Recipes and experimentation? The transmission of glassmaking techniques in Medieval Iberia

ABSTRACT

This paper explores the potential of a combined historical and archaeological approach to the study of glass production in the Iberian Peninsula in the Late Middle Ages. The historical study of technical recipes compiled during the Late Middle Ages and the Early Modern period and the compositional analysis of archaeological material offer different, but equally valuable, insights into glass production. The methodologies, potential and limitations of these techniques are summarised, and their combined use explored, with reference to a fifteenth-century letter written by one Cristóforo de Soto Mayor, its experimental reconstruction, and the comparison of these results with real archaeological datasets.

KEYWORDS:

• Glassmaking
• technical recipes
• archaeometry
• Iberian Peninsula

Acknowledgements

The work involved in the production of this paper has benefited from different sources of funding, for which we are most grateful. The work concerning medieval recipes was carried out within the framework of the project “El conocimiento científico y técnico en la Península Ibérica (siglos XIII-XVI): producción, difusión y aplicaciones” HAR 2012-37357 (Ministerio de Economía y Competitividad), directed by author 3. The experimental work was carried out within the framework of project “Addressing the Invisible: Recycling Glass and Technological Practice in the 1^st Millenium AD”, British Academy Post-Doctoral Fellowship in the School of Archaeology and Ancient History, University of Leicester, awarded to author 2.

Notes on contributors

David J. Govantes-Edwards is a professional archaeologist and student of philosophy; his research focuses on the archaeological perspectives on technology from a theoretical point of view as well as several aspects of the archaeology of al-Andalus. He is also directly involved in a number of research projects, which include the Priniatikos Pyrgos Excavation Project (Crete, Greece), the Al-Andalus Glass Project (Spain) and the Landscapes of Construction Project (Easter Island, Chile).

Chloë N. Duckworth, after being awarded her PhD (AHRC-funded) at the University of Nottingham, established an interdisciplinary research project and network (The al-Andalus Glass Project) exploring glasses and glazed ceramics from the Muslim and Christian periods in the Iberian Peninsula. She has been involved in numerous archaeological projects in the UK, Iran, North Africa, Greece and Spain. Most recently, she was awarded a British Academy postdoctoral research fellowship, which focuses on experimental and “big data” approaches to glass recycling in the first millennium AD.

Ricardo Córdoba de la Llave, Professor at the University of Córdoba (Spain), focuses his research on the way technical knowledge was transmitted during the Middle Ages, especially via the writing of technical recipe books. In this regard, he has directed several international projects which include the foremost specialists throughout Europe. He is also a central member of the al-Andalus Glass Project.

ORCiD

Ricardo Córdoba http://orcid.org/0000-0003-0186-7290

Notes

1 Duckworth et al., “El vidrio andalusí”.

2 García Porras, “El azul en la producción”, 26–7.

3 Frothingham, Spanish Glass, 52–9.

4 “In 1189 the monastery of Poblet granted to the glassblower Guillem the right to gather glasswort in return for tithe and two hundred pounds of sheet glass paid annually.” Glick, Islamic and Christian Spain, 241.

5 The earliest known recipes thought to pertain to glass are strongly framed around the creation of various colours. See Oppenheim et al., Glass and Glassmaking.

6 Duckworth, “Imitation, artificiality and creation”.

7 See for example: Pliny, Natural History 36.106, 109, 110, 190–9, 37.29; Josephus, Jewish War 2.189–90; Strabo, Geography 16.2.25; Martial, Epigrams 1.41.1–5, 12.74, 94; Statius Silvae 1.6.70–4.

8 Freestone et al., “The Lycurgus Cup”.

9 Merrifield, Original Treatises. The treatise was found in the nineteenth century in the convent of San Salvatore, in Bologna, but the authors do not know its current whereabouts.

10 In simple terms, the redox conditions refer to the potential of the atmosphere for either reduction (loss of electrons) or oxidation (gain of electrons) of the materials being heated. In practical terms, redox atmospheres are varied by altering the amount of oxygen and carbon, so that a highly oxidising atmosphere is one with an excess of O₂, whereas a highly reducing atmosphere has an excess of CO (carbon monoxide).

