Ken, your post strikes me as nonsense on both counts.

-- The waste level is exactly the same, the amount of loose grinds in the grind chamber. However, if one can single dose very accurately, one can purge some these grinds and waste less. This is mostly the case for me.

-- If you make it a zero hypothesis, you still need to decide whether to use the same dose or the same grind setting, or something in between. This requires some idea how and why the grind changes. Moreover, you have no clue whether the results on one setup will translate cleanly to any other. Given that this is a test people cannot perform for themselves, it makes brute force empirical test very tenuous.

Tomorrow, I will test my hypothesis. I will grind my regular 14 and 17 gram doses at my regular single shot settings of 20 and 25 (the zero is at 4, and a full turn is 80 notches). Then I'll attach a hopper and find out how many grams I need at the same 20 and 25 setttings to get the same flow. The full hopper dose will be lower, probably by around 1.5 grams, if my memory from the TGP serves. In addition, if I'm right, the weight difference will be smaller in terms of percentage change (i.e. full hopper use is more forgiving, since a wider range of grind settings can be successfully used for the same dosage).

Everyone who owns a grinder, espresso machine, and scale is welcome to repeat this test. If my hypothesis is true, they will find the need for a precisely right grind settings is less when using a hopper.

If this turns out to be right, and if for some users, the combination of grinder, machine, coffee, and technique makes single dosing too finicky and error prone, they have a perfectly rational reason to reject it, while for those who find it sufficiently reliable have a rational reason to accept it.

Of course, I could be wrong. It could be that the taste test will get a significant result, i.e, somewhere between a 6 - 0 to 10 - 2 in favor of hoppers. But my expectation is the margin will be far less, and that this kind of test cannot be extended to enough trials to get a significant result if the taste difference between the two kinds of grinding is smaller.

Moderator note: continued discussion of single dose grinding retention/waste split to Single Dose Grinding: How much old coffee do grinders retain?
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another_jim wrote:If some of the beans are cheek to jowl, they can't spread out, and will get crushed into stacked particles instead. These will pass out of the fixed gap in the burrs stacked, decreasing the coarse particles' average size and increasing their variance. That is what I am hypothesizing. It explains the differences in what people found, and it can be very easily be tested.

I think you have missed the point of what I am saying. You have stated as axiomatic to your hypothesis that

another jim wrote:You need to grind finer for single dose grinding. Therefore there's larger particles, a more uniform grind, and/or fewer fines

and I propose to reject this axiom as conjecture. Thus, any results from the experiment you have proposed will not in fact be conclusive, unfortunately.

Further I have concerns about the idea that cellulose can be compressed in this fashion, as it tends to have limited capacity for plastic deformation leading rapidly to failure/fracture in a dried state, which is why we soak wood before trying to bend it, etc.

another_jim wrote:Again, does anyone have a different prediction for the compared particle distributions and the mechanism causing the difference?

What I am proposing as an alternative prediction is this:

The primary issue differentiating hopper versus single dosed grinds is not within the burrs where the particles are relatively constrained but within the coarse conical grinding teeth, where the beans are unconstrained to the point of flying about in erratic "popcorning" motion in single dose grinds.

My analogy here is chopping a tomato. If you can hold it with your other hand (hopper), you can make a uniform dice. If you don't (single dose), the chopped pieces are irregular.

BUT it doesn't stop there. Then the bean fragments enter the burrs. Imagine each fragment as a rectangular loaf of crusty bread. It has six crusty sides. Cut it in half and each new loaf has five crusty sides and one smooth white side. And so on. Because you can't cut anything on its edge, the final ground particles retain the effects of the initial fragmentation process as surface irregularities.

BECAUSE surface irregularities are not necessarily dependent on particle size and fines production, I am not clear on what predictions we can make about this. However, the more irregular surfaces produced by single dose grinds will effect particle stacking behavior so we predict that in general a tighter grind will be required for single dose grinds, but that the degree of the effect will be somewhat unpredictable since surface irregularities by definition will be semi-random in nature.

FURTHER since, just as slicing that loaf of bread repeatedly yields more and more exposed flat white inner surfaces in relative proportion to the outer crust, a finer grind should likewise reduce the effect of the surface irregularities. Thus we predict that for increasing finer grinds, the difference between hopper and single dose grinds will become minimized.

Re: Jim's theory vs Adrian's theory - does the single dose/hopper phenomenon occur with flat burr grinders?

Mark

another_jim wrote: if I'm right, the weight difference will be smaller in terms of percentage change (i.e. full hopper use is more forgiving, since a wider range of grind settings can be successfully used for the same dosage).

I had a brain fart here. If a grinder is more forgiving, it will be possible to both grind the same weight at a wider range of grind settings, or use a wider range of weights for a single grind setting and still get shots with acceptable flow rates.

As it happens, this is correct. My 20 to 25 grinder setting is good for 14 to 17 grams when single dose grinding, and 12.5 to 16.3 gram doses when hopper grinding. This means that for some coffee, prep technique, and machine combinations, single dose shots will significantly variable and error prone, shot to shot, and suffer in comparison to hopper ground shots. For other combinations, this will not be true.

If this holds up, then the more precise the taste testing, the more the differences will vanish.

I'm done with this.

another_jim wrote:My 20 to 25 grinder setting is good for 14 to 17 grams when single dose grinding, and 12.5 to 16.3 gram doses when hopper grinding. This means that for some coffee, prep technique, and machine combinations, single dose shots will significantly variable and error prone, shot to shot, and suffer in comparison to hopper ground shots. For other combinations, this will not be true.

