Coins adhered to wood

Tim Campbell <tcmail [at] ix__netcom__com> writes

>The following appeared on Museum-L and is reproduced here without
>the knowledge or consent of the author.
>
>    Date: 13 Feb 2001
>    From: Brent Stauffer <philliephanatic [at] hotmail__com>
>...
>    While taking apart some broken shadowboxes, we ran into some
>    papal coins that were mounted on wooden pegs with what looks
>    like rubber cement.  We have managed to get the pegs off the
>    shadowboxes, but we can't get them off of the coins.

If you cannot employ a local conservator to advise you, I would
first try heat from a hair dryer and see if the cement becomes very
stretchy or soft enough to pry up easily without damage.  Never
forcefully try to remove them--historic metals can be brittle and
have fragile surface layers.  If this does not work, you might try
testing organic solvents like mineral thinner, acetone, etc.  There
is a wide variety of rubbery type adhesives and without knowing
which one you have you will just have to experiment.  If common
solvents do not work, you may have to try more toxic and dangerous
solvents,  but you will have to take precautions.

One thing that worked for me once on a rubber containing adhesive
was soaking the object in very hot water (but not boiling) for at
least an hour, then, while still hot, carefully try peeling it away.
Not only did the heat make it more elastic, but the water
reconstituted the latex in the adhesive and made it relatively easy
to peel without damage.  If allowed to cool off or dry out, however,
the rubber became tough and inelastic all over again. Also, repeated
soakings might be required for very thick layers.   A lot will
depend on the nature of the adhesive and how old it is.  Of course,
if the coins are corroded or unstable in any way, a water treatment
is inadvisable. I hope this helps,

Linda Roundhill
Art and Antiquities Conservation
Woodinville, WA



                                  ***
                  Conservation DistList Instance 14:49
                  Distributed: Friday, March 23, 2001
                       Message Id: cdl-14-49-005
                                  ***