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Thread: Conical vs burr grinders - a sceptic no more

  1. #51
    kbc
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    For the k10 fresh it as a very easy fix. Open the bottom and disconnect the fan connection.

  2. #52
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    1 hour video on the topic, haven't watched it all but 53:20 mark she summarises not a big taste difference. The questions at the end were brutal, coffee seems to bring out the schoolyard effect in people as noticed on here lately

    None the less my Kony looks pretty

    https://www.youtube.com/watch?list=U...&v=3XYTi6OBecA
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  3. #53
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    Quote Originally Posted by evro50 View Post
    she summarises not a big taste difference.

    Thanks for the video. Keep in mind the 'comparison' was done with brew coffee, which is a completely different animal from espresso. Regardless, the conclusion seems to suggest my Lido (conical) has grind output fairly similar to an EK43(flat)?
    Good to know.
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    I think it would be a good idea to keep the fan on.

    Hot burrs lead to hotter beans within the grinding chamber. The hotter the beans are during, grinding the more uneven the partial size distribution will be. Conical burrs have a bimodal distribution so will produce a large amount of fines. Even so, a tighter partial size distribution in therory should produce a brighter more balanced shot. Also the beans and CO2 and enzymatic compounds degrade quicker at elevated temperatures once the beans are ground so you may lose flavour and crema.

    More info on this research here:
    The Grinder Paper: Explained - Matt Perger

    And yes some grinders only have fans on the motor and not the grinding chamber, but the axle of the motor is directly connected to one of the burrs to rotate it. So if the motor gets hot, it will transfer heat through the axle to the burrs. This is the theory behind the design of the new Mazzer 'Kold'. More info here: World's First Look At The New Mazzer "Kold" Grinder - Sprudge

    It really depends on how anal you want to be and the amount of consecutive grinds you do though in your quest for the God shot.

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    Isnt that a $250 drill !
    Actually, i have seriously considered buying a decent battery electric screwdriver , just to power a hand grinder when camping !
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  6. #56
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    Quote Originally Posted by K_Bean_Coffee View Post
    It works but I won't make a habit of it.
    Yes- best not. Good way to wreck a perfectly good hand grinder. Hand grinders are hand grinders, not motorised ones.

    We already have sufficient silly stuff for internerd lemmings and Darwin award recipients ...
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  7. #57
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    Quote Originally Posted by Talk_Coffee View Post
    Yes- best not. Good way to wreck a perfectly good hand grinder. Hand grinders are hand grinders, not motorised ones.

    We already have sufficient silly stuff for internerd lemmings and Darwin award recipients ...
    I sometimes scratches me head in amazement.7599a15b62c854d3df334a536756c519.jpg
    Last edited by Yelta; 11th May 2016 at 06:14 PM.

  8. #58
    Senior Member Gavisconi007's Avatar
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    Love the small footprint.

    I'd be a bit concerned about the grind retention though!

    I can picture the review article now......"Ryobi...can it beat the Robur?"

  9. #59
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    Variable speed too!

    Cheers
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  10. #60
    Senior Member Gavisconi007's Avatar
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    Can maybe use the hammer function to remove clumps too?

  11. #61
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    Quote Originally Posted by K_Bean_Coffee View Post
    Great comments. A really good test needs 100 participants. I wish Tomorrow we will work though blind shots then share our findings with the community. One of the biggest claims for conicals is "more complexity" so this is what I'll ask people to focus on. Exciting !
    Yeah if only we had such resources!

  12. #62
    Senior Member Yelta's Avatar
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    Quote Originally Posted by K_Bean_Coffee View Post
    Great comments. A really good test needs 100 participants. I wish Tomorrow we will work though blind shots then share our findings with the community. One of the biggest claims for conicals is "more complexity" so this is what I'll ask people to focus on. Exciting !
    Keen to hear the outcome of your blind tasting session Paul.

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    I'm one of the participants. I can chip in from my own perspective but Paul can probably give more on the whole picture(noticed Paul did already as above).

    Caveats: it's done on a specific roast (too fresh unfortunately). There were some astringency that dominates due to the freshness so that may have masked the difference more than it should.

    There were a total of 7 shots done. 4 from a planar (Profitec T64) and 3 from a conical (Compak K10 Fresh).

    Anyhow, these were my notes:

    Two out of the three conical shots were more fruitier with intense flavor 'bomb'(my own descriptor), and I have guessed them correctly to be conical. One of conical shots seemed overextracted to my palate(with relatively muted high notes), and I guessed that incorrectly to be from a planar grinder.

