The Physics of Glassware
Before Dragon*Con last week, Robin and I spent an evening with our old friends Bill and Jenn. What evening between friends would be complete without the consumption of adult beverages? In particular, Jenn’s deadly and delicious blueberry martinis?
Being the nerdy physicist that I’ve always been, I took my martini glass in hand and thought. Why are these particular glasses this odd shape?
The Wikipedia page on glassware gives a good overview of the different types of glasses. Until I started appreciating alcoholic beverages (over the age of 21, of course), I never realized exactly how many different types of glassware there are. It seems that just about every class of beverages has its own associated glass container. Even beer drinkers are particular about what they drink out of a pint glass, pilsner glass, bottle, or (sigh) can.
To put it terribly analytically, a glass is a potential well. When you pour a liquid into a glass and it comes to rest, the molecules don’t have enough total energy to make it out of the bowl of the glass. They stay there until they get enough energy to leave, or the walls around them disappear. This happens by one of three mechanisms.
First, you could make a pressure differential between the ambient air pressure and a region of the surface of the liquid. Because of the lower air pressure below your lips, atmospheric pressure pushing down on the rest of the liquid’s surface causes the liquid to ascend upwards in the region with lower pressure. Complex? Not really — you probably do this either by slurping or by using a straw.
Second, the random motion of a single molecule’s neighbors could happen to give the molecule enough energy to break through the intermolecular forces holding the molecule in the liquid. You can’t really plan this; it’s called “evaporation” and it just happens. Since you can’t actually productively imbibe any of the evaporated liquid anyway, this doesn’t really count.
Finally, and probably most frequently, you tip the glass (intentionally, sipping; unintentionally, spilling) to produce a spot in the near the liquid’s surface where the wall containing the liquid effectively disappears. Now that the liquid can be free, it is. Molecules nearest the gap in the wall fall out of the glass, hopefully into a waiting mouth below. Voilà, you’ve now tasted blueberry martini.
(Quantum wine in a potential well might leak out of the sides of the glass due to the process called quantum tunneling. Classical wine has no such problem. More on that some other time.)
So that’s why glassware works in the first place. But why do different glasses look so different when their purpose is the same?
Their purpose is not the same.
Some beverages are designed to stay at a constant temperature for as long as possible. Martinis and wines are a great example. Once the beverage leaves the temperature-controlled environment in which it’s stored or made (a cocktail shaker for the martini, a sommelier’s cellar or refrigerator for wine), normal heat transfer sets in. This means that the beverage will slowly start to creep towards the ambient temperature of the room. Or worse, the temperature of the hand holding the glass. The proper hand position to hold a wine glass is actually something like this:
CC-licensed photo from deepwarren on Flickr; original here
Holding a wine glass with the hand wrapped around the bowl will transmit a great deal of heat into the wine, changing its flavor (for the worse).
The purpose of a brandy snifter, on the other hand, is designed to transmit as much heat from the hand as possible to the liquor inside. Notice that the hand completely cups the bottom of the bowl, heating the brandy and allowing the vapors of the beverage to be released.
Credit: Wikimedia foundation
Certainly there’s a great deal of history that has gone into the shapes of glassware. The history of glassblowing itself is much to blame — it’s tough to make functional, resilient pieces of glass.
At least you don’t have to understand why glasses are designed the way they are to appreciate a tasty adult beverage. Drink up!
Tags: alcohol, glassware, martinis, physics, snifter, wine, wineglass
About Me, Physics Is Phun, Uncategorized | Jim | 
September 6, 2008 10:39 pm
12 Comments
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Wine Glassware Physics Lesson anyone? | The Wine Glassware and Wine Decanters Blog — September 10, 2008 @ 4:12 am
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By Annie, September 6, 2008 @ 11:46 pm
Or, in the case of champagne, a change in the fashion of the glass to reflect a desire to keep the bubbles in the glass longer.
The champagne flute v. the saucer. My parents actually had champagne saucers as their toasting glasses for their wedding.
By Pat R., September 7, 2008 @ 2:04 am
Firstly, I have a question. Your second of the three reasons stopped me, because I saw the word “can’t.” That’s just who I am; I hear someone say it can’t be done and I think, “ORLY????” So what if someone were to evaporate an alcoholic beverage and breathe in all the resulting vapor? Would that person still need to call a cab?
And secondly, I don’t know why people are so picky about what they drink out of. Obviously, I can’t speak from experience, but other than the whole heating wine vs heating brandy, I don’t see the big deal. Again, that’s just me; I don’t care what other people think about me. Now if you’ll excuse me, I need to refill my sippy cup with Jack and Coke.
Just kidding, I don’t actually drink. And I certainly don’t have a purple sippy cup with Barney stickers on it that I take with me everywhere. <__>
By Pat R., September 7, 2008 @ 2:05 am
Oops. That did not yield the desired emoticons. I’ll try again.
<__>
By Pat R., September 7, 2008 @ 2:06 am
What is going on???? I’ll try again the opposite way, but then I give up; triple posting is enough for one night.
>_>
<_<
By Annie, September 7, 2008 @ 10:24 am
@Pat R.
There is the AWOL: Alcohol With Out Liquid method of inhaling alcohol. But it isn’t exactly the same as inhaling the direct evaporated alcohol.
By Pat R., September 7, 2008 @ 7:59 pm
Whoa, banned by half the country. Sounds dangerous.
Why didn’t it let me post my shifty eyes emoticons correctly?
By Jim, September 7, 2008 @ 11:17 pm
@Pat R.
Inhaling alcohol is dangerous; mostly because the inhaler doesn’t know how much (s)he is consuming.
Drinking alcohol takes time. This time hopefully lets the brain “veto” your continued actions. Generally, you’re smart enough to know when to stop.
I’m not enough of a wine snob to taste that a wine has been sitting for three seconds at half a kelvin higher than its ideal temperature, but some people are. We call them “crazy”.
By Pat R., September 8, 2008 @ 3:02 am
Yeah, I don’t think I’ll be huffing vapor-hol if I can help it. Then again, it’ll be another four years until I can touch the real stuff, unless this whole college-deans-trying-to-lower-the-drinking-age thing works.
If I ever meet anyone who’s that anal about their wine’s temperature, I think I’d walk right up to them and exhale right on their glass, much like one does when they’re trying to fog up a cold window, and just see how’d they react. Maybe tape their reaction, put it on YouTube.
By Jim, September 8, 2008 @ 7:17 am
@Pat R.: Ooh, wine exhaling. That’ll start a rumble in the wine bar. Some of these wines are so expensive, all things considered, that I too would probably try to maximize the flavor I got out of a single glass. Especially if I was paying a few hundred dollars for the privilege of drinking six fluid ounces of some special grape juice.
Wait… you posted this at 3:00am. Go to bed! You have school tomorrow!
By Pat R., September 9, 2008 @ 3:28 am
I had an English paper to write, and I posted after I finished.
What the…?? It’s three in the morning again? I was eating some Cheese Lover’s Pizza at like 7:30 last I checked. That’s weird.
Besides, I’m a senior. Most of us have already learned how to operate with little to no sleep. Although I wouldn’t go more than ten days without, because House told me that no one’s survived past eleven days. And House knows what he’s talking about; like Neil Patrick Harris, he plays a doctor for pretend.
By Pat R., September 9, 2008 @ 3:31 am
Again, wish I could hyperlink; I’d post the YouTube link for the Old Spice commercial. Is that something that only you are allowed to do, or am I just not doing it right?