Islamic glass weights and stamps (Egypt)

Glass weights and stamps are stamped glass pieces made in Islamic Egypt; their great advantage is that they can be dated with a precision hardly any other glass object approaches, so Nadine Schibille takes them as a chronological and compositional benchmark for Egyptian glassmaking, while granting that how far they represent the whole industry is debated. ¹

The last weight of "Egypt 2" natron composition dates to the first year of Ahmad ibn Tulun's governorship (868), after which comes a hundred-year interlude from which virtually no Egyptian glass weight or stamp is known. ² Weights reappear after the Fatimid conquest of al-Fustat in 969, by then made of soda-rich plant-ash glass. ² In the late tenth century Fatimid weights were made of Tyre-type plant-ash glass, the trade in glass now running from the Levant to Egypt. ³

Schibille analysed 33 fully opaque weights from the second quarter of the twelfth to the first quarter of the thirteenth century and found their white and aqua opacity due to tin oxide, labelling the group "Celadon" for its resemblance to jade-green celadon. ⁴ They contain up to 33% lead oxide and 27% tin oxide, and she thinks lead and tin were added together to a pre-formed glass at the working stage. ^{4 5} Some polychrome Fatimid weights have yellow and green patches resembling a lead-tin vitreous pigment known as anima. ⁴

Henri Lavoix holds that the Arabs took the use of glass weights from Byzantine monetary administration, drawing on E. T. Rogers's study of weights bearing the names of the Umayyad governors of Egypt, such as one reading "In the name of God; ordered by the amir Yazid ibn Hatim; weight of a dinar". ⁶ He cites al-Damiri for Muhammad ibn Ali advising Abd al-Malik ibn Marwan, at the time of his reform, to use glass weights that neither gain nor lose, and notes that the Cabinet des Médailles in Paris holds a glass piece inscribed "for the servant of God Abd al-Malik, Commander of the Faithful" whose weight is close to that of his dinars dated 76 and 77 AH. ⁷