Whale conservation chapter completed

We are nearing the very end of our time in the ‘whale aisle’- it has been a wonderful yet somewhat exhausting time! We made it through a heat-wave summer clad in Tyvek suits and overcame vitamin D deficiencies due to a lack of natural lighting.
The whales were affectionately given nicknames and individual specimens adopted by conservators dedicating their time to pampering those in particular, who in turn visited us in our sleep (no, really)! This blog entry provides an update of our ‘Once in a whale’ project.

Minke Whale post treatment

Minke Whale post treatment

Orca whale smiling once more

Orca Whale smiling once more

Over the past six months the seven specimens have received our undivided care and attention: Their bones have been cleared of dust and oil secretions; fragile and vulnerable areas have been consolidated; previously degraded repairs conserved; old copper and iron wires removed and replaced with stainless steel; and the skeletons’ anatomy corrected where possible through re-articulation. Since our last project update, the ribcages, mandibles and fins have been re-articulated and re-attached using new bolts and nuts.

Dolphin pre (above) and post treatment (below)

Dolphin pre and post treatment

Northern bottlenose whale pre (above) and post (below) treatment

Northern Bottlenose Whale pre and post treatment (with original teeth installed)

Minke pre (above) and post (below) treatment

Minke Whale pre and post treatment (with skull straightened)

Orca pre (above) and post (below) treatment

Orca Whale pre and post treatment

Beluga pre (above) and post (below) treatment

Beluga Whale pre and post treatment

This last stage has been very satisfying, but seeing the skeletons ‘come back together’, has also left us feeling a little lost- we nursed the whales back to health over many months, during which we grew very fond of them, and now we must let them return to the display for all to admire!

Our blog
Our blog ‘www.onceinawhale.com’ set out to capture and convey the conservation process including the material science and expected degradation pathways of skeletal material. We shared our treatment rationale and methodology, and showed before, during and after treatment images. We have been overjoyed with the international blog following we have received and are thankful to all readers who commented on, shared or ‘liked’ our posts!

As my contract at the museum now nears its end, I hand over the blog strings to my colleagues, who will continue to share the project with you!

Creative professionals and enthusiasts have been inspired to join us in the ‘whale aisle’ to illustrate, film and photograph work being carried out on the cetacean specimens. Journalists and broadcasters at Oxford Mail News and BBC Radio Oxford featured articles and interviews and our social media presence has been amazing to see. We have also loved sharing the opportunity to see the skeletons up close and learn about the conservation involved with fellow and further afield museum colleagues, conference attendees, fellow conservators and local school pupils.

During the imminent process of dismantling the scaffolding, the five skeletons will be re-positioned and elevated back into the museum space above visitor’s heads, forming a dynamic display allowing visitors to appreciate the specimens from below as well as from the upper gallery. Do come visit the whales after our reopening in February 2014!

The Once in a Whale Team - Nicola Crompton, Bethany Palumbo and Gemma Aboe (left to right)

The Once in a Whale Team – Nicola Crompton, Bethany Palumbo and Gemma Aboe (left to right)

– Thanks again to all our blog followers, more to follow soon!

Gemma Aboe, Assistant Conservator
Nicola Crompton, Conservation Intern

Down to the wire!

The next exciting new chapter in our ‘Once in a Whale’ conservation project involves the re-articulation of the cetacean specimens. This includes (where appropriate) removing old, corroded wiring from between bone and cartilage joints, consolidating the bone and re-articulating the skeletons with new wire. This blog entry gives an insight into this process and our experiences gained so far.

Bottlenose Dolphin skull dearticulated into upper and lower mandible

Bottlenose Dolphin skull, with lower mandible removed

Consolidation and repairs
Once the bones are individually removed, we assess their structure and strength. The specimens appear to be extremely varied in both their texture and structural integrity. Some skeletons are more friable and brittle than others, which could be due to variety of reasons, including their age or initial method of preparation. Unfortunately, we have no record of the latter.

Where bone surfaces are more fragile, we are consolidating the bone with Butvar B98 (polyvinyl butyral (PVB) resin ) in ethanol. This consolidant was selected for its binding efficiency combined with flexibility. With a reasonably high glass-transition temperature (Tg) of 62-68 °C, as well as favourable results in UV, light and heat exposure studies, Butvar B98 was deemed suitable for use on these specimens, as it would survive exposure to the environmental extremes of the museum’s roof space. It also dries with a matt finish to look natural against the bone.

B. Palumbo injecting consolidant before covering bone with clingfilm

B. Palumbo injecting consolidant before (experimentally) covering bone with cling-film to slow solvent evaporation

While very high UV conditions may cause cross-linking of Butvar B98, leading to an insoluble network (Horie 2010, P.145-7), we felt it’s application was justified. Although we won’t be able to remove it entirely in the distant future, it will ensure the survival of these specimens for decades to come and thus allow them to continue to serve their purpose as display specimens in the museum. We are applying the consolidant by injection into pores in the bone, or by painting directly onto the surface.

