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Byzantine glass mosaic tesserae: some material considerations1

Published online by Cambridge University Press:  26 April 2016

Liz James
Liz James*
Affiliation:
Department of Art History, University of Sussex
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Abstract

Issues about the manufacture of Byzantine mosaics and the implications of these in wider terms relating to social and economic questions about the art form have been little discussed. This paper brings together evidence about Byzantine glass mosaic tesserae gathered from archaeology, glass technology and glass analysis, and synthesizes these into a discussion of three aspects: distribution; manufacture; trade and price. It looks to examine how these different elements can be used to form a more detailed composite picture about the production and distribution of Byzantine mosaics. It also proposes ways in which glass analysis can be used in a more coherent way to extend our understanding of mosaic glass production.

Type
Research Article
Information
Byzantine and Modern Greek Studies , Volume 30 , Issue 1 , 2006 , pp. 29 - 47
Copyright
Copyright © The Centre for Byzantine, Ottoman and Modern Greek Studies, University of Birmingham 2006 

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Footnotes

1

This paper was written as the result of a Leverhulme Research Fellowship. I am most grateful to the Leverhulme Trust for their support. Many people have been most generous with their time, responses to queries, advice and references. I would like to thank in particular Robert Brill, Ian Freestone, Cesare Fiori, Claire Nesbitt, Nadine Schibille, Ann Terry, Mariangela Vandini, Marco Verità, and Michelle O'Malley.

References

2 See for example Oxford Dictionary of Byzantium, ed. A. Kazhdan et al. (Oxford 1991) 1412-13, and Cutler, A., ‘The industries of art’ in The Economic History of Byzantium, Seventh to Fifteenth Centuries, ed. Laiou, A., II (Washington 2002) 557–61Google Scholar.

3 Much of what is said is based on assumptions about early Italian mosaics, drawn from Harding, C., ‘The production of medieval mosaics: the Orvieto evidence’ DOP 43 (1989), 73–102Google Scholar.

4 The two standard accounts of Byzantine glass are both over thirty years old: Philippe, J., Le Monde byzantin dans l'histoire de la verrerie (Bologna 1970)Google Scholar, and Grabar, A., ‘La verrerie d'art byzantine au Moyen Age’, Fondation Eugène Piot. Monuments et Mémoires 57 (1971) 89–128CrossRefGoogle Scholar. Both are concerned almost exclusively with ‘luxury’ glass and objets d'art. von Saldern, A., ‘Byzantine glass: Problems of terminology and chronology’, in Gilded and enamelled glass from the Middle East, ed. Ward, R. (London 1998) 1–3Google Scholar, is equally concerned with these questions, though he does acknowledge the existence of other sorts of Byzantine glass. François, V. and Spieser, J.-M., ‘Pottery and glass in Byzantium’, in Economic History of Byzantium 593–8Google Scholar, barely discuss mosaic. Elsewhere, Philippe, , ‘Reflections on Byzantine glass’, 1st International Anatolian Glass Symposium 1988 (Istanbul 1990) 43Google Scholar, notes that it is ‘beyond doubt that glass was present in the Byzantine treasuries’ yet fails to mention the tons of glass that filled churches throughout the city. A notable exception to this trend is Mundell Mango, M. and Henderson, J., ‘Glass at medieval Constantinople: Preliminary scientific evidence’, in Constantinople and its Hinterland, ed. Dagron, G. and Mango, C. (Aldershot 1995) 333–58Google Scholar.

5 Megaw, A.H.S., ‘Byzantine architecture and decoration in Cyprus: Metropolitan or provincial?’, DOP 28 (1974) 57–88Google Scholar. Livadia: Megaw, A.H.S. and Hawkins, E.J.W., ‘A fragmentary mosaic of the Orant Virgin in Cyprus’, Actes du XIV Congrès International des études byzantins, Bucharest 1972, III (1976) 363–6Google Scholar. Kiti: Megaw, A.H.S., ‘Early Byzantine monuments in Cyprus in the light of recent discoveries’, Akten des XI Internationalen Byzantinistenkongresses, Munich 1958 (1960) 345–51Google Scholar. Lythrankomi: Megaw, A.H.S. and Hawkins, E.J.W., The church of the Panagia Kanakaria at Lythrankomi in Cyprus (Washington 1977)Google Scholar. Durrës: Thierry, N., ‘Une mosaique a Dyrrachium’, Cahiers Archéologiques 18 (1968) 227–9Google Scholar, and A. Ducellier, La Façade maritime de l'Albanie au Moyen Age (Thessaloniki c.1981) 32–4.

