Help with slowing down this simple motor

[heathphysics]

The motor that I've built is the one below its a working motor and spins fast, but I have to slow it down to as much as I can for its intended purpose. Does anyone have any ideas as to how I can make this motor spin slowly. I've tried using less wire but it doesn't work. Note: for the piece of cork, I've used wiring tape instead. Help!

 

[deakie]

Tried lowering the voltage? or putting in a resistor?

 

[Danger]

That's a very nice illustration, Healthphysics.
I agree with Deakie that dropping the voltage is probably the easiest way. I'd modify his resistor suggestion by using a rheostat. That will allow you to tune it on the fly rather than having to swap out hard-wired parts until you get the speed that you want.