But definitive evidence of the earliest glass production long eluded archaeologists.They had found scatterings of glassware throughout the Middle East as early as the 16th century B.C. and workshops where artisans fashioned glass into finished objects, but they had never found an ancient factory where they were convinced glass had been made from its raw materials.
Two archaeologists now report finding such a factory in the ruins of an Egyptian industrial complex from the time of Rameses the Great. The well-known site, Qantir-Piramesses, in the eastern Nile delta, flourished in the 13th century B.C. as a northern capital of the pharaohs.
In an interview by e-mail last week, Dr. Thilo Rehren of the Institute of Archaeology at University College London said, "This is the first ever direct evidence for any glassmaking in the entire Late Bronze Age."
Other experts familiar with the research said the findings were important for reconstructing the ancient technology of glassmaking. But some questioned the claim that Qantir represented the first evidence of primary glass production, citing previous findings in Egypt at Amarna, which are dated a century earlier.
Dr. Rehren and Dr. Edgar B. Pusch of the Pelizaeus Museum in Hildesheim, Germany, said they had excavated cylindrical crucibles and remains of glass raw materials in various stages of production. The site yielded samples of quartz grains, thought to be the main silica source of glassmaking in the Bronze Age.
One well-preserved crucible contained a block of raw glass, and many other vessels held semifinished glass and some fragments that had been colored blue, red and purple.
In the June 17 issue of the journal Science, the two archaeologists reported, "We could identify several hundred individual vessels used in glassmaking and coloring; more than 90 percent of these are crucibles, the rest being jars."
The archaeologists concluded that this was a large-scale glassmaking operation. In the first step of production, a mixture of crushed quartz and plant ash was heated at a low temperature in ceramic vessels. Salt contaminants were then washed away from the semifinished glass. Next, the glass powder was mixed with coloring minerals and heated inside the crucibles. At the end, the containers would have been smashed to remove the glass ingots.
Dr. Caroline M. Jackson, an archaeologist at the University of Sheffield in England, said the new finds "convincingly show that the Egyptians were making their own glass in large specialized facilities that were under royal control."
Writing in an accompanying journal article, Dr. Jackson noted that at Qantir, copper was used to color glass either red or blue, a relatively difficult process, and that glass ingots were the end product. This seemed to settle a dispute among scholars: whether the Egyptians at this time were able to produce and export glass, or only rework glass into luxury goods, like colorful beads and containers for perfumes.
It was one of many uncertainties about the history of glass. Archaeologists generally credit Mesopotamia, the land between the Tigris and Euphrates Rivers, as the original and primary source of glass, as early as the 16th century. But no factories have been uncovered there.
More than a century ago, the British archaeologist Flinders Petrie discovered what he considered evidence of Bronze Age glass production at Amarna. The site is dated to the 14th-century reign of Akhenaten and therefore earlier than Qantir. But skeptics suspected that the Amarna glassworks was not a production plant, only a place where glass ingots were reworked into finished goods. And if it was a primary factory, why would records show Akhenaten requesting that glass be shipped to Egypt?
Dr. Paul Nicholson, an archaeologist at Cardiff University in Wales, pointed out that new excavations at Amarna had yielded two large furnaces, "which I believe are for use in glass production." No such furnaces have so far been uncovered at Qantir, he noted.
"It is likely that neither Amarna nor Qantir are actually the earliest in Egypt," Dr. Nicholson said in an e-mail message. But the Qantir evidence "is important and Thilo has reconstructed a possible technological sequence from it," he added.
At least, archaeologists said, Amarna and now Qantir affirm that even if the technology probably began in Mesopotamia, the Egyptians seemed to acquire it in time and left direct evidence of how glass was made in the Late Bronze Age.