How to Date Pottery by Rehydroxylation
The method of rehydroxylation dating was first announced nearly two years ago, but this story in the Michigan Tech News may make the process more understandable than the earlier technical articles. And it reveals some of the complexities.
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.
The story continues here.
HT: Joe Lauer