# a (not so) quick experiment - single dosed grinders



## dsc (Jun 7, 2013)

I've done a (pretty) quick experiment today with surprising results, maybe someone else can try the following as well and report back? All you need is a flat / conical grinder which allows single dosing and three cups marked A, B, C.

1. Measure out your standard dose, lets assume this is 18g, drop that into the burr chamber, no beans on top, no weights, tampers etc.

2. Now this might be tricky on fast grinders, turn the grinder on for a brief moment so that it only grinds 6g, drop that dose in a cup A.

3. Do another 6g dose and drop that in cup B

4. Grind the remainder (should be close to 6g) and drop that in cup C.

5. Repeat points 1 - 4 two more times, so that you end up with roughly 18g in each of the A, B, C cups.

Pull shots with each of the cup doses and observe what happens. Do they all flow / extract the same, or is it all different?

Report back

Cheers,

T.


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## risky (May 11, 2015)

I'm on this later today. Very interested in the results.


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## dsc (Jun 7, 2013)

Awesome!!

T.


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## Xpenno (Nov 12, 2012)

Looking forward to hearing the results but I can't imagine that the EK will be accurate enough to grind in 6g portions.


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## dsc (Jun 7, 2013)

That's the main problem with this experiment I'm afraid, it's only really suited for slow grinders. Besides the EK probably isn't affected by bean weight issues anyway.

T.


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## coffeechap (Apr 5, 2012)

Will do this on the powered hg1 tomorrow


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## mremanxx (Dec 30, 2014)

Take it you were bored


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## dsc (Jun 7, 2013)

Just trying to understand how grind is affected when single dosing. Not that it made anything clearer in all honesty!

T.


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## risky (May 11, 2015)

Just so I understand, you will end up with 3 cups;

Cup A will be full of grounds ground in the first part of the cycle, where there was circa. 12g of beans behind them in the hopper, including the initial 'uptake' (I believe @garydyke1 has mentioned about this before when he advised against single dosing a Royal?)

Cup B will have the mid-cycle, beans already in the burrs, beans behind the ones being ground.

Cup C will have the end of the cycle, nothing behind the beans to push them through

If you want I can repeat with weight on top, or is that stage 2?


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## risky (May 11, 2015)

Cup A - 18g > 35g > 1m12s

Cup B - 18g > 35g > 18s

Cup C - 18g > 35g > 8s

So there we are. Quite startling. No idea if this helps you at all.


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## coffeechap (Apr 5, 2012)

shows the difference in the grind consistency


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## dsc (Jun 7, 2013)

Damn that's a massive difference in shot speed! what grinder is this on?

Basically what you've done is shown how the grind size or grind shape changes over the course of a single dose grind. The first shot which was a choker was made out of the first 6g of each of the three grinds. This was with 12g of beans above the 6g being ground, so with some weight behind the beans, probably no popcorning either. This produced the finest grind or the most amount of fines, enough to slow the shot well over 1min. The 'middle' bit, so the 'second' 6g was produced with just a bit of beans above (only 6g left at the end of this stage), came out coarser, or more "chopped"? Then came the last 6g, no weight above the dose being ground, probably heavy popcorning, loads of "shards" in the grind I'm guessing and perhaps no fines what so ever (or maybe the same amount as at the very beginning, but I'm guessing the shape of the rest of the beans was different)? All of this resulted in a gusher.

The above shows that during single dosing the grind is massively inconsistent, you get some 'normal' grinds, some slightly coarser and some proper rocks / shards which probably cock everything up. Yes altogether it works, but it's a bit like mixing different grind levels on a normal hopper fed grinder.

That is my take on it anyways









T.


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## Mrboots2u (May 10, 2013)

Do it again and see if you get the same results . One experiment is just a snapshot


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## Xpenno (Nov 12, 2012)

risky said:


> Cup A - 18g > 35g > 1m12s
> 
> Cup B - 18g > 35g > 18s
> 
> ...


Just as a reference, if you grind all in one go what's the shot time and also what's the shot time with a weight on the beans?


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## urbanbumpkin (Jan 30, 2013)

I don't think I can accurately measure the 1st 6g of a dose on the major.


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## dsc (Jun 7, 2013)

Don't think it matters much if it's +/-1g, you could try splitting the dose in half as well if a split into thirds is asking too much.

T.


