Monday, January 01, 2007

   from AndyS

Take the dogma out for a walk

Somebody please slap me in the face.

The "third wave" espresso world seems so strange: "temperature stability" has become religious dogma.

And common sense no longer accounts for much.

If you're wondering what the heck I'm talking about, I'll try and explain.

A decade or more ago David Schomer popularized a theory that described how an espresso machine should work. If you made a graph of the brew water temperature that the machine delivered, it was supposed to be "ruler flat" for the duration of a shot.

For David's blend, that meant the water temperature should rise as rapidly as possible to 203.5F, and remain there until the shot was finished. Other blends might have different optimum temperatures, or even several optimum temperatures, each expressing different qualities of flavor and texture. But it was a basic tenet in David's theory that the flat temp profile was necessary for the finest espresso.

Was this theory ever fairly tested? How did it become generally accepted? And how is it that the only machines acceptable for Barista Championships must perform this way?

In my opinion, the flat temperature theory, like the flat earth theory from centuries ago, doesn't bear close inspection. Here's why:

Coffee in the portafilter starts out slightly warmer than room temperature (it picks up a little heat in the grinding process). Even if you force water through it that is absolutely stable in temperature, the coffee in the middle and bottom of the puck gradually rises in temperature as the shot proceeds. It gets close to the temperature of the brew water, but never reaches it.

In other words, ESPRESSO IS NEVER EXTRACTED AT A STABLE TEMPERATURE, no matter what the brew water temperature does.

That's why insisting on ruler flat brew water temperature seems like a very peculiar requirement to make the finest espresso.

According to Michael Teahan, the Italians recognize this fact. Many Italian machine tuners prefer to start their brew water temperature very hot, gradually reducing it over the course of the extraction. This has the effect of getting the extraction environment in the basket up to temperature faster. But it still doesn't change the fact that, given the existing technology, IT IS IMPOSSIBLE TO EXTRACT ESPRESSO AT A STABLE TEMPERATURE.

But of course we all know that the Italians are backward buffoons, while we are cutting edge third wave baristas. Right? [please note, I'm being sarcastic here]

To be fair to David and his disciples, his theory has never been fairly tested because no one has an espresso machine that can accurately reproduce different brew temperature profiles. If an espresso machine could produce flat temperature profiles, rising temperature profiles, and falling temperature profiles at will, we'd be able to run some valuable experiments. Until then, we're stuck with comparing the espresso that comes from Synesso/GB5 machines (with their fairly flat profiles) to the espresso from heat exchanger machines (with their mostly falling profiles). But there are so many other variables (group and dispersion screen design, preinfusion scenarios, pressure variation, etc) that definitive conclusions are very difficult to come by.

In the absence of a technical breakthrough, many espresso machine designers have settled for a much less demanding requirement: they try and design their machines to reproduce the same temp profile with every shot. So whether you pull your shots one right after the other or a half hour apart, engineers nowadays take pains to make the machine deliver the same temperature profile each time. But this is a far cry from being able to tweak the temperature profile itself.

Hopefully more advanced machines will be introduced that will soon allow accurate temperature profile testing. Then will we replace conjecture and orthodoxy with actual experience. Until then, perhaps we should let the dogma out for a walk.

34 Comments:

Anonymous James Hoffmann said...

I think is a great post (impressive way to kick off 2007!), though I am sure the mention of the WBC testing still smarts for a few companies. ;)

I guess you got it right when you said we seem to chase repeatability as much as the flat line, so that (be it right or wrong) the profiles we do get can deliver a consistently high standard of espresso to the consumer. That isn't to say it could be better...

1/01/2007 07:08:00 PM  
Anonymous t o n x said...

Andy -

putting aside the fact that you're setting up a strawman by claiming this as dogma, do you really think it never occured to Schomer that the brew water loses heat energy to the coffee??

I'm not sure its helpful to stage this as a dichotomy of purported Italian conventional wisdom versus perceived 3rd wave conventional wisdom. There is still an awful lot we don't understand about what is happening inside the puck and many of the commonly held assumptions break down on closer inspection (as I think all of us here who wrestle with this stuff eventually figure out).

Even if someone did have a perfect understanding of what is happening during extraction I think they'd spend years figuring out how to clearly articulate it. The truth of it goes way deeper and funkier than mere engineering and ultimately we find something that "works" and dress it up with whatever explanation seems least flimsy. We're still not very far past the patent medicine stage at this point.

Some of these online dialogues and soapboxing tend to bring out dogmatic responses or overly argued pet theories. But when talking face-to-face I always find our colleagues pretty willing to get to new answers rather than defending old ones.

