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Interesting dating technique - Jack - 12th April 2012

Was put on this trail by a pottery specialist colleague...........

Only in the development/experimental phase but think of the possibilities if successful!

The Clepsydra Chronicle (Spring 2012)

Welcome to the first edition of “The Clepsydra Chronicle”, a quarterly newsletter that will be reporting developments of research into rehydroxylation (RHX). The introduction of RHX as a potential dating technique in 2009 has generated a lot of interest, and this newsletter aims to cater to this demand by providing regular updates for interested parties.
RHX is a completely new and unique approach to dating archaeological ceramics. Nothing like this has been attempted before, so we are a long way from routinely providing dating services; although commercialization is our long term aim. We would like to begin by thanking all those who expressed an interest in becoming involved with RHX. The response to the 2009 paper in Proc. Roy. Soc. A was both delightful and overwhelming. Unfortunately, we were not able to respond to all individual enquiries but we hope that many of the questions sent to us will be addressed in this and future editions of the newsletter.

The origins of RHX lie in the construction industry and the underlying principles that are exploited in this technique have been known to engineers for some time. It was only since the discovery of the RHX power time law that it became possible to apply this knowledge as a dating method. The RHX process occurs at a rate that is proportional to the fourth root of time (t1/4)law and fulfils the criteria of a scientific dating technique for archaeological material, as it is intrinsic to the object, can be associated with a specific event in the object’s lifespan and is external to any anthropogenic activity.

Meet the team

Our current funding is split over three institutions, Universities of Manchester, Edinburgh and Bradford. The Manchester team is led by Dr Moira Wilson, a physicist with a research background in water movement in porous inorganic materials. Other team members are Dr Margaret Carter, a physical chemist specialising in the deterioration processes of the major materials of construction - concrete, steel, natural stone, cement and lime masonry mortars and Dr Sarah-Jane Clelland, an archaeological scientist with a research background in applying scientific methods of analysis to archaeological materials.

The Edinburgh team is led by Dr Andrea Hamilton, an engineer and surface scientist with a background in crystal growth inside porous materials, crystal engineering, X-ray and analytical techniques applied to archaeological artefacts and modelling water transport through porous materials and crack growth. She is particularly interested in the role of contaminants on the RHX process and numerical modelling.
The Bradford team is led by Dr Cathy Batt, an archaeological scientist with a focus on integrating scientific investigations into archaeological projects, and specific expertise in scientific dating and establishing multi-method site chronologies.

Progress report

Since publishing the dates from historically dated bricks and tiles in 2009 we have been applying for funding to make the transition from building materials to archaeological ceramics. The positive response to this first paper assured us that there was a demand for this type of research and in many ways this obvious interest carried us through. We have now secured NERC funding to explore the potential for developing RHX as a method that can be applied to all archaeological and historical fired clay material. In other words, we have two years to validate RHX as a dating technique. Despite the challenges that the step from modern bricks to archaeological material presents, some progress has already been made in. We have:

  • identified a range of contaminants (organic and inorganic) present in ceramics which interfere with the rehydroxylation reaction..
  • discovered that not all types of ceramic material behave in the same way. This implies that the experimental conditions will probably have to be tailored to each material and this area requires further investigation.

From the work carried out so far we have identified a selection of ceramic materials that will provide reproducible results. We are always interested in speaking to other laboratories that have well developed RHX data sets on any type of historical ceramic and would warmly welcome any interest in developing new research funding routes through collaboration.

Current goals

Our strategy for validating RHX as a dating technique is to attempt to date as many different types of archaeological materials as possible from a range of locations and depositional environments from across the globe. As the research is very much still in the development stage, we have been working to acquire access to material which is confidently and securely dated by, ideally, a selection of other well established methods. We have already secured samples from a variety of sites worldwide and over the next two years we intend to better understand the process of RHX, how it differs (or not) in archaeological fired-clay material to bricks and to generate enough data so that we can validate this as a reliable and widely applicable dating technique.

Bluffers guide to RHX

This is a super-slow chemical reaction where atmospheric moisture is chemically recombined into fired ceramic material via a nano-scale process called single file diffusion. This leads to expansion and mass increase of the ceramic material.
Relative Humidity (RH)
This describes the amount of water vapour in a mixture of air and water vapour and is used when the rate of water evaporation is important. RH depends not only on the temperature but also on the pressure of the system under study. In nature the relative humidity in clouds is typically 101%.

