This is that hard to find UV Blacklight Reactive Invisible Ink for box marking, document marking, and other unique security applications. Only visible under black light. Ink is water resistant and very difficult to remove. Best viewed in dark or shaded area. Opticz Blacklight Reactive Invisible Printing Inks are suitable for paper marking as well as non-porous material marking. This ink is invisible/colorless and will glow bright blue under UV blacklight. This ink should NOT be used for readmission (e.g. on skin use). Industrial application only. Can be used on: aluminum, cardboard, ABS, acrylic, rubber, cellulose, acetate, formica, nylon, polystyrene, Polyethylene and most other materials and porous surfaces. Ink is solvent based so a little goes a very long way! Ink is formulated to fluoresce brightly under long wave ultraviolet light only. They do NOT glow in the dark! Fast drying and non-transferable. Ideal for applying onto an already printed surface. Please note if applied to a bright white surface that is also UV reactive, this will make the ink hard to see because bright white will glow blue when under a blacklight. Off white to medium color tones yield ther best results. Avoid eye contact and excessive inhalation. Do not ingest. KEEP OUT OF THE REACH OF CHILDREN.