The natural remanent magnetisation (NRM) of the samples was measured and stepwise alternating field (AF) or thermal demagnetisation was applied.
Samples were measured either in the UK or in Austria, which allowed the comparison of results between magnetometers with different sensitivity.
The failure of some methods may be related to the suitability of the material sampled, for example if it was disturbed before sampling, had been insufficiently heated or did not contain appropriate magnetic minerals to retain a remanent magnetisation.
Caution is also recommended for laboratory procedures as the cutting of poorly consolidated specimens may disturb the material and therefore the remanent magnetisation.
The tubes and plastered hand block specimens showed good agreement in directional results, and the samples obtained showed good stability.
This will allow investigations of heated archaeological material from older parts of antiquity than previously permitted.On each structure a variety of sampling methods were used: the tube and disc techniques of Clark et al. All samples were oriented with a magnetic compass and sun compass, where weather conditions allowed.Approximately 12 discs, tubes, drill cores or plaster hand blocks were collected from each structure, with one mould plaster hand block being collected and cut into specimens.The dig also attracts Universities from across the globe to bring students and volunteers to the site each summer for field trips. A new website has been set up by Sam Harris who is undertaking Ph D research into archaeomagnetic dating (this is explained on the website) based on samples he has taken at the Ness of Broadgar.Sam’s research should provide complimentary dates to the C14 ones we have done in conjunction with the Times of Their Lives Project.These features will provide good radiocarbon dating records, alongside the archaeomagnetic signatures for the fired subsoils within and below them.