Fractures in the bone, are being re-adhered with Paraloid B44 (ethyl methacrylate co-polymer resin) in acetone.

Repaired bone fracture in Bottlenose Dolphin's skull

Bone fracture and wiring before and after treatment on Bottlenose Dolphin’s skull

Repaired fracture on Bottlenose Dolphin's vertebrae

Repaired fracture on Bottlenose Dolphin’s vertebrae

While Paraloid B72, a Feller Class A material, has excellent ageing properties, its Tg is only 40°C. Working with the same group of resins, we selected Paraloid B44, which due to a slight composition ratio variation, has a Tg of 60°C (Horie 2010, p.159-160) and is therefore more suited to our museum environment.

Challenges and opportunities
We thought we had a dilemma on our hands when some of the old, corroded copper wiring had become stuck, particularly in cartilage joints, causing the wire to snap during attempts to remove it with pliers. Who knew what nuggets of knowledge entomologists have when encountered over a cup of tea in the staff room? When faced with mounted insects, whose metal pins have developed verdigris, entomology staff at OUMNH run an electric current through the pin to heat it, thus slightly melting remaining fats in the insects’ body, allowing the pin to slide out of the specimen.

Heating the corroded copper wire before it can be pulled out

Heating corroded copper wire on the Bottlenose Dolphin’s pectoral fin before it can be pulled out

We tried the method first using a battery, before being presented with a soldering iron- which worked like magic- just heating the copper wire sufficiently, to slightly melt the surrounding cartilage, enabling the wire to be pulled free. It really helps to talk to colleagues about your work- you never know what ideas and gadgets they may have!

Reference issues
While the bones guide the re-articulation process to some extent (e.g. spacing of ribs), working on intuition has not always proven anatomically accurate. Sourcing reliable reference material has also been surprisingly challenging. Questions such as: how inflated should the rib cage be? At what distance from the vertebrae should the floating pelvis hang? How should phalange digits be spaced and how many bones were there originally?

Left and right phalanges on Bottlenose Whale, showing spacing between digits

Left and right phalanges on Bottlenose Whale, showing spacing between digits

To answer some of these questions, we have been in touch with a number of specialists, from Alaska to Scotland. Slowly the information we need is being assembled, allowing us to articulate our specimens as accurately as possible.

Team work
While we conservators feel to some extent protective over our own ‘adopted’ specimens, this project stage encourages us to work together. Given the size and weight of ribs, sternums and skulls etc. we rely on each other to help position, support, check for symmetry and tighten joints made.

Working as a team re-articulating the Orca Whale

Working as a team re-articulating the Orca Whale (G. Aboe, N. Crompton, B. Palumbo)

Work in progress
Ribs- The Bottlenose Dolphin’s (Tursiops truncatus, Montagu, 1821) ribcage was crying out for re-wiring and re-shaping and to ensure its preservation and improve its scientific accuracy. Following the dismantling, consolidation and re-assembly with new wires, its shape was improved and strengthened with an additional wire cross-link at its widest point, the 7th rib (Post, 2012).

Bottlenose Dolphin's ribcage and wiring before and during treatment

Bottlenose Dolphin’s ribcage and wiring before and during treatment

Skull- While rewiring the Bottlenose Dolphin skull, we took the opportunity to open the mouth slightly, partly to ensure its teeth didn’t abrade each other as well as to allow visitors to study the teeth in more detail. Doesn’t he look happy now?

Bottlenose Dolphin skull before and after rewiring and widening of mandible opening

Bottlenose Dolphin skull before and after rewiring

We are under continued pressure to complete our ‘Once in a Whale’ conservation project before the scaffolding is due to be taken down, following the completion of roof repairs. Alongside that, we also have pieces of a Humpback Whale ((Megaptera novaeangliae (Borowski, 1781)) skull to address- check out our next blog entry, to see our enormous challenge ahead!

Further readings:

  • Horie, V. 2010. Materials for Conservation. Organic consolidants, adhesives and coatings. 2nd edition. London: Butterworth-Heinemann.
  • Post, L. 2012. The Whale Building Book. A Step-by-Step Guide to Preparing and Assembling Medium-sized Whale Skeletons. Self published.

Gemma Aboe, Assistant Conservator
Reviewed by Bethany Palumbo, Conservator of Life Sciences

Objects of intrigue- a relative of Moby Dick’s?

As part of our cetacean conservation project, we have recently been treating the lower mandible of a Sperm Whale (Physeter macrocephalus Linnaeus, 1758), the largest of the toothed whales. This specimen originally  came to the Museum from Christ Church Anatomical Museum in Oxford (Malgosia Nowak-Kemp, Collections Manager). Our specimen’s jaw, measuring 4.56m in length, is thought to have originated from an ‘88 foot long’ (26.82m) Sperm Whale from the pre-industrial whaling period (pre 1840), far exceeding contemporary species sizes (Malgosia Nowak-Kemp, Collections Manager). It is rumoured to be one of the largest held in a museum collection. Do you know of any larger Sperm Whale mandibles out there? 