6 Amorium: M.A.V. Gill, Amorium Reports, finds I: the Glass (1987-97) (Oxford 2002) esp. 14, 105, 262; Witte-Orr, J., ‘Fresco and mosaic fragments from the Lower City Church’, in Amorium Reports II: Research Papers and Technical Reports, ed. Lightfoot, C.S. (Oxford 2003) 139–56Google Scholar. Dereağzi: Morganstern, J., The Byzantine Church at Dereağzi and its Decoration (Tübingen 1983)Google Scholar. Sardis: Buchwald, H., ‘Sardis Church E: A preliminary report’, JÖBG 26 (1977) 265–99Google Scholar. Anazarbus: Gough, M., ‘Anazarbus’, Anatolian Studies 2, (1952), 115CrossRefGoogle Scholar. Cilicia and Isauria: Hill, S., The Early Byzantine Churches of Cilicia and Isauria (Aldershot 1996)Google Scholar. Çiftlik: Hill, S., ‘Çiftlik’, Anatolian Studies 45 (1995) 224–5Google Scholar. It should be noted that in the majority of cases cited in this paper, the presence of tesserae is simply recorded and little or no information is provided about quantity, weight or colour.

7 For the Pontos, Bryer, A.A.M. and Winfield, D., The Byzantine Monuments and Topography of the Pontos (Washington 1985) 150, 176, 238Google Scholar. It is possible that Bessarion's description of the palace at Trebizond includes a description of mosaics (ibid., 184).

8 Kartmin: Hawkins, E.J.W. and Mundell, M., ‘The mosaics of the monastery of Mar Samuel, Mar Simeon and Mar Gabriel near Kartmin; with a note on the Greek inscriptions by Cyril Mango’ DOP 27 (1973) 280–96Google Scholar. Shikmona and other sites: Ovadiah, A., Corpus of the Byzantine churches in the Holy Land (Bonn 1970)Google Scholar and Bagatti, B., Ancient Christian villages of Samaria (Jerusalem 2002)Google Scholar, e.g. 72, where Bagatti records picking up gold tesserae.

9 Delougaz, P. and Haines, R.C., A Byzantine Church at Khirbat al-Karak (Chicago 1960)Google Scholar esp. 26-7, 49 and 56.

10 Buzov, M., ‘Early Christian mosaics on the Adriatic coast’, Acta XIII Congressus Internationalis Archaeologiae Christianae, III (Split 1998) 175–86Google Scholar.

11 Megaw, ‘Byzantine architecture and decoration in Cyprus’, 74. Disappointingly, he nowhere expands on this statement. Examples include Kourion and Kalavasos: Herscher, E., ‘Archaeology in Cyprus’, American Journal of Archaeology 99 (1995) 291CrossRefGoogle Scholar. For mosaic workshops, Megaw, A.H.S. ‘Interior decoration in early Christian Cyprus’, Acts of 15th International Byzantine Congress (Athens 1976) 3–29Google Scholar.

12 Corinth: Scranton, R., Shaw, J.W. and Ibrahim, L., Kenchreai, Eastern Port of Corinth, I: Topography and Architecture, I (Leiden 1978) 105Google Scholar; Shelley, J.M., ‘The Christian basilica at the Cenchrean Gate at Corinth’, Hesperia 12 (1943) 166–89CrossRefGoogle Scholar. Amphipolis: Hattersley-Smith, K., Byzantine Public Architecture between the fourth and Eleventh Centuries AD, with Special Reference to the Towns of Byzantine Macedonia (Thessaloniki 1996)Google Scholar 106 and refs. Philippi: Kourkoutidou-Nikolaidou, E., ‘Vitraux paléochrétiens à Philippes’, Corsi sull'arte Ravennati 31 (1984) 277–96Google Scholar. Knossos: Frend, W.H.C. and Johnston, D.E., ‘The Byzantine basilical church at Knossos’, ABSA 57 (1962) 190Google Scholar. Athens: Frantz, A., The Athenian Agora, vol 20: The Church of the Holy Apostles (Princeton 1971) 13Google Scholar, and n. 22; the British Museum owns tesserae from the Byzantine church in the Parthenon. Italy: Andreescu, I., ‘Les mosai'ques de la lagune venitienne aux environs de 1100’, Acts of 15th International Byzantine Congress (Athens 1976) 15–30Google Scholar, and Andreescu, , ‘A corpus of wall-mosaics, Venice, Greece, St Sophia: progress and prospects’, Byzantine Studies Congress Abstracts 5 (1979) 51–2Google Scholar. Also Gasparetto, A., ‘Matrici e aspetti della vetraria veneziana e veneta medievale’, Journal of Glass Studies 21 (1979) 76–97Google Scholar.

