Care and Use - Ground-Glass Surfaces
Ground-glass joints and stopcocks should never be used when dry. although ground-glass surfaces seal well without the use of lubricants, it is advisable to lubricate them to prevent sticking and breakage. Ground surfaces must be cleaned prior to lubrication—dust, dirt and particulate matter may score the surface and cause leakage. Different lubricants are used for these operating conditions:
- Silicone grease—for high temperature and high vacuum
- Glycerin—for long term reflux or extraction
- Hydrocarbon grease—for general laboratory use
Lubricating Ground-Glass Joints
1. lubricate joints that must be airtight and when glassware contains strong alkaline solutions.
2. lubricate only the upper part of the inner joint. a properly lubricated joint appears clear, without striations.
3. Do not allow grease to come in contact with vapor or liquid and cause contamination.
Spread two circular bands of grease around the stopcock plug. Insert the plug into the barrel and twist several times until the assembly is completely transparent. Be careful not to use too much lubricant or the bore will become plugged.
Information courtesy of Kimble-Chase