Sperm Whale mandible below and above scaffolding platform

Sperm Whale mandible below and above scaffolding platform

The lower mandible, consisting of dense bone and cone-shaped teeth, rests upright against an architectural column at the entrance of the museum, yet is currently surrounded by a scaffolding network and a horizontal platform in the upper third of the jaw. The areas readily accessible to human touch, were visibly stained with a dark grease, while teeth showed dusty water drip marks- all of which could be reduced through treatment.

G. Aboe degreasing surfaces with ammonia

G. Aboe degreasing surfaces with ammonia

Surface areas before (dark) and after (light) treatment

Surface areas before (dark) and after (light) treatment

As conservators working beneath this imposing structure, or at a considerable height, we are made to feel very small and the work conjures up images of Moby Dick, a mythical albino Sperm Whale, immortalized in Herman Melville’s 1851 novel Moby Dick, or the Whale.

Moby Dick book illustration, p510

Moby Dick book illustration, p510

Moby Dick upon being harpooned capsized a fictional boat, killing all but one of its men, the story of which has inspired numerous adaptations and illustrations, (four of which the illustrator in me has selected for visual indulgence).

Moby Dick illustrations (R. A. Forshall, L. Pearson, Book Covet, Kiss my Shades)

Moby Dick illustrations (R. A. Forshall, L. Pearson, Book Covet, Kiss my Shades)

Interestingly, Herman Melville’s novel is based on a true story about a Sperm Whale that attacked and sank the American whaleship ‘Essex(from Nantucket, Massachusetts) in the southern Pacific Ocean in 1820.
One of the survivors, a 14 year old cabin boy at the time, Thomas Nickerson, later wrote an account of the sinking titled ‘The Loss of the Ship “Essex” Sunk by a Whale and the Ordeal of the Crew in Open Boats’, eventually published in 1984.

The Essex being struck by a whale on November 20, 1820 (sketched by Thomas Nickerson)

The Essex being struck by a whale on November 20, 1820 (sketched by Thomas Nickerson)

Both fictional and factual accounts of encounters with unsuspecting Sperm Whales, provided us with plenty of thought, while working our way up and down the jaw.

Sperm Whale hunting
During the 18th and 19th century, whalers were drawn to Sperm Whales for their ivory-like teeth (18-24), weighing up to 1kg each, embedded in the lower jaw. The teeth were crafted into practical as well as decorative pieces, such as when decorated with inked engravings, known as scrimshaw. Herman Melville, in Moby-Dick, refers to “lively sketches of whales and whaling-scenes, graven by the fishermen themselves on Sperm Whale-teeth, or ladies’ busks wrought out of the Right Whale-bone, and other skrimshander articles” (Melville, 1851, ch57).

Whaling scene carved by Edward Burdett (Nantucket Whaling Museum)

Whaling scene carved by Edward Burdett (Nantucket Whaling Museum)

Spermaceti (from the spermaceti organ) and sperm oil (from blubber) were also much sought after by whalers, since these substances were heavily relied upon for commercial applications (including soap and leather waterproofing), with increased demand caused by the beginnings of the Industrial Revolution. Sperm Whale oils were used for public lighting (including lighthouses) and for lubricating machinery, (including cotton mills), before the discovery of mineral oil.

Sperm oil bottle and can (New Bedford Whaling Museum)

Sperm oil bottle and can (New Bedford Whaling Museum)

Ambergris, another popular product with whalers, is produced in the digestive system of the Sperm Whale, and was highly valued as a perfume ingredient.

While we can only ponder on the previous life story of our Sperm Whale, we endeavour to do our best to document its museum life from hereon.

Do visit our blog again, for an update on how we’re doing with re-articulating our cetacean specimens – an exciting new phase of the “Once in a Whale” project!

 Further readings:

Gemma Aboe, Assistant Conservator

How to ‘wire a whale’ workshop

The end is in sight for the completion of the cleaning phase of our five cetacean skeletons. Next we aim to address the wire connections originally used to articulate the individual bones, since the existing wire is negatively impacting the skeletons in a number of ways.

The wires (with iron and copper inclusions) have in places badly corroded, weakening the wire and causing the deterioration of adjoining bone. The wire has already snapped in some areas.

Copper corrosion staining on bone

Copper corrosion staining on bone

Other areas such as the transverse process of the vertebrae are currently too fragile or damaged to be re-wired, as seen on the Northern Bottlenose Whale. These areas will need consolidating and in some cases infilling prior to re-articulation.

Porous and damaged transverse processes on vertebrae

Porous and damaged transverse processes on vertebrae of Northern Bottlenose whale

Where wire has been used to connect broken bones, aided with an adhesive (now brittle and discoloured), we also aim to remove this and re-adhere the sections using suitable materials.

