Safety Emporium for all your lab and safety needs
Safety Emporium for all your lab and safety needs

*The Glassware Gallery*

Glassware Joints



Standard Taper Ground Glass Joints

Ball and Socket Joints

O-ring Joints

    O-ring joints consist of two grooved flanges between which is placed a single rubber or Viton O-ring. O-ring joints are sized according to the interior bore of the joint (not the diameter of the groove or O-ring). For example, a #15 O-ring joint has an interior bore of 15mm. Like ball and socket joints, O-ring joints must be held together with a pinch clamp.

    unassembled o-ring jointassembled o-ring joint

    O-rings have distinct advantages over standard taper joints in that they are unlikely to leach grease into a reaction mixture and they are virtually incapable of siezing. However, O-ring materials can degrade when used with certain solvents or subjected to high temperatures (think about the Challenger disaster).

    O-ring joints should not be greased, however the O-ring itself should be treated with an extremely thin coating of grease. A good way to do this is to simply rub your nose with your thumb and forefinger and then rub the O-ring (honest. No kidding). Alternatively, Apiezon M grease is a good choice. When assembling an O-ring joint, be careful that no hairs or fibers stick to the O-ring as these will cause a vacuum leak. Also make certain that the O-ring is correctly sized and fully seated in the groove. It never hurts to have spare o-rings on hand.

cover illustration
The Chemist's Companion:
A Handbook of Practical
Data, Techniques, and References

by Gordon & Ford


This page was last updated Sunday, March 27, 2011.
This document and associated figures* are copyright 1996-2015 by Rob Toreki. Send comments, kudos and suggestions to us via email.
*Some of these figures are adapted from the Chemglass, Inc. catalog and have been reproduced with permission.