system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does self-disappearing ink work?

I got one of these pens for free with a calligraphy practice workbook. After about 5 minutes, the ink just vanishes as if nothing was written. I've tried it on multiple different papers and the same result occurs so it shouldn't have to do with a specific kind of paper. How does this happen?
gpt
Disappearing ink is usually reacting to carbon dioxide in the air around us, creating carbonic acid through an interaction with an agent in the ink, which causes it to "disappear" as sodium carbonate. Sometimes, the ink is photosensitive instead, which will cause it to disappear due to exposure to light.