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Stump
P47 was examined for locations where the epoxy
consolidation method
could be tested. Visual inspection and probing revealed
twenty
candidate locations that were either fully detached (but
with a clear
provenance), or where detachment was incipient. The
guiding principle
for selection was the ultimate vulnerability to
detachment and loss of
interpretive context of the stump for park visitors.
This cohort
represented a variety of characteristics, ranging in
size, shape, mass,
complexity, and levels of deterioration. |
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Stump
P47, target location for August 2019 in-situ
consolidation testing. View looking south
west. |
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Over the
course of three days, a set of 6 target locations were
prepped and cleaned, epoxy spot welded
with Araldite 2015, and left to cure while restrained in
situ.
Target location No. 14 was chosen as the best candidate to
test the
consolidation methodology. Both mating surfaces were then
cleaned of
debris with brushes and compressed air. Once the surfaces
were fully
exposed, a small pick was used to pry off any patches of
material that
had begun to delaminate, threatening to compromise the
bonding surface
of the epoxy and wood. Once this was complete, fine steel
wire brushes
were used to further clean and slightly etch the bonding
surfaces (to
enhance adhesion). After a final dust-off with compressed
air, a 1:1
blend of denatured alcohol and acetone was repeatedly
applied to both
surfaces and wiped with a clean, non-pilling, cloth rag to
remove any
oils or residues. |
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In
order
to carry out consolidation, a portion of the
stump is removed at
an area of incipient detachment, revealing a
mass of debris and
exfoliating layers (red arrows). |
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Araldite
2015
epoxy was then applied onto the detached piece in
approximately 10mm
wide ‘spots’. This diameter was predetermined by the
manufacturer’s specifications for the minimum surface
area to achieve
the shear strength required. The height of each
individual ‘spot’ was
adjusted to the necessary distance each application
would have to span.
As a rule of thumb, 1/8” gaps were maintained between
both surfaces for
access to any future removal campaign, Thus, 1/4” high
spots were
created to allow for compression. Once situated in its
final
orientation, 1/8” cardboard shims were placed as
necessary to maintain
this desired gap and to prevent rocking. Finally,
pressure was applied
to the piece and it was secured with adhesive tape. |
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To better understand the possible
effects of weathering on
the epoxy adhesion tests, seven loose test assemblies
were constructed and
placed at grade around P47. The assemblies are comprised
of previously detached
fragments of petrified wood that had long since lost
their provenance and hold
no contributing significance to the stump’s visual
cohesion.
These ex-situ pieces were then placed
in various
micro-environments in regard to solar exposure,
temperature variations in
proximity to the ground, and areas where snow
accumulation can be expected.
They will be collected after a full season of weathering
and taken back to the
CAC for performance evaluation of the reattachment
technique.
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Fragment 14, located on
P47, after reattachment. Red stucco tape is used
to stabilize the piece during curing. |
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The field testing of FLFO petrified
wood consolidation via
epoxy spot welds was successfully implemented. The full
success of this
technique will depend on laboratory testing following a
year of environmental
exposure. Overall, the pilot test was carried out with
the lowest possible
amount of risk to the existing material fabric of stump
P47. All of the epoxy
spot welds were applied to ensure reversibility with no
or minimal/superficial
damage to the existing stump or the fragments used
(based on previous lab
testing of reversibility methods). Additional ex-situ
scatter assemblies were
also tested to provide a greater understanding of the in
situ material
performances of Araldite 2015 epoxy, FLFO petrified
wood, and their bonding
under a variety of environmental conditions.
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The
inner
surface of fragment piece 14 located on P47,
with epoxy applied.
Note the saize of the sample relative to the
conservator's leg on which
it sits. |
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This
program was hierarchically prioritised in terms
of predicted treatment beneficial impact and
expense. The most pressing
solution is the elimination of environmental
stress.
FLFO stumps are the primary reason for tourist
visitation and thus
enable monument survival. Stump mothballing
being impractical, and
contrary to site values of display, the best
option is an enclosed or
semi-enclosed shelter followed by well-designed
environmental controls. |
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