Ancient clay has internal clock
- From: Jack Linthicum <jacklinthicum@xxxxxxxxxxxxx>
- Date: Wed, 20 May 2009 08:15:52 -0700 (PDT)
Just about every really ancient site has pottery around it, in the
form of broken bits if not in original form. Their new rehydroxylation
dating method, reported in Proceedings of the Royal Society A,
measures the amount of water the material has "recombined with". Brick
and tile can be dated by this method too.
"And what's strange about it is that it abides by a precise physical
law."
Ancient clay has internal clock
A new way of dating archaeological objects has been found, using water
to unlock their "internal clocks".
Fired clay ceramics start to react chemically with atmospheric
moisture as soon as it is removed from the kiln.
Researchers believe they can pinpoint the precise age of materials
like brick, tile and pottery by calculating how much its weight has
changed.
The team from Edinburgh and Manchester universities hope the method
will prove as significant as radiocarbon dating.
Edinburgh University's Christopher Hall explained: "Almost every
archaeological site has old bits of old pot but there's no good method
to date it."
Radiocarbon dating, used for bone or wood, cannot be used for ceramic
material because it does not contain carbon.
Their new rehydroxylation dating method, reported in Proceedings of
the Royal Society A, measures the amount of water the material has
"recombined with".
“ We believe the method will become standard practice ”
Professor Chris Hall Edinburgh University
Professor Hall, who described the advance as "very exciting", said it
would plug a "yawning gap in the dating methods for ceramics".
He and his team, from the universities of Edinburgh and Manchester and
the Museum of London, were able to date brick samples from Roman,
medieval and modern periods with remarkable accuracy.
They have established that their technique can be used to determine
the age of objects up to 2,000 years old but believe it has the
potential to be used to date samples around 10,000 years old.
Researchers are now planning to look at whether the new dating
technique can be applied to earthenware, bone china and porcelain.
"The recombination goes on for several thousands of years," said
Professor Hall.
"And what's strange about it is that it abides by a precise physical
law.
"If we can work out how much moisture has been taken up, we can
estimate the age of the sample."
Extreme heat
Dr Moira Wilson from Manchester University led the research. She said
the technique could also be "turned on its head and used to establish
the mean temperature of a material over its lifetime".
"If a precise date of firing were known, this could potentially be
useful in climate change studies."
The technique involves measuring the mass of a sample and then heating
it to around 500C in a furnace. This removes the water that has
combined with it over its lifetime.
The sample is then weighed in a "super-accurate" device, known as a
microbalance, to determine the precise rate at which the material will
combine with water over time.
Using the time law, it is possible to extrapolate the data to
calculate the time it will take to regain the mass lost on heating -
revealing the sample's age.
The researchers applied this technique to a range of brick and tile
samples.
They have calculated that a Roman brick sample with a known age of
about 2,000 years was 2,001 years old. A further sample with a known
age of between 708 and 758 years was calculated to have an age of 748
years.
The researchers also tested a 'mystery brick', with the real age only
revealed to them once they had completed their process. The known age
was between 339 and 344 years - and the new technique suggested the
brick was 340 years old.
The team also found that ceramic objects have their internal date
clocks reset if they are exposed to temperatures of 500C.
Bombing raids
Used on medieval brick from Canterbury, the technique repeatedly dated
the sample as being 66 years old.
Further investigation revealed that Canterbury was devastated by
incendiary bombs and fires during World War II bombing raids in 1942.
The intense heat generated by the bombing had reset the dating clock
by, in effect, re-firing the bricks.
The results also proved accurate enough to show that a brick sample
from the King Charles building in Greenwich came from reconstruction
carried out in the 1690s, and not from the original building which was
constructed between 1664 and 1649.
Professor Hall said: "This new technique could allow us to discover a
great deal about ancient artefacts by pinpointing their age and, as we
have shown in our experiments, it is also useful in determining the
age of modern materials.
"We believe the method will become standard practice."
While he pointed out that its accuracy would need to be validated many
times, he added that it is much cheaper and simpler than current
available methods.
The most widely-used technique, thermoluminescence, requires a lot of
information about the the archaeological site, he said.
"This cannot be applied to objects which have been removed from the
site to a museum. Our method does not have this problem."
Story from BBC NEWS:
http://news.bbc.co.uk/go/pr/fr/-/2/hi/uk_news/scotland/edinburgh_and_east/8058185.stm
http://www.archaeologynews.org/story.asp?ID=440684&Title=Ancient%20clay%20has%20internal%20clock
and
Fire and water reveal new archaeological dating method
20 May 2009
Scientists at The University of Manchester have developed a new way of
dating archaeological objects – using fire and water to unlock their
‘internal clocks’.
