This highly fluorescent Invisible Skin Marking Ink can be swabbed, dabbed or stamped on the skin It dries immediately with no visible trace and fluoresces a brilliant blue/white when exposed to longwave (UV) radiation Use fluorescent invisible skin marking ink with an ultraviolet light to control access or egress at facilities such as prisons, detention houses and other control areas Identifying dates, times and other symbols are easily changed with a combination of stamps and stamp pads UV743EL supplied in 32 oz (946ml) volume