How to make invisible ink blacklight

 When surfing on the net, there are several ways to make invisible ink juice at home. Take White Crayon Invisible Ink for example.

Materials: white wax crayon, white computer paper, highlighter or water color paints
Step 1: Pressing hard write a message using the white wax crayon on your paper.
Step 2: Color over the entire paper with a highlighter or paint over it with water colors and your message will be revealed.
This seems to be very easy and some guys may try it. And what's more, some still asks how to make invisible ink blacklight. As far as I'm concerned, it isn't wise to make invisible ink or black light at home at all. By one hand, we can't make the practical invisible ink black light ourselves for it needs skills and technology and maybe advanced machine. By the other hand, it's quite easy to buy these invisible ink or luminous ink reader balck light online. Why we have to spend the time and energy doing it ourselves without a good result? 
Also there are several devices that can read the invisible ink marked cards without any blacklight. They are luminous ink marked cards readers, including marked cards contact lenses and infrared sunglasses.