Ken Fox wrote:John, I'll send you some burr resistant thermocouples.

Just make sure there's a Cimbali Max attached to them.

Ken Fox wrote:He needs to rethink his explanation.

We are talking about differences among commercial grinders used in occasional domestic service. A Cimbali Junior or Mazzer Mini does not have its burrs heat up much in the sort of use that we home users put those grinders to, anymore than does a Robur, a Compak K10, or a Cimbali Max. It is quite honestly absurd to think otherwise.

The people making and posting about these observations are not using these grinders in cafes (where it doesn't much matter) but from their experience in a home setting. In a cafe, it doesn't matter if you pitch 2 or 3 shots down the drain every time the ambient humidity changes, if you are going to grind enough coffee in a shift to make 200 doubles. In a home, we notice this sort of thing because we are low volume infrequent users.

I think that Michael Teahan's explanation makes the most sense. It all revolves upon the length of the cutting/grinding surface, regardless of the type of burrs. Conicals have larger cutting surfaces than do most planars, and that is the explanation.

First of all, I said Philip "took a shot at an explanation." I don't think the "grind adjustment stability of bigger grinders" is something that he personally has noticed (nor have I). But since a bunch of you guys have observed this, I asked Philip if he could explain it. He was driving down I-5 in his car talking on the cell (handsfree, of course) and ventured a quick guess based on his experience. I repeated it here (as best as I remembered it) as a talking point to foster discussion. It wasn't intended to be a formal explanation.

Second, Philip told me that he's made actual measurements of coffee grounds temperature coming out of the burrs of various grinders. With Mazzer Mini grinders he said he's observed elevated temperatures after only about three shots ground in a row (easily typical in home use).

Third, what you're calling "Michael Teahan's explanation" does not "make the most sense." It presumably explains why some grinders make different coffee than other grinders, but it certainly doesn't explain why some grinders VARY more than other grinders.

[edited to remove some of my overreaction to Ken's original post]

AndyS wrote:...Philip told me that he's made actual measurements of coffee grounds temperature coming out of the burrs of various grinders. With Mazzer Mini grinders he said he's observed elevated temperatures after only about three shots ground in a row (easily typical in home use).

Actual measurements will trump BSing any day. But this topic did come up during the Titan Grinder testing, and Dave took some grinds temperature measurements. Based on temperature data taken in the chutes of the Mazzer Kony vs. SJ grinders, there was no compelling reason to believe that temperature plays a major role in grind quality, at least not for these grinders under typical home conditions.

Again, I'll observe that we need measurements taken in the grinding microenvironments produced by the cutting surfaces of the burrs. It's possible that the grinds are subject to rapid heating followed by rapid cooling, and this does impact flavor. If there were major differences between grinders, and temps correlated well to taste profiles in the cup, it would be worth pursuing. But right now that's even more BSing than speculations about particle size and shape (for which we at least have preliminary data).

Perhaps you could suggest a way to get near-instantaneous temperature measurements at the burr surfaces during grinding? I'm unaware of any equipment (some sort of super-duper IR thermometer?) that permits such measurements to be made.

RapidCoffee wrote:Actual measurements will trump BSing any day. But this topic did come up during the Titan Grinder testing, and Dave took some

The people that I know of who have made this observation online would very seldom grind three shots in succession (Andy's threshold), and this is unlikely to be their normal usage pattern, although it might happen on occasion. The people who I recall making this observation (of the need to change grind adjustments less frequently with conicals) include Dave, myself, Jim Schulman, Jason Casale, and to some extent Jeff.

The first time I recall this coming up was in a conversation I had with Jason Casale at the SCAA in Long Beach, 9 months ago; Jason had a Max and I had recently acquired 2 of them. We had both made the observation independently. Subsequently I saw it posted on the TGP and other related threads by others. Undoubtedly I have left some people out who have made this same observation.

In addition, when I did a mini blind tasting between the Max and an old Cimbali Cadet (same burr set and motor as the Junior), it was extremely obvious due to the side by side usage of these grinders; it is posted somewhere in the TGP thread. Only on very rare occasions did either grinder grind for more than ONE shot in a 10 or 15 minute period, no less three.

ken

RapidCoffee wrote:Based on temperature data taken in the chutes of the Mazzer Kony vs. SJ grinders, there was no compelling reason to believe that temperature plays a major role in grind quality, at least not for these grinders under typical home conditions.

Unless I misunderstood the way that the test was carried out, there is no compelling reason for me NOT to believe that temperature plays a role in the quality of the grinded coffee secondary to grinder activity. I say this because I interpreted the measurments to be from a sustained grinding of 1/2 pound of coffee. (Dave, if this is not the case, please correct me.) The problem is that people are looking at this test and drawing immediate conclusions that the issues of heat are overstated or not applicable to home use while referencing a single test that does not represent either home or cafe use anyways. At best, this type of grinder use represents a cafe which fills the doser rather than grind per shot, a practice which is considered poor.

I am being a bit critical because it is somewhat ludicrous to see conclusions drawn from tests that have had variables either introduced or removed from what is representative of real life application. For instance, although I am currently led to believe that the majority of grinder heat is a result of the burrs themselves, the motor does release a decent amount of heat. Electric motors are inefficient due to the energy required to start them. This is especially true of motors that are not being supplied power via 3 phase wiring. Again, I may be wrong in the way I interpreted the way the test was carried out, but the variable of intermittent "off/on" motor duty was removed from this test. That variable is responsible for a great deal of heat from the motor.

