First, I'm not trying to restart a debate about single dosing - just wanted to share what I've found on my own equipment.

I've read all the threads I could find here on single-dosing vs hopper-dosing, and read the blind tasting tests that were done. And I've been single-dosing myself for a couple of weeks (not a lot, I realize!). But there was always something bothering me, and that's the presumed inconsistent grind between the first part of the dose (which is weighted down by beans or a weight in the grinder throat), and the last part of the dose (which has nothing on top of it, and a weight can no longer reach it).

So I ran some tests last night, using my Fiorenzato F4e. On this grinder, the bottom of the throat narrows down, and that narrow part seems to hold roughly 7g of beans. So here's what I did:

Test 1: 18g total dose, all at once. Put it in the grinder throat, weighted with the plastic tamper that comes with the grinder (slightly sanded to allow it to slide down). Tamper weight was 35g.

In this scenario, the first ~12g had a weight on top of at least 35g, and the last ~6g was in the narrow part of the throat, with no weight able to touch it.

Result: 33g output in 24s. (This was a bit fast - I'll try to re-run these tests with a slower pour rate).

Test 2: 18g total dose, but run through 6g at a time. So load 6g, grind. Load 6g, grind. Load 6g, grind. The weight was down in the throat, but doesn't reach to where the 6g dose goes, so it's essentially just a cap to keep things from flying out.

Result: 35g output in 17s.

I'm planning to re-run the test a little more carefully - a bit finer for slower pour rates, and also run twice in a row of each configuration to eliminate any potential retention issues.

But in the end, the result (to me) shows that the last 6g of a single dose, on my equipment, is _much_ coarser in grind than the earlier part of the dose. And while many are fine with this, and perhaps there isn't a taste difference caused by this, my "OCD" simply doesn't allow me to believe this. Seems like we spend a lot on our grinders to ensure a consistent grind throughout a dose - and this impacts that a lot.

So for me, I think I'm going to go back to hopper dosing, at least for now.

This is in line with my experience: bean load has a huge impact on grind. For me, the grind consistency of a (mini) hopper full of beans outweighs the undeniable benefits and convenience of single dosing.

OTOH, I'm much less fussy when it comes to non-espresso brewing, and typically single dose my drip brew. I don't know whether grind coarsening is equally pronounced in small consumer conicals, as it is in large Titan-class grinders.

Question: why not just drop in ~6g at a time for every shot so the grind is the same throughout? Then the difference of single dose vs hoppered would just be the whole dose unweighted or the whole dose weighted, rather than a gradient of weighted and unweighted.

Or just turn on the grinder and trickle the beans in, no weighting at all.

This is exactly why I could not get single dosing to work (lowers EY%) and widens extraction evenness bell curve.
That and general lack of manual skill;)

My hopper gets a new fresh bag every 3 days. So age is zero concern for me.

CwD wrote:Or just turn on the grinder and trickle the beans in, no weighting at all.

From a consistency standpoint, this makes perfect sense to me, and in fact I suggested it many years ago. That thread, like so many others, devolved into a flame war on the respective merits of single dosing vs hopper dosing, and I lost interest in pursuing it further.

CwD wrote:Question: why not just drop in ~6g at a time for every shot so the grind is the same throughout? Then the difference of single dose vs hoppered would just be the whole dose unweighted or the whole dose weighted, rather than a gradient of weighted and unweighted.

Or just turn on the grinder and trickle the beans in, no weighting at all.

For me, my instinct (not backed up by any data whatsoever!) is that this is the most inconsistent part of the grind. Bits of bean are flying around, and I think others have said the grounds look quite different than an equivalent-coarseness regular weighted grind.

It seems like some of the grinds would come out just as expected, i.e. finely ground as you would expect hopper-loaded beans would be ground. But other pieces of the bean are coming out coarser, as they managed to find a way to escape before being ground finer. But I doubt _all_ of the grounds end up coarser, so it seems (to me anyway) that there is likely inconsistency when grinding this way.

That said, I can't think of an easy way to test this myself...

gr2020 wrote: Test 1: 18g total dose, all at once. Put it in the grinder throat, weighted with the plastic tamper that comes with the grinder (slightly sanded to allow it to slide down). Tamper weight was 35g...

Result: 33g output in 24s. (This was a bit fast - I'll try to re-run these tests with a slower pour rate)...

Test 2: 18g total dose, but run through 6g at a time. So load 6g, grind. Load 6g, grind. Load 6g, grind. The weight was down in the throat, but doesn't reach to where the 6g dose goes, so it's essentially just a cap to keep things from flying out.

Result: 35g output in 17s.

I'd like to see one more test: 18g total dose, all at once. Put it in the grinder throat, no weight but cover the throat with your hand to keep beans and fragments from flying out.

I'm wondering if the weight of the small dose of beans brings the flow rate closer to test #1 or test #2

It would also be worthwhile to compare the taste and %EY of test #1 with test #2 (and my test) after increasing the grind fineness to achieve the same flow rate as test 1.

Grinder.

HG-1: 19g in / 19g out. Single dosing enjoyment without any lost in quality of waste.

Putting a weight on top defeats the purpose of single dosing, no? In my opinion it would even further the variance in grind because at one point the beans have weight then at the end they do not.

I single dose with a K10 beans only in the throat and haven't noticed any ill effect.

Points from a fellow single doser that occassionally tried hopper dosing :

i) A finer burrs gap (grind setting) is required for single dosing - adjust finer as if you're dialing in a new coffee/grinder
ii) As you noted, the grind size changes as beans feed through, so you have a mix of particle sizes - do a mixing /WDT, and use bottomless portafilter to judge if you have done a good job mixing them
iii) Measures your dose in & out to make sure it's not due to retention, it's to learn how your grinder behaves under such operation condition

Does the variance in single dosing matter? I don't know for sure and don't think so. Yes there is more variance in particle size (from start to end) when you switch from hopper dosing. But you are also setting the burrs gap closer (grind finer). It has been presented before -that as you close the burrs gap, the grind distribution profile becomes finer, tighter and more uniform.

With hopper, you're using a bigger burrs gap. So your particle size distribution is looser (relatively) throughout.

With single dosing, you're using a significantly smaller burrs gap. So your particle size distribution starts very tightly and go looser in the end. If you mix them up, the effect might be very similar to what you get with a hopper dosing. I have no other way to verify other than it tastes fine to me and no defect detected.


For those who're into refractometry measurements, I did some tests as well. But I'm not a good note keeper so eventually I stopped taking notes. The readings are quite consistent/predctable for a given bean/roast so I also stop measuring a while ago (now planning to resume)

Note: measurements are done without filtration - considering that most said they get 19% with a hoppered conical grinder, I think mine would be in the ballpark even after filtration.


All are in single dosing mode. Aldi=commercial roast, HR=home roast (1/3 betwen end 1st crack to start of 2nd crack). Using a 18g VST and higher dose give a higher EY, but I prefer 15g dose in a VST 15g. No particular preference to the baskets, just happens to be what I am working with.

And another two points fresh off the oven :




Oh, and for single dosing, no additional weight (ie plastic tamper etc) here. Just cover the throat with a rubber pad (for noise dampening) and tamper on top.