These are the findings of an analysis of ancient Roman glass tableware that was used in Britain during the last century of Roman rule by UK researchers Caroline Jackson of the archaeology department of the University of Sheffield and Harriet Foster of the Norfolk Museums & Archaeology Service.
According to their study
published in the upcoming December issue of the Journal of Archaeological Science
, large quantities of glass were recycled in Britain during the 3rd and 4th centuries A.D.
However, the reason why this happened was not due to environmental concerns, but rather the a shortage of raw glass in the northern regions of the Roman Empire during the last centuries of Roman rule.
In an interview with Discovery News
Jackson says 'it appears much of the glass reaching Britain in the late Roman period was manufactured from recycled material.'
Believed to have originated in Mesopotamia around 2500 B.C., the art of glass-making spread to Egypt. Thereafter the most significant technological revolution - glass blowing employing a tube - occurring in the 1st century B.C. in the area of Syria and Palestine. The Romans exploited the technique and glass-making spread throughout their empire.
'We think this means the Romans were increasingly relying on recycling to produce the vessels they wanted, possibly because less glass was coming into that part of the Empire by that time,' says co-author Harriet Foster according to a Planet Earth report.
Glass takes on the colour of the various chemical elements from the sand that it is made of and thus sand from different parts of the world gives glass its own distinctive colour unless you add something else to it.
For instance, sand containing a minute amount of iron makes glass blue-green, whereas iron and sulphur make it brown.
However, the Romans already knew how to make colourless glass. If you add tiny amounts of a so-called 'decolouriser', it will come out of the furnace nearly clear. 'Although if you look closely, this glass isn't always truly colourless,' explains Foster.
The decolouriser oxidises the chemicals in the sand to remove the color and 'in the Roman period, this element would have been antimony or manganese,' said Jackson.
Colourless glass was much valued at the time. Roman author, Pliny once wrote that emperor Nero (37-68 A.D.) gave 6,000 sestertia (roughly $250,000 in today's money) for two clear glass cups (with handles) of ordinary size.
'Pliny suggests that sand for colorless glass was sourced in Italy and it has often been suggested that colorless glass manufacturing was centered in the Rhineland,' Jackson and Foster write in their study.
In order to understand more about the production and distribution of colourless glass in the late Roman period, the researchers used a spectroscopic technique to analyse the chemical composition of 128 samples of glass tableware from 19 sites across Britain.