Text, practice, and experience: an experimental approach to the archaeology of glassmaking in medieval Iberia

ABSTRACT

How might an interdisciplinary approach involving experimental archaeology improve our knowledge of glassmaking in medieval Iberia? Our current limited understanding lacks an appreciation of how surviving remains were created through the actual practice of glassmaking—herein lies the biggest single gap in knowledge. Archaeological experiments show that while the infima glassmaking recipe offers a credible guide to basic glassmaking technology, it is best interpreted as a set of learned instructions rooted in, though not describing, workshop practice. Awareness of the sensory qualities of glass, the conducting of experiments, and observation of glass production practice, all combined within a theoretical framework that embraces embodied knowledge and phenomenological aspects of space and time, suggest the potential existence of an encoded “text” of past glassmaking practice within archaeological workshop remains. The authors advocate further experimental archaeology on a more ambitious scale, exploring the sensory and performative aspects of glassmaking practice, to better learn to read the distinctive handwriting of this “text” in medieval Iberian archaeology.

KEYWORDS:

• Glassmaking
• technical recipes
• experimental archaeology
• alchemy
• transformation
• embodied knowledge
• practice

Disclosure statement

No potential conflict of interest was reported by the author(s).

Notes on contributors

John Pearson is Visiting Researcher at Newcastle University with a background in craft design and production. His archaeological research interests are post-disciplinary, centred in weaving his craft experience and knowledge together with historic, scientific and cultural studies, and a sensory and experiential approach to archaeological experiment, to enrich understanding of the social and technological aspects of past craft production, with a particular emphasis on glassmaking in medieval Spain.

Dr Chloë N. Duckworth is Lecturer in Archaeological Materials Science at Newcastle University and is a specialist in the chemical analysis of ancient and historical glass, glass recycling, the social contexts of technology, and a leading expert in the post-disciplinary study of glass from medieval Spain. For the latter, she applies a blend of historical, scientific, experimental, and archaeological research to Muslim, Christian, and Jewish contexts. She believes that all researchers studying glass should have experience in its making and working, in order to develop a proper appreciation of its material properties and resist the uncritical development of orthodoxies around the (currently) relatively limited stock of academic publications on historical glass production.

Dr Javier López-Rider is Professor of Medieval History at the University of Córdoba and member of the HUM-128 Meridies Research Group. His research focusses in two main areas: firstly, the exploitation and use of the rural landscape, the study of settlement and its interaction with the environment and nature in medieval Spain; and secondly, the science, techniques, and technology of the Middle Ages through the study of medieval technical recipes and treatises (ingredients, amounts, properties of substances, etc.), archaeological experimentation (reconstructing recipes such as wood varnish, stain removers, soaps, glass, gunpowder, body creams, hair dyes, perfumes, etc.), and material culture.

David Govantes-Edwards is Associate Researcher at Newcastle University and focusses his research on the production, circulation, and consumption of glass in the Iberian Peninsula between Late Antiquity and the Late Middle Ages, paying special attention to the transmission of technological knowledge. He follows a holistic approach, which includes the use of archaeological, archaeometric, and historical sources in order not only to trace routes of knowledge transmission but also to map them socially, examining them within their historical and social framework. He also coordinates several international research projects in Spain, which aim to investigate a number of high-profile archaeological sites with evidence for glass and glazed-ceramic production.

Notes

1 Henderson, Ancient Glass, 5.

2 For examples from the early medieval Mediterranean world outside Iberia, see Gorin-Rosen, “The Ancient Glass Industry,” 52–56; Henderson, “Archaeological and Scientific Evidence,” 226–29.

3 Charleston, “Glass Furnaces,” 11–15, Figs. 1–5.

4 Nicholson and Jackson, “The Furnace Experiment;” Sode and Kock, “Traditional Raw Glass Production;” Taylor and Hill, “Experiments.”

5 For a useful summary of these remains see Duckworth and Govantes-Edwards, “AHG Grant Report,” 9–11.

6 Jiménez Castillo et al., “Taller de vidrio,” 452–53.

7 Duckworth et al., “Electron Microprobe Analysis,” 29–30; Duckworth and Govantes-Edwards, “AHG Grant Report,” 9.

8 Salinas et al., “Glaze Production,” 2202, 2210.

9 Jiménez Castillo et al., “Taller de vidrio,” 419.

10 Henderson, “Archaeological and Scientific Evidence,” 226–29.

11 Jiménez-Castillo et al., “Taller de vidrio,” 441, 445–49, 453, 456.

12 Freestone, “Pliny on Roman Glassmaking,” 94–95; Healy, Pliny the Elder, 363; Price, “Glass Vessel Production,” 30–31.

13 Degryse, “Conclusions,” 113–14. Some sands with insufficient lime for natron glassmaking may have been suitable for glassmaking using medieval plant ash flux that contained its own lime.

