Bone

Evangelia Kyriazi <evangelia_kyriazi [at] yahoo__gr> writes

>I am a 3rd year conservation and restoration student at the
>University of Lincoln and I am writing my dissertation on the
>reconstruction of missing areas of bone. I know that plaster has
>been used in many occasions, but there are some cases where the
>bones are too thin, making plaster an inappropriate filler. Last
>year I worked on an oribi (small species of antelope) skull and I
>used Japanese tissue paper impregnated with EVA to reconstruct the
>missing areas. Do you have any suggestions upon other materials that
>could be used for the reconstruction of bone?

I am currently working as a conservation intern at the Canterbury
Museum (Christchurch, New Zealand), where we are treating the
skeleton of a blue whale (26.5 m in length) with the intention of
re-exhibition. The whale was acquired by the museum in 1908.  It was
defleshed, mounted and exhibited outdoors (which has contributed to
its current condition and instability). After approximately 85 years
outside, the skeleton was shifted indoors.

As part of the treatment process, we are filling voids left by the
removal of unstable mount materials (iron rods, nails, etc.). These
voids are fully contained, roughly circular areas within the bone.
As of yet, we have not been concerned with filling / reconstructing
any largely missing areas or whole elements (although that will come
at a later date). There are areas where the bone is quite dense, and
areas where the bone is very fragile/friable, etc., so I am working
with both conditions.

The fill material we have chosen is a combination of glass
microballoons and Paraloid B-72 40% in acetone (roughly 2:1 by
volume). I am pretty happy with the results so far--the fill is very
light-weight, is fairly easy to shape / sand, and can be painted
(dry pigments dispersed only in acetone) and textured to match the
surface of the bone. I have found that the fill needs 4 or more days
to harden enough to shape. The fill material has a relatively decent
working time, but it is useful to have the area prepped and ready to
go before you make the fill. And it is a good idea to apply Paraloid
B-72 20% in acetone as an adhesive immediately prior to filling, to
ensure attachment to the bone [Stephen Koob, "The Use of Paraloid
B-72 as an Adhesive: Its Applications for Archaeological Ceramics
and Other Materials, Studies in Conservation 31 1986-7-14]. We
anticipate (based on personal observation to date) that the fill
will retain some resiliency which will hopefully facilitate any
movement in the bone.

In the event that you are reconstructing whole bones, replacing
large areas or areas that require a great deal of structural
stability, you may wish to assess the strength of the microballoon
and B-72 combination. I don't anticipate that we will be using
microballoons and B-72 for this particular application in our
project.

Regarding the use of plaster, for bone of this age and condition we
prefer to avoid water-based materials. And we are actually removing
most of this specimen's previous plaster fills and reconstructed
elements. Understandably, exposure to the weather has made the
plaster unstable, leaving the adjoining skeletal elements vulnerable
to damage.

Melinda Bell
Conservation Intern
Canterbury Museum
Rolleston Avenue, Christchurch 8001, New Zealand
+64 3 366 9429 ext 864
Fax: +64 366 5622


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                  Conservation DistList Instance 16:53
                  Distributed: Tuesday, March 18, 2003
                       Message Id: cdl-16-53-006
                                  ***