★ When printing with invisible inks, please be aware that most white copy paper has fluorescent brighteners to make the paper look whiter.  These brighteners are usually fluorescent blue, so the invisible inks can be hard to detect on bright white paper.  So we would suggest users choose papers without optical brighteners added for invisible printings. 

★ According to our tests, light yellow copy paper or light blue copy paper don't contain brighteners.  They are good for invisible printings.