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Subject: Food for Thought: A New Way to Date Old Ceramics
From:    "H-Public editors" <[log in to unmask]>
Date:    Wed, January 12, 2011 11:59 pm
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A New Way to Date Old Ceramics
Marcia Goodrich
Michigan Tech News
http://www.mtu.edu/news/stories/2011/january/story35249.html

January 10, 2011?
If you are an archaeologist, determining when a pot was made is not
just a matter of checking the bottom for a time stamp. Dating
clay-based materials like ceramics recovered from archeological sites
can be time consuming, not to mention complex and expensive.

Patrick Bowen, a senior majoring in materials science and engineering,
is refining a new way of dating ceramic artifacts that could one day
shave thousands of dollars off the cost of doing archaeological
research.

Called rehydroxylation dating, the technique was recently developed by
researchers at the University of Manchester and the University of
Edinburgh. It takes advantage of ceramics? predictable tendency to
bond chemically with water over time.

?It?s simple,? says Bowen. First, dry the sample at 105 degrees
Celcius. This removes any dampness that the ceramic might have
absorbed.

Then, weigh the sample and put it in a furnace at 600 degrees Celsius.
The chemically bonded water, in the form of hydroxyl groups (single
atoms of hydrogen and oxygen bound together), forms water vapor and
evaporates. ?When you do that, you mimic what the sample was like when
it was originally fired,? says Bowen.

Then weigh the sample again and leave it alone. Over the next several
weeks, the ceramic will react with water in the air and gain weight.
Plot the gain against a time constant, and the shape of the curve
tells you the age of the ceramic. Theoretically.

But it ain?t necessarily so, Bowen discovered, working with his
advisors, Jaroslaw Drelich, an associate professor of materials
science and engineering, and Timothy Scarlett, an associate professor
of archaeology and anthropology. ?The dating process turns out to be
more complicated than the literature suggests,? he says.

Using shards of pottery dating from 1854 to 1888, which Scarlett
provided from an archaeological dig in Utah, Bowen tried out the
original dating technique at different temperatures and got
significantly different ?ages? for the shards. He then developed a new
equation that addresses those temperature effects, as well as the fact
that rehydroxylation is actually a two-step process: First, water
vapor physically penetrates the pottery. Then, it bonds chemically to
the pottery?s constituent minerals.

Bowen?s equation worked better, but not well enough to generate
definitive dates. Humidity fluctuations affected the samples? weights,
skewing the results. Now the research team is using new methods to
provide constant humidity and will run additional tests over the next
few months on various types of ceramics of different ages.

They won?t only be using rare, antique pottery this time, however.
?This year we are using broken pieces of brick from the Houghton
Parking Deck; it?s easier to come by,? says Bowen. ?Somebody hit it
with their car, and when I saw the pieces, I thought, ?Oh! Sample!??
If all goes as planned, each of those samples dated by Bowen and
fellow researcher Tyler Botbyl, a materials science and engineering
junior, will turn out to be about forty years old.

The researchers believe their work has huge potential. ?This will be a
new, low-cost tool allowing archaeologists to derive dates from
objects made over 10,000 years of human history,? said Scarlett.

Bowen wrote a paper on the team?s initial findings, which is being
considered by the Journal of the American Ceramic Society. The paper
was co-authored by fellow undergraduate Helen Ranck and both advisors.
His work was previously supported by a McArthur Research Internship
and a Michigan Tech Summer Undergraduate Research Fellowship. It is
currently supported by a Michigan Space Grant Consortium Undergraduate
Fellowship.

Michigan Technological University (mtu.edu) is a leading public
research university developing new technologies and preparing students
to create the future for a prosperous and sustainable world. Michigan
Tech offers more than 130 undergraduate and graduate degree programs
in engineering; forest resources; computing; technology; business;
economics; natural, physical and environmental sciences; arts;
humanities; and social sciences.

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