barry wrote:At least as far as drip coffee goes, you could talk to Carl Staub, since he used to play with these ideas a few years ago. He'd take a batch of underextracted coffee and mix it with a batch of overextracted coffee to come up with "correct" coffee that tasted bad.

As for espresso, I think you could taste the results in a mildly channeled shot, where part is overextracted and part underextracted.

So the refractometer would not compensate for drip extraction in which water poured copiously through the center of the coffee, but failed to extract around the edges, kind of like if one pours through a cone without stirring?

I'd say that the same would be true of gravimetrically determined extraction ratios as well. The shortcoming of all of the techniques we're discussing is that the results that they provide are based on the assumption that the extraction is uniform throughout the sample. We can make good arguments that this is not true. But that doesn't mean they are not useful techniques in the hands of a competent person who makes an effort to keep extraction flaws under control.

-Greg

barry wrote:I don't think talking about uneven extraction and its impact on a measurement system really qualifies as "weird theoretical situations". The question that I think Nick is getting to is "how does the system hold up in the real world?" instead of how it has performed under controlled testing. If Barista Jane pulls a 25-second 30ml shot which has suffered transient channeling, how will that compare in measurement to a 25-second 30ml shot which doesn't channel, recognizing that there will probably be subtle changes in dose, tamp, and/or grind between shots?

Do we have to assume competence here? I think it's a case of not throwing out the baby wid da bathwarder. Get what you can out of the technique and recognize that there are pitfalls in blind reliance on numbers. Use some good judgement.

In know, that's asking a lot, but that's the way the measurement world works.

Now my question is how good is the precision in the answer returned by the refractometer over a bunch of measurements, how good is the precision of a bunch of refractometers, and how stable are they over time. Gravimetric measurements are really cool because they are very fundamental (by mass, so first-principles). But they are time-consuming and not practical for quality control systems.

-Greg

Exactly my point! Thanks, brother Barry!

gscace wrote:The shortcoming of all of the techniques we're discussing is that the results that they provide are based on the assumption that the extraction is uniform throughout the sample. We can make good arguments that this is not true. But that doesn't mean they are not useful techniques in the hands of a competent person who makes an effort to keep extraction flaws under control.

I'm not disputing the usefulness of these techniques as an analytical tool, I'm reiterating Nick's question about "how does it taste" in relation to the analysis (which I don't find to be an unreasonable question at all), and pondering the utility of the tool in "real world" conditions. As I mentioned to you as we passed the booth in Atlanta, "those who can understand the information probably don't need the specialized software, while those who need it probably don't understand it enough to use it properly."

Conductivity meters, hydrometers, and refractometers are all useful tools in the analysis of coffee, but one must investigate and recognize where the limits of utility might be. You know that I'm not against gizmos and tools and the such, but I caution against developing a blind allegiance to "the numbers", where the attitude of "it must be good because the meter says it is" replaces "damn, this tastes great!"

Well I think that the correlation of "how does it taste" to the measurement is the whole crux of the deal. If they ain't related, then what's the point?

-Greg

In a sound system, 'perfect alignment' according to the sound software may occasionally differ from 'what sound good'. Seeing as we're gonna want to listen to the show as opposed to watch how it lines up perfectly on the laptop, I go with the latter.
The human brain is so danged complicated and sensitive that the numbers will get you to the neighborhood, but the flavor will guide you to the right place.
The same thing (sort of) applies to Sweetmaria's crema guide, and 'puckology'. All of these things may tell you something about the cup, but all of them may or may not be telling the whole story.
"It depends", is a phrase that comes up a lot when I'm training someone new...

I don't think anyone is seriously suggesting replacing taste with blind allegiance to numbers. That said I wish people had perhaps looked a little bit more at the numbers to explain why many cups of coffee brewed in an updosed fashion on various brewers started well, but cooled and ended up more than a little disappointing.

What interests and excites me about measurement and the data you could get is the potential for insight into the process, and better understanding where changes in the coffee that come with an altered variable actually come from.

I might be very happy with how my espresso tastes, but closer analysis may suggest possibilities that may improve it further that I might not have been nudged and guided towards without cold, emotionless data suggesting so.

There are so many interesting experiments in all this that could produce data that could help us all better understand how to diagnose bad shots better and to achieve frustratingly elusive espresso.

barry wrote:"those who can understand the information probably don't need the specialized software, while those who need it probably don't understand it enough to use it properly."