Old repair on vertebrae (wire and adhesive)

Old repair on vertebrae (wire and adhesive)

Re-articulating the cetacean skeletons also gives us the opportunity to question their anatomical accuracy and modify angles and poses where appropriate and possible.

Bethany Palumbo, Conservator of Life Sciences gave Assistant Conservator, Gemma Aboe and Conservation Intern, Nicola Crompton a crash course in articulation methods, focusing on drilling and wiring, in preparation for working on re-articulating the whale skeletons. This blog aims to share our workshop experience.

Tools/equipment used:

  • Dremel drill
  • Pliers
  • Wire cutters
  • Mechanical pencils
  • Dust masks
  • Galvanised steel wire (0.5mm -1.25mm Ø)
  • Practice bones

    Tools and equipment used

    Tools and equipment used

How to re-articulate skeletons: drilling bone

  • The first step is to find the natural position for two bones to be joined, e.g. rib heads will sit comfortably against their associated vertebrae.

    Finding natural position for two bones to join (Nicola Crompton on left)

    Finding natural position for two bones to join (Nicola Crompton on left)

  • Next, decide on the angle of the drill hole. It is important to drill in an area of bone which is strong enough to support the wire joint but is also relatively concealed, so the wire doesn’t negatively impact the aesthetics of the specimen.
  • Pencil an entry spot and desired exit spot on the first bone, this will help to control your drilling (pencil marks may be erased later if necessary).
  • Decide on a drill bit of a suitable size. We used 1mm-2.5mm drill bits for our practice.
  • Drill the hole with gentle force, careful to not break the surrounding bone which may be fragile.
  • Use an extended pencil lead to mark a suitable entry spot through the drilled hole on the second bone (to be joined).

How to re-articulate skeletons: wiring techniques

  • Twist two wire ends to secure fastening using pliers.

    Twisted wire end fastening

    Twisted wire end fastening on practice bone

  • Loop single wire ends to secure fastening, using small long-nosed pliers.

    Wire ends looped

    Wire ends looped on practice bones

  • If working with a broken bone, cross two wires and twist ends to secure fastening, (a useful technique where extra strength is required).

    Wires crossed and twisted on repair

    Wires crossed and twisted on repair on practice bone

  • We are looking into the possibility of using (jewellery) wire crimps to secure fastenings.

Comments and conclusions of workshop:

  • Drilling bone does not smell pleasant, drilling cartilage is worse, so be prepared.
  • Drilling bone produces a fine dust, so wearing a dust mask is recommended.
  • Although we looked at alternative options for wire, such as monofilament thread, we decided to work with galvanised (zinc) steel wire for its strength, corrosion resistance, affordability and fire resistance. The whales will eventually be articulated with Grade A galvanised steel wire.
  • Conduct your drilling and wiring of bones at a desk if possible, where you can manipulate and rotate bones and wires freely, (an easier challenge than working in situ on fragile and complicated joints). We will take apart the specimens where appropriate and work on each section individually before re-assembling the specimens.
  • Over tightening the wire fastening on the bone is easily done, leading to potential cracks and tears in the bone. Examples of this can be seen on the Minke Whale and Northern Bottlenose Whale. We will have to be careful that this does not reoccur.

    Torn original drill holes on

    Evidence of tears in bone surface from over tightening of wire

  • We practised using wire diameters ranging from 0.5mm to 2mm. These sizes will be used on the cetacean skeletons, in order to match existing drill holes. We will only re-drill holes where completely necessary.

If any of our blog readers can recommend other re-articulation techniques, particularly wiring methods, we’d love to hear from you!

In the meantime, we are in the process of completing (degreasing) work on our Sperm Whale jaw (Physeter macrocephalus, Linnaeus, 1758) – do visit our blog again for what may be a Moby Dick themed post…

Gemma Aboe, Assistant Conservator
Reviewed by Bethany Palumbo, Conservator of Life Sciences

The whale’s way

This blog entry allows a very visual insight into our conservation progress.

Following condition assessing and documenting the cetacean specimens, treatment plans were made (see previous blog ‘Treatment decisions, decisions, decisions‘). Hands-on conservation commenced with dry cleaning the specimens one by one, to remove over 100 years worth of accumulated dust. This was followed by the second treatment phase focusing on addressing degraded oil residues formed on the surface of the bones.
Along the way, a few discoveries were made…

1) Removing layers of dust with a vacuum and brush

Vacuuming Bottle-Nose Whale vertebrae

Vacuuming the Northern Bottlenose Whale vertebrae (Hyperoodon ampullatus (Forster, 1770))

2)    Reducing degraded oil residues on bone surfaces with an ammonia solution

Treating the Beluga Whale’s ribcage with ammonia from within/ treated area of Bottle-nose Whale sternum