13 For an account of wall and roof mosaics up to the fourth century, see Sear, F., Roman Wall and Vault Mosaics (Heidelberg 1977)Google Scholar. The re-use of tesserae by Basil I is seen as evidence for a drop in production, Cutler, 'Industries of art', 560.

14 C. Lightfoot and E. Ivison, ‘Concluding remarks’, in Gill, Amorium Reports: The Glass, 259-64, though they feel it plausible that everyday glassware would be of local manufacture.

15 Ibid., citing Oxford Dictionary of Byzantium, 1412-13. Witte-Orr, ‘Fresco and mosaic fragments’, says that the 23,000+ tesserae recovered perhaps made up 1% of the total required.

16 Goren-Rosen, Y., ‘The ancient glass industry in Israel: Summary of the finds and new discoveries’ in La route du verre. Ateliers primaires et secondaires du second millénaire av. J.-C. au Moyen Age, ed. Nenna, M.-D. (Lyon 2000) 49–63Google Scholar, dealing only with Israel, is the nearest thing to a gazetteer of glass factories and workshops.

17 See, for example, Harden, D.B., ‘Ancient Glass III: Post-Roman’, Antiquities Journal 128 (1971) 78–117Google Scholar.

18 For the continuation of this industry into the Byzantine period, see Freestone, I.C. and Gorin-Rosen, Y., ‘The great glass slab at Beth She'arim, Israel: An early Islamic glass-making experiment?’, Journal of Glass Studies 41 (1999), 105–16Google Scholar. Also Goren-Rosen, ‘Ancient glass industry in Israel’; M.-D. Nenna, M. Picon and M. Vichy, ‘Ateliers primaires et secondaires en Egypte à l'époque Greco-romaine’ in La route du verre, ed. Nenna, 97-112; Freestone, I.C., Ponting, M., Hughes, M.J., ‘The origin of Byzantine glass from Maroni Petrera, Cyprus’, Archaeometry 44 (2002) 257–72CrossRefGoogle Scholar. My thanks to Ian Freestone for this reference. For some problems and a suggestion of smaller-scale regional centres of production, at least in the West, see Jackson, C.M., Baxter, M.J., Cool, H.E.M., ‘Identifying group and meaning: An investigation of Roman colourless glass’ in Échanges et commerce du verre dans le monde antique, ed. Foy, D. and Nenna, M.-D. (Montagnac 2003) 33–9Google Scholar.

19 Brill, R.H., ‘Beth She'arim’, Notes and News, Israel Exploration Journal 15 (1965) 261–2Google Scholar, and Freestone and Gorin-Rosen, ‘The great glass slab at Beth She'arim'. I.C. Freestone, Y. Gorin-Rosen, and M.J. Hughes, 'Primary glass from Israel and the production of glass in Late Antiquity and the early Islamic period’ in La route du verre, ed. Nenna, 65—6.

20 Freestone, Gorin-Rosen, Hughes, ‘Primary glass’ 52–4.

21 Aldsworth, F. et al., ‘Medieval glass-making at Tyre, Lebanon’, Journal of Glass Studies 44 (2002) 49–66Google Scholar.

22 Aldsworth et al., ‘ Medieval glass-making’. For Apollonia and its production of raw and manufactured glass, see Tal, O., Jackson-Tal, R.E. and Freestone, I., ‘New evidence of the production of raw glass at Late Byzantine Apollonia-Arsuf, Israel’, Journal of Glass Studies 46 (2004) 51–66Google Scholar.

