Touch 'N Flip

Ever wonder how a touch plate, like the kind you see on some elevators and lamps work? This circuit will give you a feel for how the touch plate works in a circuit and you can expand on the circuit to suit your project needs. The touch plate can be a small piece of metal or aluminum foil. Start the circuit by moving S2 to the set position and then back to the previous position. Now press S1. One of the LED's will light. Now touch the touch plate and the LED's will flip on the opposite way. The sensitivity of the plate will vary depending on the humidity. Adjust the VR and capacitor that is connected to S2 to adjust the sensitivity.

From : http://home.maine.rr.com/randylinscott/apr21.htm