Why doesn't my capacitive stylus work unless my hand is near it?

I was trying to build a little mechanical auto-tapper for my iPad to repeatedly hit a button (e.g. 'I'm still listening'). While I could make my own stylus using conductive materials, I still had to be touching it. So I bought a cheap capacitive stylus. It works even when wearing gloves, but I still have to be holding it in my hand. If I hold it with something else, e.g. cardboard, it does not work. Anyone know why? Any ideas how to finish my auto-tapper?