    One of the planar shot (shot no. 1) was outlier as Paul later admitted the flow was a bit fast. That was the worst shot of the day that everyone agreed. So we were left with 3 valid planar shots, and 3 conical shots to compare.

    Two out of the three planar shots, had what I described as woodiness which I associated with flat burrs. I am not a calibrated taster, so probably some would have described this as chocolatey notes. The last of three planar shots(no. 7) was pretty decent. It has the fruitiness characteristic that was close to conicals (but was slightly less in magnitude than the later identified conical shots, according to my note).

    For me, my favourite (among the 7) was shot number 2 which came from a conical - it was most creamy with a silky body and topped with the pleasant fruity/bright notes. Worth noting some (Paul I think) did have shot number 7 (planar) as their favorite. My top three shots would have been ranked in the order of conical(no. 2) > conical (no.6) > flat (no. 7) out of the 7 shots.

    There're more caveats though. I have had plenty experiences tasting and playing with conicals/flat at home (bragging alert: Grinders I've had at home, but not simultaneously: Super Jolly, Major, HG-1, Compak K10, Robur, Rosco mini, Compak K3,Compak K6, Mythos, Lidos, Pharos, and a few more). So I kinda knew what I expect to taste because I had a rough idea what I would expect if there's a difference. I suspect others would be in handicap to guess which came from which grinder. But if rated based on preference, I think many liked the shot no. 2, no.6 , and no. 7 (relatively because the beans, as mentioned, were too fresh - a snobs's problem: too fresh roast! - and leaves an astringency on palate - you'd have to be able to zero/filter that defect in order to taste correctly - and I like to believe I was able to ).

    Also, the blind tasting were done in an interval of 3-5 minutes. So that'd obscure the difference a lot more as you'd have to depend on your memory to be able to compare. Me and Paul later (after the blind session) pulled two shots side by side from the T64 and K10. We thought the difference was day and night, but wondered why it wasn't so obvious on the blind tasting (It is certainly possible that we're both biased!)

    The shot no.5(from planar) was a bit weird. My note stated that it has a weak body and nothing else noteworthy. But some liked that. This kinda shows that preference plays a role, and perception might differ even for the same cup/shot.


    My own conclusion:
    i) Conical doesn't guarantee a god shot (as evident in shot no 3)
    ii) Planar shot can taste good - shot no 7
    iii) everyone has slightly different preferences and different tasting threshold(which can probably be trained through experience), but most agree how a good/bad shot should taste like.
    iv) there's a potential difference between planar and conical (big call I know from a limited 7 blind shots, and a few other non-blind shots. But this is consistent with my past experiences.). When conical shot is done correctly/optimally, you get the silky fruitness that is way more elusive on the planar (doesn't mean it doesn't exist - I just don't know if it can do that -like how you can't prove negative).
    v) Both planar and conical can make good shots with correct technique (nothing new).
    vi) One last interesting observation, when we're blinded, we are much less confident with what we are able to taste (but luckily, the results showed that our palates are all working fine if you account for individual preferences ) .
    Last edited by samuellaw178; 16th May 2016 at 11:47 AM.
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  14. #64
    Senior Member Yelta's Avatar
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    Interesting observations, certainly nothing that will see me rush out and trade the Mazzer in on a conical.
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    one interesting thing is the size and cost - anyone know of any smaller and cheaper conicals? There are heaps of great flatt burr grinders in the $1-$1.5k range but I'm not aware of any conicals.

    I do have a lido-e which is fantastic but for normal use prefer some power...
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  16. #66
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    Quote Originally Posted by Coffman View Post
    one interesting thing is the size and cost - anyone know of any smaller and cheaper conicals? There are heaps of great flatt burr grinders in the $1-$1.5k range but I'm not aware of any conicals.

    I do have a lido-e which is fantastic but for normal use prefer some power...
    Used Kony Es, and manual Roburs fall within this price range. Plus K10 WBC sub $1000 used. Any of these are top end conical grinders.

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    Quote Originally Posted by Yelta View Post
    Interesting observations, certainly nothing that will see me rush out and trade the Mazzer in on a conical.
    Yep, once you are into semi commercial - commercial gear, by far the biggest changes in flavour outcomes come from the quality of the green coffee, how it was processed and the quality of the roast. Then comes good technique in extracting the best from it with whatever equipment you have at hand.

