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Department of Mechanical, Aerospace and Civil Engineering

RHX method in dating archaeological ceramics

RHX dating, a method of dating archaeological ceramics that is now being used to predict expansion in structural masonry, was developed in our Department. This has significant implications for future conservation practice.

Until recently there has not been a general method that can precisely date archaeological ceramics. Heritage professionals would benefit from an independent method of precisely determining the age of ancient and historic fired-clay materials.

Led by Dr Moira Wilson, a succession of researchers based in MACE developed the RHX dating archaeological ceramics technique.


Multi-coloured broken ceramic pieces
A range of structural ceramics have been precisely dated using the RHX dating technique.

This method has been successfully applied to a range of structural ceramics. It is self-calibrating, so avoids any problems due to differences in firing temperature, mineralogy and microstructure. There are still challenges to be overcome in the transition to a mainstream archaeological dating technique that is applicable to the full range of archaeological ceramics routinely recovered.

The University of Manchester is consistently directed to contributing to the competitiveness and quality of life through applied science. English Heritage exists to protect and promote England's spectacular historic environment and ensure that its past is researched and understood. Since RHX dating was first presented in 2009 it has been a valued collaborator. When RHX dating becomes general practice it will enable those practitioners working in the heritage sector to make more informed decisions on the significance of fired-clay artefacts and monuments.

Research background

The long-term moisture expansion of bricks has been known to structural engineers for some time as it is the cause of cracking in brick masonry due to expansive stresses.

Archaeological investigations are a well-established aspect of the UK economy worth an estimated £100 million annually in England, with a vital role in building development and encouraging tourism.

Collaborative research at the Universities of Manchester and Edinburgh has shown for the first time that this process happens at a constant, but diminishing, rate over thousands of years. In 2003 Dr Moira Wilson at The University of Manchester and Christopher Hall at the University of Edinburgh worked out the kinetics of this process, enabling them to calculate the rate of expansion. Their research also discovered that this process was due to a cumulative material process, which they termed rehydroxylation.

Rehydroxylation is the super slow, progressive alteration by chemical reaction of fired-clay material with environmental moisture. All fired clay - bricks, tiles, pottery - expand on aging due to the uptake of moisture. This alteration causes a small but measurable mechanical expansion and associated increase in mass. Dr Moira Wilson's research not only provided the ability to predict expansion in structural masonry but identified the causal factor.

Dr Moira Wilson went on to hypothesise that the predictable uptake of environmental moisture in fired clay material via rehydroxylation could provide a method of directly dating archaeological ceramics and has since been collaborating with the University of Bradford and the British Museum. Ceramics are arguably the most ubiquitous find on archaeological sites worldwide, so the potential application of RHX dating is significant.