The Egyptians are often understood to be one of the populations that first invented glass, and the history of glass manufacture in Egypt is extensive. The focus in Egyptian glass studies, like with studies of Roman glass, tend to be on manufacture – how and where glass was made. There is discussion of trade, but the majority of studies focus on the recipes used or the extent of manufacture at a particular site.
Since the focus tends to be on glass manufacture, many of the objects examined are not necessarily glass, but are directly connected to its manufacture. Crucibles, raw ingredients (e.g. antimony or natron), and glass samples from Mesopotamian, Roman and Egyptian sites are analysed in a number of ways to see how they relate to each other. There is also a focus on glass vessels, chunks, or ingots, particularly if any of them are unfinished (again relating back to manufacture).
Geographical: All studies include specimens from within the modern nation of Egypt, and some analyze samples from outside this boundary. If outside sources are used, they are either Roman (spanning across Europe) or Mesopotamian (spanning much of the Middle East). There is a large amount of focus on Amarna, Malkata, and Qantir within Egypt itself. This could be due to the abundance of material for these sites in terms of manufacture, but may also be due to the fact that most studies are written by same authors who, naturally, tend to work at the same sites. It does seem that these three sites are seen as highly important in the glass industry, though, so their emphasis may be only slightly due to author bias.
Chronological: Studies of Egyptian glass range quite widely in chronology due to the extended success of the Egyptian empire. These studies generally range from the second millennium BC through the second millennium AD, though most focus on either New Kingdom Egypt or the period of transition between Roman and Islamic styles of glass.
There are two techniques or issues discussed in Egyptian literature that warrant mention. First is Sayre’s description of vessel manufacture. He states that they were not blown, but instead formed by placing glass over a core made of sand, which may have been held in a cloth bag. The glass and core were heated repeatedly and rolled over a stone surface to create the smooth wall of the vessel. Surface decorations were applied afterwards by rolling rods of various colors onto the surface.
Another technological point is that opaque white glass may have been used as the starter for all colored glass. This would lead to issues when making translucent glass, and so I assume the intent of the statements is that white opaque glass was the starter for all opaque colored glasses. The claim is based on glass chunks and debris found at Amarna, all of which are a milky, opaque white. This would suggest that glass is colored after major glass production, but opacified before.
Chemical compositions of Egyptian glass remain largely the same as those of Roman or Islamic glasses. There is a shift from v-Na-Ca glasses early in the Egyptian industry to m-Na-Ca glass during the Roman period. There is then another shift back to an almost identical v-Na-Ca glass after the decline of Rome.
According to Roman studies, a shift occurred from m-Na-Ca glass to v-Na-Ca glass in the 8th and 9th centuries AD. Yet, according to the Egyptian studies, this is not so much a shift to a new technique as a reversion to an old one. The Egyptian sources note that around the rise of Rome, Egyptian glass shifted from v-Na-Ca to m-Na-Ca, then around the decline of Rome it shifted back to v-Na-Ca. The potash recipes used are nearly identical across time, suggesting a reversion from m-Na-Ca back to an older method. Scholars suggest that a lack of natron supply as well as political turmoil caused a decrease in the availability of natron sources, and so the shift back to potash was made to accommodate the demand for glass.
Antimony and cobalt were the main colorants, but copper and tin were also mentioned. Some sources also seem to allude to a possible m-Na-Al glass, but I haven’t found anything else about it. Shortland and Tite link m-Na-Ca glass to the use of cobalt and v-Na-Ca glass to the use of copper as colorants and suggest that Egypt imported glass as well as produced it locally to offset demand. Shortland suggests that antimony sources for colorants may have originated in the Caucasus, but remains cautious about the assertion. Degryse and others found that oxygen and neodymium measurements of glass cannot help to distinguish between Egyptian and Mesopotamian glasses, but that strontium levels provide a better means of distinction, which has interesting implications for chemical sourcing.
Many large theoretical discussions center on 1) the infrastructure of manufacture and 2) the use of opaque white glass as a base for colored products. This means that there could be primary, secondary and even tertiary manufacture sites. The first site would make the glass (either opaque white or colorless), the second would color it, and the third would form it into a finished object.
This would mean that when chemical composition analysis occurred, the recipe for the glass itself would point to the primary workshop, while the colorants used would point to a separate manufacture workshop. Yet, the colorants themselves seem to affect the chemical composition of the glass. If this is the case, then the chemical compositions of glass would take us to the coloring workshop, not just the origin of the glass itself. Additionally, if any glass-working site wished to color their own glass, then there is no way to tell the difference between a coloring workshop and a forming workshop that colors their own glass.
On the other hand, it seems very unlikely that a single workshop would focus solely on coloring the glass, let alone focus on a single color of glass. Perhaps if both the glass making and glass coloring workshop were located in the same village or very close to each other, but otherwise it seems like a waste. Having a secondary coloring workshop means that they would need to re-melt the original glass, color it, then send the re-hardened chunks to the glass working site, who would then re-melt the glass once again. It seems like an awfully large amount of work for something that could be completed by either workshop on each end, when the glass was already melted.
Similarly, it is not unusual to think of colorants being exchanged, as they are easier to exchange than the raw materials for glass itself and not much is needed to produce the necessary color. Just because a colorant does not occur naturally at a site does not mean it was not used. If coloring did occur at working sites, then it would open up the world of raw glass exchange. If only opaque white and colorless glass is changing hands, it allows the workshops to color the glass however they choose. That would require their ability to procure colorants and make the glass industry far more complex than we currently understand it to be.
Rehren mentions the idea that crucibles were made by a potter, not the glassmakers themselves. This is interesting, not because it isn’t true, but because glass scholars rarely ever mention this fairly clear connection between the glass and ceramic industries. Rehren also found that the white layer on the surface of the crucibles served to protect the vessel from corrosion and the glass from contamination. Thus, where we see glass on crucibles are probably hot spots, where the white, protective layer has melted and the molten glass has been allowed to touch the vessel.
Degryse, P, A Boyce, N Erb-Satullo, K Eremin, S Kirk, R Scott, AJ Shortland, J Schneider, and M Walton
2010 Isotopic Discriminants between Late Bronze Age Glasses from Egypt and the Near East. Archaemetry 52(3):380-388.
1997 Ramesside Glass-colouring Crucibles. Archaeometry 39(2):355-368.
2000 Rationales in Old World Base Glass Compositions. Journal of Archaeological Science 27:1225-1234.
2001 Aspects of the Production of Cobalt-Blue Glass in Egypt. Archaeometry 43(3):483-489.
Sayre, Edward V
n.d. Analytical Studies of Ancient Egyptian Glass. Report on Research carried out by the Department of Chemistry, Brookhaven National Laboratory, Upton, NY.
2002 The Use and Origin of Antimonate Colorants in Early Egyptian Glass. Archaeometry 44(4):517-530.
Shortland, AJ and MS Tite
2000 Raw Materials of Glass from Amarna and implications for the Origins of Egyptian Glass. Archaeometry 42(1):141-151.
Shortland, Andrew, Lukas Schachner, Ian Freestone, and Michael Tite
2006 Natron as a flux in early vitreous materials industry: Sources, beginnings and reasons for decline. Journal of Archaeological Science 33(4):521-530.
Smirnou, M and TH Rehren
2011 Direct Evidence of Primary Glass Production in Late Bronze Age Amarna, Egypt. Archaeometry 53(1):58-80.