Hermetic seal
![A Taper Joint Stopper with PTFE Sealing Ring. Optical transparency of the narrow sealing ring pressured by glass joint (right).](/Images/godic/202501/17/Glindemann_PTFE_Sealing_Ring_for_Taper_Joint_Glassware3004.JPG")
![Grease is used to lubricate glass stopcocks and joints. Some laboratories fill them into syringes for easy application. Two typical examples: Left – Krytox, a fluoroether-based grease; Right – a silicone-based high vacuum grease by Dow Corning.](/Images/godic/202501/17/Laboratory_grease_13004.jpg")
A hermetic seal is the quality of something—a container, structure, etc.—being airtight (excluding passage of air, oxygen, or other gases). Used technically, it is stated in conjunction with a specific test method and conditions of use.