Ugh. Due to an inflight mishap, the bottom of most pages of my (new) US passport have some minor butter stains. I've removed much of it by absorbing into brown paper, but the stain residue remains. It's not really noticeable if you aren't looking for it, and the photo page is untouched. US Customs didn't even notice, and the bottom of most pages have a convenient mountain image.

I'd really like to clean it off if possible, especially since this is a brand new passport.

Does anyone know of any safe way to remove the greasy butter stains from the passport? Iron on cloth, baking soda, or something very absorbent?