Description

• Title:
  An outline of the major methodological issues in testing the chemical composition of historical glass (selected examples)
• Creator:
  Stawiarska, Teresa;
  Bis, Magdalena
• Description:
  The article is an attempt to identify the basic methodological problems related to research on the chemical composition of historical glass. These are methods for interpreting the results of analyses and the classifications of glass developed by various researchers (Polish included) concerning many eras and areas, mainly from the European continent. Among the vast and constantly growing literature on the subject, we only take into the consideration the publications, which in our opinion are the most important for this work, and which contain the most representative examples of the methods used. We realize that this is our subjective and arbitrary choice. The study is addressed to archaeologists undertaking archaeometric research of historical glass. The text concerns the methods commonly employed on archaeometric analyses of glass. It has been found that quantitative analyses, e.g. ICPS, AAS, SEM and EPMA, servewell in terms of the classification and interpretation procedures concerning the main glass-making components as well as colouring, discolouring and tinting agents (as part of Principal Components Analysis – PCA). On the other hand, other analyses, such as NAA, LA-ICP-MS, SSMS, allow the detection of concentrations of elements with extremely low (ultratrace) content and the isotope characteristics of glass. Conducting such a two-stage research model is the most beneficial.Among the methods for comparing the results of present analyses to those used previously is the ternary diagram. This illustrates the differences in the formulas applied tothe production of different types of glass and to compare more components than the main oxides.In the technological systematics of antique glassware, adopted by most researchers, the first level of division is the basic composition: sodium (ancient), potassium and lead. The first three levels of glass classification are well-reflected in the scheme proposed by Maria Dekówna. At the second level there are variations in basic composition, and at the third chemical types of glass. Problems with the interpretation of the results mainly appear at the second and third levels, due to the lack of generally accepted and generally applicable threshold values for individual components that would allow for an unambiguousassignment of a given type of glass to a specific group. Various, often unclear, concentration limits of elements of compositional significance are adopted: sodium (Na2O), potassium (K2O), lead (PbO), calcium (CaO), magnesium (MgO) and aluminium (Al2O3). The rules of what to include under the name of lead glass are widely discussed as are its varieties and chemical types.Some researchers apply the classification scheme proposed many years ago by J.L. Szczapowa and extended over time by the introduction of several new indicators. Others, after dividing glass varieties according to their basic composition, group them into the categories of low, medium or high concentrations of certain basic oxides (e.g. LMG, HKG, LMHK), or according to the concentrations of some sand admixtures (e.g. HA, HIMT). The proposed divisions are not always applied consistently and, as a result, are incomprehensible at times. Much attention is also paid to technological additives (discolouring agents, colouring and opacifying agents); their deliberate introduction is also subject to classification and interpretation.Interpretation of the results of analyses using mathematical and statistical methods, introduced in the later decades of the 20th century, included the use of the clustering algorithm, with an appropriate selection of indicators, in line with the rigours of glass-making technology. Extensive statistical programmes using cluster analysis, principal component analysis and discriminant analysis are also currently in use.Isotope analyses, which have revolutionized research on historical glassware, are aimed at determining its ‘geological provenance’. Analyses of the isotopes of lead (Pb) as well as the rare earth elements (REE) – strontium (Sr) and neodymium (Nd), allow the identification of alkaline and lead raw materials as well as the sands used for glass-making. For the determination of silica sources, the strontium (Sr) and neodymium (Nd) indicators actuallyreflect the geological characteristics of the lime contained in the sand. The text presents the most characteristic examples of methods for comparing the results of the glass analyses used by several groups of researchers at the end of the 20th century and the beginning of the 21st: Robert H. Brill and Colleen P. Stapleton, Julian Henderson, Simone Cagno, Karl Hans Wedepohl, Ian C. Freeston, Patrick Degryse, and Polish researchers, e.g., Maria Dekówna, Tomasz Purowski, Sylwia Siemianowska, Joanna Then-Obłuska and Barbara Wagner, as well as Jerzy Kunicki-Goldfinger with their teams. To sum up, the authors point that that there is no one universal method for analysing the chemical composition of historical glassware. As technology advances, new research methods are being introduced and tested, and those previously employed are either beingdeveloped or gradually abandoned. It is important to be aware not only of their usefulness, but also the limitations resulting from their application. Considerable risk is involved in comparing the results of analysis achieved using different methods. The results regarding the analytes, whose content is below the detection limit of one method but not of another, do not allow comparison. Attention is paid to the terminology used in this multifaceted research area, where ambiguously defined terms are regularly introduced.;
  Celem artykułu jest wskazanie niektórych, zasadniczych kwestii metodycznych związanych z badaniami składu chemicznego szkieł zabytkowych, które występują na etapie interpretacji rezultatów analiz oraz klasyfikacji technologicznej szkieł. Zarysowane tu problemy dotyczą szkieł z różnych epok i obszarów, głównie z kontynentu europejskiego. Są one omawiane z odwołaniem do przykładowych prac i zabytków, według nas najważniejszych dla poruszanych tu zagadnień, oraz wybranych publikacji zawierających główne ustalenia lub metody oraz dalszą literaturę przedmiotu. Tekst niniejszy jest adresowany do archeologów podejmujących badania archeometryczne szkieł zabytkowych.
• Object availability:
  free access
• Rights:
  Prawa autorskie (c) 2023 Teresa Stawiarska, Magdalena Bis;
  https://creativecommons.org/licenses/by-nd/4.0
• Date:
  2023.06.27
• Type:
  info:eu-repo/semantics/article;
  info:eu-repo/semantics/publishedVersion
• Language:
  Polish;
  pol
• Source:
  Acta Universitatis Nicolai Copernici Archeologia; Tom 38 (2022): Acta Universitatis Nicolai Copernici. Archeologia.; 265-315;
  2392-1234;
  0137-6616
• Format:
  application/pdf
• Publisher:
  Uniwersytet Mikołaja Kopernika w Toruniu
• Relation: https://apcz.umk.pl/AUNC_ARCH/article/view/40530/35902
• Subject:
  historical glass;
  archaeometry;
  physico-chemical glass analyses;
  methods of interpretation of analysis results;
  szkła zabytkowe;
  archeometria;
  analizy fizykochemiczne szkła;
  metody interpretacji wyników analiz
• Identifier: https://apcz.umk.pl/AUNC_ARCH/article/view/40530
• Data provider:
  Akademicka Platforma Czasopism
• Can I use it?:
  seek permission
• Type:
  text