[NHCOLL-L:1132] Re: Mammoth Teeth

[Adrian M Doyle]

>
>Angela,
>
>As a palaeontological conservator of over 21 years, perhaps I can help you
from my own experience.
>
>It is quite common for mammoth teeth to dry out, expand and fragment -
this is usually prevented by slowly allowing the specimens to dry out if
wet or buy controlling the environment, specifically humidity.
>
>As a rule, specimens which come under the label of 'sub fossil bone' are
susceptible to drying out because of the organic content (collagen) and we
include fossil bone, antler, teeth and Ivory under this label. 
>
>Over many years it has been discovered that the best humidity range is no
lower than about 50-55% with an upper range of 60% (in case there is iron
pyrite present) with a weekly fluctuation of no more then +/- 5%. 
>
>The 'elastic' nature of the material can sometimes be forgiving and at the
moment I am about to engage in further experiments with dimensional
transducers to attempt to quantify bone movement over a range of humidity
levels on pieces of a mammoth scapula. (Provisional results to be presented
at a meeting in York, England later this year)
>
>From your replies, Charles Sturm has quite rightly suggested Butvar as a
potential consolidant for this type of material but I would disagree with
the choice of solvent.
>
>In our Palaeontological Conservation Unit, we use Butvar B76 in
2-Propanone (acetone) as an adhesive, since acetone is very volatile the
join holds quickly (it is still advisable to give sufficient time for the
solvent to fully evaporate and the polymer to set).
>
>However, we use Butvar B98 in Propan-2-ol (isopropanol) as a consolidant,
which has a smaller molecular size and is carried further into the bone
before evaporating since it is less volatile.
>
>There are a wide range of 'Butvars' of differing molecular size requiring
different solvents, but we have been using these two types for over 30
years with great success.
>
>In my own experience, polyvinyl acetate emulsion has been successful as a
consolidant and adhesive and whilst irreversible, does overcome the need
for extraction facilities since it is water based.
>
>I am also aware of work using Paraloid B72 as a consolidant and adhesive
on this type of material but have little experience using this method.
(There are papers on using epoxy resins as consolidants but I would
strongly advise against this practice!)
>
>The factors to consider include access to fume extraction,
irreversibility, working practices, time available and the nature of the
material.
>
>For your interest, there have been several publications in the UK on this
subject which I list below in no particular order:
>
>"The Conservation of Sub-Fossil Bone". Doyle A. The Geological Curator Vol
4 no 7 (1987) pp 463-465.
>
>"A Summary of the Care and Preventive Conservation of Sub-Fossil bone for
the Non Specialist or Pleistocene Problems - The Sub Fossil Bone Senario".
Andrew,K. The Biological Curator vol 5 (1996) pp 24-28.
>
>"The Consolidation of Pleistocene Bone and Tusk at Ipswich Museum."
Pearson, J. Life After Death: The Conservation on Natural History
Collections. UKIC Conference Proceedings  (1992) pp 33-35.
>
>Comparing Gap-Fillers used in Conserving Sub-fossil Material. Larkin N,
Makridou,E. 'The Geological Curator' vol 7 (2) (1999) pp 81-90.
>
>I hope this is of assistance.
>
> 
>
Mr Adrian M Doyle
Conservation Scientist
Palaeontology Conservation Unit
Department of Palaeontology
The Natural History Museum
Cromwell Road
London SW7 5BD
U.K.

Find out more about the Palaeontology Conservation Unit at :

http://www.nhm.ac.uk/palaeontology/cons/cons.html
http://www.nhm.ac.uk/science/consulting/fossildetail.html

email: amd at nhm.ac.uk
voicemail: +44 (0)20 7942 5116
fax: +44 (0)20 7942 5546 


IMPORTANT NEWS:  There will be a phased, temporary closure of the NHM
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