Rehydroxylation dating : assessment for archaeological application

• Main Author: Barrett, Gerard Thomas
• Published: Queen's University Belfast 2015
• Subjects: 666
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.695220

Investigations are carried out into the mass gain behaviour of fired clay ceramics following drying (130°C) and reheating (SOO°C), and the application of these mass gain properties to the dating of archaeological ceramics using a modified rehydroxylation dating (RHX) methodology, a component based approach. Gravimetric analysis is conducted using a temperature and humidity controlled glove box arrangement (featuring a top-loading balance) on eighteen samples of varied known ages and contexts; this occurs following transfer from environmentally controlled chambers where subsamples of these samples are aged at three temperatures (2S0C, 3SoC, 45°C) following drying and reheating. The sample set consists principally of post-medieval bricks, but also includes some post-medieval pottery as ·well as both Etruscan and Roman ceramics. A suite of techniques are applied to characterise these ceramics, including XRO, FTIR, p-XRF, thin-section petrography, BET analysis, TG-MS and permeametry. Significant findings are presented related to the drying of samples, the causes of poor mass gain behaviour, the mass gain behaviour following drying at 130°C and the chemisorption processes involved, the relationship between the mass gain behaviour following heating at 130°C and SOO°C, the appropriate models and descriptors of this behaviour, as well as the relationship Of the mass gain behaviour to the chemical, mineralogical, and structural properties of the ceramic involved. For RHX dating, a component based approach is presented and applied. The results are inconclusive, with the estimated ages of most samples generally far too large, neither confirming the effectiveness of a component based approach nor the use of a tA1/4 or tA1/n model. The effects of a range of factors (uncertainties, contamination, mineral alteration, short term heating effect) on the estimated ages are examined and discussed.