And no, NOT from a cat! I have been helping a friend decorate and foolishly, because we had no paper masking tape, we used double-sided sticky tape on the windows when we painted the frames. And now we are left with a horrible mess that won't come off. We have tried hot water, detergent, white spirit, and acetone. I am beginning to think scratching it off is going to be the only way, but even that is incredibly difficult. I am scared of scratching or breaking the glass panes, which are old and very thin. Does anyone have any ideas for a solvent?