Waterlogged wood

Hans Piena <h.piena [at] chello__nl> writes

>In 1957 the Russian dug up a burial wagon in Armenia, dating from
>1300 BC. Based on the Russian literature and analyses I know that
>the waterlogged wood was treated with glycerol (9 parts) and PVA (1
>part). Since 1957 the different parts of the wagon have shrunk and
>deformed considerably.
>
>Maybe not all the water was replaced by the impregnation media and
>has evaporated over time which caused deformation. Maybe some of the
>impregnation media has come out?
>
>I have been asked to find out whether the parts can be given back
>the proportions they had when they were found.
>
>Has any body heard about comparable problems or and  publications on
>comparable topics? Could swelling the wood with warm water and
>reimpregnating it with PEG be a solution?

I would suspect that the wood was not fully impregnated, hence the
loss of the remaining moisture has caused it to shrink. In 1957 it
may not have been known that large waterlogged objects need at least
five years of impregnation (depending on size, of course) before all
water can be considered displaced. It is important to remember that
waterlogged wood has lost the components that make up its cellular
structure and PEG can only "shore up" the cellular walls as it
immediately displaces the water within the cell.

In my experience, I have never been able to successfully re-saturate
desiccated wood. The checks caused by the wood's loss of structure
never close and the deformations never quite go away. Also, it is
almost impossible to control the way in which the deformed wood will
re-expand. Waterlogged wood is often greatly deteriorated when it is
removed from its saturated environment, as it is nothing but
cellulose no longer bound together.

I would give great pause before tampering with such a delicate
object. My fear would be that re-saturating it would irreparably
damage the wood. In locations of great deterioration (such as
flaking or chipping), I would implement a regular maintenance plan
of cyclododecane as a temporary consolidant. For display purposes, I
would use an educational approach in the labelling or text panel
that explains what may have occurred. I would include information on
the fragility of waterlogged wood and perhaps, a historical
photograph showing the condition of the cart after it was originally
treated. As conservators, we have to remember that everyday promises
new treatments and methods and we can only do our best with failed
early treatments such as this.




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                  Conservation DistList Instance 15:8
                   Distributed: Tuesday, July 3, 2001
                        Message Id: cdl-15-8-001
                                  ***