Edgar,
pottery can be dated more accurately than +/- 100 years, for example Roman
Samian ware, which was subjected to a quickly changing fashion. Samian
ware from Italy or southern France often shows potters stamps and the
potters are known from securely dated (coins, C14) archaeological contexts
to have operated only for a few decades in total and a particular Samian
style was in fashion only for a couple of years. However, what Time Time
try to get across is that pottery may have been in use for quite some time
before it was broken/deposited, and this is especially true for the fine
wares which were used only occasionally or were mostly for display.
Metal objects on the other hand are mostly dated archaeologically, i.e.
typologically, by archaeological context/stratigraphy, closely datable
associated finds such as coins or certain types of pottery, or by
scientific dating methods applied to other associated materials/features
such as thermoluminescence dating, archaeomagnetic dating or C14 dating.
It is however generally possible to date iron-based artifacts using
radiocarbon dating. Have a look at
http://www.tms.org/pubs/journals/JOM/0305/Cook-0305.html
for this method. The obtained date ranges can be even greater than with
conventional archaeological dating. The observed physical make-up and
production techniques of metal artefacts are rather problematic for dating
purposes as these functional factors changed only little over time. This
is equally true for the typology of metal tools. Chemical composition can
be a broad indicator to some degree as it is known for example that mainly
Irish Copper and early Bronze Age artefacts can have a rather high arsenic
content. This is however complicated by the reuse of scrap metal in later
periods.
So, overall, pottery remains more closely datable than metal objects and
it is for this reason that pottery is one of the cornerstones of dating in
archaeology. I think dating metal objects more closely is one of the
archaeometallurgical research questions of the future and the attempts
made with radiocarbon dating are an interesting move in this direction.
Irene
Dr Irene Schrufer-Kolb
Associate Lecturer in Classical Studies
The Open University
Southern Region, Foxcombe Hall, Boars Hill, OXFORD OX1 5HR
Tel./FAX: +44-(0)1280-823102
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