If this holds up, then the more precise the taste testing, the more the differences will vanish.

Jim, you lost me with the last comment, which seems to contradict the previous paragraph. (Not trying to argue, just asking for clarification. ) And before you check out, please expand upon the details of your testing methodology. Thanks.

another_jim wrote:If a grinder is more forgiving, it will be possible to both grind the same weight at a wider range of grind settings, or use a wider range of weights for a single grind setting and still get shots with acceptable flow rates. This means that ... single dose shots will significantly [be] variable and error prone, shot to shot ... in comparison to hopper ground shots.

Exactly, though it still does not address what exactly makes a grinder more forgiving.

dogshot wrote:Re: Jim's theory vs Adrian's theory - does the single dose/hopper phenomenon occur with flat burr grinders?

I don't see why not, but I am not arguing with Jim on this -- my idea is NOT mutually exclusive from his.

another_jim wrote:Ken, your post strikes me as nonsense on both counts.

-- The waste level is exactly the same, the amount of loose grinds in the grind chamber. However, if one can single dose very accurately, one can purge some these grinds and waste less. This is mostly the case for me.

While I agree that Ken may have missed the mark (I agree with Shadowfax on his assessment of single dosing), I'm not sure that I agree that the waste is the same. I can purge my grinder by pulsing, brushing, vacuuming, chopstick, and in the case of the Rockys, tipping. If you've got a hopper full of beans, it's difficult to run the chamber empty. In the case of both of my Majors and both of my Rockys (and, of course, both of my hand-grinders!) what goes in comes out. To the gram. Of course, there is a certain amount of retained bean that lives, like trolls, under the burrs. After trying to remove that sediment by hand with tools and implements of destruction without removing the burrs from their carriers, I am convinced that there is a minimal amount of exchange between new beans and the original loss from the first two or three dosages after cleaning.

If you don't include the fact that the amount of waste in single dosing is much, MUCH reduced, you'll never understand why we like it so much.

drdna wrote:Further I have concerns about the idea that cellulose can be compressed in this fashion, as it tends to have limited capacity for plastic deformation leading rapidly to failure/fracture in a dried state, which is why we soak wood before trying to bend it, etc.

I think roasted coffee has ~ 5% moisture. When bending wood in carpentry, you make it thin, and notch it, so that it has room to bend (wood is somewhat flexible, try cutting a thin layer with a table saw). I have a moisture meter but here http://www.woodbin.com/ref/wood/emc.htm you can see is about 9%.

Cheers

PS: ideal moisture content of roasted coffee for grinding is 5%. But that can change with storage humidity. Drier beans create more brittle grounds -> more fines.

RapidCoffee wrote:Jim, you lost me with the last comment, which seems to contradict the previous paragraph. (Not trying to argue, just asking for clarification. ) And before you check out, please expand upon the details of your testing methodology. Thanks.

The inference is as follows: the more painstaking the testing protocol, the more case by case variance is reduced. If the only difference between the two types of grinding is shot to shot variance, then the more painstaking the test, the more that specific difference is eliminated. Sort of a Heisenberg meets Catch 22 effect. Variance testing is best done by gathering large samples from everyday use, as is done by QC departments.

My testing protocol hardly deserves the name. I have several different roast profiles of the GCC Sidamo that I'm using to correlate optimum dosing to different roasting profiles (a piece of research somewhat too arcane for posting). All the roasts dosed the same way, 20 to 25 grinder settings for 14 to 17 grams doses. I combined all the roasts so I would have enough to keep the 200 gram mini-hopper filled (it's some plastic pipe Ken assembled). I checked for any bizarre non-linearities by doing two single dose shots at the extremes, and there was no change. I then attachd the hopper, ground through a dump shot, and tried at the various doses (I already knew the required dose would drop by about 1.5 grams)

The 15.5 gram at 25 setting shot flowed fast, and it settled at 16.3. The 12.5 gram shot at 20 flowed properly. Oddly enough, the middle of the road shots at 22.5 flowed a little slow.

All the shots tasted slightly flat, since they are all relatively down dosed; but they weren't quite as flat as I expected. If I were setting up a zero hypothesis taste test, I'm not sure if I would use the same dose for both alternatives, or whether I would use both slightly higher grind settings and slightly less weight for the hopper shots ...

... I would suggest making the detailed ancillary choices in taste tests less controversial by making taste tests a contest between the tester and testee. The testee (aka "there is a difference") picks the coffee, the dose, the machine set up, and all other variables for one alternative. The tester (aka "there is no difference") picks whatever parameters, other than the actual test conditions, which make the other alternative as much like the first as possible. If the testee cannot distinguish the alternatives, the tester wins; if the testee can distinguish, he or she wins.

another_jim wrote:...The testee (aka "there is a difference") picks the coffee, the dose, the machine set up, and all other variables for one alternative. The tester (aka "there is no difference") picks whatever parameters, other than the actual test conditions, which make the other alternative as much like the first as possible. If the testee cannot distinguish the alternatives, the tester wins; if the testee can distinguish, he or she wins.

My feeling on this is that it seems to me like it becomes a barista competition rather than a grinder comparison. "I'll make my favorite shot my way and you see if you can match it your way"

It's hard for me to see this as less "controversial" than adjusting the two grinders to produce the same flow for the same dose and see if a couple of blind tasters can distinguish the difference.