It has been several months since my last post looking at blue whale on the move but finally the long process of cleaning and conserving each individual bone has been successfully completed and the conservators are now just embarking on surface scanning the bones in high definition. Conservation can be an extremely slow process but it is worth the time and effort. During the past 9 months the team have cleaned and conserved over 220 individual bones. This equates to over 110m2 of whale bone surface area.
During this time we also planned the final position and articulation of the whale for its suspension in Hintze Hall so the armature design could commence. This post outlines the conservation treatment and articulation planning phase of this project.
Once we had de-installed the whale skeleton it was easier to see what the conservation challenges were going to be as we could inspect each bone for damage and prepare treatment proposals.
We have also made the most of the opportunity to carry out scientific research into a range of conservation issues as the blue whale has been inaccessible for complex study for over 80 years. By understanding how the specimen has altered and may possibly change in the future, we can evaluate and develop effective conservation treatments and as well as aid in the discovery of previously unknown information relating to the specimen itself.
Micro-computed tomography (CT) scanning was carried out on the first eight caudal vertebra. (The remaining skull and postcranial bones are, alas, too large for our scanner.) CT scanning allows us to produce a three dimensional X-ray of each bone.
We decided to micro-CT scan the whale vertebra for several reasons:
- CT scanning has enabled us to perform non-destructive analysis and have a look at the internal structure without causing damage.
- This data provides information regarding possible deterioration in the interior structure of the bone that would otherwise not be visible.
- We can carry out comparative analysis of the condition of dorsal (top) and ventral (bottom) surfaces and how they may have been affected by dust and debris.
- Finally we could also see even more metal pieces inserted into the bone that were not always visible to the naked eye.
Thorough preliminary testing of potential conservation materials is a standard part of any conservation project. This includes analysis of cleaning techniques, adhesives for repair and consolidation and materials for fillings losses.
Sometimes these tests are carried out on the actual specimen itself or sometimes they are carried out on a similar material. The analysis attempts to satisfy many of the issues that conservators must consider when working with specimens going on display. For this particular project we have looked at how various chemicals will age, how they affect the overall appearance and how stable they are in changing environmental conditions.
A number of adhesives and solvents were tested for consolidation and repair, with Paraloid B44 (ethyl methacrylate co-polymer resin) in Acetone and Butvar B98 (polyvinyl butyral) in Ethanol being considered the most appropriate. Early in the project it was known that the environmental conditions of Hintze Hall would range throughout the year, potentially reaching extremes in relative humidity and temperature. Thus adhesives with higher glass transition temperatures were to chosen to ensure that the repairs made would remain stable throughout the year and over time.
Ethical implications were discussed before any treatment processes were carried out, bearing in mind historic integrity, improvement of structural stability and aesthetic values. Luckily, the bone structure of our blue whale skeleton is stable and requires little intervention. In fact, most of our more complex conservation treatments have focused on historic repairs and of course removing all the nails, bolts, rods and metal wire embedded within almost every bone. (Image 4)
Unfortunately, little information was documented about the condition of the skeleton at the time of original preparation and articulation. We could see, however, that the historic repairs were all fabricated using similar techniques and with the same materials, so they were all done around the same time.
The old repairs are composed of plaster of Paris, reinforced by metal wires inserted into drilled holes on either side of each repair. The metal wires exhibit a superficial layer of corrosion, but are still visibly stable in cross-section.
In the first instance we focused on stabilizing the existing repairs, as they are part of the history of the specimen. Repairs are carried out in a number of ways depending on the size of the gap between plaster and bone.
Treatments included cleaning, consolidation, repairs and gap fills as well as replacement of original armature and loose nails and staples in the unfused bones. Cleaning included removal of surface debris with museum vacuum cleaners and soft brushes followed by smoke sponge (vulcanised natural rubber).
We decided to remove the oil superficially from the bone surface to improve the aesthetic appearance while at the same time removing what had become acidic and sticky due to oxidation. A number of solvents and application types were tested and oil removal using ethanol and cotton swabs was found to be the most effective whilst being the least aggressive and desiccating to the bone.
The majority of the transverse processes of the thoracic and lumbar vertebra exhibited historic repairs (presumably from the time of articulation in the 1930s) that had become unstable over time and required stabilization. In an effort to maintain their historic integrity a principle of minimal intervention was applied wherein the least amount of repair would be carried out in order to facilitate stabilisation and would only be increased if absolutely necessary.
About half of these vertebra could be repaired simply by injecting a solution of Butvar and ethanol, the other half simply by inserting Japanese tissue paper or microballoons with Butvar and ethanol.
Each bone had an individual treatment report which included treatment maps providing details of where each fill, repair and area of consolidation was carried out and the specimen will be monitored regularly to check for changes over time.
The skull was by far our biggest conservation challenge – literally and figuratively. It posed many complex conservation issues, access proved difficult and we had to have a special platform made. Treatments on the skull included consolidation of friable surfaces, adhering bone fragments, fabricating detachable fills, oil reduction and, of course, cleaning.
Cleaning, stabilising and conserving such a large and complex object can be time consuming. Over 700 conservation hours have been spent on this part of the skeleton alone.
After extensive research, carried out by Richard Sabin, Vertebrates Collections Manager, we knew what the new pose of the blue whale skeleton should look like. Whether we could achieve it was another challenge. As the idea was to have a much more dynamic pose that would be totally different from the 1934 mount, we wanted to be able to visualise it completely before committing to the new armature design and construction.
The specimen will also be suspended from several arches across the length of the Hintze Hall and we needed to be sure we had planned everything accordingly. There is literally no room for error when you are dealing with a 4.3 tonne specimen. We decided the easiest way to achieve this was by using the data from a low resolution Lidar scan we had of the whale that had been taken at the beginning of the project.
This was used to produce a 3D print in a smaller scale so that the team could articulate the model in a number of postures in order to refine the final position. The model which was produced by our armature company is around 1.5 metres long while the real skeleton while the real skeleton extends to around 25 metres.
Our in-house team of joiners and painters also created a scale replica of Hintze Hall so we could suspend the model across the arches and see how the specimen might look. Not only does the model look amazing, but it actually serves a purpose.
We were absolutely delighted to be awarded the International Institute of Conservation Keck Award for 2016. This international award, which is presented every two years, goes to the individual or group who has contributed most towards promoting public understanding and appreciation of the accomplishments of the conservation profession.
So thanks to everyone reading these blogs and following the blue whale story on #WhaleWednesday and #WhaleMove across Facebook, Instagram and Twitter. We have also enjoyed meeting the public who have visited our Pop-up Conservation Studio in the Museum’s Darwin Centre over the past few months.
The next phase of the project has just started with conservators and scanning teams using recently purchased 3D surface scanning equipment to fully scan each individual bone to a high resolution.
By capturing this information, we can make even more data available to researchers for future study giving them accurate virtual access to the blue whale. The scanning is taking place in the Pop-up Conservation Studio for the next few weeks and will be the subject of my next post. Drop by and take a look if you are in the Museum!
One Reply to “Whale preparation: conserving the blue whale skeleton and planning articulation | Conservators”
Comments are closed.