Treating the Beluga Whale’s (Delphinapterus leucas (Pallas, 1776)) ribcage with ammonia / treated area of Northern Bottlenose Whale sternum

Northern Bottle-Nose Whale's (Hyperoodon ampullatus, (Forster, 1770)) oil soaked skull versus treated vertebrae

Northern Bottle-Nose Whale’s oil soaked skull versus treated vertebrae

Beluga Whale vertebrae before and after ammonia treatment

Beluga Whale vertebrae before (showing water marks) and after ammonia treatment

3 Reducing degraded oil residues on cartilage/bone areas

Bottle-Nose Dolphin fin before and after ethanol/ammonia treatment

Detached Bottlenose Dolphin (Tursiops truncatus Montagu, 1821) fin before and after ethanol/ammonia treatment

4 Removing miscellaneous foreign matter 

Giving the Killer Whale a dental check-up (swabbing with ethanol)

Giving the Killer Whale (Orcinus orca (Linnaeus, 1758)) a dental check-up (incl. swabbing with ethanol)

Old piece of cotton wool in Killer Whale skull cavity (undated)

Old piece of cotton wool in Killer Whale’s skull cavity, suggesting previous unrecorded treatment

5 Discoveries made during treatment

Pencil figure ‘3’ on 3rd chevron of Dolphin (undated)

Pencil figure ‘3’ on 3rd chevron of Bottlenose Dolphin (undated curator’s mark?)

First edition catalogue label ‘1673’ on rib of Killer Whale (Orcinus Orca, (Linnaeus, 1758))

First edition catalogue label ‘1673’ on rib of Killer Whale

Early (honest) treatment evaluation

While we are finding that oils on the bone surface are efficiently being solubilised by treatment with ammonia, we do not know how far the solution penetrates the bone and how much it facilitates a migration of oil from the core to the surface. It is difficult to judge to what extent treatment removes the currently degraded oil residues on the surface, without actively drawing out oil from the bone matrix. In some treated areas the bone surface takes on an orange tint, suggesting un-oxidised oils have indeed been drawn to the surface. Unfortunately at this stage, and without further analysis, it is difficult to predict the level of remaining oil in the bone and how distant in the future the cetacean specimens may require re-treatment.

While this phase of the cetaceans’ treatment is physically demanding (exasperated by working in Tyvek suits during a heatwave), and repetitive given that the project involves five large, suspended cetacean skeletons, the work is nevertheless rewarding. We’ve each adopted our own whale family members, who are affectionately seen through a new chapter in their museum lives.

Join us again for our next blog entry, where we will share images from our ‘bone rearticulation workshop’…

Gemma Aboe, Assistant Conservator

Treatment decisions, decisions, decisions

Our conservation work is driven by the date at which the museum scaffolding is scheduled to be de-assembled, in preparation for the museum reopening in early 2014. This limited period of time plays its part in our choices, regarding preparatory research, scientific analysis, decision making and ultimately the conservation treatment.

We are very thankful to national and international fellow conservators and scientists, who have kindly shared their experiences, research and techniques working on similar materials. This generosity has allowed us to streamline our own treatment decisions.

Whales suspended in scaffolding tunnel (photo Michael Peckett)

Whales suspended in (incomplete) scaffolding tunnel (photo Michael Peckett)

Treatment criteria
To ensure ethical conservation treatment, a number of issues are given consideration.

Our specimens have been assessed for the risks they may have been exposed to in the past, but also those they may face in the future e.g. through continued display. Treatment must aim not only to address existing damage, but also to best protect the specimens from envisaged risks, where these cannot be eliminated (such as high light exposure and unstable environmental conditions).

Throughout our treatment, we aim to use materials and methods which will prolong the survival of the cetacean specimens and where appropriate offer detection and reversibility of our interventions, should the collection’s values or needs change in the future. Before reaching a final decision on treatment choices, the treatment itself is risk assessed, and potential risk management strategies are put in place.

Treatment aims and objectives
Following condition assessments of our cetacean specimens (see blog entry ‘Not so extra-virgin whale oil’), we composed a list of treatment options. These are placed in a table grouped by priority and likely sequence of treatment, though some actions may overlap.


Evaluation of treatment tests
Given that our first priority is to attempt degreasing of the bone surfaces (removing oil residues and trapped dust), we undertook treatment tests following recommendations from conservators at the University Museum of Bergen (Turner-Walker 2012).

Spot-tests were carried out with both polar and non-polar solvents, whereby a solvent was applied to the bone with a toothbrush, the oil saturated surface gently scrubbed, before residues were wiped off the bone with a woven cloth.

Northern Bottlenose Whale degreasing tests

Northern Bottlenose Whale (Hyperoodon ampullatus (Forster, 1770)) degreasing tests

Echoing results achieved in Bergen, we found that non-polar solvents, such as turpentine did not achieve removal of degraded oil residues (since oxidised and cross-linked oil degradation products are thought to be mainly polar) (Turner-Walker 2012). Polar solvents, e.g. ethanol helped to remove the most upper layer of oil stained and dust saturated surface areas, however did not achieve satisfactory reduction in oil degradation residues.

