dk nkf - Nordisk Konservatorforbund Danmark

the Confederate ironclad CSS Virginia (1862) in
the Battle of Hampton Roads. In 1973 researchers
discovered the remains of Monitor in 240 feet of
water. After extensive research and planning, the
National Oceanic and Atmospheric Administration
(NOAA) and the US Navy began excavating and
recovering the significant components of the
Monitor for treatment at The Mariners’ Museum
(TMM) in Newport News, Virginia.
This paper will describe the USS Monitor
conservation project and its efforts to preserve the
ship’s industrial technology. The history of the
design and construction of USS Monitor is providing
valuable insight into the technology employed and,
as a consequence, guiding the approaches adopted by
conservators when dealing with the large objects and
sophisticated engineering of the period. Case studies
of the Worthington bilge pumps, ventilation engine,
and propulsion assembly conservation treatments
will highlight the aforementioned issues.
Deterioration in Marine
Environments
The preservation of historic industrial materials from
marine archaeological sites is significantly different
than those excavated from terrestrial burial or those
preserved in non-archaeological contexts. Depending
on the material type and the salinity, water depth, pH,
oxygen availability and other environmental factors
artifacts may be relatively well preserved, or suffer
severe deterioration in the time they lay submerged on
the ocean floor. [1] The presence of chloride salts in
seawater is particularly detrimental to metal artifacts
as they promote corrosion. Metals, particularly iron,
form a thick surface layer called concretion composed
of corrosion products, calcium, sediments, and
marine life. While concretion formation is part of the
deterioration process of marine metal artifacts, it can
also be beneficial in that it can slow down corrosion
rates and preserve other artifacts, including organic
materials, which may become incorporated into the
concretion matrix.
The process of archaeological recovery also affects the
preservation of marine material. While it affords the
opportunity for thorough conservation and successful
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stabilization, it also disrupts the artifacts’ physical
and chemical equilibrium and exposes them to higher
levels of oxygen than were present in the submerged
burial environment. In the case of metal artifacts, this
can lead to higher corrosion rates and further loss of
material unless preventive measures such as controlled
aqueous storage conditions and cathodic protection are
taken.[2] The recovered artifacts required controlled
aqueous storage as a pre-treatment to prevent rapid
deterioration upon excavation.
Treatment Goals
The primary goal of the USS Monitor conservation
project is stabilization of the artifacts recovered from
the wreck for display and study at The Mariners’
Museum. The marine archaeological context of
the Monitor material necessitates the removal of
sediments and concretion, desalination, dehydration,
and storage in controlled environmental conditions
for all artifacts. In the case of complex mechanical
assemblies such as the Worthington pumps and
ventilation engine, artifacts are disassembled
whenever possible to allow more extensive treatment
and effective desalination of all surfaces. The
recovered artifacts would require controlled pretreatment
storage indefinitely and would deteriorate
over time, in some cases quite rapidly, without these
steps. Mechanical components then require reintegration
and re-assembly following stabilization
treatments in order to present as clear a picture
as possible of the appearance and function of the
original object.
Thorough documentation of the objects before,
during, and following conservation and a detailed
description of the conservation treatments used is
one of the most important aspects of the conservation
process. Documentation includes the recording of
any details of the materials used, manufacturing
techniques, and evidence of the working life of the
object. Analyses such as material characterization
and metallography performed in order to guide
conservation treatment also yield important
information on the materials and industrial processes
used to produce the artifacts.