system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why sometimes my pen writes on my hand but not on paper

Sometimes at work a pen will seem to "dry out," and it won't write at all on paper. I can scratch a piece of paper for a good minute and nothing happens but as soon as I try to write on my palm, the pen works almost immediately. What's going on here?
gpt
Ball point pens literally have a small ball inside them. When you write, the ball rolls along happily, smearing ink in its tracks. Every now and then though, the ink dries just a tad around the ball, and it gets stuck. When it comes to ball point pens and your skin, it's like rubber gripping; it pulls it along easier than dry paper.