The problem: old Moa bones require cleaning
In late 2018 several mounted moa skeletons were given to the Museum’s conservation labs to be separated at the joints and cleaned. The skeletons had come into the Museum in the 1930s or earlier and had then been assembled to display complete skeletons. Many of our visitors will have seen these Moa skeletons on display in our Origins galleries.
After nearly a century, the bones had become dirty and grimy, and parts had become separated, so they were no longer appropriate for display. As well as this, when assembling the skeletons, the original preparator had been quite liberal in applying putty, fills, paint, and lacquers where bones were originally damaged or missing. This meant that the true surface of the bone was often quite difficult or even impossible to see. As a result, the bones were useless as scientific specimens and the anatomical features of the bones were not visible for diagnostic purposes.
For these reasons, it was decided that the bones would be more valuable if they were disassembled, cleaned, and repaired, so they could be inspected individually (joint faces included) and used as scientific specimens, rather than display specimens.
This shows the alter ego of the Museum: as well as an entertainment and learning venue for people to view old treasures on display, it is also a valuable, modern research resource for the scientific community around the world today. For example, if a scientist wants to study how moa moved, they can access real moa bones at Auckland Museum and can analyse how the joints worked. The same goes for any other scientific questions a scientist may have about the hundreds of thousands of other species and specimens the Museum holds. Likewise, the same holds true for any historical questions that historical researchers may have (for example, about how people used to make different objects, or use them, or when they made such things, and so on).
More (Moa) Problems
As conservation treatment progressed on the disassembly of the skeletons, many problems were found:
The bones were very weak and fragile in places. There was heavy wear, where movement and vibration had worn down the surfaces in contact. These fragile areas needed to be strengthened before the bones could be handled without crumbling.
Old Repairs: In the Way
Many of the bones had been broken in pieces before assembly. Putty and fillers were often holding them together. The breaks weren’t all aligned well and putty needed to be cleaned out from between the breaks, which meant taking the breaks apart and putting them back together more appropriately.
Old Repairs on top of Old Repairs
It was found that there were several layers of old treatments and repairs. At least four different fill materials were found, several different adhesives, and several different paints and lacquers. All these materials could either be dissolved (were soluble) in different solvents or were so aged and degraded that they were no longer soluble in anything. In the end, the material that responded to water was softened with damp poultices and picked away carefully. Minor adhesive and paint removal was done with acetone and ethanol. Any material that couldn’t be dissolved or mechanically removed without causing more damage to the bone was left in place.
Aging Materials and Acid Damage
Some of the lacquers and adhesives that had been used had discoloured to a dirty brown colour. The degradation of at least one of the lacquers must have produced acids in the process, because some bones were powdery and soft (especially the ribs). The surface lacquer had cracked, shrunken, and peeled away, pulling up the surface of the bone with it. The lacquer could not be fully removed, partly because it was holding the surface of the bone in place, and partly because it was no longer very soluble in anything. The best that could be accomplished was to strengthen the bone underneath with a consolidant, while adhering the loose surface in place along with the aged lacquer. Where possible the discoloured lacquer was removed, thinned down, or at least softened and flattened in place.
What is Real and What is Hidden?
Some of the bones were not bones at all. They were sculpted and painted putty that replaced missing bones, or filled large losses. The putty and paint extended over the loss edges, so where real bone was present, the surface was not visible. For example the entire sternum of one moa was found to be a fabrication
The Impact of Handling
The condition of the bone underneath all the layers was often found to be quite weak and damaged, with numerous cracks, splits, and crumbly areas. When the fill was originally applied, the pressure had caused further damage, and it was difficult to remove fill layers without fragments of bone coming off with it.
The Treatment: Getting it All Apart
The actual treatment in the long run was quite simple, but time consuming. Although various solvents were tested to see if they could remove the overburden of aged, old repairs, most cleaning was done by softening with water, and mechanical scraping away to reveal the original bone. High technology was not needed, but patience, care, and time were required.
Blog by Auckland Museum Conservator Valerie Tomlinson