I've heard a number of people talk about profiling brew temperature... when someone builds that machine I'll be knocking on their door to play with it. But are you suggesting that temperature stable machines are just a fad? A cult-of-Schomer wrong turn that some machiavellian machine companies have blindly seized upon? ;)

- t

(p.s. - glad to see you manning the fort here!)

1/01/2007 09:50:00 PM  
Anonymous Anonymous said...

I always thought PID's were a big waste of money. Most of the time I think people just like saying 'PID' to sound third-wavey.
Thanks Andy.

1/01/2007 11:12:00 PM  
Anonymous Anonymous said...

On the other hand, one could always look at an 'unyielding' temperature to be a quirk in itself.
Why does the burden have to be on the barista and their machinery? We can always look at the angle of customizing the roast to fit the machine... Can roaster technology increase to create specific roasts for specific brewing temperatures, or for specific machinery--every time? And then there's the oft and recently mentioned grinder technology. As soon as we 'master' one area of coffee science, we soon realize how many other areas we've neglectled to learn.

1/02/2007 03:38:00 AM  
Blogger wheretherearewolves said...

Guys I love the passion, and the obsession! With all due respect to Schomer I was visiting his cafe weekly as a teenager over 15 years ago, I feel many of the law's that have been established through his gospel are bordering elitist and not always correct in the practical world. The other day I wanted an afternoon single espresso, short simple delicious, but many of the Schomer practicioners will never ever pull a single, only a double. The idiotic, bigger is better mentality, is really starting to be annoying. In Italy a study was done on the effects of caffeine and a double shot produced from a 19 gram pull from a Synesso is just not good for your health, go ahead and think you're hardcore and flex your muscles, but the fact is Schomer has created a technique and flavor profile that is good but not healthy for the average bear.
THERE ARE INFINITE AMOUNTS OF MAKING AND DRINKING COFFEE THAT ARE JUST AS GOOD.
COMMONSENSE AND EXPERIENCE WILL RULE IN 2007!

RETURN TO AUTHENTICITY.

1/02/2007 03:36:00 PM  
Blogger AndyS said...

@James:
I certainly agree that the flat profiles can deliver a consistently high standard of espresso. But the point of the post was, as you say, that perhaps the espresso could be even better...

@tony:
>do you really think it never occured to Schomer that the brew water loses heat energy to the coffee??
David is of course a very bright guy. But at least from what he's written, you'd conclude that it didn't occur to him. I talked with David briefly at the Seattle SCAA show. He said that as far as temperature was concerned, he considered the problem SOLVED. I'm saying, are you sure?
>when talking face-to-face I always find our colleagues pretty willing to get to new answers rather than defending old ones.
Agreed, but this blogger medium isn't face to face. Sometimes you have to use hyperbole to get the discussion moving, no?
>But are you suggesting that temperature stable machines are just a fad?
If "temperature stable machines" means reproducible flat line profiles, then maybe it is a fad, I don't know yet. If "temperature stable machines" includes reproducible profiles of any reasonable shape you want, then it certainly isn't a fad.
Sorry that my original post wasn't clear: I think reproducible temperatures are very important. But I think the flat line profile was annointed as god-like for reasons of convenience, not because it's superior.

@anonymous:
>Most of the time I think people just like saying 'PID' to sound third-wavey.
Hahaha, I'm a pretty cynical guy, but I've never thought THAT!
BTW, what's your real name?

1/02/2007 04:21:00 PM  
Blogger Java Doc said...

Andy, I think you have just about everything right. I hope that doesn't come as too much of a shock.

Flat line profiles came out of the dogma of twin boiler machines of the early 90's when there were marketing pitches about how seperating the boilers and eliminating steam pressure fluctuations from steaming milk would lead to more stable brew temperatures. No thought was given to whether this actually occured or had a realistic impact on quality.

It was part of the "Starbucks must know more than we do mentality" that was pervasive at the time, though no one will EVER admit to believing it.

I have spent time in the Starbucks test facility in around 1993. My grandmother knew more about machines than they did and she wasn't even Italian.

The ability to repeat a profile, whichever you choose, is really most important. Flat lining the feed temperature (not the extraction temperature, as you have clearly reasoned) is easy. WBC testing was not about which machine made the best coffee; it was a matter of which machine performed to the indicated specifications.

I am still hearing different stories about whether ort not the GB5 was, in fact, superior to the Aurelia or the 'not so stock' Brasilia.