  18. #68
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    Quote Originally Posted by Steve82 View Post
    Yep, once you are into semi commercial - commercial gear, by far the biggest changes in flavour outcomes come from the quality of the green coffee, how it was processed and the quality of the roast. Then comes good technique in extracting the best from it with whatever equipment you have at hand.
    Ahhhh, how refreshing! common sense and logic, rare commodities in this day and age.
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    Quote Originally Posted by Yelta View Post
    Interesting observations, certainly nothing that will see me rush out and trade the Mazzer in on a conical.
    Of course! Not everyone wants to go deep into the rabbit hole, and you have plenty of variables to play with as is (even with a planar). The objective of the test is not meant to push everyone to buy a conical -no way me, Paul, or others would recommend that. It does seem to show that there're some inherent (and subtle) differences between the two (at least the propensity to pull shots with different characterstic). Whether you care enough for the subtle difference, that's individual's call. And as mentioned, you certainly could play with the grind and dose to optimize. That'd keep you busy for a long long time


    Also, very important, when I mention conicals, it refers to the bigger version (68mm+) as used in Robur, Kony, HG-one etc. Have no tiniest clue about Kony but it's probably in the bigger category based on what others are saying. The smaller ones (like Lido, and Rosco Mini) are not quite the same as the bigger one for some reason - I wish they are (then I wouldn't have to house big beasts in my home)!
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  20. #70
    Senior Member Gavisconi007's Avatar
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    Quote Originally Posted by K_Bean_Coffee View Post
    Hi guys,

    Of the 6 shots the 3 favourites (agreed by most) were 2 from the conical and 1 from the planar.

    One snob (Sam) who knows conicals and planars well could pick the difference between the conical and planar shots. He got 5/6 correct.

    It was generally agreed that the concial shots were brighter
    Pretty much as expected. I won't be changing back to a planar any time soon!
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  21. #71
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    Also, very important point here as it's easy to be taken out of context. The above discussion/comparison is on espresso only! Don't read into that if that's not what you normally drink. Just saying it before anyone goes and makes brew coffee and complains there's no difference (duh), or spent big bucks and has noticed no differences.

  22. #72
    Super Moderator Javaphile's Avatar
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    Of course there's always the possibility that some of the testers may have been able to tell the difference between the two grinders based on their sound. Making the blind, not so blind.


    Java "Devil's what?" phile
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    Toys! I must have new toys!!!

  23. #73
    Life-long Learner DesigningByCoffee's Avatar
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    Quote Originally Posted by K_Bean_Coffee View Post
    I'll do another day of testing by myself with at least 10 shots back to back next weekend.
    Doing that blind would be fun to watch!
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  24. #74
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    Certainly a possibility. But at least for me, I focused on how the shot tastes and we were chatting among ourselves while waiting. If I had to do it, I may be able to make out/learn how the two grinders sound after 3-4 shots (but I didn't put an effort to make out the sound and had no clue which shot came from which during tasting). All I did was to take notes of how the flavors pan out based on a few criteria that stands out (acidity, body, perception). The guessing (of which grinder) only came after all 7 shots were done tasted and the notes were all already on paper (I couldn't have changed my notes by then). Because after 7 shots, I noticed there were some difference in the notes, and there are some that fared 'subjectively' as better. Then I said to myself, what the heck, let's judge the better shot (with fruitier and non-woody profile) as conical, and average shots (less interesting) as flat. Paul then revealed what was which grinder. I expect to get my guess all over the place. Using that guessing criteria, I certainly misjudged the muted shot as flat.

    I wouldn't claim the test we did as absolute and there're definitely space for improvement (protocols). But we did what we can, and shared what Id observed. Obviously, you can take it or leave it.

    If you think about it this way:

    What the test tell us:
    i) Is there a differece in the shots? All else equal, yes. Subtle? Definitely. Noticeable? Yes to some, maybe not to others.
    ii) Can you make good shots with either? Yes.
    iii) Does preference make a difference? Hell yes.
    iv) Do you need a conical to make good shots? Definitely not.

  25. #75
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    Hi all,
    Is there much difference in noise from the conicals (Macap M7D and Compac K10) to my Macap M4D?

    I like an early morning coffee however my teenager (room directly over kitchen) isnt as keen...

    I will upgrade sometime soonish - and toying with the idea of a conical

    Thank you for advice
    Dave

  26. #76
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    They do vary,

    Macap M7/Compak K10/ Compak E10/ Compak F10/Mazzer Robur all about the same...

    Mazzer Kony-E (smoother/quieter) as are Compak E&F Master series....

    You will find the latter similar but smoother when compared to your M4D. I'd call all of the others noisier.

