Report to the members of Doncaster Naturalists’ about the Mayor’s Bog Oak chair examination 23 March 2023.

Present: Robert Howard : Dendrochronologist, Peter Robinson: Curatorial and Exhibitions Officer Doncaster Museum , Colin Howes and Nora Boyle Doncaster Naturalists’ Society

The chair had been removed from display on 22nd and stored in the art store in the top floor art gallery. It was examined in the art gallery, though the reduced light levels made for poor visibility and the need to illuminate the specimen by torch lights on i phones.

Construction : This initial examination was quite a surprise, revealing this hefty and apparently solid piece of furniture consisted of a complex jigsaw of separate components, skillfully assembled using a variety of joints and pegs (wooden dowels colloquially referred to as treenails, trunnels, or pegs) … no metal nails or screws were employed in its construction!

Clearly the cabinet maker, George Collinson of High Street, Doncaster, who had created the chair had been a supreme master at his craft, discussions suggested that a cabinet maker should be invited to provide a detailed technical description of the piece.
Action : Peter said he would talk to his cousin on this matter who is a cabinet maker.

Maintenance : Originally having a matt black patina, at some stage the chair had been varnished, giving its current luster. The curved chair back however was indeed matt, revealing evidence of charring, probably having been placed too close to an open fire, gas fire or radiator. A piece of carved twig beneath the left arm-rest and a carved acorn from the right side of the ornate chair back were missing, possibly having snagged on mayoral robes over the years. Also it seemed the legs may have been drilled to receive casters for mobility in the past and at some stage one modern screw had been used in the chair back.
Action: These observations led to the suggestion that former Mansion House janitors should be contacted for anecdotes on the management and maintenance of the chair.

Dendrochronological dating : It had been originally surmised that a core could be taken from across the width of the thick wooden seat, this potentially producing the greatest number of rings to compare with a dated reference series. However, on examining the underside of the seat, a fine crack from front to back revealed the seat was constructed from three separate pieces. Robert counted the annual growth rings on the largest piece, finding only 30.
Conclusions : Since a number of samples with at least 50 rings on each would be necessary to achieve a dating match, this effectively ruled out dendrochronology as a dating method for this specimen.

Robert advised that “Even if it was one piece I can tell straight away that it probably would not be suitable for dendrochronology. The method relies on getting a match between sample and reference patterns and in order to get a positive match it’s rather like finger prints or DNA you have to have a certain amount of rings in your sample to get a positive match with your reference pattern. One that is reliable and meaningful. In order for that to happen you need 50 ish rings in your sample. This is particularly so with a single sample and its very rare that a single sample will date on its own. We like to take a lot of samples and combine the data to make a composite data set and it’s that that’s compared to your reference patterns to give more representative data.”

Carbon 14 dating : Peter then asked if carbon 14 dating would be an option. Robert agreed that was a possibility but several samples would need to be taken to determine whether or not all the parts sampled were the same age. 5 sites were identified.

In order to proceed further the amount of material needed to carry out the carbon dating would have to be determined and also the cost of taking and analysing the samples. Robert has his own contacts but Colin thought Peter could arrange the procedure himself. The cost of such dating was mentioned.
Action: Peter indicated that he was well versed in fund raising which might be deemed necessary should the cost be more than anticipated for dendrochronology.

There was much discussion about the history of the chair including studies of cabinet making techniques, collections of anecdotes from former Mansion House Janitors and indeed from former Mayors. Colin suggested there was material for several separate papers on aspects of the chair.

Subsequently Robert Howard sent this letter to Peter Robinson.

“Morning Peter. Good to meet you and the team yesterday. Interesting object, but sorry dendro was a non-starter (worth checking out though). I’m sure an examination by a furniture maker/joiner would be worthwhile.

As for C14 dating, I’m sure it could be attempted. A couple of things to consider, however, is what the results might tell you. Without sapwood (this all having been removed by the maker of the chair), a date from some outer rings will only identify a date after which the tree was felled (which could be an indeterminate number of years). Plus, if it is a bog oak, you might want to consider if it is all from the same tree or multiples, and if multiples, are they the same date.

I suppose C14 results might show that the tree is possibly of, say, prehistoric, Roman, or later date (proving that it’s probably not prehistoric/Roman etc), but still no be very specific.

I’m just thinking of the efforts you might need in fund raising.

Let me know thoughts. Cheers, Robert”

This is as far as things have progressed at the moment. We’ll keep you informed of further developments.
Nora and Colin.