14 Govantes-Edwards et al., “Glassmaking,” 275.

15 Barkoudah and Henderson, “Plant Ashes,” 297–98; Tite et al., “The Composition,” 1284–85.

16 Girón-Pascual, “Cenizas, cristal y jabón,” 216–17.

17 Guillaume Sedacer’s Sedacina Chapter XXII, discussed in Barthélémy, La Sedacina, “récipe soudam vel filiginem vel salicornium et conbure in magna quantitate in magna fóvea et convertetur in speciem lapideam salsuginosam,” XXII.4.

18 Pere Gil’s Historia natural de Catalunya, discussed in Whitehouse, “The ‘Epistola Abbreviatoria’,” 357–58.

19 Lacueva-Muñoz, Comerciantes de Sevilla, V1 814, V3 824, V3 1710, V4 204, V4 304, V4 475.

20 Duckworth, “Neither of the East nor of the West.”

21 Girón-Pascual, “Cenizas, cristal y jabón,” 216, 219–20.

22 Estrella and Asla, “El aprovisionamiento de leña,” 186–88, 190, 194; López-Rider, “La producción de carbón,” 821–27; López-Rider, “The Vegetal Landscape,” 2, 18–19.

23 Estrella and Asla, “El aprovisionamiento de leña,” 190; López-Rider, “La producción de carbón,” 821–22, 825–27, 829.

24 Bernat and Serra, “El forn de vidre,” 103; Capellà Galmés, “Artesanos vidrieros en Mallorca,” 772, 782.

25 Charcoal made from holm oak and heather were of particularly high calorific value. See López-Rider, “La producción de carbón,” 833–36.

26 Taylor and Hill, “Experiments,” 262–64.

27 There is growing literature calling for greater sensory awareness in archaeology. Some scholars argue for a paradigmatic reformulation of all archaeological theory and practice around multisensoriality, such as Hamilakis, Archaeology and the Senses, 196–97, 202–03; Tringham and Danis, “Doing Sensory Archaeology,” 48–49, 68. Others prefer a pragmatic embrace of diverse sensory studies within archaeological thinking, see Skeates and Day, “Sensory Archaeology,” 4, 14; “Afterword.”

28 Hurcombe, “A Sense of Materials,” 537.

29 Duckworth, “Sensory Perception and Experience of Glass,” 233–35, 240–41.

30 Smith, “Alchemy,” 32.

31 Von Kerssenbrock-Kosigk, “Introduction,” 12; Wright, “What Is Glass?” 314.

32 Newman, “What Alchemists Knew,” 35; Smith, “Alchemy,” 24.

33 Carmona et al., “Islamic Glasses,” 444–45; de Juan Ares and Schibille, “Glass Import and Production,” 13/19–14/19, and “La Hispania antigua y medieval a través del vidrio,” 201; Duckworth et al., “Electron Microprobe Analysis,” 46–47; Duckworth, “Glass Production,” 387.

34 Martinón-Torres, “Why Should Archaeologists,” 25–30; Moreland, Archaeology and Text, 77–78.

35 Martinón-Torres, “Why Should Archaeologists,” 15–16, 32–33.

36 Hawthorne and Smith, Theophilus; Gearhart, Theophilus.

37 For detailed discussion of these descriptions of glassmaking, see Govantes-Edwards et al., “Glassmaking.”

38 Guillame Sedacer, Sedacina Chapter XXII, discussed in Barthelemy, La Sedacina ou l’Oeuvre au crible.

39 Hieronymus Müntzer, Itinerarium Hispanicum, discussed in Duckworth, “Glass Production,” 387; Whitehouse, “The ‘Epistola Abbreviatoria’,” 357.

40 Pere Gil, Historia natural de Catalunya, discussed in Whitehouse, “The ‘Epistola Abbreviatoria’,” 357–58.

41 Glick, Islamic and Christian Spain, 274–75.

42 Epstein, “Transferring Technical Knowledge,” 64.

43 David Whitehouse Curatorial Files.

44 Govantes-Edwards et al., “Glassmaking,” 272–73, and 286–90 for a complete Latin transcription and Spanish translation by David Whitehouse.

45 Govantes-Edwards et al., “Glassmaking,” 279 n84, notes that the bishop has not yet been convincingly identified.

46 Duckworth, “Glass Production,” 387; Govantes-Edwards et al., “Recipes and Experimentation?” 184–85; Whitehouse, “The ‘Epistola Abbreviatoria’,” 355–57.