23 Sardis: von Saldern, A., Ancient and Byzantine Glass from Sardis (Cambridge, Mass. 1980)Google Scholar; C. Foss and J. Ayer Smith, ‘Sardis', in Economic History of Byzantium, ed. Laiou, II, 615-22. Sepphoris: O. Dussart, 'Quelques indices d'ateliers de verriers en Jordane et en Syrie du sud de la fin de l'époque hellénistique à l'époque islamique’, in La route du verre, ed. Nenna, 91-6, esp. 91. Jalame: Excavations at Jalame: Site of a Glass Factory in Late Roman Palestine, ed. G. Davidson Weinberg (Columbia 1988).

24 Goren-Rosen, ‘Ancient glass industry in Israel’.

25 Stern, E.M., ‘Ancient and medieval glass from the necropolis church at Anemurium’, Annales du 9e congrès de l'association internationale pour l'histoire du verre (1983) 35–64Google Scholar. The same is suggested for Philippi in Greece: Hattersley-Smith, , Byzantine Public Architecture 69, 85Google Scholar.

26 Jalame, ed. Weinberg.

27 Foy, D., ‘Un atelier de verrier à Beyrouth au début de la conquête Islamique’, Syria 77 (2000) 239–90CrossRefGoogle Scholar.

28 Stern, E.M., ‘Early exports beyond the empire’, in Roman Glass: Two Centuries of Art and Invention, ed. Newby, M. and Painter, K. (London 1991) 151Google Scholar; Pinder-Wilson, R. and Scanlon, G., ‘Glass finds from Fustat: 1967-1971’, Journal of Glass Studies 15 (1973) 12–30Google Scholar.

29 Bezborodov, A. and Abdurazakov, A.A., ‘Newly excavated glassworks in the USSR, third-fourteenth centuries AD’, Journal of Glass Studies 6 (1964) 64–9Google Scholar; Bortoli, A. and Kazanski, M., ‘Kherson and its regions’, in Economic History of Byzantium, ed. Laiou, , II, 659–65Google Scholar. On Russian glass, see also Ivachenko, Y., ‘Le verre proto-Byzantine; recherches en Russe 1980-1990’ in Le Verre de l'antiquité tardive et du baut Moyen Age, ed. Foy, D. (Val d'Oise 1995) 319–30Google Scholar. Preslav: Jordanov, I., ‘Preslav’, in Economic History of Byzantium, ed. Laiou, , II, 667–71Google Scholar. Turnovo: Dochev, K., ‘Turnovo’, ibid., II, 673–8Google Scholar. I have been unable to get hold of the reports of these finds. Also see the summary by Noonan, T.S., ‘Technology transfer between Byzantium and Eastern Europe: A case study of the glass industry in early Russia’, in The Medieval Mediterranean: Cross-cultural Contacts, ed. Chiat, M.J. and Reyerson, K.L. (St Cloud, Minn., 1988), 105–11Google Scholar. My thanks to Robin Cormack for this reference.

30 Dell'Acqua, F., ‘Ninth century window glass from the monastery of San Vincenzo al Volturno’, Journal of Glass Studies 39 (1997) 36Google Scholar; Gasparetto, A., ‘A proposito dell'officina vetraria torcellana’, Journal of Glass Studies 9 (1967) 50–75Google Scholar

31 Jacoby, D., ‘Research on the Venetian glass industry in the Middle Ages’, Journal of Glass Studies 33 (1991) 119–20Google Scholar; Jacoby, , ‘Raw materials for the glass industries of Venice and the Terrafirma, c. 1370—c. 1460’, Journal of Glass Studies 35 (1993) 65–90Google Scholar.

32 Bass, G.F. and van Doorninck, F.H. Jr, ‘An eleventh-century shipwreck at Serçe Limani, Turkey’, International Journal of Nautical Archaeology and Underwater Exploration 7 (1978) 119–32CrossRefGoogle Scholar; Bass, G.F., ‘The nature of the Serçe Limani glass’, Journal of Glass Studies 26 (1984) 64–9Google Scholar. Also A.J. Parker, Ancient Shipwrecks of the Mediterranean (Oxford 1992) for other wrecks with glass. For trade in glass in a Roman context, Price, J., ‘Trade in glass’, in Roman Shipping and Trade: Britain and the Rhine Provinces, ed. du Plat Taylor, J. and Cleere, H. (London 1978) 70–8Google Scholar.

