Grind, not Dose - Page 2

Beginner and pro baristas share tips and tricks for making espresso.
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cannonfodder
Team HB

#11: Post by cannonfodder »

If you have a double basket that is full and you are getting the proper flavor, when the shot starts to flow fast you cannot updose more. You can change to a triple basket and dose down or if you are using the standard Faema style ridged basket, you could get a Marzocco ridgeless basket which will hold another gram or two of coffee.
Dave Stephens

Ken Fox

#12: Post by Ken Fox »

There's an Elephant in the Room but no one can see it :mrgreen:

First let me say that I haven't evaluated Jim's suggestion because the air here in the Idaho Rockies is pretty dry most of the time and we just don't have that much variation in grind required, on a daily basis, and it just hasn't come up as an issue, yet.

That having been said, Jim and I both have high end conical (Compak K10 WBC) or hybrid planar-conical (Max) grinders. The grind quality we are starting with is VERY different than the grind quality that many readers of this thread have, with their smaller planar grinders (Rocky, Mazzer Mini, Cimbali Jr., et. al).

I don't think that Jim or I could even speculate on what effect, if any, this approach would have for our less-well-equipped brethren. I certainly don't care to bring up one of my old grinders from the basement in order to test this :mrgreen:

Another comment, which bears no reference to Jim or his prognostications, or to this particular thread, but rather to the whole idea of threads initiated by what I might call the gurus when they make potentially "seminal" posts (A few people out there might even think I am a guru, but hopefully you (the reader) are not one of them!):

Whenever there is a post initiated by a guru, there are "reflexive" posts that come on almost immediately heralding the new nuggets of information that have been disgorged and thanking the guru for his (obviously correct) prognostications.

No one here, not Jim, not me, not Dan, not Andy S., not Greg S., not Dave, not . . . . . really have much of a clue about any of this. People have more or less experience, they are more or less creative, and are more or less good at expressing themselves. But in reality, most of the ideas that anyone here has, regardless of experience level, turn out to be nothing more than a fart in a windstorm. If I had 10 cents for each idiotic idea I'd posted about that turned out to be nothing more than a crock of BS, I'd be rich enough to retire. OK, I already am retired, but you get the idea.

ken
What, me worry?

Alfred E. Neuman, 1955

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michaelbenis

#13: Post by michaelbenis »

Good points, Ken. And assuming it's just a sudden but likely temporary change in the weather (e.g. you live in England :D ) you may just want to vary your tamp.... or preinfusion if that's easy...

You can pull this elastic from all sorts of different directions to get the tension you want....

Helpful message from Jim, though, that we should never think it is ONLY grind that needs adjustment.... but as you say some of that will depend on the grinder.

Cheers

Mike

PS: Sunny today (2009 ration clearly finishing), so it's easy.... ahem... comparatively :-)
LMWDP No. 237

FredK

#14: Post by FredK »

another_jim wrote: In espresso extraction, the flow rate is largely determined by the amount of fines in the puck, while the extraction rate is determined by the average size of the coarse particles.
Why would you think the flow rate and extraction rate are based on two different things? Flow rate and extraction rate are based on the same thing, a combination of fines, coarse particles, medium particles, all particle sizes in fact, plus tamp pressure. Doesn't make any sense that the flow rate is based on one thing and extraction on another. Flow and extraction rates are based on the same thing, just inversely proportional. As rate increases, extraction decreases.

You may say the fines plug up the holes in the basket, but the entire flow rate is a function of all the particles sizes and tamp pressure. You have to look at the big picture, if you did a particle size distribution, you'd get a bell curve, hopefully. As this curve shifts from left to right it will determine the flow rate and extraction rate, assuming tamp pressure is constant.

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another_jim (original poster)
Team HB

#15: Post by another_jim (original poster) »

FredK wrote:Why would you think the flow rate and extraction rate are based on two different things? Flow rate and extraction rate are based on the same thing, a combination of fines, coarse particles, medium particles, all particle sizes in fact, plus tamp pressure.
This is wrong -- read the book on Illy. Fines amount to less than 1% of the coffee by weight, so they play no part in the extraction or taste. On the other hand, they are the cement that obstructs the passage of water, so play a disproportional role in the flow.

Ken Fox wrote:That having been said, Jim and I both have high end conical ... grinders. The grind quality ... is VERY different than the grind quality that many readers of this thread have, with their smaller planar grinders (Rocky, Mazzer Mini, Cimbali Jr., et. al). ... I don't think that Jim or I could even speculate on what effect, if any, this approach would have for our less-well-equipped brethren.
Wrong again, I can speculate on anything in the universe :wink: Less flip, my advice is actually more useful for low end grinders:
  • During the TGP, I found that the high end conical grinders produce extraction levels from 22% to 24% (measuring undissolved solids as well) at any workable dose or grind setting. In other words, the coarse particles stay at roughly the same average size, and adjusting the grind setting only adjusts the flow rate, aka the fines. In other words, these are ideal espresso grinders -- you change the flow, but leave the extraction close to optimum. Since these grinders are already so consistent, moving from varying grind to varying dose will have almost no effect.
  • During my extraction studies, I found that the smaller planar grinders varied from about 16% to 24% extraction rates, with the lower end producing mostly appalling shots. Suppose you have the grinder set ot get a nice round tasting shot, and the next day the flow is choked. If you coarsen up the grind, the coffee will extract less, and the taste will go to hell. Lower the dose instead, and the shot has a good chance of remaining as is.
As Ken points out, I'm a guru, and I try very hard to oversimplify things. But at least that way, you'll always know for sure when my advice doesn't work.
Jim Schulman

Ken Fox

#16: Post by Ken Fox »

another_jim wrote:During the TGP, I found that the high end conical grinders produce extraction levels from 22% to 24% (measuring undissolved solids as well) at any workable dose or grind setting. In other words, the coarse particles stay at roughly the same average size, and adjusting the grind setting only adjusts the flow rate, aka the fines. In other words, these are ideal espresso grinders -- you change the flow, but leave the extraction close to optimum. Since these grinders are already so consistent, moving from varying grind to varying dose will have almost no effect.

