Wednesday, April 27, 2011

Fixing the Flippers

The Sei whale skeleton, positioned in the whale hall next to one of the large windows has sustained, over many years, degeneration of the finger bones that are situated in the flippers. The bones have cracked and split and in some places fallen away completely. This has left gaps where finger bones should be and lots of missing pieces of bone.

A picture of the left flipper before the restoration work began. The degraded fingers bones can be seen.

It was decided after discussions with the curators of the whale hall that we would repair the broken, and replace the missing bones to make the overall appearance of the flippers better. This would be carried out using special conservation techniques that could easily be reversed and removed so that the skeleton was not permanently altered. We do not want to 'trick' people into thinking that our repairs and replacements are real bone and although from a distance the flippers now look complete, when up close it is obvious which parts of the flippers are bone and which are not.

Zina undertook the task of restoring the Sei whale flippers and began by making moulds of some of the intact finger bones in order to make replica casts that could be used to replace the missing bones. She used alginate (a substance used by dentists for making moulds of peoples mouths) to make moulds of the finger bones and then Jesmonite AC100 (which is similar to plaster of paris) to make the exact casts from the rubbery alginate moulds. The bones were cast in two halves and stuck together on the flipper with more Jesmonite.

One half of a Jesmonite finger bone cast in position and ready to be completed.

Two Jesmonite bone casts secured in position on the phalanx at the bottom of the picture, ready for painting.

Once in place Zina very carefully (and cleverly) painted the Jesmonite bone casts with acrylic paint.

Two jesmonite finger bone casts in position. The cast to the right has been completed with paint, allowing it to blend in with the other bones.

The next task was to repair and fill the bones that had badly degraded. Zina did this by first protecting the broken bone surfaces by painting them with thick Paraloid B72 (the special conservation glue we've talked about before). As Paraloid is easily removed it creates an invisible reversible layer between the bone surface and the clay so that the infilling can be removed at any time. She then used moulding clay (Apoxy Sculpt) to fill in the gaps and model the missing parts of the bone. When dried the clay was painted so that it did not stand out from the other flipper elements.

Zina working on a degraded bone. The gap where part of the bone has fallen away is filled in.

Two bones with infills.

A comparison between a painted bone infilling (to the right of the picture) and an unpainted infilled bone (to the left of the picture).

As a finishing touch Zina repaired and replaced the cork between the bones. I think you'll agree the finished flipper looks great!

The finished flipper. A great improvement!

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