33 van Doorninck, F. Jr, ‘Byzantine shipwrecks’, in Economic History of Byzantium, ed. Laiou, , II, 903Google Scholar.

34 Henderson, J., ‘Glass trade and chemical analysis: A possible model for Islamic glass production’, in Foy, and Nenna, , Échanges et commerce du verre, 109–23Google Scholar.

35 Lledó, B., ‘Mold siblings in the eleventh century cullet from Serçe Limani’, journal of Glass Studies 39 (1997) 44Google Scholar. Freestone, Ponting, Hughes, ‘Byzantine glass from Maroni Petrera': the other source has yet to be identified. For similar work in Italy, see Uboldi, M. and Verità, M., ‘Scientific analyses of glass from Late Antiquity and early medieval archaeological sites in northern Italy’, Journal of Glass Studies 45 (2003) 115–38Google Scholar.

36 Philippe, Le Monde byzantin, 4; Davidson Weinberg, G., ‘A medieval mystery: Byzantine glass production’, Journal of Glass Studies 27 (1965) 127–41Google Scholar; François and Spieser, ‘Pottery and glass in Byzantium', 593-8.

37 R. Ward, ‘Introduction', in Gilded and Enamelled Glass, ed. Ward, x.

38 See, for example, Philippe, ‘Reflections on Byzantine glass', 40-6, an article that does not mention mosaics.

39 Saraçhane: Hayes, J., Excavations at Saraçhane in Istanbul, II. (Princeton 1992) 399–421Google Scholar. Mosaic and window glass appear in vol. 1. Kariye and Pantokrator: Megaw, A.H.S. ‘Notes on recent work of the Byzantine Institute in Istanbul’, DOP 17 (1963) 349–67Google Scholar. Lafond, J., ‘Découverte de vitraux historiques du Moyen Age’, Cahiers Archéologiques 18 (1968) 231–8Google Scholar, argued that the stained glass was Western. Most recently see DelPAcqua, F., ‘The stained glass windows from the Chora and Pantokrator monasteries: A Byzantine “mystery”’, in Restoring Byzantium. The Kariye Camii in Istanbul and the Byzantine Institute Restoration, ed. Klein, H.A. (New York 2004) 68–78Google Scholar. Von Saldern, ‘Byzantine glass’, 1-3, believes Constantinople must have had specialized glass workshops dealing with ordinary and luxury glassware.

40 The Miracles of St Eugenios imply that monks from Trebizond obtained their glass lamps from Constantinople and from Phasiane in Armenia: J.O. Rosenqvist, ‘Lamps for St Eugenios: A note on Byzantine glass’, Eranos 92 (1994) 52-9, miracles 5 and 18, which Rosenqvist dates to the ninth or tenth centuries. The Life of St Photeine mentions a glass-smelting workshop in ninth-century Constantinople:Talbot, A.-M., ‘The posthumous miracles of St Photeine’, AB 12 (1994) 88–104Google Scholar and Mundell Mango, M., ‘The commercial map of Constantinople’, DOP 54 (2002) 202Google Scholar.

41 Bouras, C., ‘Aspects of the Byzantine city, eighth to fifteenth centuries’ in Economic History of Byzantium, ed. Laiou, , II, 517Google Scholar.

42 Price, ‘Trade in glass’.

43 Von Saldern, ‘Byzantine glass from Sardis’, 92-4.

44 Beibel, F.M., ‘The mosaics’ in Gerasa, City of the Decapolis, ed. Kraeling, K.H. (New Haven 1936) 297–354Google Scholar, esp. 514 for the glass dump and 517-18 for the ‘glass court’; Mayer, C., ‘Glass from the North Theater Byzantine church and surroundings at Jerash, Jordan 1983-83’, in Preliminary Reports of ASOR-sponsored Excavations 1982-85, ed. Rast, W.E. and Zeiger, M. (Baltimore 1988) 175–222Google Scholar. For Petra, Z.T. Fiema et al., The Petra Church (Amman 2001) esp. 96-8, 370, 379 (which also deals with the analysis of the tesserae).

