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d’archéologie orientale - Le Caire

Verre byzantin et islamiqueByzantine and Islamic Glass

Maria Mossakowska-Gaubert

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Poids en verre, fouilles de Fusṭāṭ (© IFAO)Glass weight, Fusṭāṭ excavations (© IFAO)
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FREESTONE, Ian C. ; SCHACHNER, Lucas ; SHORTLAND, Andrew ; TITE, Michael
Natron as Flux in the Early Vitreous Materials Industry: Sources, Beginnings and Reasons for Decline
Journal of Archaeological Science 33
Elsevier, 2006, p. 521-530
http://www.sciencedirect.com/science/journal/03054403

[-4000, 900]
• Natrons as the flux in the production of vitreous materials (glazed stones, faience and glass):
– limted used of natrun in early 4th millennium B.C. for glazes of beads from Egypt,
– there is no conclusive evidence from the second millennium B.C. for the use of natron as the main flux in glass,
– the introduction of natron as a flux in glass becomes apparent from around the beginning of the 1st millennium B.C.,
– by the 5th century B.C. natron was the flux used west of the Euphrates in the great majority of glass (to the East, plant ash continued to be used as a flux),
– glass continued to be based on natron across the Levant, the Mediterranean and Europe until around the 9th century A.D.
– 9th century A.D. – phenomenon of replacment of natron as flux:
- Near East – by soda-rich plant ash; in Syria-Palestine by the early 9th century, in Egypt - occurred half a century later.
- Western Europe – by potash-rich plant ash.

• Natron sources in antiquity – written sources:
ancient: aramaic documents from Ancient Egypt, Strabo, Pliny the Elder, Eustathius, ‘Historia Monachorum in Aegypto’;
mediaeval: al-Qalqashandī;
moderrn: Claude Sicard.

– Egypt:
- Wadi Natrun - the best attested deposits;
- other possible natron sources (possibility of the confusion in the texts between the exploration of natron and that of common salt):
al-Barnuj (Western Delta),
at-Tarabiya (Eastern Delta),
al-Kab (Upper Egypt),
Biʾr Natrun (on the route to Darfur).

– Beyond Egypt:
- salt lakes near to al-Jabbul (Northern Syria) - doubtful,
- Lake Van (Armenia) - almost certainly an important source of natron from the Roman period onwards,
- Lake Pikrolimni (Mecedonia) - attested as source of natron from the 1st to 7th century A.D.

• Natron sources – results from fieldwork:
– Wadi Natrun:
- series of evaporific lakes;
- chemical analyses on the deposits: Lucas (1912), Wenigswieser (1992), Oxford University Egyptian Desert Expedition (2002-2004):
halite is the dominant mineral in the most of the lakes through most of the year,
trona (sodium carbonate mineral) forms in exploitable quantities only in certain lakes, and at certain times of year; usually present together with significant amounts of chlorides and/or sulphates.

– al-Barnuj:
- two evaporific lakes;
- chemical analyses on the evaporic crusts: Oxford University Egyptian Desert Expedition (2004):
al-Barnuj I: rich in trona and halite; al-Barnuj II: abundant halite, minor or trace amounts of trona.

• Wadi Natrun and al-Barnuj as probably the primary sources of the natron in the glass production.

• Possible reasons for the decline in use of natron in the glass production:
– demand for natron had begun to exceed the possible supply from Egypt;
– reduction of evaporation from the lakes because of reduction in temerature or an increase in rainfall – there are no records of climatic changes during the 9th century A.D. that could have affected the precipitation of natron from the Wadi Natrun and al-Barnuj lakes;
– political disturbances (revolts, unrests, Berber incursions) in the Delta and the Wadi Natrun region during the 7th, and especially the 8th and 9th centuries A.D. – probably a dominant factor in causing the shortage of natron.
Egypte Egypt Wadi Natrun production
Delta Al-Barnuj production

Version 5, données dudata date 30 janvier 2013January 30th 2013