Coffee, I wrote, must never be served in a clear glass cup. It will taste richer and more robust when served in an opaque cup or mug (white is best). “It’s just simple physics.

It was a joke. I was kidding. (Sorry!) I know about as much about physics as I know about … well, the nearly infinite number of things I know almost nothing about (though I do think the coffee LOOKS darker/richer in an opaque mug, and hence I am tricked into thinking it is).

But I loved your responses.

Dennis Pierson: I can’t stand it anymore. I’ve got to know why the opacity of the container affects coffee. I believe you said in your column that it was a basic law of physics. Okay, so science was not my strong suit – but I can’t figure out what difference it would make. I know I run the risk of appearing really stupid if you were simply being facetious (of course, it would not be the first time … or even the second) but I guess I trust you more than I fear being naive (talk about the lamb being led to slaughter). Please answer this so I can have peace of mind while running. It’s practically all I’ve thought about on my recent jogs.

Marc A. Armstrong: Nonsense. Black coffee will taste hotter longer in whatever container is the better insulator, and glass is a better insulator than porcelain. It’s simple physics.

Darcy Horrocks: Eh? Pish and, indeed, tosh! As a gentleman, I must take issue with your bald assertion. Shape can affect taste (ask any sommelier or anyone who’s drunk from glasses blown to match the wine) but colour/transparency can only affect mood. American coffee tastes watery because it’s brewed that way: find an Italian deli and ask for a Ristretto(ree-STRAY-toh): same coffee, incredible flavour. Or worse, go to Italy. But be prepared never to be able to drink Starbucks again! (This email to be taken terribly terribly seriously indeed.)

Robert G. Doucette: Regarding your observation on the physics of coffee served in glass cups: HUH? It has been a few years since I spent my days as an active physicist, but I don’t recall how the optical properties of the coffee cup affects the taste of the coffee. Now, there may be some chemistry involved, certainly some psychology, but probably not physics. On the other hand, the material of the coffee cup could affect the thermodynamics of the coffee. Ceramics are better insulators than glass. The temperature of the coffee and the texture of the mug would be different than expected. So the total experience of the coffee may be different.

Bill Nagler: If coffee tastes watery in a glass mug because light passing through the mug pushes the coffee molecules apart, why does coffee taste better in a white mug than in a black one? Theoretically, a white mug will keep the coffee molecules farther apart than a black mug. Or is it that the coffee molecules are held too close together in a black mug? Or does the color of the mug significantly effect [sic] the epithelium of the lips and tongue?

Joe Robinson: The best coffee is served in Latin American countries. And it’s not the type of coffee, but the way it is prepared and served. When I was in Honduras on business last year, the waiter would come around with two stainless steel pitchers (no, not regular and decaf!). He would first ask “cafe?”, at which time he would fill your cup half way with a really strong, dark brew from one pitcher. Then he would ask “con leche?”, and if you said “si” he would fill the rest of your cup with hot milk from the other pitcher. Very few people drink the coffee black. In Panama, coffee is prepared and served in a similar fashion. I haven’t had a good cup of coffee since I’ve been back in the States!

Christina O’Sullivan: That paragraph on Strong Coffee was a “Eureka.” You know, the Sad Thing is that I live in Seattle, and with hundreds of espresso joints abound, you would THINK some of the better places in town would know better. The very very best place in Seattle does use white opaque mugs. The place I frequent has glass mugs, but I take my mochas to go by and large.

Charlie McDannald: Amen! I thought it was just me, but even Starbucks (who should know better) at most Barnes & Noble stores does this. Also, the coffee should be in a short, wide mug, rather than a tall drink glass.

Thanks, one and all.


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