Not all “black-lights” are equal, it must be a wave length in the range of 365nm.  Very important!  Fluorescent type black-lights are typically the best option, LED black lights can work but I would recommend testing. The wrong wave length will change the colors and not be as bright of an effect.  Remember always paint with the blacklight on and the brightness of the effect is determined by the amount Watts of blacklight at the surface, the Inverse Square Rule applies.  A common mistake is to apply way to much ClearNeon to increase the brightness instead of adding brighter “watts” of blacklight.  If you do that you will begin to see color/non invisible in normal light conditions.