Estimated Lifetime Temperature (ELT)

As rehydroxylation is a chemical process, the rate of reaction is temperature dependent. Therefore it is necessary to provide an estimate of the temperature that an individual object has been exposed to during its lifetime (i.e. since manufacture). We have developed a model based on climatic data that can calculate the ELT for most locations worldwide over the last 5000 years to within 0.1?C

This instrument is a gravimetric, dual sample water vapour sorption analyser. The technique involves very accurately measuring the weight

change of 0.5-5g samples after they have equilibrated at a range of relative humidities. The weights of one or two samples are constantly monitored and recorded as the relative humidity is held constant (or can be altered) by the blending of dry carrier gas with a saturated water vapour stream. It is a commonly used to determine the amount of water vapour which will be adsorbed by a material as a function of the relative humidity surrounding that sample.

Clepsydra (literally "water thief") is the Greek word for water clock. This is a device for measuring time via the regulated flow of liquid into (inflow type) or out from (outflow type) a vessel where the amount is then measured. Along with the sundial, water clocks are probably amongst the oldest quantitative instruments. There is evidence that they were used in Egypt and the Mesopotamian region from the second millennium BC.
In the next edition of “The Clepsydra Chronicle” we will be addressing some of the frequently asked questions about rehydroxylation.

Please send any correspondence to

Interesting dating technique - moreno - 12th April 2012

If your interested: Bernard McKay, and Ian M. Betts, I.
2009 Dating Fired-Clay Ceramics Using Long-term Power Law Rehydroxylation Kinetics.
Proceedings of the Royal Society 465:2407-2415.

Technique validation studies, like the ceramic rehydroxylation (RHX) dating project led by the University of Manchester and University of Edinburgh, U.K. is done in collaboration with educational and other non-profit organizations (i.e. The project is currently under way to increase web-based dissemination and accessibility of archaeological data.

Interesting dating technique - kevin wooldridge - 12th April 2012

This has been publicised before....I remember seeing the guy from Manchester talking about it. It might have even been publicised on BAJR.....

Interesting dating technique - kevin wooldridge - 12th April 2012

May 2009 in fact....!&highlight=rehydroxylation

Interesting dating technique - Jack - 13th April 2012

Ooops, shows how much I pay attention.

Still, exciting stuff.

Interesting dating technique - BAJR - 13th April 2012

Good enough for another punt though... can't believe it has been 3 years! what a memory Kevin!

Interesting dating technique - Wax - 14th April 2012

The rumour in this neck of the woods it that this process has the potential to date fired clay (ceramics) to the year of last firing. The implications of that to archaeology and the world of dealers in antique ceramics is enormous. Some one with a more a scientific back ground might be able to confirm or deny this

Interesting dating technique - pdurdin - 14th April 2012

Their website is sorely lacking in information. I look forward to the next newsletter though!

Interesting dating technique - Dinosaur - 14th April 2012

Will it be pitched commercially at a price anyone outside academia and the art world can afford?

We don't use half the techniques currently available due to cost, OSL springs to mind speaking as someone currently enmeshed in a programme with wince-inducing bills and another where we've got the samples but I suspect that's as far as it's going to go.....C14 and dendro are popular because they're cheap, cheerful, and gives a 'simple' one-off result (actually the last few times I've had dendro done they haven't been able to match the sequence, but am bound to strike lucky eventually and chainsaws are always fun)

Interesting dating technique - kevin wooldridge - 14th April 2012

My understanding is that it isn't necessarily year specific, but possibly within a decade or two. The process relies on the weight of the clay now and the weight immediately after firing. The difference is due to the ceramic reabsorbing moisture and the computation of that at a consistent rate equalling the length of time since the initial firing. I think there are some problems with the technique particularly with prehistoric pottery fired at lower temperatures or with ceramic that has been re-fired as part of the manufacturing process or subject to subsequent heating, but in theory the principle and the maths are sound.

Why it hasn't taken off as a common place technique in the past 3 years might be due to a number of factors. Specialist labs with extremely precise weighing machinery for one, widespread distribution of the background data needed to make the computation and perhaps inherent conservatism amongst archaeologists i.e the date ranges we have for ceramics or fired clay are precise enough for day to day analysis and further clarification is an unnecessary expense...