Challenging assumptions is what I have been trying to do from the very beginning, and your article very nicely proposes the same charge.

When you are ready to build the machine that will allow you to control everything, let me know.

I'll send over the drawings.

Michael Teahan

1/02/2007 07:23:00 PM  
Blogger AndyS said...

> When you are ready to build the machine that will allow you to control everything, let me know.
> I'll send over the drawings.

Send 'em over!!!!

1/02/2007 07:41:00 PM  
Blogger Tony said...

"But of course we all know that the Italians are backward buffoons, while we are cutting edge third wave baristas. Right?"

I certainly hope, that you mean this as sarcasm.

1/03/2007 11:28:00 AM  
Blogger AndyS said...

Tony, yeah, it was meant sarcastically. I edited the blog to note that.

1/03/2007 02:16:00 PM  
Anonymous Robert said...

>I edited the blog to note that.

Which to me seems totally unnecessary. If people can't read the sarcasm in your statement then they are... buffoons.

Great article!

>THERE ARE INFINITE AMOUNTS OF MAKING AND DRINKING COFFEE THAT ARE JUST AS GOOD.
COMMONSENSE AND EXPERIENCE WILL RULE IN 2007! RETURN TO AUTHENTICITY.

I agree. Sometimes I drink my wine from the bottle.

1/03/2007 06:07:00 PM  
Blogger default said...

i ever measured the temp schomer style on a prosumer hx machine, but my probe is IN the puck, the temperature of the shot couldn't go more than 75-80c. when one considers the percolation theory inside the puck, then there are few other issues, like the density of the third bottom of the puck, the speed of the water entering the puck (orifice), etc.

i might be wrong, but most of the italian espresso machine manufacturer are machine assemblers. when i look at a the drawing of the aurelia, i don't know what would make this machine so temperature stable. it's just a normal hx machine. the most temp stable hx machine i've seen is kees' mirage because he has a theory that different from normal hx.

i agree with you that repeatability is so much more important.

1/03/2007 06:58:00 PM  
Blogger AndyS said...

> If people can't read the sarcasm in your statement then they are... buffoons.

It would pain me to think that someone who was not a native English speaker might be offended.

1/03/2007 07:28:00 PM  
Blogger mikep said...

"When you are ready to build the machine that will allow you to control everything, let me know.

I'll send over the drawings."

What?! That machine wasn't built already (like maybe 30 years ago and currently residing in the Raiders of the Lost Ark wharehouse)?
;)

1/04/2007 10:35:00 AM  
Anonymous Mr. Fish said...

Of course we should question everything, however there is no doubt in my mind that among the professional machines on the market right now, the GB/5 produces far superior in the only department that matters; TASTE. And of course consistency matters! Don't you want your espresso shot to be as good as the guy in front of you just got?

1/04/2007 01:15:00 PM  
Blogger AndyS said...

"there is no doubt in my mind that among the professional machines on the market right now, the GB/5 produces far superior in the only department that matters; TASTE."

I am happy for you that there is no doubt in your mind. But this article wasn't necessarily about "machines on the market right now," it was more about where the future of machines might lead.

1/04/2007 04:37:00 PM  
Anonymous Soren said...

In addition to questioning the temperature curve, I wonder about the actual correct temperature. Why do we always assume that all coffee wants to be hit with the same temperature water? I am not sure that a dark French roast, that ended its roast at 470 degree, needs to be shot at the same temperature of a city roast, that only made it up to 415 degrees. It seems logical to me that the darker roast would benefit from lower water temperature due to their softer, and more chemically transformed state, than their medium roasted cousins.

1/05/2007 10:51:00 AM  
Blogger AndyS said...

"Why do we always assume that all coffee wants to be hit with the same temperature water?"

Ummm...we don't. Recommended temperatures range from 207F for Malabar Gold down to the low 190's for many Italian blends.

1/05/2007 04:47:00 PM  
Blogger Terry Z said...

Yeah! Bravo........

Terry "w1r3d1" Z

1/06/2007 09:37:00 AM  
Anonymous Soren said...

Thanx, I never got it until I asked. You can see how this can happen; even in your example, you talked about the bean, not the roast. Your specific example points out particular variables: acidity, high vs low quality robusta, bean, the drying process, and roasting style. How do these factors affect proper temperature, and in which direction do they adjust temperature?

1/07/2007 01:15:00 PM  
Anonymous barry said...

well said, andy. as you know, i've always felt goal of getting a flat-line brew temp was more an issue of controlability and repeatability than flat-line for flat-line sake. fun fun fun... lots of stuff to play with!

--Barry

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