Bloom on lead

Maria Saffiotti Dale <msaffiottidale [at] lvm__wisc__edu> writes

>I am seeking information on the recommended treatment, routine
>maintenance, and optimal display of a lead sculpture (Raymond
>Duchamp-Villon, "Le Cheval", 1914, cast 1950s; ex-Morton Neumann
>Family collection) which regularly "blooms." We have been
>maintaining it in-house by gently reducing the white oxide layer
>with very fine #0000 synthetic pads followed by the application of a
>coat of Renaissance wax.

That the lead forms corrosion again after treatment gives suspicion
that there must be a pollutant in its environment. It is best, I
think, to check the show-case/box very thoroughly for pollutants.
What kind of wood was used? There are some woods that can evaporate
very harmful compounds for lead, like formic acid, acetic acid and
formaldehyde. It is stated that the wood is painted, but is the
paint film free of pores? And is the paint itself free of harmful
compounds? Also the textile could be the incentive for the
corrosion.

I would try and test the materials of the showcase with a so called
Oddy-test, to see if they indeed contain corrosive compounds. So, a
peace of the wood, paint and cloth (all apart) in a Erlenmeyer
flask, with a bit of distilled water and a clean piece of lead above
the materials, closed, and put in a stove (25-60 degrees Celsius) to
speed up the reaction.  Exact technique to do this is best asked
from a metal conservator or a art researcher (see also for example
the articles on

    <URL:http://www.metmuseum.org/Works_of_Art/
        objects_conservation/mo_pdf/met_objective_spring2003.pdf>

or

    <URL:http://www.iaq.dk/iap/iap2001/2001_15.htm>).

    **** Moderator's comments: The above URL has been wrapped for
    email. There should be no newline.

If there is no reaction (white lead formation) the materials are OK.
Maybe then the showcase is not really airtight, so that a constant
new air-flow can penetrate the case and flowing over the object, the
object acting like a filter and absorbing all the contaminants. When
there is a lot of (new) wood nearby, or other harmful materials,
they can provide a continuous supply of new corrosive gases.

I hope this helps,

Mrs. Joosje van Bennekom
metalconservator
Stedelijk Museum Amsterdam


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                  Conservation DistList Instance 18:40
                 Distributed: Monday, February 28, 2005
                       Message Id: cdl-18-40-006
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