During my extraction studies, I found that the smaller planar grinders varied from about 16% to 24% extraction rates, with the lower end producing mostly appalling shots. Suppose you have the grinder set ot get a nice round tasting shot, and the next day the flow is choked. If you coarsen up the grind, the coffee will extract less, and the taste will go to hell. Lower the dose instead, and the shot has a good chance of remaining as is.
And how exactly would one go about proving this, one way or the other (e.g., in actual use)?

Any "data" obtained is going to be confounded by several factors, not the least of which is that many, likely most, of the more critical tasters who post on the coffee internet, have already upgraded to higher end grinders. A disproportionate number of the lower end grinders are going to be found in the homes of the least experienced readers, whose taste may be less experienced.

ken
What, me worry?

Alfred E. Neuman, 1955

FredK

#17: Post by FredK »

I find it hard to believe that fines play no role in taste or extraction. Fine particles have more surface area, hence extraction would be greater than larger particles.

I see how fines will clog up the portafilter allowing slower flow, but this leads to more extraction simply because the water has more time interacting with the coffee. It doesn't matter if the fines are causing a reduced flow rate, it doesn't matter what causes it, but if the flow is slower, the extraction is greater.

Also, are you saying that when you change the grind setting, you are only changing the amount of fines, and all the coarse particles are the same? Changing the setting should be changing the average particle size across the entire grind. Like mentioned before, there should be a bell curve particle size distribution, and changing the grind simply moves the average particle size up and down the graph.

I'm no espresso guru, but I've been a chemist for 15 years and have done some work with particle sizes, milling, and distributions for raw materials in a couple different settings. And I think that flow rate and extraction are based on the same physical characteristics, just inversely proportional. You can't say the flow rate is based on one thing and extraction another.

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another_jim (original poster)
Team HB

#18: Post by another_jim (original poster) »

You need to be familiar with the coffee literature, otherwise your experience with other aggregates will mislead you. The distribution of coffee grind sizes is not unimodal and close to normal; it is bimodal and extremely log-normal.

-- The fines are roughly 1/10th the diameter of the coarse particles, and therefore, roughly 1/1000 of the mass. They migrate to the bottom of the puck, interlock with the coarse particles and create an aggregate that controls the rate of flow.

-- The extraction is the same in principal as for all coffee brewing methods. It depends on the amount of time each particle is exposed to water, and its size. Therefore, given a proper flow rate and extraction time, it is best calculated from the size of the one coarse particle which forms the mass median (the particle at which half the mass of the puck is in larger particles, half in smaller particles). Any other measure of centrality is highly misleading, since with the log normal distribution, a far greater count of small particles is needed to balance the mass of a few larger ones.

Now lets brew this aggregate in our heads and see what happens.

If you look towards the bottom of the cited page, you'll see a cumulative mass graph of the particle distribution. It shows
-- 25%. roughly, of the mass in fines, at particle sizes from 10 to 100 microns,
-- 25% of the particles in the "small coarse" sizes from 100 to 300 microns,
-- 50% in the "large coarse" sizes from 300 to 1000 microns.

Espresso shots vary from 20 to 35 seconds, and around 1:1 to 2:1 in water to puck volume. So from tightest to loosest of shots, coffee to water exposure will vary by a factor of 4.

The fines have a volume of 1/10th to 1/100th of the coarse ones, so the 4 times variation in brewing parameters is meaningless to them. They will always over extract or maximally extract in the first few seconds of the shot, and will be a constant as far as the cup taste is concerned.

The smaller coarse particles are from 1/10th to 1/3rd of the size of the larger ones. If the large coarse particles are extracting any where close to normally, these particles too will be more or less maximally extracted by the time the shot is half way through. Their extraction will vary a little but, but not much, and their contribution to the cup will be close to the same for all shots anywhere close to decent.

That leaves the 50% by weight of large particles. These are the ones that are creating almost all the variation in extraction rates. If they under-extract, the brew tastes exaggerated and balanced towards sour, if they over-extract, the taste starts going flat and finally overbalanced bitter.
Jim Schulman

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another_jim (original poster)
Team HB

#19: Post by another_jim (original poster) »

AndyS wrote:BTW, are you saying that drum roasts always produce more fines than air roasts?
It's almost always been the case when I cloned a roast on my P1 from either a home or commercial drum. I've done this at least a half dozen time now, and I always notice the effect. However, one of the coffees Ken sent was an exception, and ground at the same setting; so it's not universal. I do not know what the mechanism is.

We still don't really know what constitutes two **identical** roasts when done on different machines. The Q auction group at the SCAA wants to standardize roasts, but absolutely doesn't want to get into comparing a whole bunch of roast process readouts. Who can blame them? So they've decided to standardize on whole bean + ground bean agtron readings (57 whole bean and 62 ground for sample roasts used in jury cupping). The average Agtron gives an idea of depth of roast, while the difference between ground and whole gives an idea of the roast speed.

I'm 99% certain that roasts from two machines that are identical by these criteria would cup slightly differently, but I guess they'll always be close enough to keep jury rankings fairly close.
Jim Schulman

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Worldman

#20: Post by Worldman »

Wow! This really (truly) does make my head spin! Apparently, I AM dense.

Len
Len's Espresso Blend
www.lensespressoblends.com