Wooden barrel with iron bars

Ulla Klemela <ulla.klemela [at] nba__fi> writes

>A wooden barrel full of small iron bars was lifted from a medieval
>wreck-site in the Finnish coast of the Baltic Sea in 2006. The iron
>had corroded readily during the centuries of submersion forming a
>concretion around the whole barrel and infesting the wood badly with
>corrosion products.  Upon excavation in the lab about half of the
>largely mineralized iron bars were removed and subsequently
>stabilized. The remaining whole still consists of hundreds of iron
>bars corroded together and several wooden planks of the barrel.
>
>It is now dry and the plan is to leave it like that and display it
>partially excavated. The problem is how to stabilize and display
>such a composite artifact. ...

If the wood has dried out without any consolidant or treatment, it
may be so altered by the large amount of iron compounds which had
permeated the barrel that it won't shrink if kept dry.  Are there
any small pieces of wood which could be tested on exposure to a very
dry atmosphere (below 35% RH) ?

If there is a risk of shrinkage, I would test a consolidant like
Paraloid B72, just applied to the wood to minimise shrinkage.  I
have used this on very salt damaged wood from ancient Egypt which
was being displayed in a museum with no environmental controls which
oscillated between very dry and very damp conditions and the result
was highly satisfactory.

Does anyone have any thoughts on vapour phase corrosion inhibitors
in a sealed display case? Hope this helps,

Helena Jaeschke
Conservation Development Officer
Royal Albert Memorial Museum
Exeter Ark
3 Exton Road
Marsh Barton
Exeter EX2 8LX
+44 1392 665951


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                  Conservation DistList Instance 23:17
                 Distributed: Sunday, November 15, 2009
                       Message Id: cdl-23-17-006
                                  ***