‘The idea came about by accident,’ explains Wilson, when researchers in Manchester found they could use heat to shrink samples of brick of all ages, from modern to Roman.
They found a relationship between the brick’s age and the amount of shrinkage; older bricks showing more shrinkage.
Any scientific method for dating pottery is very attractive.’ Currently the most well developed method is thermoluminescence dating.
This makes use of trapped electrons in lattice defects that build up in crystalline mineral inclusions in pottery (quartz, feldspar and calcite) after firing.
On reheating, the electrons escape and the amount of energy released, in the form of light, indicates the age of the ceramic.
Batt herself is an expert in archaeomagnetic dating, which is used to date samples such as hearths, found on archaeological sites. ‘Something that would add into that mix would be really useful,’ Batt says.
During firing at over 400°C, chemically combined water is driven off.