best for spark transfer; dull or sharp edges?
Cats aren't sharp, that's why they can build up a pretty fierce charge on a dry winter day when you pet them. If cats came with sharp edges they would discharge more easily and you wouldn't get a shock that you could notice. Balloons are the same, but they won't claw and bite you if you try to stick them to the wall with static electricity. Hey! I was 7 years old.