%. While the 57 purple Roman glass fragments found in the literature contain on average 2.1 ± 0.9 wt% of MnO, the manganese oxide concentration interval goes from 0.95 to 3.82 wt% (Arletti et al, 2013(Arletti et al, , 2010Bonnerot et al, 2016;Boschetti et al, 2017;Cagno et al, 2014;Cosyns et al, 2014;Freestone and Stapleton, 2015;Gallo et al, 2013;Ganio et al, 2012;Mirti et al, 2008;Möncke et al, 2014;Rehren et al, 2015;Rosenow and Rehren, 2014;Schibille et al, 2016;Silvestri et al, 2014;Van Der Linden et al, 2009). There are thus many glasses with virtually the same concentrations in iron and manganese oxides which have totally different colours.…”