45 Shugar, A.N., ‘Byzantine opaque red mosaic glass tesserae from Beit Shean, Israel’ Archaeometry 42 (2000) 375–84CrossRefGoogle Scholar. My thanks to Ian Freestone for this reference.

46 Gasparetto, ‘A proposito dell'officina vetraria torcellana’.

47 Verità, M., Renier, A. and Zecchin, S., ‘Chemical analyses of ancient glass findings excavated in the Venetian lagoon’, Journal of Cultural Heritage 3 (2002) 261–71CrossRefGoogle Scholar. I am grateful to Marco Verità for this reference.

48 See Henderson, J., The Science and Archaeology of Materials: An Investigation of Inorganic Materials (London 2000) 29–38Google Scholar. Newton, R.G., ‘Recent views on ancient glasses’, Glass Technology 21(1980) 173–83Google Scholar, makes the case that it is improbable that ancient glassmakers added small proportions of colorants, suggesting that they did not have the chemical knowledge necessary. I am very grateful to Ian Freestone for discussion on this point.

49 For chemical fingerprinting, see Henderson, J., ‘The scientific analysis of ancient glass and its archaeological interpretation’ in Scientific Analysis in Archaeology and its Interpretation, ed. Henderson, J. (Oxford 1989) 30–62Google Scholar; also Verità, M., ‘Tecniche di fabbricazione dei materiali musivi vitrei: indagini chimiche e mineralogiche’, in Medieval Mosaics: Light, Color, Materials, ed. Borsook, E., Gioffredi Superbi, F. and Pagliarulo, G. (Florence 2000) 47–64Google Scholar. Brill, R.H., ‘Scientific investigations of the Jalame glasses and related finds’, in Jalame, ed. Davidson, , 263Google Scholar, states that ‘glasses made in different factories, at different times, can be distinguished on the basis of their compositions.’ Freestone, I.C., ‘Compositions and affinities of glass from the furnaces on the island site, Tyre’, journal of Glass Studies 44 (2002) 67–77Google Scholar, suggests that there is enough difference in the composition between the Serçe Limani glass and the glass from Banias to suggest that it might be possible to distinguish glasses from different primary production centres. Henderson, ‘Glass trade and chemical analysis’, is positive about the prospects for analysis. Also see the suggestions for future research made by Brill, R.H. and Pongracz, P., ‘Stained glass from St-Jean-des-Vignes (Soissons) and comparisons with glass from other medieval sites’, Journal of Glass Studies 46 (2004), 131–2Google Scholar.

50 For the significance of the River Belus, see Pliny, Natural History 5.75 and Strabo, Geography 7.16, 25. For other Classical references, see Trowbridge, M.L., Philological Studies in Ancient Glass (Urbana 1930)Google Scholar. Although Cutler, ‘Industries of art’, 560, n. 20, suggested that since the raw materials for glass were universally abundant, there was no technical reason why tesserae could not have been produced anywhere, Freestone and Gorin-Rosen, ‘The great glass slab at Bet She'arim’ on sand, and Nenna, Picon and Vichy, ‘Ateliers primaries et secondares’ on natron make it clear that specialized raw materials were required.

51 Sayre, E.V. and Smith, R.W., ‘Compositional categories of ancient glass’, Science 133 (1961) 1824–6CrossRefGoogle ScholarPubMed. For a detailed account, Henderson, Science and Archaeology of Materials, 24–108.

52 For nuances and issues, Whitehouse, D., ‘The transition from natron to plant ash in the Levant’, Journal of Glass Studies 44 (2002) 193–6Google Scholar.

53 Freestone, Gorin-Rosen and Hughes, ‘Primary glass', 65-83. Also, for the transition between Roman and Islamic glass, see Dussart, O., Velde, B., Blanc, P.-M. and Sodini, J.-P., ‘Glass from Qal'at Sem'an (Northern Syria): The reworking of glass during the transition from Roman to Islamic compositions’, Journal of Glass Studies 46 (2004), 67–83Google Scholar.

