Schematic of rehydoxylation dating method. Credit: Moira
Carbon dating has been used for decades to provide accurate ages of ancient organic materials. Now archeologists have a similar – and fairly simple – technique for accurately dating heat-fired ceramic materials: rehydroxylation dating.
The method exploits the ceramic property of chemically reacting with atmospheric moisture after firing. This reaction causes the material to very slowly gain weight over its lifetime.
A team of members from the Universities of Manchester and Edinburgh discovered rehydroxylation dating and is currently working with the Museum of London. Together, they have been able to date brick samples from a number of historical eras with great accuracy.
The breakthrough actually began in 2003 when the groups discovered a framework for calculating how the rate of reaction between ceramic and water varies over time. They take a small sample of the ceramic and then weigh it with a microbalance. They then heat the sample to 500ºC (thus removing the water). The sample is again monitored with a microbalance to establish the rate at which the ceramic rehydrates. Then, it is a relatively simple matter to calculate the age of the ceramic by extrapolating the information to calculate the time it will take to regain the mass lost on heating
Thus far, they have much success with objects up to 2,000 years old and believe they can extend the technique another 8,000 years.
Tests included a ‘mystery brick.” Archeologists had already knew the age of the brick was between 339 and 344 years. The rehydroxylation method predicted that the brick was 340 years old.
The full research team was comprised of Moira Wilson, Margaret Carter, William Hoff, Ceren Ince, Shaun Savage and Bernard McKay from UM, and Chris Hall from UE plus Ian Betts from the Museum, and the team’s findings have been published online by the Proceedings of the Royal Society A.
Wilson noted that their method might be useful if several other applications. One obvious one she mentioned would be to detect forgeries in the archeological world. But she also raised another intriguing application. “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,” said Wilson. “This could potentially be useful in climate change studies.”