Importance of espresso cup shape

[reeeneeee]

Since it's not clear that the thickness of cups perceptibly affects heat retention, I've been wondering what other variables might distinguish one cup from another. I think that one might be cup shape:

(annoying precalc ahead; you can skip to the bottom if you want)

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The surface of a shot of espresso is always some cross-section of the demitasse it's in. So it's logical that the shape of this cross-section at the brim of the cup would determine how the espresso falls and is introduced to one's palate.

Most cups are roughly paraboloids, like these:



Their cross-sections are ellipses with major axes touching the brim, so the espresso always falls in a pretty thin stream.

But now take these very overblown ACF tulips that flare at the top:



If you're drinking a double, any cross-section of this cup is going to hit short of the brim, at or before the inflection point (the place where it changes from convex-->concave). And after that, the espresso just flows down the flared part in a pretty wide, flattened stream.

I guess you could model this with paraboloids and other rotated 3d shapes, but I am mathematica-stupid and it probably isn't necessary anyway.

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in short
1) cups that flare out at the top introduce espresso in a wide, flattened stream
2) normal, paraboloid-ish cups introduce espresso in a thinner stream

(i did some highly unscientific experiments with my own cups which seem to corroborate this)

Since it seems like a wider, flattened stream would better open up the flavors of espresso, perhaps we should all be investing in some flared-out tulips? Thoughts?

[Abe Carmeli]

Cup shape and its affect on our taste buds come up a lot on wine forums. In fact, there is a wine glass manufacturer whose claim to fame is the very same premise.

I have cups of all shapes, but a particularly interesting one is Danesi. It looks like a ball with its top cut. That shape creates an even narrower stream of liquid than the regular shape, such as Illy's collection cups. The flip side of a narrow stream is that it is thicker (taller). I suspect that the thickness of the stream enhances the sensation of "body" in the cup. I will run some tests on it, and this is very subjective, but I intuitively use this cup more than any other cup for that very reason.

[HB]

It's curious this topic should come up, as I've thought about it from time-to-time after Intelligentsia announced their new choice of barware:



I think this replaced a more 'parabolic' shaped cup. It seems like a rather impractical choice for a busy cafe. The sides are thinner and more likely to break. Because of its narrow base and height, it also seems more likely to tip over. So I assume they had reasons beyond aesthetics for choosing it. Maybe Matt Riddle has some insight that would apply to this thread?

Another shape that got my attention was similar to these Lavazza cups:



(Image courtesy of Chris' Coffee Service)

One of the few cafes in Paris that served a killer ristretto used a smaller version of this cup. The interior bottom of the cup was smaller than a dime and it flared to about the size of a half-dollar coin. This shape seemed to enhance the presentation of the crema by leaving so little room for liquid at the base, just the opposite of the one Abe posted. Even so, my favorites are still the heavy Nuova Point.

PS: Abe, what a beautiful view!

[ThaRiddla]

It's curious this topic should come up, as I've thought about it from time-to-time after Intelligentsia announced their new choice of barware:

We actually chose this coffee for a few reasons:

cup shape - This cup shape is called a "tulip" shaped cup. We initially chose this shape of cup for those of us at the company that were competing. In the demitasse size we found that it held crema longer and in better quality than the other traditional round-bottomed cup. There was less area on the top exposed to the air, and the shape allows for great retention. We ended up liking the cups so much that we went with the same company and style for the Black Cat cups. In the cappa size, they are also great for pouring latte art in. The shape gives you a little bit more time to get your design out than the previous style, and again, the tulip shape holds the design better.

heat retention - Whether it was the quality of the ceramic or the thickness of the walls of the cup (which are thicker than the previous style) they retained heat better and more consistently than the previous style. I'm still on the fence about which retains heat better (if either) the thin walled cups or the thick....but I will say this: the thicker wall on the bottom provides more material to retain the heat, so these cups stay hotter for longer than the previous style.

printing - this company sent us a plethora - I mean TONS of samples to see their quality of work. We were impressed with just about every design. They've been doing this for a long time, and they're great at it.

size - This was a bonus for us. The demitasse is actually only 2 fl oz to the tippy tippy top, so when we pull our shots to our standard of 1.75 fl oz it comes just to the top of the handle. It's impossible to pull a shot over 2 oz into this cup. The cappuccino is 5 oz. so it's more concentrated and the espresso taste is more intense. Great for competition.