54 Freestone, I.C., Bimson, M., Buckton, D., ‘Compositional categories of Byzantine glass tesserae’, Annales du 11 congrès de l'association Internationale pour l'histoire du verre 1988 (1988) 271–80Google Scholar. Verità, M., ‘Analisi di tessere musive vitree del battistero della basilica di San Marco in Venezia’, in Scienza e tecnica del restauro della basilica di San Marco (Venice 1999) 567–85Google Scholar looks at fourteenth-century tesserae from San Marco. The glass is significantly different from that of the thirteenth-century tesserae. My thanks to Marco Verità for this reference.

55 Fiori, C., Vandini, M., Mazzotti, V., ‘Colore e technologia degli ‘smalti’ musivi dei riquadri di Giustiniano e Teodora nella Basilica di San Vitale a Ravenna’, C+CA 33 (2003) 1–20Google Scholar. My thanks to Cesare Fiori and Mariangela Vandini for this reference.

56 Ruffini, A., Fiori, C., Vandini, M., ‘Caratterizzazione chimica di vetri musivi antichi. Parte 1: metodologie d'analisi e risultati; parte 2: elaborazione dei dati analitici’, Ceramurgia 29, 4 (1999) 285–98 and 29, 5 (1999) 361-8Google Scholar. Verità, M., Profilo, B., Vallotto, M., ‘I mosaici della basilica dei Santi Cosma e Damiano a Roma: studio analitico delle tessere vitree’, Studi Rivista della Stazione sperimentale del vetro 5 (2002) 13–24Google Scholar reveal the difference between sixth-seventh and seventeenth-century tesserae at the church of SS Cosmas and Damian in Rome and suggest that a comparison with tesserae from the Great Mosque in Damascus would be informative. My thanks to Cesare Fiori, Mariangela Vandini and Marco Verità for these references.

57 Evidence about opaque red glass supports this proposition: Brill, R.H. and Cahill, N.D., ‘A red opaque glass from Sardis and some thoughts on red opaques in general’, Journal of Glass Studies 30 (1988) 16–27Google Scholar.

58 For Centcelles, see H. Schlunk, Die Mosaikkuppel von Centcelles (Mainz 1988). The analysis of tesserae is on pp. 184–9. On opacifiers, Verità, ‘Tecniche di fabbricazione’.

59 One tessera provides evidence for tin opacified glass at Nea Mone: I.C. Freestone, S.G.E. Bowman, D. Buckton, ‘Recycling in the production of Byzantine enamel’, unpublished research paper.

60 For an account, see Fiori, C., Roncuzzi-Fiorentini, I. and Vandini, M., ‘Colours and stories of the Italian mosaics’, in The Art of Ceramics: The Blend of Art and Science in Technology, ed. Claussen, N. (Techna 2001) 149–72Google Scholar. My thanks to Cesare Fiori and Mariangela Vandini for this reference.

61 Dell'Acqua, ‘Ninth century window glass’, 36 and n. 13; Buckton, D. ‘“Necessity the mother of invention“ in early medieval enamels’, Transactions of the Canadian Conference of Art Historians 3 1982 (1985) 1–6Google Scholar; Freestone, Bowman and Buckton, ‘Recycling in the production of Byzantine enamel’, unpublished research paper; Freestone, I.C., Bowman, S.G.E. and Stapleton, C.P., ‘Composition and origin of Byzantine and Early Medieval enamel glasses’ in Catalogue of Medieval Enamels in the British Museum, ed. Buckton, D. (London, forthcoming)Google Scholar. My thanks to Ian Freestone for allowing me to see and cite both of these key articles well in advance of publication.

62 Brill, R.H., Chemical Analyses of Early Glasses, vol. 1: The catalogue; vol. 2: The tables (New York 1999)Google Scholar begins this by bringing together Brill's analyses (including Byzantine tesserae) in tabular form. A third volume of analysis is awaited.

63 See the discussion by Freestone, Ponting and Hughes, ‘Glass from Maroni Petrera’, and Henderson, ‘Glass trade and chemical analysis’.

64 Mango, cited by Mundell Mango and Henderson, ‘Glass at medieval Constantinople’ 339, n. 24; François and Spieser, ‘Pottery and glass in Byzantium’ 595. However, they do not explain from where the estimate of five grams is derived.

