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Florissant Treatment and Testing

In-Situ Consolidation Using Epoxy
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.

P47 stump
Stump P47, target location for August 2019 in-situ consolidation testing. View looking south west.
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.

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).

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.

Ex-Situ Experiments

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.

Fragment in place
Fragment 14, located on P47, after reattachment. Red stucco tape is used to stabilize the piece during curing.

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.

Sample 14
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.
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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