There were a couple of other factors, but they were menial compared to the pluses listed above.

[Abe Carmeli]

PS: Abe, what a beautiful view!

Come to visit when you're in NY, it is worth a special trip as I was told . It is Central Park as seen from my terrace. The lake in the middle is the park reservoir.

[fredfal]

I have cups of all shapes, but a particularly interesting one is Danesi.

Abe,

I know this is a really old thread, but do you happen to remember where you got the Danesi cups? Very cool.

Thanks,

[Abe Carmeli]

Abe,

I know this is a really old thread, but do you happen to remember where you got the Danesi cups? Very cool.

Thanks,

I got it in Rome. But you can get it online here:

http://www.zoxx.com/cart.php?target=category&category_id=133

[fredfal]

Thanks Abe.

No Rome plans, so the link helps a bunch.

[cpl593h]

Thanks Abe.

No Rome plans, so the link helps a bunch.

They can also be found on eBay, searching for "Danesi espresso cup"

[espressme]

Since the thread is re-opened, I wonder if a part of the heat retention of a cup is that a smaller base / thinner bottom ring has less conductive path for heat to leave the cup into the saucer or counter especially when damp?
Best regards to all!
richard

[fredfal]

Since the thread is re-opened, I wonder if a part of the heat retention of a cup is that a smaller base / thinner bottom ring has less conductive path for heat to leave the cup into the saucer or counter especially when damp?
Best regards to all!
richard

Okay, so I'm a geek (coffee and otherwise). I did a little calculating and here's what I've come up with:

I used this formula for conduction:

heat transfer (Deg C/min) =[kA(T hot - T cold)]/d


"k" is the thermal conductivity of the material.
"A" is the area
"T hot" is the hotter temperature (the cup - I used 85C)
"T cold" is the cooler one (the saucer - I used 25C)
"d" is the distance, but it's a constant, so it doesn't affect the outcome - I used one centimeter

I googled the thermal conductivity of porcelain and it's 0.002 or so. It's such a small number that the temperature loss from the cup to the saucer is pretty negligible (0.1 to 0.2 degrees per minute).

You're correct about the water, though. The thermal conductivity of water is 0.6.

If the saucer or the cup is wet, it will transfer heat much faster (70 degrees per minute). Of course, that's if you were to rest a hot cup on the surface of a large tub of room temperature water.

A SMALL amount of moisture will accelerate the heat transfer from the cup to the saucer, simply by increasing the surface area that the heat can be transferred, but since the amount of water is so small, the water will quickly heat up to the temperature of the cup, but will then slowly transfer this heat to the saucer.

Effectively, by having a wet cup and/or saucer, you're not significantly changing the thermal conductivity of the materials, just increasing the surface area for the heat to transfer. That 0.1 to 0.2 degrees per minute will increase to MAYBE 1.0 degrees per minute at the most. And that's if the water is room temp. If the water is hot, it will be much less than 1.0.

So, no, I don't think the footprint of the cup matters much, especially since we geeks usually empty the demitasse within 30 seconds anyway and hardly have a chance to set it down.

Sorry for the long post. Hope this answers your question.

edit: while I had excel open, I also figured that the heat loss between the surface of the espresso to the surrounding air is on the order of about 4 degrees C per minute.

Better GULP it down before it cools off!

[espressme]

snip...
Sorry for the long post. Hope this answers your question.
edit: while I had excel open, I also figured that the heat loss between the surface of the espresso to the surrounding air is on the order of about 4 degrees C per minute.
Better GULP it down before it cools off!

Hello,
I prefer a long post. It covers enough territory to qualify the information and remove hazy concepts. Also it allows re-reading to examine the basis of a concept.

I agree with the down the hatch espresso action( allowing for mouth feel). "Cleo's" shots seldom lose temp. and I have the coolest red brown mustache.
Thanks! I learn something every day!
Richard