Dating fired-clay ceramics using long-term power law rehydroxylation kinetics

1. Moira A. Wilson1,*,
2. Margaret A. Carter1,
3. Christopher Hall2,
4. William D. Hoff1,
5. Ceren Ince1,
6. Shaun D. Savage1,
7. Bernard Mckay1 and
8. Ian M. Betts3

+Author Affiliations

1.
1
School of Mechanical, Aerospace and Civil Engineering
, University of Manchester,
PO Box 88 Manchester M60 1QD
, UK
2.
2
School of Engineering and Centre for Materials Science and Engineering
, University of Edinburgh,
The King’s Buildings Edinburgh EH9 3JL
, UK
3.
3
Museum of London Archaeology
, Mortimer Wheeler House,
46 Eagle Wharf Road London N1 7ED
, UK

1. Author for correspondence ([email protected]).

Abstract

Fired-clay materials such as brick, tile and ceramic artefacts are found widely in archaeological deposits. The slow progressive chemical recombination of ceramics with environmental moisture (rehydroxylation) provides the basis for archaeological dating. Rehydroxylation rates are described by a (time)1/4 power law. A ceramic sample may be dated by first heating it to determine its lifetime water mass gain, and then exposing it to water vapour to measure its mass gain rate and hence its individual rehydroxylation kinetic constant. The kinetic constant depends on temperature. Mean lifetime temperatures are estimated from historical meteorological data. Calculated ages of samples of established provenance from Roman to modern dates agree excellently with assigned (known) ages. This agreement shows that the power law holds precisely on millennial time scales. The power law exponent is accurately 1 4, consistent with the theory of fractional (anomalous) ‘single-file’ diffusion.