# How can I get this glass stopper out? Need troubleshooting!

I placed a glass stopper in a $$\pu{100 mL}$$ round bottom flask while my solution was still warm and let it cool overnight. Now I think I created a vacuum seal and I can’t force the stopper out to filter my product. I’ve tried heating it up again but to no avail. I don’t want to slip oil in there and risk getting it in.

Anyone have a good idea?

• Sometimes tapping the joint lightly can help let some air in. – Zhe Oct 4 '18 at 19:04
• Cooling the stopper helps, LN2, dry ice. – Karl Oct 4 '18 at 21:06
• Have you access to an ultrasound bath? – Waylander Oct 4 '18 at 22:03