How to make secret pen ink?

Question

how do i make secret ink the type of ink that only appears when you shine a blacklight on it, anyone know how to make it?

thank you for answering

Answer 1

it's kinda disgusting but I hear urine shows under a black light . Pretty cheap though!

Answer 2

You don't need a blacklight to see writing done in lemon juice. Just shine a light through the paper, like a flashlight behind it or hold the paper over a table lamp.

The Muse

Answer 3

lemon juice?