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CCI Newsletter, No. 32, November 2003
On Display: The Southampton Swivel Gun
by Tara Grant and Charlotte Newton, Senior Conservators,
Conservation Processes and Materials Research
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In October 2002, a small swivel gun was found during
excavation of a ship buried on the beach at Southampton,
Ontario, on Lake Huron. It was excavated by a team
headed by archaeologist Ken Cassavoy, under a permit
issued by the Ontario Ministry of Citizenship and
Culture. Historical research, conducted by the
archaeologist and marine historians from the area, has
led to a tentative identification of the ship as the
Weasel, built in Detroit [in present-day Michigan]
in 1786, and apparently lost at Southampton in 1798. If
identification can be confirmed, this would be the
earliest known shipwreck site in the Upper Great Lakes.
The 1.03-m-long cast iron swivel gun, weighing about
90 kg, was covered with a thick encrustation of smooth
pebbles, sand, iron corrosion, and iron spikes and
nails. The soft, black, porous corrosion was identified
as siderite (FeCO3). Siderite is a stable,
non-conducting iron corrosion product formed when iron
is buried in a low-oxygen, highly carbonated soil found
in limestone areas or shell middens. The cast iron
barrel appeared to be in good condition with a
significant amount of iron remaining. The wrought iron
swivel mount was heavily corroded and unable to move.
The bore was blocked with a pebble-based concretion.
X-radiography could not determine the cannon’s condition
or if it was still loaded. |
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| One of the
major problems for iron artifacts is contamination with
chlorides during burial. Because the salt promotes
corrosion, extensive chemical or electrochemical
treatment is required to remove the chlorides and
stabilize the iron. However, tests of the storage water
and corrosion analysis of this gun found no detectable
levels of chloride. Treatment was, therefore, a
straightforward mechanical removal of the concretion
layers using hammers, chisels, and dental tools and
brushes. Cleaning the bore revealed that the cannon did
not contain a charge. The cleaning produced an even,
hard surface with many details still visible including
the touch hole and an inscription. Because the cannon
was going into a museum environment and the surface was
stable, no surface coating was applied. The swivel gun
is currently on display at the Bruce County Museum,
Southampton, Ontario.
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