Unrolling a lead scroll

Lucy Skinner <lucy.skinner [at] gmail__com> writes

>I am working as site conservator on an archaeological dig in Turkey
>where a small lead object was excavated last week. It is a strip of
>thin lead, rolled up and squashed flat during burial. ...
>...
>I have
>considered electrolytic reduction to convert the crust of lead
>carbonate back to metallic lead and heating the lead to soften it
>before attempting to unroll it. ...

I have treated lead coins and seals that were brittle and encrusted
with carbonate using the anion resin exchange method, described in
the 2nd edition of:

    Plenderleith and Werner.
    The Conservation of Antiquities and Works of Art
    (pp 270-272)

It's an aggressive method that will remove corrosion to the original
metal surface and has to be carefully monitored, but it is useful
when a readable surface is desired.

I've had some success using a Leister hot-air tool to warm folded
lead tokens for re-shaping.  The melting point of lead is
621.43 Deg F.

You also might consider backing the object before attempting to
unroll it.  A thin Japanese paper adhered with B-72 should provide
enough strength and support to expose the inner surface and allow it
to be cleaned.

A digital microscope can also be useful with this type of object, if
you have one available in the field lab.  I've used it to enhance
the engraving on archaeological coins and lead seals.

Paul Storch
Objects Conservator
St. Paul, MN


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                  Conservation DistList Instance 25:15
                Distributed: Tuesday, September 20, 2011
                       Message Id: cdl-25-15-015
                                  ***