My son recently graduated and the landlord is refusing to return the £1000 deposit from the student house. One of the reasons he's giving is that there was Christmas "spray-on snow" left on one window and he needed "extremely expensive solvent" to remove it. He won't produce receipts.
Now I would have used a Stanley-blade holder to scrape it off, or try white spirit, acetone, cellulose thinners or Nitromors; none of which are THAT expensive. I'm sure he's trying it on, or are there solvents as precious as printer ink? The landlord is a builder by the way...