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.
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".
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.