11 Theophilus Presbyter, On Divers Arts, 47–74.

12 Agricola, De re metallica; Biringuccio, Pirotechnia.

13 Isidore of Seville, The Etymologies, 328.

14 Theophilus, On Divers Arts.

15 Pfandl, Itinerarium Hispanicum.

16 Glick, Islamic and Christian Spain, 241. Otte, Sevilla y sus mercaderes, 88-9.

17 Martinón-Torres, “Why Should Archaeologists”, 26; Córdoba, “Un recetario técnico”, 8.

18 Martinón-Torres, “Why Should Archaeologists”, 27; Smith and Hawthorne, “Mappae Clavicula”, 15.

19 Goody, The Logic of Writing.

20 Morel-Fatio and Rodríguez, Viaje de Felipe II, 31.

21 Pérez-Arantegui and Pardos, “Lustre recipes”, 164.

22 Barthélemy, La Sedacina ou l’oeuvre au crible; Neri, The Art of Glass.

23 Rodriguez, Lapidario; Barthélemy, La Sedacina ou l’oeuvre au crible.

24 Amasuno, “En torno a las fuentes”.

25 Martínez Lorca, Maestros de occidente.

26 Hill, “Arabic alchemy”.

27 Córdoba, “Un recetario técnico”, 9.

28 Best and Brightman, The Book of Secrets; Wyckoff, Albertus Magnus; Albert the Great. On the Causes.

29 Whitehouse, “The Epistola Abbreviatoria”, 355–7.

30 Pfandl, Itinerarium Hispanicum, 34–5.

31 Jiménez, “El vidrio andalusí”, 117; de Gayangos, Mohammedan Dynasties, 148 (Vol I); 311 (Vol II).

32 Henderson, Ancient Glass, 263–5; Young and Latham, Religion, Learning and Science, 328–41, 405–23.

33 For detailed coverage of the most common analytical techniques available to archaeologists, see Pollard and Heron, Archaeological Chemistry.

34 Bass et al., Serçe Limani, 4.

35 Carmona et al., “Islamic glasses”, 439–45; Duckworth et al., “Electron Microprobe Analysis”, 27–50.

36 Window glass is a specialism in itself, and going into details about these compositional studies is well beyond the scope of this paper. For results and discussion, see Bazzochi, Las vidrieras góticas; Carmona et al., “Vidrios y grisallas”; Alonso et al., “Un vidrio medieval”.

37 Whitehouse, “The Epistola Abbreviatoria”.

38 On dating the text, see Whitehouse, “The Epistola Abbreviatoria”, 355.

39 The term barrilla is a generic name used to refer to a group of plants rich in sodium, the ashes of which were profusely used in glassmaking. The term originates in the Iberian Peninsula but became widely recognised throughout Europe due to the good reputation of barilla ashes from at least the seventeenth century.

40 See for example Tanimoto and Rehren, “Interactions between silicate and salt melts”, 2567.

41 Duckworth et al., “Electron microprobe analysis”, 42.

42 E.g. Biringuccio, The Pirotechnia, 127.

43 Whitehouse, “The ‘Epistola Abbreviatora’”, 357.

44 Whitehouse, “The ‘Epistola Abbreviatora’”, 356.

45 Bimson and Freestone, “The Portland vase and other Roman cameo glasses”, 58.

46 Duckworth et al., “Electron microprobe analysis”, 32–7; Duckworth et al., “Non-destructive µXRF analysis”, 9–10.

47 Whitehouse, “The ‘Epistola Abbreviatora’”, 356.

48 Duckworth and Govantes Edwards, “Medieval glass furnaces”.

49 Córdoba, “Technology, craft and industry”, 110.

50 Theophilus, On Divers Arts, 59.

51 Agricola, De re metallica, 592.

52 Duckworth and Govantes-Edwards, “La produccion de vidrio”.

53 Biringuccio, The Pirotechnia, 131.

54 Komaroff, “Color, precious metal, and fire”, 47.