dk nkf - Nordisk Konservatorforbund Danmark

Figure 6: Cyclododecane wax applied to the wrought iron
crossbar of the ventilation engine.
the artifact and original drawings instead of X-ray
images to locate original surfaces.
Hand tools such as chisels, flat-head screwdrivers,
micro spatulas, Popsicle sticks, scalpels, hammers,
and hand-held pneumatic scribes were used to
remove hard concretion and soft sediment (Figure
5). The condition of the ventilation engine was
consistent with that of the Worthington pump; cast
iron components were structurally stable but fragile
and graphitized, wrought iron parts were deteriorated
with little to no original surface remaining, and
copper alloy parts were in very good condition. A
preliminary study determined that the density of the
remaining cast iron is around 6.2 g/cm 3
Conservators observed that even slight water
movement could disturb the tenuous hold between
strands of wrought iron. To prevent this loss, liquid
cyclododecane wax at 60 o C was applied to friable iron
with brushes and disposable pipettes. Cyclododecane
is a volatile organic wax that is applied as a melt to the
friable metal. The solidified wax has been successful
at preserving the remaining material since it was
applied in October, 2008 (Figure 6). Cyclododecane
wax can be completely removed through sublimation
at atmospheric conditions or through application of
warm or hot air. [11]
132
Once significant amounts of concretion were
removed, the ventilation engine was connected to an
ER circuit powered by a direct current rectifier. The
artifact connection provided acceptable electrical
conductivity throughout the iron casting with internal
resistance around 20 ohms. Platinum-niobium coated
copper wires were used as anodes for the ER circuit.
The wires were cut into lengths of 1 meter and
sheathed in perforated 1.5” PVC piping to prevent
electrical shorts. The anodes were suspended from
the platform frame with monofilament lines and steel
hooks and positioned near the surface of the artifact.
Conservators used their judgment to place the anodes
in a configuration that would provide maximum
coverage to the artifact (Figure 7).
Chloride diffusion into solution is monitored regularly
and, as of February 2009, is around 2 ppm per day
of immersion. The concretion and sediment removal
due to ER has proven incredibly beneficial during
disassembly.
As with the Worthington pump, the treatment goal is
to disassemble the engine into as many components
as safely possible for desalination and concretion
removal. Initial disassembly attempts were futile due
to adherent concretion and sediment. At first, only the
frame end could be removed from the main casting.
The fasteners between the two were completely
corroded and the joint had no rubber gasket, allowing
for simple disassembly. Other joints were tightly
bonded due to intact fasteners, adherent gaskets, and
sediment. Threaded fasteners often require modified
tools for safe removal; standard crescent wrenches
were filed down to fit a bolt head, wrenches and
Figure 7: Electrolytic reduction setup for ventilation engine.