The large black glass perfume bottle has a stuck stopper as well. I have tried using hot and cold, penetrating oil, but alas, it won't budge and I too am afraid I will break it. So it stays intact. Any other ideas on removal.
Ep.
heat the bottle gently in warm water under 125 deg. remove it from the water and put a little CLR around the seal. if there is any gap at all ,as the bottle cools it will draw the CLR in around the stopper and loosen any mineral deposits that are between the stopper and the bottle. be patient ! you might have to do this a few times.. it has worked for me a few times in the past. actually once was on a larkin!