Rats and shoes and conservation talk. Cogge Sive Navis Magna conference part 2

What a beautiful shoe! Many of them, two of which had been brought on display on the second day of the Cogge Sive Navis Magna conference, about which we already talked about in the previous posting.

There they now were in the lecture room, together with the compass and the leather pouch found upon excavation. A very beautiful divider’s handle too with a four-faced figure carved on it. A 14th century compass! That's a rarity. Small, if you think about it, considering the size of the ship.

Rats! It was actually the rats, they caught our attention almost the first thing when we heard about the Lootsi wreck. The ones they'd found upon excavating this medieval ship, under a tar barrel. Nicely preserved, intact and wet. Not mummified or anything like that. Impregnated by tar, the magical pine substance so vital to shipbuilding for ages.

Of course this medieval ship had a barrel of tar. It's always handy onboard a huge ship in constant need of maintenance. And of course there were rats on board. Those rodents so abundant and always close to humans. Survivors of climate changes and pandemias. Carriers of diseases, but of knowledge too. Of course they're there under that tar barrel on board our ship!

We haven't seen them, so far, as they're resting in a freezer back at the Tallinn university lab. But now, on the second day of the conference, Lisette Reinvars and Priit Lätti, the archaeologists in charge of the Lootsi shipwreck project, who were deservedly ending the lecture part of the day, showed pictures of them and all the other finds in their presentation.

Lisette Reinvars and Priit Lätti at the Cogge Sive conference. Photo: Eero Ehanti

But before their talk we had the privilege of hearing a few brilliant presentations by our fellow conservators. First there was our friend Amandine Colson, who presented her findings online about the decades of the Bremen Cog after her discovery back in the 1960s.

The way she divided the decades until now in phases was based on scientific research and close monitoring. This is of great importance, also from our point of view. Especially from our point of view! How will our ships, the Tallinn ones, behave in the decades to come? How will they live, as years pass and people come to see them in museums?

Amadine Colson presenting online at the Cogge Sive conference Photo: Eero Ehanti

Amandine's call for collecting real data and predicting and anticipating rather than ritualistically analyzing for the sake of analyzing was a very valid one and close to our philosophy as well. If something's not needed or really useful, don't do it. Her example of structural health care and how to adapt that to preventive conservation was very interesting.

So how about our ship, monitoring her? At the moment the Lootsi Cog is not in its final position and the supporting system will change. So at the moment the monitoring is more concentrated on the drying process, for which we have 50 points where the moisture in the wood is measured once a week. To measure the changes of cracks and joints our colleague Priit suggested using plastic Vernier calipers. Those are cheap, easy to use and in the Vasa ship in Stockholm they’ve been used with success.

Measuring moisture in the wood. Photo: Eero Ehanti

then about those pointy shoes, very much alike to the one we found just a while ago. One of those was conserved by Maria Pommer, a whole one, with just a slight grin in the pointy tip of it. Otherwise pretty much perfect. A very good conservation result as well, natural color and soft feel, which is not a given when conserving waterlogged leather. Good conservation job became evident from Maria's presentation.

Then it was Priit’s and Lisette’s turn to take the stage. They walked through the excavation and what has happened since, including presenting all the finds from the ship. This was hugely interesting to us, because many of those were found before our involvement and we're not involved in conserving them.

And of course they showed the rats! How could they not, they’re such an amazing find, resting there, with bellies full of information about life onboard a Hanseatic cog in the early 1300s. Those almost intact animals found under a tar barrel, perfectly preserved thanks to good conservation qualities of that pine substance. Those rats surely have stories to tell, having spent almost 700 years underneath a barrel on board this ship. Both on research tables and as sources for a fictionalizing approach to the story of this ship. Somebody should definitely get into the latter approach too and we’ll make sure it happens.

Photo courtesy of the Estonian Maritime Museum

And yes, we had a talk as well. A show, in which we briefly went through the conservation process of the Kadriorg cog which participants of the conference saw the previous evening.

The way how the wreck is presented at the Fat Margaret came as a surprise to many who have seen the Bremen cog with all its supports outside of the hull. In contrast, the Kadriorg cog is just floating in the air and is a very impressive sight.

Also, the speed of the process from the found 2015 to the exhibition 2019 was surprising to many experienced marine archaeologists who have used to the world where conservation processes are time consuming and very expensive.

We tried to tell what was the starting point of the conservation process and which steps we chose. We set a realistic goal for conservation taking into account the condition of the wreck, location and projected future. The decision to not use any chemicals was somehow bold but as sustainable development has been discussed so much also in conservation, we decided to give it a go.The choices we made proved to be successful and the result is at Fat Margaret for anyone to see and enjoy.

And now we’re in our second shipwreck conservation project, treating the Lootsi wreck with a very similar approach, even though it’s much bigger and has some different features. The main difference is that the wreck had to be cut in four pieces. This was inevitable because it could not have been possible to lift and transport it in one piece. As cutting was a very drastic operation it also has a silver lining. The structure and shape of the ship is much easier to understand, which is great for the coming exhibition.

But cutting the planks also made the end grains of the wood open and there was a fear that the planks would dry too fast and crack. The sustainable conservation solution for this was to use beeswax to seal the end grains.

Another difference is rudder fastenings made of iron. Well preserved impressive structures, now under a hard crust. One is now cleaned by using mechanical methods and what was expected happened. Iron as a very reactive metal in contact with oxygen after cleaning started to corrode immediately. Two reasons for this are that there are soluble salts which cannot be removed because the iron is attached to the wood and the high RH in the tent. Some protection was obviously needed.

After consultation with colleagues our dear friend and most respected colleague Dr. Ian MacLeod from Australia suggested use of fish oil. Fish oil is well known for all of us who are bit older as we have been privileged to consume it daily for health purposes. Fish oil we used was Möller’s famous brand diluted in white spirit, which helps the oil to penetrate. Many layers were applied and when acidic drops occurred those were neutralized with sodium carbonate paste. We will follow this one exposed and protected iron this winter before opening other ones.

After the talks we all went to the tent to see this wonderful wreck. It was very fruitful to discuss and study together the wood used, manufacturing methods and traces of use. We are very happy to be part of this group of experts which will help all of us involved in creating a holistic view of the wreck and its contexts.