A Very Delicate Skull

Things are moving along quickly and we have almost completed cleaning the Sei whale skeleton.

However, the skull on this skeleton requires a lot of careful and painstaking work. The cranial bone has deteriorated considerably is now extremely thin and delicate. In addition there is a lot of exposed trabecular bone (the honeycomb like bone found beneath the smooth surface bone). This makes cleaning the bone very difficult as we do not want to damage it any further.
This picture shows how paper thin some of the bone on the skull is.





There is evidence of past repairs to the skull as there are thin strips of bone, that appear to have fallen off, screwed back onto the premaxilla, often with small wooden supports added. We have also discovered fragments of bone lying in the skull which have fallen off the maxilla, vomer and nasal bones.

Gordon has been tackling the skull and has modified our usual cleaning methods to work in this area. In order to clean the very thin bone he applied a solution of ammonia with a soft brush to the bone surface, left it for 5 minutes and then using the soft bristled brush gently foamed the solution on the surface, lifting the dirt. This was then removed either with a vacuum cleaned or with tissue paper to blot off the excess, so that no rubbing or scrubbing was required.

The parts of the pre-maxilla that had previously been screwed back on were removed and carefully stored so that they can be re-attached more sympathetically later on in the project. All the small fragments we found were glued back into place (a bit like doing a whale skull jigsaw puzzle). This was achieved using a special conservation 'glue'called paraloid (acryloid) B-72. The important thing about paraloid is that it is 'reversible' - that is, it can easily be removed in the future using acetone. The use of non permanent 'glues' is an important aspect of conservation as it means you can repair a specimen with the possibility of non destructive change if necessary in the future.

The paraloid was used in combination with Japanese tissue paper to stick the paper thin bones together. The tissue paper was used as a reinforcing agents as the edges of the bones were just too thin to stick to each other.

Here are some pictures of the Sei whale as it is being cleaned....

The Sei whale skull work is nearly completed and the team are moving onto the Humpback whale - once again we have found a name - Roger!