65 McCormick, M., Origins of the European Economy: Communications and Commerce AD 300-900 (Cambridge 2001) 96.Google Scholar

66 Ibid., 97.

67 The sources are all Muslim and all tenth century, referring back to eighth-century building activities. For arguments about their validity, see Gibb, H.A.R., ‘Arab-Byzantine relations under the Umayyad Caliphate’, DOP 12 (1958) 219–34Google Scholar, texts on 225, and Cutler, A., ‘Gifts and gift exchange as aspects of the Byzantine, Arab and related economies’, DOP 55 (2001) 247–782Google Scholar. For the mosaics, see Stern, H., ‘Notes sur les mosaiques du Dôme du Rocher et de la mosquée de Damas à propos d'un livre de Mme Gautier Van Berchem’, Cahiers Archéologiques 22 (1972) 201–36Google Scholar; Hillenbrand, R., Islamic Architecture (Edinburgh 1994) 73Google Scholar.

68 For the Great Mosque in Córdoba: H. Stern, Les Mosaïques de la Grande Mosque de Cordoue (Berlin 1976), and, for the relevant texts, see P.-A. Jaubert, La Géographic d'Edrisi II (Paris 1999: reprint of Paris 1836—40) 60 and Dodds, J.D., ‘The great mosque of Córdoba’, in Al-Andalus: The Art of Islamic Spain, ed. Dodds, J.D. (New York 1992) 22Google Scholar.

69 In this case, inspired by fear to give away the tesserae. Text in Mango, C., Art of the Byzantine Empire (Toronto, 1974) 221–2Google Scholar; also Cutler, ‘Industries of art', 561.

70 As is suggested by Cutler, ‘Gifts and gift exchange’, esp. 253-4.

71 Wenzel, M., ‘Islamic gold sandwich glass: Some fragments in the David Collection’, Journal of the Royal Asiatic Society of GB and Ireland 1988 (1988) 45–72Google Scholar; Filippini, P., ‘Blown gold-sandwich glasses with gilt-glass trailed inscriptions’, Annales du lie congrès international de l'association Internationale pour l'histoire du verre 1995 (1995) 113–28Google Scholar.

72 Mundell Mango, M., ‘Beyond the amphora: Non-ceramic evidence for Late Antique industry and trade’, in Economy and Exchange in the East Mediterranean during Late Antiquity, ed. Kingsley, S. and Decker, M. (Oxford 2001) 87–107Google Scholar, esp. table 5.1.

73 Cutler, ‘Industries of art’ 560.

74 Mundell Mango, M., ‘The monetary value of silver revetments and objects belonging to churches, AD 300-700’, in Ecclesiastical Silver Plate in Sixth-century Byzantium, eds Boyd, S.A. and Mundell Mango, M. (Washington 1992) 125–6Google Scholar.

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76 Verità, M., ‘Technology and deterioration of vitreous mosaic tesserae’, Reviews in Conservation 1 (2000) 68Google Scholar. My thanks to Marco Verità for this reference. Supporting evidence for the thinness of the gold is found in Bomford, D., Dunkerton, J., Gordon, D. and Roy, A., Art in the Making: Italian Painting before 1400 (London 1990) 22Google Scholar, discussing Cennino Cennini's claim that over 100 sheets of gold leaf could be made from one florin (weight anything between 3.55 g and 3.34 g). I am very grateful to Michelle O'Malley and Christopher Poke for debate on this.

77 Eufrasiana: Terry, A. and Maguire, H., ‘The wall mosaics of the cathedral of Eufrasius in Poreč: third preliminary report’, Hortus Artium Medievalium 7 (2001) 131–66CrossRefGoogle Scholar and A. Terry and H. Maguire, Dynamic Splendor: The Wall Mosaics in the Cathedral at Porec (Penn State, forthcoming); Dereazi: Morganstern, Byzantine Church at Dereağzi 103-5; Hagia Sophia: Hawkins, E.J.W., ‘Further observations on the narthex mosaic in St Sophia at Istanbul’, DOP 22 (1968) 151–66Google Scholar.

78 Harding, C., ‘Economic dimensions in art: Mosaic versus wall-painting in Trecento Orvieto’ in Florence and Italy: Renaissance Studies in Honour of Nikolai Rubinstein, ed. Denley, P. and Elam, C. (London 1988) 503–11Google Scholar.

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