47 Whitehouse, “The ‘Epistola Abbreviatoria’,” 355, 357.

48 Govantes-Edwards et al., “Recipes and Experimentation?”

49 Whitehouse, “The ‘Epistola Abbreviatoria’,” 356.

50 See Lucas, “Project Glass Recycling!: Week 1,” and Paynter, “Experiments,” 288–90, for illustration and discussion of these interactions.

51 Salicornia ramosissima, harvested dry near Córdoba in June 2019 and burnt to ash.

52 An unspecified mixture of halophytic plants including salicornias, harvested dry from various locations in southern Spain in July and August 2015, roasted to 600°C and ground to ash.

53 Salicornia ramosissima, harvested dry near Córdoba in July 2019 and burnt to ash.

54 For Soda di Catania, see Tite et al., “The Composition,” 1286, Table 1.

55 Grogged refers to fired clay, ground and graded, that is added to a wet clay body to assist drying, reduce shrinkage, and provide strength in firing.

56 Pearson, “Text, Transformation and Practice.”

57 See also Smedley and Jackson, “Medieval and Post-Medieval Glass Technology.” Their experiments testing the effects of grain sizes and variability on packing densities of granulated raw materials that make up a batch found that measuring “parts” by weight rather than by volume, as well as producing batches with raw ingredients in relative proportions that would react readily at temperatures achievable in medieval furnaces, would deliver more consistency in their relative proportions over repeated glass batches. This was so despite inconsistencies of grain size and variability in raw materials obtained, thus enhancing glassmakers’ ability to produce a reliably consistent glass.

58 Frothingham, Spanish Glass, 27.

59 Larcher, Physiological Plant Ecology, 186–202, 298–329, 416–28; Tite et al., “The Composition,” 1285.

60 Guillame Sedacer, Sedacina Chapter XXII, discussed in Barthelemy, La Sedacina ou l’Oeuvre au crible.

61 Lacueva-Muñoz, Comerciantes de Sevilla, V4 204, V4 304, V4 475.

62 Rasmussen, How Glass Changed the World, 48.

63 Pere Gil, Historia natural de Catalunya, discussed in Whitehouse, “The ‘Epistola Abbreviatoria’,” 357–58.

64 Guillame Sedacer, Sedacina Chapter XXII, discussed in Barthelemy, La Sedacina ou l’Oeuvre au crible.

65 Hieronymus Müntzer, Itinerarium Hispanicum, discussed in Duckworth, “Glass Production,” 387; Whitehouse, “The ‘Epistola Abbreviatoria’,” 357.

66 Henderson, The Science and Archaeology of Materials, 38, 88.

67 Barkoudah and Henderson, “Plant Ashes,” 311; Tite et al., “The Composition,” 1285. Later experimental work suggests a two melt model for the chemistry of glass and scum formation, see Tanimoto and Rehren, “Interactions,” 2567, 2572.

68 Tite et al., “The Composition,” 1286, Table 1, 1289; Verità, “L’invenzione,” 15–29.

69 Taylor and Hill, “Experiments,” 262.

70 Lucas, “Looking Through the Glass.”

71 Duckworth et al., “Electron Microprobe Analysis,” 36–37; Jiménez-Castillo et al., “Taller de vidrio,” 441, 445–49, 453, 456.

72 Salinas et al., “Glaze Production,” 2202, 2210.

73 Jiménez-Castillo et al., “Taller de vidrio,” 452–55. The presence of a sandy barrier across the basin suggested deliberate containment of molten glass (whether gathered hot or extracted as a cooled slab) rather than accidental spillage.

74 Jiménez-Castillo et al., “Taller de vidrio,” 438.

75 Lucas, “Looking Through the Glass;” Taylor and Hill, “Experiments,” 255, 262.

76 Duckworth, “Sensory Perception and Experience of Glass,” 234.

77 Carruthers, The Book of Memory, 1, 2, 4, 8; Moreland, Archaeology and Text, 35.

78 Smith, “Alchemy,” 32.

79 Goody, The Domestication of the Savage Mind, 37; Moreland, Archaeology and Text, 84–85.

80 Epstein “Transferring Technical Knowledge,” 64.

81 Epstein “Transferring Technical Knowledge,” 36; von Kerssenbrock-Kosigk “Introduction,” 12.

82 Bordieu, Outline of a Theory of Practice; Gosden, Social Time and Being, 117, 119.

83 Tilley, A Phenomenology of Landscape, 9–11.

84 Gosden, Social Time and Being, 120–21.

85 Thomas, Time, Culture and Identity, 57, 59, 62.

86 For detailed descriptions of glassworking experience, see Liardet, “Learning by Hand;” O’Connor, “Embodied Knowledge in Glassblowing.”