I am currently cleaning a lot of laboratory mess. My memory is still sound and clear. We left it clean and very orderly two years ago. I came back and see a lot of mess. It is not surprising, no one else dared maintain the laboratory after we left. Students using the facility might be thinking that cleaning what they used are not their responsibility.
While cleaning, many glass jars with expired content are hard to open. Maybe we capped it too tight way back two years ago. Drying my hand before opening attempt didn’t work. Using rag as reinforcement didn’t work as well. I have no other tools intended for this. All my hand tools capable of gripping are not fitted to hold the cap which is almost 1/2 as wide as my palm.
The idea suddenly rushed in when I saw the big kitchen knife. I got the knife and slightly pried off the lid. Doing it caused metal cap deformation, releasing the vacuum and making the opening a lot easier. The vacuum created by hot sealing was reinforcing the cover tightness.
It was very effective. I managed opening more than 50 tightly sealed jars with this technique. You can try it but please do it carefully. Forceful prying might result to glass breakage and body injury.