Newsletter – Issue 161, January 2007
For those of you who were not at the AGM, Dave Jones, after many valuable years on the Committee including a spell as Chairman, has decided to stand down. I am sure you will all join us in thanking Dave for his sedulous work on the Committee and in hoping that we will still see him at all of our digs, ground resistance surveys and other Society activities. Jill Strobridge was voted onto the Committee at the AGM.
Having been to Iran in January we come down to earth (!) in February with Dr Stephen Carter on A Soil Scientist’s Guide to Archaeological Sites – Wednesday, 14th Feb at 7.30pm at 23a Fettes Row.
The March lecture is by Andrew Broom – The Appin Murder 1752 – Tuesday, 13th March.
The National Museums of Scotland Conservation Unit
On a cold bright day, the 31st October, about 12 members of the Society were shown round the Conservation Unit at Granton. 0ur host was Dr Theo Skinner, Conservator of Marine and Wetland Archaeology.
The undoubted star of the show was the Tay log boat. Most of us had seen dugout boats before, but were still impressed by the sheer size of this one. It was 9.25 metres long, about 1.5 metres wide and must have been more than a metre deep. It weighed about 2.4 tonnes. Part of the bow had been eroded, but the stern was in good condition with a stern post that slotted into a deep groove. The stern post had been removed, and was lying in its own tank of water. The main hull was under polythene, being continuously sprayed with fresh water. The cover was removed so we could see every detail of its blackened 3000 year old surface. It was, Dr Skinner told us, not hollowed out by fire but carved out with an axe or adze. The oak of which it was made would not burn easily enough for fire to be effective. I peered closely but could see no axe marks. I didn’t doubt Dr Skinner’s deductions, but was impressed by the skill of our Bronze Age predecessors.
As well as the groove for the stern there were 2 step‑like ridges, another shorter groove, and holes in each side of the hull just below its rim. None of these features had yet been explained. Along the bottom of the boat a long crack appeared to have been repaired by a black glutinous substance. No doubt future analysis will clarify its nature.
Trying to picture the boat in action, it was clear that any oarsmen would probably have had to stand up. It was an impressive object. They must have had very large oak trees and fine craftsmen 3000 years ago.
After spraying with fresh water to remove the salt, it will be sprayed with or soaked in polyethylene glycol. When 30 per cent of the water has been replaced, the boat can be freeze‑dried before going on permanent display. To do this to the complete boat would cost £150,000, but the budget is only £25,000. The solution, unbelievably, is to cut the boat into three and process it piecemeal.
We were shown many items of interest: some from a ship called the Swan that sank in the Sound of Mull in the 1650s, others from a ship called the Dartmouth. A small ceremonial brass cannon had a cast iron carriage ornamented with a lion holding the globe. Three of the four carriage wheels were found, and a replica made to replace the 4th. Cast iron contains a lot of carbon and sea water gradually corrodes and leaches out the iron. The surprising result of this was that the original wheel, now largely composed of graphite, was many times lighter than the replica.
In another vivid demonstration, Dr Skinner showed us a computer animation of how waterlogged wood shrank as it dried ‑ unless it was properly conserved.
A large tank contained pieces of timber from the hull of the Dartmouth. These had been under water since 1974. Originally Dr Skinner’s predecessor had hoped to conserve them by a new process that involved the alarming prospect of heating them in a bath of acetone. Fortunately this plan has been abandoned.
We were shown small slivers of wood and challenged to identify them. They were Roman writing tablets from Newstead similar to those from Vindolanda but without the writing!
Three, it has to be said, rather undistinguished pieces of wood we were told came from our own Fast Castle excavations and would soon be returned to us.
To demonstrate how the distortion of wood made it difficult to reconstruct objects our host then showed us a wooden mould he had made with conserved strips of wood tied around it. It was, he told us, a small barrel. Neatly side‑stepping the question of why anyone would go to the bother of making such a pint‑sized barrel, he informed us that this reconstruction had taken him the best part of a month.
I was impressed by the patience and dedication of Dr Skinner and his colleagues ‑ it is not a job that everyone could do. We, who marvel at the exhibits in museums, owe a lot to them, and it was a great privilege to be able to see behind the scenes. Thanks to Bill for arranging the visit, and to Dr Skinner who, in his quiet way, imparted a lot of interesting information in a short time.
Finally, I can’t resist pointing out that Dr Skinner is not just a ‘back‑room boy’. On his computer was a beautiful seascape of a channel between wooded headlands. I asked him if this was the Sound of Mull where the Swan had sunk. ‘No’, he said, ‘that’s the view from the back of my boat.’