>
>     However, what I noticed was, after the initial application of a water
> doplet,
>     the resistance would quite rapidly increase (over minutes not hours).
>     It started off at something like a few tens of kOhms, and ended up a
few
> hundred
>     kOhms after a few minutes... even though the doplet remained the same
> size.
>

The morale: use AC, without any DC component, dus as if it were an LCD.
Wouter.