Anne,
That's true - moisture would leak in. The double bagging is a good solution.
Besides damaging the stone, tape would soon peel off, too. This has
generated a lot of interest, and I've had two other possible solutions to
that problem:
One lady who does leave her contact info experienced the ruined card, and
started buying the inexpensive laminating sheets to seal the card into. She
skewered them with an artificial flower stem made of metal inside. That
seems to work for her for a longer time period of time.
I also heard it was an old practice, at least in the Texas-Oklahoma area, to
leave messages near grave markers in Mason jars, the rings of the lid coated
with mineral oil or petroleum jelly. That would also delay rusting. That
lady said some people even used double jars (a small one inside a larger one)
and put marbles or colorful stones between them. Makes them decorative and
is a good anchor. Everyone treated them with great respect, and clean-up
crews would make sure to put them back where they were. That would work
until the neighbor's cows got out and into the cemetery to break the jars!
Thanks for your input - I can't wait to try out one of these methods!
Pat