To me, espresso is such a mystery. Each coffee is so different, each roast is so different, each day removed from the roast day brings changes, every change in dose reveals or conceals a coffee nuance.... Do you really mean to say that you understand all this so completely, and that you have no interest in a tool that might shed just a little more insight into the extraction process?

barry wrote:I caution against developing a blind allegiance to "the numbers", where the attitude of "it must be good because the meter says it is"

It's NOT ABOUT blind allegiance to any particular number. It's about being tired of NOT KNOWING WHY changing this variable or that one makes the espresso so different.

A few posts back you and Nick seemed interested in seeing what this system could do. Yet now you guys seem only interested in coming up with ways to "fool" it or reasons why it won't work. Weird.

AndyS wrote:A few posts back you and Nick seemed interested in seeing what this system could do. Yet now you guys seem only interested in coming up with ways to "fool" it or reasons why it won't work. Weird.

Well, no, Andy. We put forward a known, real-life extraction problem and wondered how it was handled and how well it was handled. Not weird at all. Curious.

King Seven wrote:I don't think anyone is seriously suggesting replacing taste with blind allegiance to numbers.

I know, but I also know what happened with the LM Chronos machines, and what I've personally seen happen with PID machines.

What interests and excites me about measurement and the data you could get is the potential for insight into the process, and better understanding where changes in the coffee that come with an altered variable actually come from.

Agreed wholeheartedly. I've spent a fair amount of time down that rabbit hole.

I think we all need to step back and check how measuring solubles lead and concentrations would work in the real world. I see two possibilities:

1. Quality Control
a. Get the right dose, grind, shot temperature, pressure and volume for your espresso. By "right" I mean the one that you think tastes best.
b. Find the extraction numbers for this.
c. Make sure the shots you are making and/or selling conform.

2. Finding Alternatives
a. There is a hyperplane of constant solubles extraction and concentration in the "space" of extraction variables (dose, grind, shot time,etc). In other words, you can change dose, shot timing and volume in such a way that the extraction and concentration stay the same.
b. Now if taste is more directly correlated to these later figures, being able to tweak dose and shot times to either get to a target in solubles or while maintaining that target could be very useful.
c. The same can be done for brewed coffee. If both coarser grind at 4 minutes steep and finer grind at 3 minutes steep give you a 20% extraction, will they taste the same, or are there boundary and local effects we need to know about?
d. Many of Barry's and Nick's reservations presuppose that an exploration like this will produce surprises. But you can't do the exploration without having these shortcut instruments (trust me, I know, unless you want to compete with Jane Goodall in persistence, you do not want to bake pucks to get enough data to answer questions like these)

King Seven wrote:I might be very happy with how my espresso tastes, but closer analysis may suggest possibilities that may improve it further that I might not have been nudged and guided towards without cold, emotionless data suggesting so.

Replace 'cold, emotionless data suggesting so' with 'experimentation as suggested by a fellow geek', and this may well be the motto of on-line espresso fora world-wide. Or should be, at least.
Nice one, James!

Nick wrote:In most quantitatively-measured situations, you can have a severely unbalanced extraction and still nail the numbers.

To any well-trained barista, a severely unbalanced extraction due to channeling is obvious. The shot should get dumped immediately. In your cafe, if these kinds of shots are getting served to customers, you have more problems than a refractometer can solve.

To be honest, I simply don't care whether Extractmojo and the refractometer can accurately measure the constituents of such a shot. And I don't see why you should care either.

IOW, I concede your point: the system is NOT designed to confirm that a channeled disaster of a shot does, in fact, SUCK. OK?

barry wrote:The question that I think Nick is getting to is "how does the system hold up in the real world?" instead of how it has performed under controlled testing. If Barista Jane pulls a 25-second 30ml shot which has suffered transient channeling, how will that compare in measurement to a 25-second 30ml shot which doesn't channel

EVERY espresso shot suffers "transient channeling." Your job as cafe owner is to train Jane well enough so that the degree of channeling is acceptably low in shots that are served. If you and Jane both do your jobs and the degree of channeling is low, my experience indicates that the refractometer can do a very nice job of measuring both concentration and extraction yields. And then, as Jim explained, that's where it starts to get interesting. But if you never try the system because you're busy thinking about scenarios where it might not work, it WON'T get interesting!

It still seems weird to me: Nick and Barry are the last two cafe owners that I'd expect would let theoretical objections deter them from at least experimenting with this technology.

Also, Nick, the refractometer accurately measures how much mass has been extracted from the dry coffee, and therefore helps to determine the structural properties of the puck. As a result it is a very valuable aid during construction projects for obtaining the proper permits from the local building inspector.