Silicon caulk

Alan J. Hawk <hawk [at] afip__osd__mil> writes

>I am in the process of deinstalling exhibits that were built in
>circa 1968. Some of the artifacts were mounted on plexiglass shelves
>with clear silicon caulk.  These are stuck fast and are tight enough
>to prevent a razor blade from slicing through the caulk.  Does
>anyone have any good suggestions about the least damaging method
>separating of artifacts from their mounts or is this something best
>tried by a professional?

Some years ago I had encountered a similar problem that has been
successfully resolved by this following method. The item was a
heavily corroded bronze stuck fast by silicon on a plexiglass stand.

Because of the powdery surface, I want to emphasize that you should
not apply any force whatsoever onto the artefact.

A solution of 1/3 deionized water 1/3 ethanol 1/3 acetone was
applied alternatively under local immersion--partial drying. The
ethanol was used as a wetting and penetrating agent, while the
acetone act was a mild solvent for the plexiglass. Then, the water
can be considered in this case as a separating agent; it is there
mainly to prevent the rapid drying of solvents. After the plexiglass
was discarded, a mechanical separation from the silicon and the
artefact was done step by step (under the same chemicals) followed
by a very slow peeling action. Those processes are in any cases to
be done by professionals as your artefacts my be sensitive to the
products used. Therefore the application of such a method is the
real issue of our question.

David Cottier-Angeli
Jeweller & Metals Conservator
Geneva


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                  Conservation DistList Instance 14:34
               Distributed: Wednesday, December 20, 2000
                       Message Id: cdl-14-34-002
                                  ***