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## risky (May 11, 2015)

Right I will repeat tomorrow night if I get a chance as this morning I noticed that the burrs were chirping at a far courser setting that usual. Opened the grinder up after this and cleaned out the burrs and the chirp point moved much finer.

@Xpenno I did want to try that but for the above reason it wasn't possible, however I do have a note from my previous experiments when I made my dosing device that time without the weight on was almost exactly double that with no weight. Quite a considerable adjustment in the grind setting was needed. Basically gave you a lot more room to adjust your grind as with weight you had to set the grinder a lot courser.

@dsc Grinder is a Super Jolly, new steel burrs, probably less than 3kgs through them.

@urbanbumpkin you might be surprised, I was. I've never switched the grinder off mid-grind but of course the beans in the burrs causes the burrs to stop spinning almost immediately when the motor shuts off. I found I could pulse the grinder and get 0.5g out per time pretty much.


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## risky (May 11, 2015)

Also @dsc Cup C is clearly visibly courser. Much more 'chaff'/silverskin visible also.


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## Xpenno (Nov 12, 2012)

risky said:


> Right I will repeat tomorrow night if I get a chance as this morning I noticed that the burrs were chirping at a far courser setting that usual. Opened the grinder up after this and cleaned out the burrs and the chirp point moved much finer.
> 
> @Xpenno I did want to try that but for the above reason it wasn't possible, however I do have a note from my previous experiments when I made my dosing device that time without the weight on was almost exactly double that with no weight. Quite a considerable adjustment in the grind setting was needed. Basically gave you a lot more room to adjust your grind as with weight you had to set the grinder a lot courser.
> 
> ...


Cool, I was more interested in comparing the whole unweighed shot to the 3 split shots. This would tell us a little bit about where the standard single dose sits within the comparison of the three I.e. is it 15s or 45s?


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## risky (May 11, 2015)

I'll try that tomorrow.

From previous notes, no weight on beans full shot resulted in a 12 second shot, compared to 24 seconds for weighted, that was 17g>35g, however the grind setting would have been different.


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## Xpenno (Nov 12, 2012)

risky said:


> I'll try that tomorrow.
> 
> From previous notes, no weight on beans full shot resulted in a 12 second shot, compared to 24 seconds for weighted, that was 17g>35g, however the grind setting would have been different.


Nice one, sorry for being a pain, the EK grinds 20g in about 2 seconds so it's not really an option for me to test


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## risky (May 11, 2015)

Out of interest @dsc have you approached Socratic Coffee about maybe doing an experiment along these lines? I know they are just doing one at the moment about the effect of new vs. old burrs on the grind.


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## dsc (Jun 7, 2013)

risky said:


> Out of interest @dsc have you approached Socratic Coffee about maybe doing an experiment along these lines? I know they are just doing one at the moment about the effect of new vs. old burrs on the grind.


Had no idea they are doing something like this, might give them a shout, although I won't be home for the next week and a half, so wouldn't be able to participate in anything (of course they could try it themselves and report back).

My results are quite different, I've done some testing yesterday but had to add more freezed beans to the last shot as I ran out, so I thought I'd re-do it with the same batch for all three cups. Yesterday I managed to hit the weight distribution better, today I cocked up a bit and got the following:

A: 18.2g in - 37.2g out in 32sec - 9.1%TDS which gives 19.38% extraction

B: 19.0g in - 36.9g out in 34sec - 9.5% TDS which gives 19.22% extraction

C: 16.5g in - 36.8g out in 24sec - 8.0% TDS which gives 18.59% extraction

As you can see extraction rate is fairly good, all shots where sort of in the middle of either Normale or Lungo on the VST software. Taste wise I wasn't impressed with any of them, but I was tasting this when it was all cold, so that might've had an effect. I'm also not sure the burrs I'm using are seasoned all the way, so this might not be perfect.

One thing to mention which I forgot before is to thoroughly mix the 3 x 6g doses before you throw everything in the basket.

T.


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## GlennV (Mar 29, 2013)

That is interesting. I would have expected some change (though not as much as risky observed!). So, I had to try this myself

A: 18->36 37sec

B: 18->36 40sec

C: 18->36.2 26sec

(I seem to be getting the hang of these brewista scales ...)

Without splitting: 18->36.4 26sec (which is the interesting bit)

I ground a slightly more than 18g each time, and reduced each 3x6ish dose to exactly 18g.