Further recommended testing involved applying a 5%v/v ammonia solution in deionised water to the oily bone surface by the above mentioned method. A process of oil saponification was achieved, producing a soluble soap scum, which could be wiped from the surface. Encouragingly, this method (using a low ammonia percentage) proved to be very effective in reducing the oil degradation products on the whale bone surfaces tested.

Minke Whale degreasing tests

Minke Whale (Balaenoptera acutorostrata Lacépède, 1804) degreasing tests

In areas where oil soaked dust is engrained in the bone surface (despite vacuuming), we found toothbrush scrubbing the surface initially with ethanol helped to remove engrained surface dust. Followed by treatment with ammonia, the oily scum residues could be wiped off or wet vacuumed away.

Assessing the use of ammonia to degrease bone surfaces
Following successful treatment tests using ammonia, the treatment of choice is assessed, based on its justifiability and associated risks.

Can it be justified?
Given the variety in condition and cartilage preservation of our cetacean skeletons, it is our preference to treat the bone in situ with aqueous ammonia. This allows specific areas to be targeted, (rather than indiscriminately submerging them in a degreasing solution of choice). Visual and pH treatment tests showed limited ammonia application is non-detrimental to the bone, and indicated the method to be efficient in terms of cost, time and ease of use.

Nicola working on whales in protective gear

Nicola working on whale in protective gear

What are the risks to the conservators and specimens?
Ammonia is hazardous to humans (corrosive/toxic vapours). To avoid health implications, conservators are to wear protective equipment (including vapour masks) and work in a ventilated space. Exposure periods are interspersed with regular breaks and accidental splash contact areas are rinsed with water (e.g. eye wash station).

The risk of over-wetting the bone is avoided by working in small areas at a time, applying aqueous ammonia by brush (not directly on bone), followed by prompt wiping clean/wet vacuum suction of the worked surface area. The treated area may be further dried by wiping the surface with ethanol.

To try avoid abrasion of the bone surface during treatment, soft bristle toothbrushes or woven wipes are used, allowing pressure to be adjusted. Should detrimental effects be noticed, treatment is to be discontinued in the affected area. Areas of visibly weak or delaminating bone are not to be treated.

The risk of aqueous ammonia (alkali) swelling or weakening cartilage structures, suggests exposure to ammonia in these areas ought to be limited/avoided. Following contact with ammonia, cartilage areas may benefit from wiping with a cloth dampened with a deionised water/ethanol solution to remove alkali residues.

Do keep an eye out for our next conservation blog entry, where we will present our first treatment in progress images!

Further readings:

  • Turner-Walker, G. 2012. The removal of fatty residues from a collection of historic whale skeletons in Bergen: An aqueous approach to degreasing. In proceedings of: La conservation des squelettes gras: méthodes de dégraissage, At Nantes, France

Gemma Aboe, Assistant Conservator
Reviewed by Bethany Palumbo, Conservator of Life Sciences

We are not alone and not the first!

Review of whale bone de-fleshing and de-greasing case studies
In this blog entry we briefly reflect on skeleton preparation techniques, to gain an insight into how our cetacean skeletons may have been initially prepared, what effect these methods may have had on the current condition and if lessons for treatment can be gained. Following this we present three case studies on how other institutions have attempted to degrease whale bones. Their success and relevance to our cetacean specimens may help to shape our treatment decisions.

Woodcut from 1574, showing men flensing a whale (Hull Museums)

Woodcut from 1574, showing men flensing a whale (Hull Museums)

Possible de-fleshing knife incision evidence on  Bottlenose Whale processes

Possible de-fleshing (knife incision) evidence on Northern Bottlenose Whale (Hyperoodon ampullatus (Forster, 1770)) processes

We found two main methods historically employed to de-flesh skeletons for museum display or handling purposes. Our specimens vary considerably, in that some are more oil-rich than others, while the survival of cartilage on fins and vertebrae disks also differs. This would suggest that the specimens were prepared by different methods or individuals. De-fleshing involves first mechanically removing larger pieces of flesh, followed by methods including maceration or the use of dermestid beetles.

Pectoral fin on Lesser Rorqual Whale showing no cartilage remaining

Pectoral fin on Minke Whale (Balaenoptera acutorostrata Lacépède, 1804) showing no cartilage remaining

Warm water maceration
This technique involves placing whale skeleton components in (warm) water tanks (encouraging bacteria development) over several months, occasionally changing the water baths in an effort to clean and degrease the bones, aided by bacteria action (which break protein bonds by releasing proteases). While the Smithsonian Institution found this method to be effective to some extent (during the 1980s and ‘90s), they consequently found lipids accumulating and strongly adhering to the bone surface following maceration (Ososky 2012). Warm water maceration may be risky, as it can potentially dissolve cartilage and any unfused bone.

