Monday, August 5, 2019
Ordinary printer paper is darkened by a high power UV laser, and then the affected area disappears in four minutes! This is caused by fluorescent brightening agents that are added to printer paper, which are temporarily overloaded by the intense UV light. It seems that oxygen plays a role in this, as hydrogen peroxide applied to the marks cause them to disappear instantly, and prevent them from being formed again by the laser. Performing the experiment in argon appears to slow the disappearing ink effect.