A memo dated 12th February 2007, putting forward the case for the further investigation of the sheet bronze bowl from the
electron microprobe analysis – to analyse the composition of the metal;
optical microscopy – to investigate manufacture and the history of the object (there are indications that the bowl may have been repaired on site: bronze working crucibles and rivets and rivet heads)
macro investigation during sampling to detect whether the sample was taken from a repair, etc.
The macroscopic analysis could be undertaken without damaging the bowl but the electron microprobe analysis required a 1mm square piece of metal to be taken from an area of the bowl that has already been damaged. While two or three samples from different parts of the bowl are best, he is not in favour of making new holes in undamaged areas of the bowl, so would only take samples where feasible.
A Committee meeting considered the proposal and it was agreed to invite Dr. Northover to take the samples in
The following discussion of the bowl is based upon the notes taken by Nancy Hollinrake during the sampling.
Steve Minnitt mentioned that the archive of the GLV excavation seemed to record that the bowl was somewhat flattened when it was recovered from the peat outside of the crannog, but the degree of flattening was not clear. Nevertheless, its current shape is likely to be the result of some modelling by the excavators, as is the unidentified coating (probably lacquer) which has been applied to the bowl and, as Dr. Northover remarked, makes visual inspection difficult. Steve verified that there was no note as to what the coating is or when it was applied, which is a similar situation with the coating applied to the iron objects.
Despite superficial similarities with the Spettisbury bowl, also analyzed by Peter, the
These inconsistencies suggest that the bowl has been cobbled together from two different bronze vessels. The entire top sheet is a single ring of metal. The bowl was probably finished on a lathe.
The join between the two bronze sheets displays two blind rivet holes next to each other plus another, separate two blind holes elsewhere along the join; either these were punched in slightly the wrong place and not used or they refer to an earlier use. Faint scribed lines next to the rivets may be setting-out marks or may, equally, refer to former use of the metal sheet.
The bowl has been broken and repaired in antiquity in two places:
the rim has multiple repairs impossible to fully understand without a microscope and possibly an X-ray;
the base of the bowl carries a patch between two flat-head rivets, which in its turn has probably been repaired.
The bowl was, therefore, a well-used heirloom object for some time before it was deposited in the peat just outside of the palisade fence defining the limit of the settlement. On first sight, Peter suggested that the bowl was made in
Sampling took place in the back room of the museum. Since this room’s closure after the theft of bronze artefacts, it has proved very useful as storage cum meeting space for the Tribunal.
Two samples were taken for electron microprobe analysis to analyse the composition of the metal, one from each of the broken areas around the repairs.
Peter recommends that the bowl should be X-rayed to provide further information about the rim and its repairs. He and Steve agree that the bowl should be taken to the English Heritage labs at Chippenham for 3x X-rays, one taken at each of the triangle of rivets, with possibly one shot taken of the repair at the base. This is estimated to cost somewhere around £100-£200. A binocular microscope will be available there for Peter to use for closer investigation of the bowl and he will be able to take magnified photographs through his computer. Steve has offered to make the necessary arrangements. They would like to undertake similar analysis of the rivets from the GLV, which appear to have been made there, but only after the bowl has been analysed.
The bowl will be taken personally by Steve or a member of his staff. We will try to make sure a member of the GAS Committee will also be present. The target date is early July.
Peter will mount the samples in permanent mountings and undertake the microprobe analysis. He will undertake the microscope analysis, view the X-rays and consult other investigations and the literature before he writes his report. He will also revisit his analysis of the Spettisbury bowl and other similar cauldrons and, if possible, look at the Fore bowl. He has a reference collection of hundreds of samples from bronze bowls and other artefacts from all over Europe and it may be best to allow the
Peter informs us that he has begun background research into the bowl and that it would appear that everyone has followed Bullied’s original description and analysis without any reinspection; no one has observed that it was made from two different vessels.
The bowl has been returned to its case amd the case has been locked.
31st May 2007