Cartilage remaining on Beluga Whale’s scapula/pectoral fin joint

Cartilage remaining on Beluga Whale’s (Delphinapterus leucas Pallas, 1776) scapula/pectoral fin joint

Dermestid beetles
Encasing the whale bones in a warm, humid ‘bug chamber’ with scavenging dermestid beetles (though considered a museum pest), used to be a popular practice at the Smithsonian Institution (True, 1892) and is still a common method for removing flesh from bones. The rapid cleaning technique is sometimes followed by immersion of the bones in an  ammonia solution (e.g. 3%), before drying the specimens (Ososky 2012). If timed right, it is possible to preserve the cartilage and ligaments with this method, as the beetles will consume these harder protein-rich areas last.

De-greasing methods
While researching how to de-grease our whales, we came across a number of treatment methods which have been tested and applied by other Natural History museums. Our review focuses on techniques using enzymes, various solvents and aqueous ammonia.

Enzymatic degreasing bath at Beaty Biodiversity Museum, 2009

Enzymatic degreasing bath at Beaty Biodiversity Museum, 2009

Research carried out by the Natural History Museum of Nantes in 2012, aimed to test the efficiency of enzymatic degreasing of whale bones (Balaenoptera physalus), using commercial lipase products e.g. Lipase DF15 (Poisson et al. 2012). These enzymes are designed to catalyse esterification* of free fatty acids, (mainly found to be oleic acid and palmitic acid), to essentially reverse the degradative hydrolysis reaction. *Esterification converts an acid (harmful to the bone) into a (less harmful) ester and water, by combination with an alcohol, e.g. ethanol (through a condensation reaction). After incubating bone samples for 72h however, the enzymatic degreasing achieved, was limited. While oils on the bone surface were efficiently solubilised, the enzyme did not penetrate the bone and thus did not facilitate a migration of oil from the core to the surface (Poisson et al. 2012).

Degreasing effect achieved after swabbing bone surface with ethanol (Turner-Walker 2012)

Dust reduction and degreasing effect achieved after repeated swabbing of bone surface with ethanol (Turner-Walker 2012)

Organic solvents
Test-cleaning of oily historic whale skeletons at the University Museum of Bergen was carried out using paper poultices wetted with organic solvents in 2012 (Turner-Walker 2012). Intuitively oils were expected to be soluble in non-polar solvents (incl. cyclohexane, xylene, toluene and methyl chloride), these however proved ineffective. Instead, polar solvents (incl. acetone, isopropyl alcohol and ethanol) had an improved cleaning effect. This is explained by the transformation of unoxidised oils to oxidation degradation products and cross-linked oil films on the bone surfaces, which themselves are polar (Turner-Walker 2012).

Aqueous ammonia
Researchers at the University Museum of Bergen then proceeded to test clean whale bones using a 25% solution of ammonia, brushed onto the surface with water, before removing foam residues with a wet vacuum-cleaner. This method proved very successful at degreasing bone surfaces (Turner-Walker 2012). Ammonia, being an aqueous alkali, is capable of breaking ester molecule groups in fats into their glycerol and fatty acid elements, producing sodium or potassium salts (soluble soaps) via saponification (Mills and White 1999). The foam may be wiped from the surface, while excess ammonia off-gases and low-molecular ammonium salts are expected to leave the bone structure via sublimation (Turner-Walker 2012).

Radius and ulna of Humpback Whale during aqueous ammonia cleaning (Turner-Walker 2012)

Radius and ulna of Humpback Whale (Megaptera novaeangliae (Borowski, 1781)) during aqueous ammonia cleaning (Turner-Walker 2012)

Please watch out for our next conservation blog entry in which we will present our treatment criteria and results of our own degreasing tests.

Further readings:

Gemma Aboe, Assistant Conservator

Not so- extra virgin whale oil

Mechanical and chemical deterioration
Having familiarised ourselves with the composition of whale bone and oil, this blog entry allows us explore the deterioration of the various natural materials found on our cetacean specimens. This will aid accurate condition assessing (see images) and facilitate targeted conservation treatment.

Rain drop stains on Bottlenose whale (Hyperoodon ampullatus)

Water stains on Northern Bottlenose Whale rib (Hyperoodon ampullatus (Forster, 1770))

Deterioration of whale bone
Bone is sensitive to environmental factors. Being hygroscopic, bone will absorb and release moisture with relative humidity fluctuations in the museum, (which due to the leaky roof have been in constant fluctuation).
Excess moisture may cause hydrolysis of the protein’s peptide linkages, causing swelling and structural weakening (due to a reduction in molecular weight) (Cassman et. al 2008). Moisture may also promote mould and micro-organism development, capable of degrading hydroxyapatite (a calcium phosphate mineral), through the release of acids.
Extreme dryness may lead to shrinkage of the bone, causing warping, cracking and delamination (O’Connor 2008).