Ancient brick
The simple method promises to be as significant a technique for dating
ceramic materials as radiocarbon dating has become for organic
materials such as bone or wood.
A team from The University of Manchester and The University of
Edinburgh has discovered a new technique which they call
‘rehydroxylation dating’ that can be used on fired clay ceramics like
bricks, tile and pottery.
Working with The Museum of London, the team has been able to date
brick samples from Roman, medieval and modern periods with remarkable
accuracy.
They have established that their technique can be used to determine
the age of objects up to 2,000 years old – but believe it has the
potential to be used to date objects around 10,000 years old.
The exciting new findings have been published online today (20 May
2009) by the Proceedings of the Royal Society A.
The method relies on the fact that fired clay ceramic material will
start to chemically react with atmospheric moisture as soon as it is
removed from the kiln after firing. This continues over its lifetime
causing it to increase in weight – the older the material, the greater
the weight gain.
In 2003 the Manchester and Edinburgh team discovered a new law that
precisely defines how the rate of reaction between ceramic and water
varies over time.
The application of this law underpins the new dating method because
the amount of water that is chemically combined with a ceramic
provides an ‘internal clock’ that can be accessed to determine its
age.
The technique involves measuring the mass of a sample of ceramic and
then heating it to around 500 degrees Celsius in a furnace, which
removes the water.
The sample is then monitored in a super-accurate measuring device
known as a microbalance, to determine the precise rate at which the
ceramic will combine with water over time.
Using the time law, it is possible to extrapolate the information
collected to calculate the time it will take to regain the mass lost
on heating – revealing the sample’s age.
They have calculated that a Roman brick sample with a known age of
around 2,000 years was 2,001 years old. A further sample with a known
age of between 708 and 758 years was calculated to have an age of 748
years.
The researchers also tested a ‘mystery brick’, with the real age only
revealed to them once they had completed their process. This known age
was between 339 and 344 years – and the new technique suggested the
brick was 340 years old.
During the course of their research, the team also found that ceramic
objects have their internal date clocks reset if they are exposed to
temperatures of 500 degrees Celsius.
Used on medieval brick from Canterbury, the technique repeatedly dated
a sample as being 66 years old. Further investigation revealed that
Canterbury was devastated by incendiary bombs and fires during a
Second World War blitz in 1942. The intense heat generated by the
bombing had reset the dating clock by effectively re-firing the
bricks.
The results also proved accurate enough to show that a brick sample
from the King Charles building in Greenwich came from reconstruction
carried out in the 1690s and not from the original building which was
constructed between 1664 and 1669.
Lead author Dr Moira Wilson, Senior Lecturer in the School of
Mechanical, Aerospace and Civil Engineering (MACE), said: “These
findings come after many years of hard work. We are extremely excited
by the potential of this new technique, which could become an
established way of determining the age of ceramic artefacts of
archaeological interest.
“The method could also be turned on its head and used to establish the
mean temperature of a material over its lifetime, if a precise date of
firing were known. This could potentially be useful in climate change
studies.
“As well as the new dating method, there are also more wide-ranging
applications of the work, such as the detection of forged ceramic.”
The three-year £100,000 project was funded by the Leverhulme Trust,
with the microbalance - which measures mass to 1/10th of a millionth
of a gram – funded by a £66,000 grant from the Engineering and
Physical Science Research Council (EPSRC).
Researchers are now planning to look at whether the new dating
technique can be applied to earthenware, bone china and porcelain.
Notes for editors
For more information please contact Alex Waddington, Media Relations
Officer, the University of Manchester, 0161 275 8387 / 07717 881569.
Dr Wilson is available for comment by arrangement.
The paper, entitled ‘Dating fired-clay ceramics using long-term power-
law rehydroxylation kinetics’ has been published online and is due to
appear in a future edition of Proceedings of the Royal Society A. A
copy of the paper is available on request.
The full research team comprised Dr Moira Wilson, Dr Margaret Carter,
Prof William Hoff, Ceren Ince, Shaun Savage and Bernard McKay from The
University of Manchester, Professor Chris Hall from the School of
Engineering and Centre for Materials Science and Engineering at The
University of Edinburgh and Ian Betts from The Museum of London.
The Canterbury Archaeological Trust provided additional samples and
information for the study while Ibstock Brick Ltd provided kiln-fresh
bricks.
http://www.manchester.ac.uk/aboutus/news/display/?id=4684
.
- Follow-Ups:
- Re: Ancient clay has internal clock
- From: SolomonW
- Re: Ancient clay has internal clock
- Prev by Date: Female view of the Hohle Fels "Venus"
- Next by Date: Re: Fishing 'risk to Channel wrecks'
- Previous by thread: Hi-Res Karnak "White Chapel" images.
- Next by thread: Re: Ancient clay has internal clock
- Index(es):
Relevant Pages
|
