Lead corrosion

I am currently preparing a large number (ca. 1000) of toy soldiers
for an exhibit that will first be displayed at our museum, and then
will travel to at least three other venues.

These lead alloy toy soldiers have been donated to the museum,
complete with their storage cabinets, made of plywood and masonite,
with cardboard liners and corrugated cardboard used as dividers
(ugh!).

In examining the first group of toy soldiers, I found a significant
number (12 of 64) that showed signs of lead corrosion.  This has
manifested itself in 3 ways so far:

    1.  Gray or dark brown crusts on areas of bare metal (this may
        be stable and will be monitored, untreated).

    2.  Gray fuzz along seams and other areas of bare or thinly
        painted metal.

    3.  Pits in painted surfaces where the paint has been spalled
        off by the erupting crystals which are generally white: i.e.
        typical lead white, basic lead carbonate

In all three cases, the lead content of the corrosion has been
confirmed by Plumbtesmo lead test papers.  No further scientific
analysis of the crystals has been, or likely will be, done. (Note:
there are popped bubbles in the paint with either bright metal or
white underpaint showing; these are negative for lead and have quite
a different morphology from the spalled areas when viewed under
magnification).

We will be improving the storage of the toy soldiers, (albeit slowly
as there are about 5,000 in the total collection) and during exhibit
and transport, we will be paying attention to their preventive
conservation needs.  The corroding pieces seem to run in certain
groups, and not in others.  This suggests a problem with the alloy
used in casting them, or in some other common usage or environmental
condition (previous display by the donor, particularly vicious
cardboard, etc.)

A search for treatment methods for lead corrosion has come out top
heavy with methods for treating archaeological lead, with some
treatments for other artifacts made only of lead.  So far, all
methods seem unsuitable for the toy soldiers.  My problem is to find
some method of halting or slowing the lead corrosion when much of
the surface is covered by paint. Many of these soldiers were
purchased, already painted by Britains (Britains was a mass
manufacturer of lead toy soldiers); the paint is reputed to be
'enamel', and is usually glossy.  Some have a white mat undercoat.
Some have been 'converted' with details repainted by the collector,
but again, there are no details as to the type of paint.

We will be displaying these during the winter at our museum, in a
gallery with no humidity control, but humidity range is from near
50% in fall and spring down to about 20 % with a few days near 15%
in mid-winter.  The exhibit may then be moved for the summer to one
of our galleries with controlled humidity at 50%.  If there is no
way to treat the pitting lead corrosion, we may have to reconsider
using these pieces in the travelling portion of the exhibit.

Note, we are aware of the hazards of lead and are taking proper
precautions, including use of a HEPA vacuum.
Any advice will be gratefully received,

Carol Brynjolfson

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                  Conservation DistList Instance 13:5
                 Distributed: Wednesday, June 30, 1999
                        Message Id: cdl-13-5-006
                                  ***