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Glassware safety is the set of habits that keep laboratory glass from breaking in use and from injuring the people who handle, wash and discard it. The University of Nebraska-Lincoln (UNL) Environmental Health and Safety office states that broken glass is one of the most common causes of laboratory injuries, typically from mishandling or misuse of glassware. This guide covers laboratory glassware used by lab staff, technicians and students: flasks, beakers, tubing, ground-glass joints and vacuum equipment.
Who uses it: bench scientists, lab technicians, teaching-lab staff and the people who wash up and dispose of glass. For PPE, eyewash and spill equipment around the bench, see the lab safety equipment checklist.
Why laboratory glass breaks
Any abrasion reduces the strength of glass, making it more susceptible to breakage under impact, pressure or thermal shock (a sudden temperature change), according to UNL’s Safe Operating Procedure on ground glass and glassware. A scratch is therefore a weakness, not a cosmetic flaw. UNL recommends borosilicate glassware for all laboratory glassware except special applications that use UV or other light sources; the Type I borosilicate glass entry explains the material, and the types of laboratory glassware guide covers the product classes.
UNL also advises checking that the glass is chemically compatible with what it will hold, because some chemicals react with or damage glass, and confirming that the piece can withstand the temperature and pressure changes of the work.
Inspect glassware before every use
UNL says to inspect glassware before each use and discard it if it is scratched on inner surfaces, chipped, cracked or damaged in any way. Western University’s glassware safety page lists the defects to look for as chips, cracks, scratches and star cracks, and says chipped or cracked items should be repaired or discarded.
| What you see | Action stated by the sources | Source |
|---|---|---|
| Scratch on an inner surface | Discard | UNL |
| Chip | Discard (UNL); repair or discard (Western) | UNL, Western University |
| Crack or star crack | Discard (UNL); repair or discard (Western) | UNL, Western University |
| Glass not designed for vacuum | Do not use it for vacuum work | UNL, Western University |
Handling and carrying
- Never carry bottles by their necks. Hold a cool flask by the neck while supporting its base, and use a cart for large bottles of dense liquid (Western University).
- When fitting tubing into stoppers or hose connections, UNL calls for heavy gloves, tubing that is fire polished or rounded and lubricated, and hands held close together. It suggests considering plastic or metal connectors instead of glass.
Heating, cooling and thermal shock
Heat and cool large glass containers slowly, and use Pyrex or other heat-treated glass for heating (Western University). UNL notes that abrasion makes glass more susceptible to thermal shock, so inspect vessels before heating them.
Vacuum and pressure work
Use only glassware designed for vacuum work for that purpose; Western University adds that thick-walled round-bottomed vessels are the type to use. UNL says vacuum-jacketed glassware should be handled with extreme care to prevent implosions, and that equipment such as Dewar flasks should be taped or shielded. Western University gives the same advice for evacuated equipment. UNL also says glass blowing should not be attempted without proper annealing facilities.
Ground-glass joints and stopcocks
UNL says ground-glass joints and stopcocks should be lubricated to prevent sticking and breakage, after cleaning the surface first. Lubricate only the upper part of the inner joint; a properly lubricated joint appears clear, without striations.
| Lubricant | Use stated by UNL |
|---|---|
| Silicone grease | High temperature and high vacuum |
| Glycerin | Long-term reflux or extraction |
| Hydrocarbon grease | General laboratory use |
Washing and drying glassware
UNL’s guidance for the wash area:
- Wear heavy, water-resistant rubber gloves with textured palms and eye protection.
- Coat washer support pins with a non-abrasive material.
- Wash by hand with plastic-core soft brushes or soft sponges, and do not reach inside glassware.
- Use rubber mats in sinks and on counters, and do not overload sinks, dishwashers or soaking bins.
- Do not leave round glassware on flat surfaces where it can roll.
- Dry on adequately supported drying racks.
Cleaning up broken glass
UNL states that tongs, a dustpan and a broom are the best tools for cleaning up broken glass. If hands are used, handle only large pieces and wear heavy-duty gloves. Western University says not to pick up broken glass with bare or unprotected hands, and recommends tongs for large pieces in a sink and cotton held in tongs for slivers.
Disposal of glass
UNL states that disposing of broken or intact glass as ordinary refuse is not acceptable, and that proper disposal depends on the glass’s previous use and its condition. Western University says glass contaminated with biological, chemical or radioactive material must be decontaminated before it is discarded. Where glass is contaminated with blood or other potentially infectious material, broken glass is treated as a sharp; see sharps disposal regulations for laboratories.
Common mistakes
- Reusing a flask with a scratched inner surface because it still looks usable.
- Putting non-vacuum glassware under vacuum.
- Carrying a bottle by its neck.
- Heating a large vessel quickly.
- Reaching a bare hand into a beaker or flask to clean it.
- Putting broken glass in the ordinary trash.
Single-piece cautions appear in the Erlenmeyer flask and volumetric flask guides.
FAQ
Is glassware safe to use if it has a small scratch?
UNL says to discard glassware that is scratched on inner surfaces, chipped, cracked or damaged in any way, because abrasion reduces the strength of glass.
What kind of glass is recommended for laboratory work?
UNL recommends borosilicate glassware for all laboratory glassware except special applications that use UV or other light sources.
Can I put ordinary glassware under vacuum?
No. Both UNL and Western University say to use only glassware designed for vacuum work for that purpose.
How should I clean up broken glass?
UNL names tongs, a dustpan and a broom as the best tools. Western University says not to pick up broken glass with bare or unprotected hands.
Can broken glass go in the ordinary trash?
UNL states that disposing of broken or intact glass as ordinary refuse is not acceptable; disposal depends on the glass’s previous use and condition. Check your own institution’s glass disposal procedure.
Which lubricant is used for ground-glass joints?
UNL lists silicone grease for high temperature and high vacuum, glycerin for long-term reflux or extraction, and hydrocarbon grease for general laboratory use.
Sources
- University of Nebraska-Lincoln Environmental Health and Safety, “Ground Glass and Glassware Safety” Safe Operating Procedure (revised 12/22): https://ehs.unl.edu/sites/unl.edu.business-and-finance.university-operations.ehs/files/media/file/s-groundglass.pdf. Date checked: 2026-10-29.
- Western University (Canada), Human Resources, “Working with Glassware”: https://www.uwo.ca/hr/safety/topics/glassware.html. Date checked: 2026-10-29.
