Preservation of 12th century burial

First of all I should briefly introduce the situation. In December
2009 and January 2010 archeologists excavated 12th-13th century
burial place in East-Estonia, Kukruse. As the temperature outside
was minus 20 degrees per Celsius, a huge excavation tent was used
where the temperature of plus 15 degrees was obtained. One of the
female burials was extremely outstanding (plenty of finds, whole
coffin probably made of one trunk and the bones were in good
condition) therefore the archeologists decided to take out this
burial as a block (we call it monolith--in our terminology it means
skeleton with earth and finds).

For this the burial with surrounding ground was left on a higher
platform, which was opened from three sides. Then the burial was
covered with plastic, paper, sand and some plaster. After that a
wooden crate was built around the monolith. Five thick steel plates
were pushed under it and then two bigger plywood plates were pushed
under the steel plates. The measurements of the crate were 3 m
(length), 1,5 m (width) and 70 cm (depth). The weight of the "whole
thing" was circa 3 tons. With special equipment archaeologists
managed to cut out and lift up this huge monolith and transported it
safely to laboratory in Tartu where the finds and bones were
properly unearthed.

During the work in laboratory the monolith was kept moist, but now
when the work has come to an end, it has been decided that the grave
will remain partly unopened and it will be preserved as a whole, it
has left to dry up. One of the reasons to let it dry was quite high
fluctuation of relative humidity in a working room, but there were
also other problems.

Grave goods of the burial consist of variety of materials: chest
ornaments of silver (breast plates), ornaments and tools of bronze
and iron, glass beads from necklace, wooden coffin, textile (mainly
tracks of textiles in iron corrosion), leather (some traces of
footwear, ceramic (vessel), bones and teeth of the skeleton. Metal
finds of silver and iron will be removed from the monolith and will
be conserved separately.

Now I am getting to the subject in which I need your advice. As this
kind of monolith in Estonian culture context is unique, we have
decided to preserve it as a whole. This decision was not easy
because monolith's further fate is problematic - it is certain that
it will be exhibited after 4 years in Estonian National Museum, but
meanwhile it must be properly stored.

The present crate around the monolith is made of pine wood, it is
heavy and large, it is not tight and therefore it is not
transportable inside the building. We want to make monolith lighter
by cutting it thinner from all sides and by removing larger part of
the extra thick soil layer (circa 20 cm) under the coffin. Besides
that, we would like to remove steel plates from under it in order to
take an X-ray and finally it needs a transportable exhibit crate or
box.

The most important is not to harm the already half excavated finds
and bones on the top of the monolith while operations under the
monolith are conducted. Unfortunately the sandy based (also full of
stones) earth of the monolith is not horizontally even, side next to
right arm is deeper while its feet lie much higher (difference is
circa 20 cm).

Does anyone know how to do it all safely--cutting, thinning, and
removing of the plates and crate? Is it at all possible to do it?

Does anyone have good experience applying cyclododecane to
archaeological finds? We have tried to use it on small
archaeological finds, but as it is described in literature, it
didn't work.

Does anyone have good experiences using dry ice (CO2) on
archaeological finds? Could it work on our big monolith while
operating under the skeleton?

Does anyone have an experience in using plaster of Paris or lime
milk in making the soil thick and unbreakable during the removal of
the metal plates and thinning the soil under the burial?

In some stage the use of synthetic glue (probably Paraloid B 72) to
fix some very tiny and fragile details is on the agenda, but I would
prefer not to do it if it is avoidable. Are there alternatives to
this synthetic glue? For instance we probably need to fix the
ornament from bronze spirals somehow, as it will fall apart during
the drying process.

Of which material and what kind of new crate you would recommend for
mentioned monolith?

Could any of you give some references to the problems addressed
here?

Ideas, suggestions and comments are very welcome! We would very much
appreciate all kind of feedback from those who have experiences with
similar projects.

P.S. You can find the photos of the problematic monolith at

    <URL:http://www.folklore.ee/~tonno/Konservaatoritele/>

Kristel Kajak
Object conservator
University of Tartu
Institute of History and
Archaeology
Lossi 3, Tartu 51003
Estonia


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                  Conservation DistList Instance 24:13
                 Distributed: Thursday, August 19, 2010
                       Message Id: cdl-24-13-017
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