Cleaning laboratory glassware is important because contaminated or dirty glassware can lead to inaccurate results in the lab.
A good way to confirm that your glassware is clean is to make sure that distilled water uniformly wets the surface, according to Corning. This tells you that the surface is free of grease and other contaminants that could alter the volume being measured or introduce impurities into the liquid.
What Is the Proper Procedure for Cleaning Laboratory Glassware?
One basic procedure is to start with the gentlest methods, scraping off any solids and then using brushes and normal soaps and detergents. If this doesn't get the job done, move on to longer soaks and harsher cleaners. Finally, when the glassware is fully clean, rinse it thoroughly and allow it to dry.
Here are some ideas and pointers that will help with each stage of this process:
Clean It as Soon as You Can
Wash glassware in hot water or a glassware washer as soon as you're finished using it to avoid the formation of hard-to-remove residue. Corning recommends soaking glassware in water if it's impossible to wash it immediately after use.
Use the Right Brush
Scrub all parts of the glassware thoroughly with laboratory glassware cleaning brushes. Make sure you have a variety of brush sizes on hand suitable for cleaning laboratory glassware of all kinds, including test tubes, funnels, flasks and bottles. Corning suggests choosing a brush with a wooden or plastic handle instead of a metal handle, to help protect glassware from accidental scratches or abrasions. An overly worn brush can also cause accidental scratches if its bristles no longer prevent the spine of the brush from hitting the glass.
Don’t Forget the Cleaner
When washing laboratory glassware, many soaps, detergents and cleaning powders can be used. According to Corning, cleaning agents with mild abrasive action will give better results on very dirty glassware, as long as the abrasive doesn't scratch the glass.
Try Giving it a Soak
If basic cleaners don't get the job done, or if there's material in places where brushes can't reach, a next step is to try a long soak in a gentle solvent, according to the University of Wisconsin Office of Chemical Safety. The efficacy can be enhanced with heat soaking or mild agitation.
If All Else Fails, Get Aggressive
Occasionally, more aggressive cleaning solutions may be necessary when laboratory glassware is extremely dirty. These solutions are often highly corrosive, involving concentrated acids or bases, and can cause injury. Consult the "Other Cleaning Methods" section of Corning's "Suggestions for Cleaning Glassware" for more information on the appropriate solutions, techniques and protective equipment.
Sterilize Before Cleaning When Necessary
Some glassware should be sterilized before cleaning, according to life sciences manufacturer MilliporeSigma. This includes glassware contaminated with blood clots and glassware on which viruses or spore-bearing bacteria are present. Glassware can be sterilized in autoclaves, steam ovens or by boiling for 30 minutes with in water with 1% to 2% soft soap or detergent.
Rinse All Glassware
Detergent or cleaning fluid residue can contaminate your work the next time you use the glassware. Corning recommends this procedure for rinsing:
- First, rinse glassware very thoroughly with running tap water, filling, shaking and emptying it at least six times. Run very hard water through a deionizer or reverse osmosis system before using.
- Then, rinse all glassware in a large bath of distilled or high purity water.
- Finally, rinse each piece individually in high purity water.
Dry It, Too
Laboratory glassware can be air dried. Corning recommends hanging glassware from wooden pegs or placing in baskets facing downward, with a clean cloth at the bottom to keep the mouths of the vessels clean. Glassware can also be oven dried at temperatures lower than 140° C, though glassware used for volumetric measurements should be dried at temperatures of no more than 80° C to 90° C.