This was using a 68mm conical.


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## urbanbumpkin (Jan 30, 2013)

I'm not going to be around for the weekend so probably wont get a chance to try this out till next week.


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## urbanbumpkin (Jan 30, 2013)

GlennV said:


> That is interesting. I would have expected some change (though not as much as risky observed!). So, I had to try this myself
> 
> A: 18->36 37sec
> 
> ...


Did you taste any of these?


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## risky (May 11, 2015)

I tried my middle one, the 18s shot. It was OK, nothing amazing but then I've never had a stellar shot from these beans hence why I'm using them for this experiment.


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## risky (May 11, 2015)

The plot thickens...

17>36.5>14 No weight

17>37.2>17 634.7g stainless steel bar as weight

Makes you wonder if it's worth the effort of using weights...

The issue is likely to be, as has been speculated, the difference in the cup.


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## GlennV (Mar 29, 2013)

urbanbumpkin said:


> Did you taste any of these?


I did, as it happened. The 26s C shot tasted similar to the 26s unsplit shot, although with less mouthfeel (and the 37-40s A&B shots were rather potent). That's not the point though really, the difference in the cup that matters, if any, is that between hopper and single dosing, when properly dialled in. Doing side by side tests, with matched grinders (68mm conical), I find no consistently tastable difference when both are properly dialled in. Others have reported similar findings on home-barista. Yet others have reported that they can taste a difference. I never did a side by side test, but never had much luck single dosing a 75mm flat. As I understand it, @dsc proposed this test in part in an attempt to get to the bottom of this.

It would be nice to get more results in. As things stand the two large conicals tested (mine and dsc's - I'm assuming his is a large conical) seem reasonably consistent between the start middle and end of the single dosed grind (range of 26s>40s, or 24s->34s respectively), whereas the 64mm flat is very inconsistent (range of 8s->72s).


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## dsc (Jun 7, 2013)

Thank you gents for participating, indeed it would be great to have more data, so far it's fairly limited, but it seems that non-weighted flat burr doses are rather on the coarse side of things. Conics seems to be doing well to be honest and I'm positively surprised.

One more thing to try on a conic / flat is re-grinding coarse doses. Go heavy coarse on a full dose, then go rather fine / espresso level. You might notice that you need to go finer than if you were to grind the whole dose at the correct espresso setting. Also make you dose the coarse grinds slowly to not stall the motor as I think it might be loaded more when grinding something else than whole beans (the burrs get more densely packed with coffee).

Regards,

T.


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## GlennV (Mar 29, 2013)

I repeated the experiment with the Anfim Super Caimano (75mm flat). Grinder was set a bit finer than I'd like, but I wasn't going to repeat it.

Without splitting: 18g->30g 36s

A: (made from the 1st thirds) 18g->29.5g 65s

B: (made from the 2nd thirds) 18g->29.8g 63s

C: (made from the last thirds) 18g->31.4g 34s

So, more variation than the conicals, but nothing like as much as risky found with the super jolly. Interestingly again, just as I saw with the big conical, the shot made from the 3 lots of 6g from the last third of the grounds © pulled in a similar time to the normal shot. I didn't dare taste A or B. C was rather thin and underextracted in comparison to the unsplit shot (which was powerful but tasty).


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## Rob1 (Apr 9, 2015)

What's the retention on the conicals? Isn't clearing the grinds 6g at a time impossible due to the way the grinds fall into the chamber across the entire circumference. So let's say retention is hypothetically 18g. The first 6g will be across the bottom of the burr chamber, the next 6g will pile on top of that, and the next 6g will pile on top of that. As the vanes spin around to clear the dispense the grounds they go through a hole in the side of the chamber and get completely mixed up?

I can see how it would work on an HG1 or a Pharos.

On a flat you'll get the same thing but with much less retention (so effect might be insignificant).

If you're purging the conics things don't get any better. The only way I can see to do it is to vacuum the whole chamber out and then grind 6g of a 18g dose, open up the burr chamber and sweep it out manually so you get 6g into a container, then reassemble and grind 6g of a 12g dose, repeat previous procedure and then grind 6g with no additional weight.


