Hello /sci/, starting a month ago whenever I leave my notes on my desk and go to sleep there's a grease/water spot roughly the same size (twice the size of a thumbprint) in roughly the same spot no matter what. It doesn't matter what kind of paper or book I leave there, and it often seeps through multiple pages from the top. This is a problem because it leaks ink everywhere if it happens to intersect with any notes taken in pen.
What is it? Humidity? G-G-Ghosts?