Sorry for the wide distribution, but I'm casting a wide net in the hopes of a speedy solution.
My daughter is trying to build a simple Volta's pile for a school project. We took twelve shiny new US pennies, twelve circles of aluminum foil cut slightly smaller than the pennies, and twelve 1-inch squares of paper towel soaked in salt water. I can't seem to get any current off of the thing. First we tried touching two wires together in a darkroom, but couldn't see any sparks. Then I got out my trusty Radio Shack battery tester, but its needle wouldn't budge. Then I soaked the paper towels in heavily salted vinegar, but got the same results. I also tried using several individual pennies and pieces of foil, but still can't get the battery tester to measure anything.
I'm pretty sure that the battery tester's uncalibrated meter is measuring voltage, not current, so I'd expect it to show *something*. All US pennies since 1982 are copper-coated zinc wafers, so I'd expect there to be enough Cu to react with the vinegar. The foil is plain heavy-duty Reynolds wrap for baking, so I don't expect that there's any coating. The salt is Morton's iodized table salt. My stranded wire will light a flashlight bulb from a AA cell, so it doesn't have any internal breaks.
This whole thing has me stumped. If anyone can offer any suggestions, I'd love to hear them; otherwise I'll probably try using an old piece of copper pipe wrapped in wet paper towels and foil, and if that doesn't work I'll buy a steel bowl and try a ball of foil floating in vinegar.