An ancient glass object has kept many international scientists busy in recent years. An extensive archaeometric investigation by the Paz Laboratories in Bad Kreuznach finally revealed a sensation: the object is even more valuable than previously thought. It dates back to the beginnings of glass production
Antique glass artifact with palm frond decoration from the Meijer Collection. Photo: Meijer Collection
Antique glass artifact with palm frond decoration from the Meijer Collection. Photo: Meijer Collection
The fascination of a fragile object that has survived for several thousand years and can tell of the decline of a culture is great. It is secrets like these that fascinate collectors of antique objects. A small, elongated glass artifact with palm frond decoration from the famous Dutch W. Arnold Meijer collection has been the subject of much research in recent years. The owner acquired it at an auction in Amsterdam in 2001. In 2006/07, it was on display in a special exhibition at the Allard Pierson Museum, the archaeological museum of the University of Amsterdam. In the accompanying publication, the exceptionally beautiful piece was expertly annotated (Egypt, New Kingdom, around 1500 BC).
Following a claim by a London antiquities dealer who questioned the authenticity of the object, the collector arranged for an extensive archaeometric examination to be carried out by the Paz Laboratories in Bad Kreuznach. The scientific cooperation of experts from various disciplines of archaeology, restoration, material analysis and geology ultimately revealed a sensation: the object was even more precious than previously estimated, dating back to the very beginnings of glass production. The oldest glass artifacts are dated to around 3,000 to 4,000 years BC. They were discovered specifically in Egyptian royal tombs. Hollow glass was considered a status symbol.
Boaz Paz, head of the Paz Laboratories for Archaeometry in Bad Kreuznach, initially examined the translucent, dark blue glass artifact using the non-destructive method of X-ray fluorescence analysis. “We analyzed the glass vessel, the white, thread-like decoration and the colored components. From the data obtained, conclusions could be drawn about the recipe used for glass production, the color components and the flow and opacifying agents. In addition to the typical glass composition and the metallic admixtures, anomalies emerged that had to be clarified by further quantitative analysis of the inner glass matrix. In order to arrive at reasonable results,” the doctor of chemistry continues, “interdisciplinary work is required.”
The owner believed in the authenticity of his object and allowed tiny samples of the glass matrix to be taken. “Once we had taken these, we had them examined under a scanning electron microscope by colleagues at the Institute of Geosciences and then analyzed the generated results. We discovered that the glass – in line with the results from the surface analysis – exhibited anomalies that did not correspond to conventional ‘textbook compositions’. Metallic inclusions were visible that one would not initially expect to find in glass.” Through collaboration with other research groups and with the help of various literature sources, important clues were obtained that allowed the technological process of glass production to be specifically traced back to the beginnings of glass production.
“Archaeologists have described the parallel development of glass and metal production, which often took place in a close spatial context. In the beginning, metallic components similar to those used in the manufacture of metal objects were used in glass production. One setback, however, was that fluorine could also be measured in all three colors of glass; some isolated particles even contained greatly increased quantities. This element is widely regarded as a reference to cryolite, a modern flux that was first found and described in Greenland in 1799. Fortunately, the Heidelberg specialists, who have a background in geology, quickly realized that the fluorine-containing particles were mineral calcium fluoride, i.e. fluorspar.”
This very common mineral, the calcium salt of hydrofluoric acid, was found in large quantities in Ancient Egypt. Objects were also made from it. At this point, the research had already been going on for two years. “The next thing we noticed were encrusted structures in the hollow body of the transparent glass,” continues Boaz Paz: “We got ourselves an endoscope and discovered that the burnt sand core was still inside. What a sensation! Sand-cored jars were created long before the time of glass blowing and contain quartz, which in turn can be dated due to the firing process (heating to over 500 °C). A sufficient amount of material could be extracted from the inside of the vessel, which had been fused with the glass body during production. We sent this spectacular find to Oxford. There are independent specialists in thermoluminescence analysis with whom we work closely. We received feedback relatively quickly. Based on the samples of the sand core, the artifact could be absolutely dated: The object dates back to the very beginnings of glass production (3200/4900 BC). We were very pleased with the result. Overall, all our investigations have revealed many secrets about the vessel, which can also help other colleagues with future assessments.”
However, much research is still needed to learn more about the materials and techniques used in the fine art of ancient glassmaking.
Read more in RESTAURO 3/2017.