Foto4easy Funny Magic Invisible Ink Disappearing Pen with Blue Ink Ball Point Vanishing in 1 Hour Sign pen with invisible ink. It writes as smoothly as common pen with the same color (Blue ink) when it is writing. The ink will automatically disappear in a hour without any remains or signs left. Paper-saving and environmental-friendly. You dont need to worry about wasting your paper when you are practicing your writing and taking some unimportant notes. You can also leave some secret message or important information to some specific person without being discovered.