Ancient glass beads provide evidence of industry and trade routes at the time of the Romans

Aug 12, 2013
One of the glass beads investigated (actual size). Credit: Institute of Nuclear Chemistry, JGU

The raw materials for ancient glass beads found in former Rhaetian settlements in Bavaria clearly did not originate from this region. This is the conclusion following an analysis of the beads at the TRIGA research reactor of the Institute of Nuclear Chemistry at Johannes Gutenberg University Mainz (JGU). A total of 42 glass beads from four different sites were examine, 38 of them dating to the early Roman imperial period (30-60 A.D.) and four from the late Roman period (4th century A.D.).

"We were able to clearly demonstrate that all of the from the four sites are made of soda-lime glass," stated Barbara Karches of the JGU Institute of Nuclear Chemistry. The use of sodium to manufacture the glass indicates that the raw glass must have been produced in the vicinity of soda lakes rather than in the inner land. The investigations have also provided important information for historians on industry and technology, trade routes, and the lifestyle of people at that time.

The majority of the glass beads studied came from excavations undertaken in the vicinity of Oberammergau. The location at which they were found were within what represented a cult site for the Rhaetians who once settled there. The glass beads, which were used as jewelry by the locals, show traces of exposure to sacrificial fires. Other objects found there appear to have been positioned deliberately in definite patterns. "The analysis of these beads was particularly interesting for us because the items found at the cult site have provided the first that this region was already settled in the 1st century B.C.," explained Christian Stieghorst, co-supervisor of the study. With the help of a technique called neutron activation analysis (NAA), it proved possible to identify the various elements present in the beads from Oberammergau and the other sites at Heimstätten, Auerberg, and Neubiberg. The technique involved exposing the specimens to radiation in the TRIGA research reactor. When bombarded by neutrons, the atomic nuclei of the material under investigation initially become unstable. As they return to their normal state, the nuclei emit characteristic gamma radiation that has a unique profile for each element and can thus be used for identification. "TRIGA as a radiation facility offers the ideal conditions for obtaining a chemical fingerprint of specimens by completely non-destructive means," stated Dr. Gabriele Hampel, operations manager of the research reactor.

The investigations showed that all the beads are made of soda-lime glass with a sodium oxide content of up to 20 percent. This means that the raw material sodium or possibly even the finished raw glass must have originally come from somewhere near a soda lake like those in Wadi El Natrun in Egypt. In antiquity, it would not have been possible to artificially achieve a temperature of 1,800 degrees Celsius, which is the temperature required to melt pure sand to make glass. It was thus necessary to add a fluxing agent to lower the melting point, usually in the form of potash or natural soda. Potash was freely available everywhere and was used depending on the location of the glass manufactory. Potash made from seaweed or plants growing along a coastline contains more sodium because of the saline soil, whereas inland plants contain more potassium. As it is a very complex process to extract the sodium from potash, naturally occurring soda from Egypt was more frequently used.

Some of the beads stand out because of their striking colors. They were colored blue to opaque black using cobalt, copper gave them a green color, while manganese helped produce a violet color or to decolorize glass given a yellow tint by the presence of iron. Ancient manufacturers achieved a brown color for the beads with the help of iron oxide.

"We were surprised by the unusually high silver content in the Oberammergau glass beads, particularly the unexpected distribution," stated Karches. These were glazed beads which were manufactured using a two-stage treatment process. The glass inner core was first coated with a thin layer of silver and then with another layer of glass. It was a new insight and one of the more relevant results of the TRIGA investigations conducted at Mainz that silver had been used to produce the glazed beads.

Explore further: Unique entry complex discovered at Herodian Hilltop Palace

add to favorites email to friend print save as pdf

Related Stories

Researchers measure Brazil nut effect in reduced gravity

Apr 09, 2013

(Phys.org) —A combined team of researchers from the Technical University of Braunschweig in Germany and Kobe University in Japan has determined that the Brazil nut effect is less pronounced as gravity is ...

AGC creates 15% lighter glass for mobile devices

Apr 25, 2011

(PhysOrg.com) -- Asahi Glass Co. (AGC), a Tokyo-based makers of flat glass, automotive glass, display glass, chemicals and other high-tech materials and components, has announced the creation of a the world's ...

An all-glass lab-on-a-chip

Jul 04, 2013

Lab-on-a-chip devices are microfluidic cells that incorporate pipes, reaction vessels, valves and a host of other implements typically found in laboratories. These components are typically carved into a flat ...

Sunlight and air powers access to sterile water

May 04, 2012

Researchers at the University of Hull (UK) are developing a way to produce constant supplies of sterile water, powered simply by sunlight and air. The device is aimed at remote communities where conventional systems using ...

Corning VP says Gorilla Glass headed for automobiles

Jun 12, 2013

(Phys.org) —Corning Senior Vice President, Jeffrey Evenson told audience members at this year's MIT Technology Review's Mobile Summit, that its Gorilla Glass will very soon be used in automobiles. Currently, ...

Spinning up antibacterial silver on glass

Jun 27, 2013

The antibacterial effects of silver are well established. Now, researchers at Yonsei University in Seoul, Republic of Korea, have developed a technique to coat glass with a layer of silver ions that can prevent growth of ...

Recommended for you

Ancient clay seals may shed light on biblical era

Dec 20, 2014

Impressions from ancient clay seals found at a small site in Israel east of Gaza are signs of government in an area thought to be entirely rural during the 10th century B.C., says Mississippi State University archaeologist ...

Digging up the 'Spanish Vikings'

Dec 19, 2014

The fearsome reputation of the Vikings has made them the subject of countless exhibitions, books and films - however, surprisingly little is known about their more southerly exploits in Spain.

Short-necked Triassic marine reptile discovered in China

Dec 17, 2014

A new species of short-necked marine reptile from the Triassic period has been discovered in China, according to a study published December 17, 2014 in the open-access journal PLOS ONE by Xiao-hong Chen f ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.