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This sculpture was carved from the mandible of a bow
head whale by the Inuit artist Henry Evaluardjuk in
1968. Unfortunately, circumstances dictated using fresh
bone which still contained a great deal of the oil and
fat which characterize this family of marine mammals.
This choice resulted in a continual oozing of oil from
the surface of the sculpture and an unpleasant odour
as a fraction of the exudate became rancid on exposure
to the atmosphere. Analysis of samples of the oil revealed
that it was unlikely to dry out and that the bone would
therefore continue to ooze oil for a long time to come.
It was decided that complete extraction of the oil by
solvent would be necessary to clean the bone and prevent
a recurrence of this problem. It was understood that
the surface colour of the bone would probably not be
altered by this process; dark areas where the spongy,
inner bone had been exposed during carving, and areas
where the dark, outer surface remained would not be
visibly lightened. As these contrasting areas contributed
to the sculpture quality of the piece this was considered
advantageous.
Solvent extraction of oils and greases
from bones (primarily for natural history specimens)
has been traditionally carried out with large quantities
of volatile solvents. This is expensive and also hazardous
to the health of operators. For the treatments of the
Evaluardjuk sculpture a variation on this method was
devised where the solvent trichloroethane was enclosed
in a close-fitting polyethylene bag surrounded by a
water jacket. Thus, a much smaller volume of solvent
was used and losses and health hazards due to evaporation
were minimised. Such a small volume of solvent became
quickly contaminated with the extracted oil so, rather
than discard it, it was purified by distillation and
returned to the bag.
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Figure 1.
Figure 2.
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Extraction
The apparatus shown in Figures 2 and
3 was constructed. The input and output pipes were arranged
so that solvent would flow from one end of the enclosure
to the other. The output pipe to the pump was at the
lowest point of the bag. After mechanical cleaning to
remove dried connective tissue from the interior, the
sculpture was sealed into a double-layered polyethylene
bag and laid in the tank on Ethafoam blocks carved to
shape. The bag was connected to the solvent output and
input pipes and the water jacked filled, causing the
bag to be pressed evenly against the surface of the
sculpture. Fifteen litres of trichloromethane were run
into the bag and left overnight. After this initial
soaking the solvent appeared a dark brown colour. Distillation
was begun using the apparatus shown in Figure 3 and
the purified solvent run back into the bag. A mercury
switch connected to a float in the distillation flask
caused the pump and heater to operate alternately, making
the distillation an automatic process. Losses due to
evaporation were occasionally made up with fresh solvent.
The process of extraction of the oil was judged to be
complete after 12 weeks when the solvent appeared almost
clear. At this point all the solvent was drained from
the bag and the sculpture removed. The rancid smell
was greatly decreased and the areas which had been black
and sticky were much lighter in colour. Once the solvent
had dried out the sculpture was prepared for mounting.
Mounting
The sculpture was mounted on a base
formed from a filled epoxy resin laid over a steel plate
as shown in Figure 4. A padded steel rod was attached
to the base and inserted into the hollow interior of
the bone. This heavy base and interior rod provided
rigid support and also gave enough mass to prevent toppling.
The visible parts of the base were veneered in a dark
wood varnished to match the decor of the display gallery.
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| Figure 4. |
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