Here's a very interesting page:
http://www.azom.com/details.asp?ArticleID=1140

Note the bit on Austenitic Grades, which all of the 300 series fall into.

 

EUREKA, thanks Ron

Do capacitor plates vibrate in response to pulsed DC or AC only? I'm guessing a static charge would not cause movement....

Maybe THAT's why the purported high voltage was needed... I'm guessing that a low voltage charge is not strong enough to produce any significant vibration, especially in such a dampening median as water...

Now I think I understand the point of the dual 555 driver circuit -- the superimposed waveforms can be tuned separately, one to coincide with the "capacitor vibrations" and the other to match the electrical resonance.

I'm going to get busy finishing the 555 circuit and use it to excite a step up coil, which will be connected in series to an inductor, the water capacitor, and then another inductor.

Thanks a ton all your wisdom, I'll post if I make any developments, though I'm sure I'll be back to ask more questions about FETS because eventually I want a 12V gate signal to switch 100V DC on/off.

 

EUREKA, thanks Ron

Do capacitor plates vibrate in response to pulsed DC or AC only? I'm guessing a static charge would not cause movement....

I am no expert on the subject of movable plate capacitors. I searched for "movable plate capacitor". Some heavy theory can be found here and here. Good luck in understanding it.
Here is some speculation:
Since the attractive force between the plates is only a function of the absolute voltage across the plates (polarity is unimportant), you will never get repulsion, and if you apply pure AC (no DC bias), the motion frequency will be double the applied frequency of the voltage. If you apply a varying voltage with a DC bias, the motion frequency should be the same as the frequency of the applied voltage. A pure AC square wave would result in impulses of motion only during the finite transition times, because the attractive force would be equal and constant during the positive and negative levels of the input voltage. Inertia and motional resistance due to the water would seem to prevent much motion. A sinewave would seem to allow for more motion. As the frequency goes up, the amplitude of motion would be reduced, due again to plate and water inertia and motional resistance.
As I said, this is speculation. I have zero experience with this.