Marker comes prepared to use and is formulated to fluoresce brightly under long wave ultraviolet or LED blacklight. Magic Secret Agent Spy Pens, Sherlock Hones Invisible Ink Pens Occasion Pack Is available in three Ink Colours! The best way that Invisible Ink Pens work is fairly simple. Colored coded cap designates the ink color inside for quick, simple reference. Mark skin or your valuables for quick, simple identification in blacklight. The brilliant/daring pink, read more