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Subject: Brass time capsule

Brass time capsule

From: George W. Cannon <gwc4>
Date: Tuesday, November 3, 1998
Clint Fountain <cfountain [at] mail__dos__state__fl__us> writes

>The Museum of Florida History has recently come into possession of a
>box made of sheet brass, 17 5/8" X 17" X 1", which bears a plaque...
>...
>The problem: how to open the box with zero probability of damage to
>the contents, and with minimal damage to the container and its
>coating.

Of concern is the make up of the solder.  Most solder is a mixture
of lead and tin.  Usually the higher the lead content, the higher
the melting temperature.  Solder used in plumbing joints is often
5/95 solder being 5% tin and 95% lead, and usually is melted
(sweated) using a torch.  Solder used in the stained glass industry
is usually 50/50 or 60/40 solder.  The 60/40 will have the lower
melting temperature but still requires a substantial amount of heat
to melt.  Also of concern is the width and mass of the bond or
solder joint.  If the box overlaps and the solder covers a large
area having seeped into a tight joint, it may be difficult to
extract.  If the solder is a simple bead on the surface, it will
likely be easier to remove. The heat can be localized by using a
cool damp cloth on the adjoining areas as a heat sink. Solder which
is soft enough may possibly be carefully cut with a sharp blade if
the bead is thin and narrow.

Besides suction bulbs (which do a poor job on large areas), there
are wick type materials which can be applied and heated with the
solder. They are made up of fine braided copper wire, and will wick
away the liquid solder. I would avoid using anything on a vacuum
system as the possibility of fire from hot solder and strong air
flow could be dangerous.

Regardless of the method used, you can expect that the lacquer will
suffer from the heat and you may see some discoloration in the brass
as well.

George Cannon
Preparator
Herbert F. Johnson Museum of Art
Cornell University
Ithaca, NY 14853
607-254-4617

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                  Conservation DistList Instance 12:41
                 Distributed: Tuesday, November 3, 1998
                       Message Id: cdl-12-41-002
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Received on Tuesday, 3 November, 1998

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