WHY
A MOUNT?
Written
by Steve Short of the Portland Art Museum | |
Evolution
and production of exhibit object mounts arise out of a variety of reasons: |
•
The need or desire to optimize "view"-ability within
the context of the display.
• To
provide or maintain a degree of security for the object.
•
Geographical factors, the museum or gallery is in an area known
to experience the occasional earthquake, tremor or seismic jolt. |
| |
| The
object maybe occupying a freestanding pedestal in a high-traffic "blockbuster"
exhibit hall or it maybe in a quiet, out-of-the-way gallery in a sturdy built-in
wall case. Whatever the situation, there will be a set of conditions and the presence
of various elements within the "object's environment" which create a
complexity of new relationships when other materials such as the mount are introduced. |
| Kiss
my Brass ! | |
|
Often the
best solution in a museum environment to present an object d'art or artifact for
viewing, is through the use of brass rod or tubing elements joined with silver
solder. One creates a supporting structure that -- ideally -- disappears into
the display setting environment or against the surface of the object to be shown. The
use of brass and solder gives you the choice to anneal, or to temper, certain
parts of the structure in order to soften sections of the metal for bending and
fitting, or to harden sections in order to increase the rigidity of the structure.
|
| Yellow brass
and silver jeweler's solder are excellent materials to mount objects for exhibit,
given their strength and workability. This form of brass contains approximately
30% zinc, the balance being copper and small amounts of other metals, such as
lead. This material under "normal" conditions is quite stable; as is
its partner, silver solder. |
|
| Tech
talk |
| Zinc
is a willing anode to silver solder's relative cathodic tendency. The willingness
of zinc to give up its ions toward silver solder results in a condition known
as "galvanic" corrosion (1). While the white, flaky blooms of
galvanic reaction may not necessarily pose an immediate threat to the object;
left unchecked this trend could lead to joint weakening and possible mount failure.
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There are four
conditions that are considered necessary for the occurrence of this phenomenon:
• Anode: a metal surface that gives up metal
ions (corrodes).
• Cathode: a metal surface
that picks up metal ions.
• Metallic bond:
a continuous metallic path that allows current from anode to cathode.
•
Electrolyte: a medium that conducts ionic current between anode and cathode.
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The continuous metallic
path resulting from the fusing or soldering process of the silver and brass both
inside and on the surface of our mount cannot be avoided. What we can do is to
attempt to eliminate one of the four conditions from the equation, in this instance
the electrolytic medium. One
method to achieve this would be to isolate the solder joint and the immediate
surrounding area by treating it with an airtight coating of non-water soluble
thermoplastic acrylic resin such as Paraloid B-72. All pits and burrs must be
carefully eliminated to protect the metallic marriage from the unwelcome residence
of moisture and salts. These elements are present both in the air and in paint
binders and pigments that might be used to paint out sections of the arms and/or
fingers of the mount.
All of this may be obvious to anyone familiar with the behavior of metals, but
not everyone enlisted into the ranks of so many small squadrons of mount-makers
is going to be aware of the full extent of cause and effect loops inherent in
tight deadline installations. At
every turn, the simple application of a solution to a problem in a "controlled"
environment creates, conceivably, numerous other new relationships in that environment.
As we continue to solve each new set of problems, we will be witness to the new
relationships spawned by our solutions and practices -- and unless we are great
adventurers, we hope there will be nothing the color of catastrophe to add data
to our stacks -- and life will quietly continue. Then again...maybe silence isn't
the best sound to be coming from the gallery. |
|
| (1)
Galvanic corrosion (also called ' dissimilar metal corrosion') refers to corrosion
damage induced when two dissimilar materials are coupled in a corrosive electrolyte. Reference:
· http://corrosion.ksc.nasa.gov/html/galcorr.htm
-- The Kennedy Space Center Corrosion Technology Testbed
· http://www.mfa.org/_cameo/frontend/
-- CAMEO (Conservation Art Materials Encyclopedia Online)
· http://www.corrosion-doctors.org/Aircraft/galvdefi.htm |
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