Daguerreotype base-metals

I have always seen Daguerreotypists use silver-plated copper as their plate.
What happens if you substitute copper for another metal? Perhaps pewter?
The pewter would be silver plated so is there any chemical reason for us to
keep using copper?

Further, once plated, could I engrave the back of the plates by scraching
away at the silver plating (on a silver-coated copper plate) or would that
cause oxidation of the copper over time and, thus, ruin the dag.?

Thanks,
Jon
Received on Tue Apr 6 21:59:40 2004