The ink does not always rub off. If any residue is left on the spectators hand their is no illusion.
I personally found that more often than not the ink does not completely rub off. My theory on this
is everyone has different oil content in their skin, including the performer. I do not think
moisture content alone is enough to "do the trick"
I like the suggestion of the other review to
use water in your hair, however do you really want to run to a bathroom before performing this?