Yesterday, I bought some "magic" rollerball pens (those with water-based ink), available in red, blue and black.
They look and write like a normal pen, but have an eraser at the upper end, just like a pencil. You can erase the ink with this eraser, but the real miracle is: A few seconds in the freezer at −18 °C, and the ink becomes visible again.
Some additional facts:
- The eraser of the pen is translucent and feels wax-like, but is quite hard for an eraser.
- It does not rub off anything, you don't get that typical crumbs.
- Normal erasers do not have any effects on the ink, just as expected.
- It's the perfect ink eraser: You can erase a letter and directly write a new letter on it with the same pen, like a pencil.
- The process can be repeated. You can erase the ink and recover it in the freezer several times.
I know those ink erasers from school or those "magic pens" which change the color of the ink of other pens, and also know, how it works.
But this pens are new to me. Has anyone an explanation of their principle of work?