Lead

Alan J. Hawk <hawk [at] afip__osd__mil> writes

>I have a model of a ship made in 1875 for the Centennial Exposition.
>Some of the parts (such as the steering wheel and pullies) were cast
>from lead. However, the lead has developed a heavy white powdery
>coating (which I assume is oxidation) that is falling to the floor
>of the case.  What is the best treatment to stabilize the lead?  I
>was considering gently brushing off the powder and then painting the
>lead with Arcoloid B-72 liquid.  Would that be a good approach? What
>are your suggestions?

The corrosion of the lead is more than likely being caused by the
display case exuding organic acids.  I would expect that by now this
should have stopped, but you never know.  Whatever treatment you
decide on, it should include dealing with the display case.

For treatment of the lead I suggest you apply a poultice of 5% w/v
EDTA solution in a CMC gel. This should remove the corrosion
products & leave the remaining lead metal behind. A coating of B-72
should help to prevent further corrosion.

For the display case I suggest you introduce an adsorbant material
(eg activated charcoal or an "anti-tarnish" impregnated paper or
material). Putting ventilation holes in the display case would also
help. These should be covered with a finely woven fabric, such as
Stabletex, to keep the dirt and bugs out.

George Bailey
Objects/Metals Conservator
Australian War Memorial
+61 2 62434436


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                  Conservation DistList Instance 14:34
               Distributed: Wednesday, December 20, 2000
                       Message Id: cdl-14-34-004
                                  ***