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## GlennV (Mar 29, 2013)

Rob1 said:


> What's the retention on the conicals? Isn't clearing the grinds 6g at a time impossible due to the way the grinds fall into the chamber across the entire circumference. So let's say retention is hypothetically 18g. The first 6g will be across the bottom of the burr chamber, the next 6g will pile on top of that, and the next 6g will pile on top of that. As the vanes spin around to clear the dispense the grounds they go through a hole in the side of the chamber and get completely mixed up?


I see what you're getting at but no, that's not how it works. I can't speak for other conicals, but with the MC the grounds do come out in order. I've tested this by alternating between coffee and grindz (and reported the results here previously) and it takes less than 2g to go completely from one to the other, even without brushing out the chute in between (and is significantly less if you do). I've just now stopped the grinder mid grind (just before the last chunks went though to the lower part of the burrs) and opened it up to see what was inside:









That's 1.2g in the chute and 2g in the grind chamber. Of the 2g in the grind chamber, 1g was large chunks that had fallen down when I removed the outer burr (and wouldn't pass though a kitchen sieve). Presumably part of the remaining 1g was also still in the lower part of the burrs when I stopped the grinder. So, there's no more than 1g of grounds in the grind chamber during normal operation. I don't know where numbers like 18g come from - there simply isn't room to hold 18g in there!

Retention is actually much higher in the Anfim, as the chute is larger.

I wasn't going to comment too much on the results, as there are so few of them but, just to put the numbers in context, for the MC I measured 11-14s difference between C and A/B (A 37s, B 40s, C 26s). From experience, to effect such a change in extraction time would takes a grinder adjustment of about 3 numbers on the scale (out of 50 for a whole revolution). It's a 1mm thread, so that would be an approx 60micron change in vertical burr displacement, corresponding to a 30 micron difference in the spacing between the faces of the burrs themselves (as they're conical). A 30 micron change in average grind size is not large. If you look at the particle size distribution graphs floating around then having a 1/3 of the dose 30 micron coarser isn't going to make much of a difference in the grand scheme of things (except to flow rate, it would appear).


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## MWJB (Feb 28, 2012)

GlennV said:


> If you look at the particle size distribution graphs floating around then having a 1/3 of the dose 30 micron coarser isn't going to make much of a difference in the grand scheme of things (except to flow rate, it would appear).


It may not affect the median grind size at all, nor the largest grinds found, but wouldn't it shift the mode & maybe push the distribution further from a normal distribution?

At a fine espresso grind 40 microns might represent half a standard deviation.


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## monkey66 (Aug 8, 2014)

This is interesting but surely starting and stopping the grinder could completely throw the data as this is not how we grind.

I know against protocol but I am tempted to try a similar test with my grinder and usual tamper weight. As I am doserless I am thinking that I will use a long folded piece of paper and move it along as the ground coffee comes out. From this I should be able to chop up thirds in rough chronological order.

Not quite the same test but the last part of my grind does not have any weight as the tamper hits the throat of the doser and stops before all the coffee is ground

I hope this test will be an accurate representation of how I normally grind and therefore indicate of I am loosing out on quality by not having a constant load.


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## GlennV (Mar 29, 2013)

MWJB said:


> It may not affect the median grind size at all, nor the largest grinds found, but wouldn't it shift the mode & maybe push the distribution further from a normal distribution?


Who knows, it was just a ballpark estimate - it's a small number whichever way you look at it.

The point I'm making is that one shouldn't interpret the results as suggesting that the taste will be as if it were a mix of 2/3 from a 40s shot and 1/3 from a 24s shot, it will be far more subtle than that.


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## dsc (Jun 7, 2013)

From what I found 0.03mm in burr distance (vertical) is enough to take or add a few seconds to an extraction using the same dose.

I'm really curious what happens in that 1/3rd of the grind, whether its simply ground coarser, has less fines or more builders / shards?

T.


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## GlennV (Mar 29, 2013)

dsc said:


> From what I found 0.03mm in burr distance (vertical) is enough to take or add a few seconds to an extraction using the same dose.


I was estimating 0.06mm vertically, which is approx 0.03mm between the burr faces (more like 0.025mm actually - the face is a bit less than 25degrees to the vertical and you need to multiply by the sine of this angle of course.)



> I'm really curious what happens in that 1/3rd of the grind, whether its simply ground coarser, has less fines or more builders / shards?


I think it's mainly just that bit coarser. (Not very scientific, but it's relatively straightforward to pick out the largest grinds by rubbing the grounds between your fingers.) It's weird how all the chaff comes though at the end though.


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