Why Chemists Rinse Their Glassware Three Times (and Why You Should, Too)
In a past life, I was a laboratory assistant in a chemistry lab, where I used very little of the knowledge that I gained while studying chemistry in four years. I retired from the industry over a decade ago, but some habits have stuck with me, especially when it comes to glassware.
I love chemical glassware. I have an (admittedly terrible) Erlenmeyer flask tattoo on my lower back and tend to gravitate toward kitchen equipment that looks like it belongs in a lab. At school, I never objected to “washing up,” i.e., splashing around in an acid bath, cleaning glasses, round-bottomed glasses, and—yes—Erlenmeyers of all the organic and inorganic material stuck to their innards. After a cleansing dip in an acid bath and a neutralizing splash in an alkaline bath, I rinsed each piece of glass three times to remove the last residue from the baths.
The triple rinse was not a personal chicanery, but something that everyone did, and it was what I was advised to do when my classmate Trevor first showed me the process of washing dishes. “Each rinse removes 90% of residue,” he explained. “By the time you’ve done this three times, you’ve removed 99.9% of it.” It made an impression on me, and I still find myself rinsing things – especially dusty glasses – three times.
To confirm what Trevor told me 13 years ago, and to get a little nervous, I went to the Alconox website to see if they had similar advice. (Alconox makes industrial cleaners similar, if not the same, to the ones we used in my student lab.) I wasn’t disappointed:
Various college and university glassware cleaning procedures requiring three rinses (triple rinse). We also know of historical documents published by the early adopters of laboratory glassware detergents from laboratory glassware manufacturers that recommend a triple rinse… The logic behind triple rinse is that when you fill and empty a vessel three times with water each time, you dilute by 2 orders of magnitude. . Theoretically, you can leave 1% of what was in the vessel each time you empty it, so each rinse is diluted 1:100 with fresh rinse water. Triple rinsing results in a 6 orders of magnitude reduction in water soluble residues that might be present in a dirty wash solution.
Is it overkill for glassware in your kitchen? Yes. I doubt you’re working with any reagents or chemicals that pose a residue threat, but there are times when a triple rinse seems justified, say when rinsing a wine or beer glass. In fact, beer snobs take glassware cleanliness almost as seriously as chemists. “Beer cleanliness” is a whole concept: a dust-free, residue-free standard that is designed to ensure you get the best results from your beer. From craftbeer.com :
A clean beer glass does not contain any impurities: disinfectant residue, beer, dirt, food, detergents, grease, chapstick [sic], lipstick, lip balm, boogers, or anything else that could give escaping CO2 a place to cling to. . These areas of dirt act as nucleation centers, allowing bubbles to cling to and collect around the point. Any time you serve beer in an uncleaned glass, you (or your customers) will quickly see the hidden sediment that remains on the seemingly clean glass.
… The Brewers Association ‘s Beer Quality Manual (DBQM) describes that a clean beer glass is one that “forms a proper froth head, allows lacing during drinking, and never shows bubble stains adhering to the sides of the glass in liquid beer.” “.
Bubbles stuck to the inside of a beer glass are the most obvious sign that the glass is not clear of beer. I don’t care what causes these buds, but I don’t want to drink it, and neither do you.
To clean beer glasses (or wine if you are a wine lover) you need to wash them separately from other glassware, let them air dry so that there are no lint or fibers left in the glass, and give them a quick rinse before filling them with beer (or wine). How many times you wash is up to you, but I always choose three to remove as many potential nucleation sites as possible (or at least 99.9% of them).