Did you know that Pera Museum’s Anatolian Weights and Measures Collection houses a gift by Neslişah Sultan, the granddaughter of both the last Ottoman Sultan Vahdettin and the last caliph Abdülmecit?
Made as a jewellery item out of early Islamic glass weights and used in Egypt, this Ottoman period artefact is a donation to the Pera Museum by Princess Neslişah Sultan (Osmanoğlu), Princess Imperial of the Ottoman Empire and Princess of Egypt.
The bracelet is made using gold and gilded silver, and the glass weights themselves.
These Islamic weights were called “sanja”s. (sence in Turkish) Traditionally some of these had names of caliphs, governors, imam’s, and verses from Qur’an inscribed. The weights, however, were rarely for measuring commodities: they were often for weighing coins against, to make sure they were of the right weight.
With glass weights, it wasn’t possible to scratch or scrape off parts of the object, leading to a decrease in the value of the weight, unlike their metal counterparts. This attribute made the glass weights preferable as they rendered it difficult to cheat during commerce and trade.
The colors of the sanjas varied per the raw material added during production. Usually the colors blue, green and the shades of blue-green were made with iron and cobalt oxides. The amber color is thought to be derived from sulphur and carbon, whereas dark blue is thought to be achieved with the help of manganese.
These object were made by putting the glass melted in a furnace, on a smooth surface. The molten glass on the surface would take a circular and flattened form, due to surface tension. The hot glass would be stamped. Thus the center would be sunken, whereas the edges would be raised.
The Islamic glass weights would characteristically have an iron makeweight flake put behind the object or inside the glass. The weights that had values intolerably different than the desired official weight were quickly recycled and melted down in the furnace, to prevent them from illegally coming into circulation later on.
The Islamic glass weights were used during the Abbasid, Ayyubid and Fatimid periods. The first completely-Arabic glass weights were issued by the Caliph Abdulmalik in 692 AD. During the Abbasid period, both faces of the sanjas began to be stamped: one face would feature Shahada (Islamic profession of faith), and the other the name of a caliph, governor or imam.
Glass weights similar to sanjas were used in the earlier periods as well, since the Ptolemaic and Byzantine periods. These earlier objects were stamped with a monogram or the portrait of the ruling emperor or governor, to prevent the vendors from cheating.
In the next blog post about the Suna and İnan Kıraç Foundation Anatolian Weights and Measures Collection we will be focusing on these earlier glass weights.