Yet, from this single test, there is opinion that heat issues have been "debunked" or misrepresented by others' current opinion and thought.

Just because we geeks have some decent instruments to obtain accurate data doesn't make our findings meaningful.

Ken Fox wrote:The people that I know of who have made this observation online would very seldom grind three shots in succession (Andy's threshold), and this is unlikely to be their normal usage pattern, although it might happen on occasion.

Ken,

Maybe I am out of the norm, but when I make espresso at home, I usually make my wife and I (and sometimes my three year old) an espresso followed by a cappuccino every morning. With a seasoning shot, possible additional shots for grind adjustment (a sure thing when changing coffee), and four drinks, I easily prepare five to six shots in succession.

I'm not stating one way or the other about heat issues with that usage pattern, just giving my pattern which meets or exceeds the "thre shot" threshold.

.

Matthew Brinski wrote:Yet, from this single test, there is opinion that heat issues have been "debunked" or misrepresented by others' current opinion and thought.

To the best of my knowledge, nobody is claiming heat issues have been categorically excluded from grinder evaluation. If you have criticisms of the data that was presented, why don't you run your own experiments and generate new measurements for the rest of us to chew on? Further armchair quarterbacking is optional.

One more piece of speculation here, and then I'm done: coffee beans are subjected to high temperatures (400-500F) for long periods of time (many minutes) during the roasting process. Unless the beans are heated to much higher temperatures during the much shorter grinding process, this argues against heat being a major factor. Grind particle properties (size, shape) are more likely to play a significant role in determining pour characteristics, especially when evaluating grinder forgiveness (not taste).

Matthew Brinski wrote:Ken,

Maybe I am out of the norm, but when I make espresso at home, I usually make my wife and I (and sometimes my three year old) an espresso followed by a cappuccino every morning. With a seasoning shot, possible additional shots for grind adjustment (a sure thing when changing coffee), and four drinks, I easily prepare five to six shots in succession.

I'm not stating one way or the other about heat issues with that usage pattern, just giving my pattern which meets or exceeds the "thre shot" threshold.

.

Matthew,

I don't recall you're ever having commented on the need or lack of need to change grinder settings with planar grinders vs. conical ones.

Of the people who have made this comment, most are either single or have spouses who don't drink coffee. I hate to dismiss an idea out of hand, but heat build up in commercial grinders used in a home setting as an explanation for this phenomenon simply does not pass the "sniff" test.

I'm personally exceptionally familiar with grinders using the Cimbali Junior 64mm planar burr set (includes the Cadet also), having used them for about 12 years. I've now been using Maxs, and was using a Compak K10 conical for some months. All of these grinders have seldom been used for grinding more than 40g of coffee at a time, and most usually about half of that. The frequency with which these planar grinders need adjustment for changes in coffee or humidity is about 1-2x per day. With the conicals the difference isn't subtle, it is obvious enough that anyone would notice it. The conicals have their grind settings changed 1-2x a week, tops.

ken

I saw little benefit in the thermocouple in the grind chute test I did when I had the Kony and SJ out. So I did not bother to repeat the process on the rest of the grinders. I thought we had come to the conclusion that there are too many things happening inside that burr set at a micro environment level for the probe check to be of any real significance but it has been a few months since I read it.

I am content in knowing that this is not a single observation and appears to be consistent with the bigger is better theory of grinding burrs. The reasoning my elude us and having a measurable item for the apparent change would be nice but I am not going to obsess over it. I will leave that to the engineers that design these things. The validation of the observation is good enough for me. I think I will spin up the Robur for one last shot before she gets packed up and moves on.

RapidCoffee wrote:Actual measurements will trump BSing any day. But this topic did come up during the Titan Grinder testing, and Dave took some grinds temperature measurements. Based on temperature data taken in the chutes of the Mazzer Kony vs. SJ grinders, there was no compelling reason to believe that temperature plays a major role in grind quality, at least not for these grinders under typical home conditions.

Again, I'll observe that we need measurements taken in the grinding microenvironments produced by the cutting surfaces of the burrs. It's possible that the grinds are subject to rapid heating followed by rapid cooling, and this does impact flavor. If there were major differences between grinders, and temps correlated well to taste profiles in the cup, it would be worth pursuing. But right now that's even more BSing than speculations about particle size and shape (for which we at least have preliminary data).

Perhaps you could suggest a way to get near-instantaneous temperature measurements at the burr surfaces during grinding? I'm unaware of any equipment (some sort of super-duper IR thermometer?) that permits such measurements to be made.

FWIW, comparisons of temperature measured just above the burrs and immediately after the cutting process done by a company that is heavily involved in grinder manufacture indicate that the work of cutting the coffee, the friction produced when coffee passes out of the burrset is remarkably similar between different manufacturers of flat burrsets and different manufacturers of conical burrsets. There apparently is some difference between flat and conical burrsets. The conclusion drawn from the comparisons was that there was little to gain heat-wise from rethinking burrset shapes, but lots to be gained in managing heat flow from other sources in the grinder. For our use - folks using commercial gear in a light duty environment, temperature issues are pretty much moot.

-Greg