Bone delamination on Killer whale cranium (Orcinus Orca)

Bone delamination on Killer Whale cranium (Orcinus orca (Linneaus, 1758))

Variations in temperature also impact the stability of the bone, with excess heat leading to the destruction of protein and loss of moisture, while the combination of heat and moisture may damage the ossein (collagen forming organic matrix).

Areas of loss on protein rich Killer whale phalanges (Orcinus Orca)

Areas of loss on protein rich Killer Whale phalanges (Orcinus orca (Linnaeus, 1758))

Bone is also light sensitive, thus exposure to visible and UV light (e.g. through the glass roof), will over time cause bleaching through oxidation. UV light also affects exposed proteins, e.g. comprising the skin (on phalanges), causing yellowing and friability, due to chain scissions.

Deterioration of whale oils
Oils are composed of triglycerides (esters of glycerol and long chain fatty acids). There are three main mechanisms by which oils chemically decompose or ‘rancidify’ (a term used for edible oils/fats): hydrolysis, bacterial action and oxidation.

Oil drips on chevron of Bottlenose whale (Hyperoodon ampullatus)

Oil drips on chevron of Northern Bottlenose whale (Hyperoodon ampullatus (Forster, 1770))

a) Hydrolysis: occurs when the oil’s ester groups are broken down by water (such as high humidity), or catalytic amounts of mineral acids*, into their component glycerol backbone and free fatty acid chains (Mills and White 1999). The process can lead to an alteration in the oil’s viscosity, colour and odour, such as when volatile carboxylic acid is released. Hydrolysed oil products form polar bonds with the whale bone tissue (hydroxyapatite), and can be seen as drips absorbed on the bone surface. It is thought the higher the free fatty acid content in whale oil, the darker the oil, ranging from pale yellow to dark brown (Turner-Walker, 2012).

b) Bacterial action: includes bacteria and lipase (enzymes), which catalyse the breakdown (of ester bonds) or the hydrolysis of lipids (oils). *Micro-organisms causing acid dissolution of bone mineral, may further lead to free fatty acids forming insoluble salts with calcium in/on the whale bone.

c) Oxidation: occurs when oil is exposed to oxygen in the air, initiating a free radical process, leading to cross-linked films and/or bond breaking (particularly in unsaturated fatty acids with reactive double bonds) and the formation of degradation products (Miller 2013; Mills and White 1999).

Oxidation degradation products include hydroperoxides, free fatty acids, pungent carbonyls, aldehydes and volatile carbolic acid (phenol).
Cross-linking of oil compounds to form a rubbery solid, occurs when bonds form between neighbouring fatty acid chains via a free-radical process, to form a polymer network, characteristic of a ‘dried’ oil film (Gorkum 2005). The blackening of fatty areas is due to oxidation being an exothermic reaction, i.e. they burn.

Blackened oil compounds on Killer whale ribcage (Orcinus Orca)

Blackened oil compounds on Killer Whale ribcage (Orcinus orca (Linnaeus, 1758))

The rate at which oxidation of oil occurs, depends on the availability of oxygen, light, temperature and humidity as well as any transition metals, all of which may act as pro-oxidants (Miller 2013).

The adsorption of atmospheric oxygen in whale oil, and the desorption of (volatile), low molecular weight degradation products, causes weight and volume fluctuations in oil-soaked bones and surface films, potentially weakening the bone structure (Turner-Walker 2012).

Un-oxidised oil in the bulk of whale bones may wick to the surface via capillary action through the bone’s porous structure, allowing a thick, sticky, fully-oxidised oil film to accumulate on the bone surface. The exposed oil along with its acidic degradation products may not only attract dust, but also dissolve the bone mineral hydroxyapatite, reducing the bone rigidity.

Oil soaked and dust covered spinous processes on Lesserfin whale (Balaenoptera physalus)

Oil soaked and dust covered spinous processes on Minke Whale (Balaenoptera acutorostrata Lacépède, 1804)

Once an oil film has hardened, oxygen diffusion and the resulting degradation process slows, sealing in un-oxidised and partially oxidised oil reserves (Turner-Walker 2012).
Can you predict our conservation dilemmas to come?

Further readings:

  • Cassman, V. et. Al (eds). 2008. Human remains: Guide for museums and academic institutions. Lanham: AltaMira Press
  • Miller, M. 2013. Oxidation of food grade oils. Available at: http://www.oilsfats.org.nz/Oxidation%20101.pdf. Accessed: 11/06/2013
  • O’Connor, T. 2008. The archaeology of animal bones. Texas: Texas A&M University Press
  • Turner-Walker, G. 2012. The removal of fatty residues from a collection of historic whale skeletons in Bergen: An aqueous approach to degreasing. In proceedings of: La conservation des squelettes gras: méthodes de dégraissage, At Nantes, France

Gemma Aboe, Assistant Conservator