I remember when I was in elementary school, I watched a mystery detective movie with a few friends. In it, there was a small shop where several teenage detectives were studying any evidence they could find, especially paper evidence. They discovered some writing: text written with a ballpoint pen could be seen, but text written with a gel pen or carbon-based pen could not be seen.
I don’t know why, but whenever I think about gel pens or carbon pens and ballpoint pens, I always associate them with this movie, because it was completely different from what I used to imagine. When I used ballpoint pens, I always felt like they barely wrote or didn’t write well, while gel pens and carbon pens wrote so much easier. So I don’t know whether my intuition is right, or whether the movie’s logic was correct.