Paul__B:
fungus:
A piece of foil in the base of the jar works.Insofar as it is actually (capacitively) coupling itself to the bench on which it is sitting which is itself well coupled to the "real" "ground"/ "earth"/ whatever. If on the other hand, the jar is picked up, it will lose this.
It still seems to work OK if you pick it up.
You also can trigger it by standing the jar on your hand.
Paul__B:
fungus:
A piece of foil stuck to the side of the jar works too, but not as well as a piece in the base.Needs to be a ring of foil in the neck of the jar, not too close to the lid but so the hand approaches this as it approaches the lid. Whilst it may not be as sensitive, it will be much more reliable as it will not be affected by what the jar is - or is not - sitting upon.
I don't need it to be mega-reliable, it just has to light up if people mess around with it.
It's more important to be able to hide the mechanism. A big ring of foil around the jar kinda spoils that.
I'll play around a bit more today....