[slategruen]

A handful of my professors don't allow us to use this kind of pens, especially for major examinations. The issue was the ink disappears when exposed to heat. Yes, you could place the paper in a fridge when that happens but what kind of professor will have time to do that? Other times, some erasures unintentionally appears just by placing the paper near an A/C.

I never use these pens anymore because of it's weird use case: writings which doesn't need to be kept long-term and at the same time you're sure will be handled properly (temperature-wise).

[thesh4d0w]

If you put the "erased" paper in the freezer, all the ink will show up again.