jonr wrote:If one wanted "even extractions" with espresso, I'd look at reducing the puck depth. We know that the higher concentration at the bottom of the puck produces less extraction there.

I realize this is a bit of an aside, but to be sure I understand: You're referring to the fact that after extraction, the bottom of the puck will be damp with more concentrated liquid coffee, because it has effectively transported brewed coffee from the top of the puck downward (as opposed to the top of the puck, which just received fresh water)? Or, are you referring to something about particle distribution or possibly fines migration?

The former - water already containing coffee extracts less solubles. So you get greater (aka uneven) extraction from the top of the puck.

It's been tried and it just doesn't work. I have tried it and it didn't work. I still have the set of screens that I used but I don't use them anymore. I learned that the science behind good extractions related to the size, shape, quantity, etc... of coffee grinds is still not fully understood nor linear. I have read some of the best grinders actually produce quite a bit of fines and the burrs they are equipped with are designed to do so. I am not talking about an uneven grind that is random and all over the place. Consistent fines seem to be very important in getting a good extraction.

There are all sorts of hypothesis floating around such as fines act as little plugs to keep the coffee from gushing around and through gaps in the larger grinds which I believe is probably true but in my opinion nowhere near the whole story.

My experiments with the screens produced confusing results that were not very useful to me. Some shots came out better due to screening out fines and most came out worse, all in terms of flavor (very unscientific.) The results also varied with different coffees it was then I knew I was in over my head and needed a lot more that a set of screens to study and understand this.

There are people right now studying this using laser analysis to also take the shape of the grinds into consideration. It gives me whole lot of respect for the people in the old days who were able to design grinder burrs that produce great tasting coffee using trial and error because of the lack of available technology. The art of producing good grinds is quite old and has developed impressively despite it's artistic evolution and limited science in terms of examining grinds to assist. That is my impression and experience.

Has the topic of diminishing volatile compounds during the sieving process been brought up? There is a relatively long time between grinding to sieving to brewing which opens up even a wider window for loss of aromatics of R&G coffee. Whether or not this is noticeable is another study altogether.

I have yet to see an analysis on absolute time between grinding and extraction and the difference on EY and taste. We all agree that the sooner you extract after grinding the better, however I'd be curious if there is as much of a cliff as there is during bean rest.

I was also thinking about sieving, it would seem to me some amount of particles to fill empty voids of space in the puck are a necessity. Most grindgers go for bimodal distributions of particle size. It would seem to me a double sieve, one with relative fines and one with coarser grinds makes a lot more sense. Has anyone tried this? Is there a system that works with a bimodal grind size sieve?

coffeekid wrote:This may be incredibly naive, but have there been any attempts to make a pressurized immersion brewer, with a targeted volume similar to espresso? I have imagined a brewer that has a 60 - 90ml chamber, creates 4 - 12 bars of pressure, agitates the grinds while under pressure, and then releases them. Conceivably, this would render water flow with even the finest uniform particle distributions a non-issue, would eliminate several other issues around consistency of distribution and tamping, and could allow for high and even extractions.

I've jumped on the extraction bandwagon lately. I became a pro (opened a roastery) 4 months ago and amid learning everything non-coffee about running a business, I've also gotten to invest in some new coffee tools.

Until this past week, my seminal espresso experience was a shot of heartbreaker espresso from cafe grumpy about 7 years ago. Cafe grumpy was good, but Heartbreaker was roasted by Novo (those guys know coffee - they stopped roasting and started 90+).

Anyway, my new high water mark was a shot of espresso that I made off our current washed ethiopian. One of the investments I made was in a series of IMS single baskets - These are the first singles baskets I've used that I can get a non-channeling shot on. I pulled a ristretto single using only 10g of the coffee. I finally tasted a light roasted espresso that was properly extracted. Not sour. Sweet. Super sweet. I mean 1 and a half teaspoons of sugar sweet.

I know this isn't new for some folks, but I've been most places and tasted many shots (stumptown/portland scene, NY scene, intelly, DC scene, bird rock, handsome) and EVERYONE underextracts the lighter roasts. (underextracted? - some of my visits were years ago). I'm sure most of that was because it's a cafe and who is gonna train baristas to pull good singles? I bet the owners/roasters/managers messed around with properly extracted singles in the back and on off times. But this was my first experience of this. And it's possibly the biggest moment in my coffee journey to date.

It's an oversimplification, but right now it seems extraction unifies so many disparate variables. Temperature. Time. Grind size. Dose. Put them all in the framework of extraction, then play around with them.

So this whole thread has been my questions over the past month. Let's sieve - OK, that won't work. Now what about this "static" espresso suggestion that I quoted - I started thinking about that maybe a week ago. But flow rate has got to act as agitation - so we obviously need to agitate if we won't have flow. Or do we, because immersion brewers don't need the agitation that pourovers provide. So can we make an "immersion" espresso machine, in contrast to the "pourover" models we use now?

One thing I've learned (and proven, by finding this thread) is that someone else has almost always thought of and tried my "good ideas." Saves me time and money, so I don't mind. But that's why i'm quoting this question, and bringing it back up - anyone done what coffeekid asks?

popeye wrote:...anyone done what coffeekid asks?

I've used a pressurized portafilter...

Yeah, and I get your point. But immersion and percolation (drip) are different brew methods, and espresso is percolation, not immersion, due to the flow of water through the bed. Coffeekids idea seems like a fairly obvious experiment, and that's why i'm fairly sure it's been done before. But i'm waiting to hear of how/when/where and results.