I've never seen a spark. But inadvertently, one time, my finger was still on the raw wire and ther was a charge indeed. It woke me right up! Zap.
Anyhow, if you read Pat's instructions carefully, she specificcaly says not to touch the wires for too long, because the protons and electrons then start going back and forth and you won't know what you end up with - something to that effect.
The link to her specs is right below, and below a few more posts is a thread with a lot of different links on it.