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    Thanks very much Paul and Chris,
    Food for thought
    Cheers
    Dave

  28. #78
    Senior Member Gavisconi007's Avatar
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    Guys is noise really such a big concern? Any Titan conical worth it's salt will grind a double in two to five seconds-hardly a big noise issue. Just saying

  29. #79
    Senior Member magnafunk's Avatar
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    Quote Originally Posted by K_Bean_Coffee View Post
    Conicals are pricey $$$
    Not if you visit the for sale section

    (I hope a bit of blatant self promotion is ok, I gotta move one of these grinders!)
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  30. #80
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    I'd agree 100% Paul. They certainly are different. Not better, just different!

    Under milk, it's harder to detect a difference and milk drinkers should be mindful of this when selecting a grinder.

  31. #81
    Life-long Learner DesigningByCoffee's Avatar
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    Quote Originally Posted by K_Bean_Coffee View Post
    Conical - brighter, more complex, more acidic, more fruit.
    Planar - more base/choc and caramel. Less acidity, less fruit.
    Which is best? There's no answer to that. It depends on the flavours you want in your espresso. Also, your budget.
    Hit the nail on the head

    These were my findings too.
    FWIW, I sometimes miss the extra chocolatey bite & edge that the planar M4 gave through milk. Every now and again I get a brew from my M4 (that I sold to a mate) or an identical one my brother bought at the same time. I'm always surprised by the richness and aroma that cuts through. But as an avid espresso drinker now - I like the conicals for my doppio's.
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  32. #82
    Senior Member gonzob's Avatar
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    Please excuse my ignorance here, but how does a conical produce a different taste to a planar? I thought the idea with grinding was to create small regular-sized particles. Better grinders are able to keep the clearances between the burrs to finer tolerances, or have differently shaped blades and grooves resulting in more repeatably-sized particles. But what happens with conicals?

    Is it that conicals produce differently-shaped particles (visualise "flakes" rather than "pebbles" here..)? That might mean a greater surface-area-to-volume ratio, thus getting better extraction, but why the change in taste?

    Now some of you may be saying that because I bought a Mazzer Mini (planar) just before this topic started I'm now a bit put out. No, nothing like that. No. Not at all. No

    Gonzo
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  33. #83
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    Don't think it is so much a change in taste, but rather a broadening out of the existing flavour profile.
    That's how I see it anyway and maybe it is down to the cuttings being more flake shaped than granular, I don't know really but the difference is very real and noticeable.

    Won't be swapping my Kony-E for quids...

    Mal.

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    Quote Originally Posted by Coffman View Post
    one interesting thing is the size and cost - anyone know of any smaller and cheaper conicals? There are heaps of great flatt burr grinders in the $1-$1.5k range but I'm not aware of any conicals.

    I do have a lido-e which is fantastic but for normal use prefer some power...
    casadio istantaneo is the only I can think of.

  35. #85
    Senior Member Gavisconi007's Avatar
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    A used Titan conical would be much better value IMHO, unless the OP has a particular aversion to buying brand new and losing significant $$$ the minute he turns it on. Good commercial conicals are built like tanks so a used option is unlikely to result in disappointment- obviously avoid heavily used grinders which are fairly obvious- hundreds of portafilter chips at the base is a give-away sign.

  36. #86
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    Yes and no. When a 5YO Macap M4D can bring $800, I reckon it has retained value pretty well.

    As always, brand choice will influence retained value. A big, doser, ex-cafe conical might be cheap to purchase, but difficult or impossible to sell. As always, there are cons to consider with pros.
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  37. #87
    Senior Member Gavisconi007's Avatar
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    For someone looking to get into conicals (ie. a wise person), a good condition used grinder is still a very viable option compared to dropping a few thousand on a brand new shiny model that will give an identical result in the cup. IMHO anyway.

  38. #88
    Senior Member Yelta's Avatar
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    Quote Originally Posted by Gavisconi007 View Post
    For someone looking to get into conicals (ie. a wise person),
    Hmmm, so the implication is that if you don't aspire to a conical your a dumb ass, not so!

    Bear in mind that wisdom and intelligence are two entirely different things, I constantly see people of seemingly high intelligence offering poor advice on all manner of subjects on this and other forums.

    You seem obsessed with conical's and beat the conical drum whenever the opportunity arises, the rest of us who are able to look at and assess things a little more objectively, are quite capable of making our own decisions regarding the equipment we choose and don't need to be told we lack wisdom for not following in your foot steps.

    You've made your point, perhaps time to give it a rest, it's getting a little tedious.

    To each his own.
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  39. #89
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    Quote Originally Posted by Yelta View Post

    You seem obsessed with conical's and beat the conical drum whenever the opportunity arises, the rest of us who are able to look at and assess things a little more objectively, are quite capable of making our own decisions regarding the equipment we choose and don't need to be told we lack wisdom for not following in your foot steps.

    i think someone needs to develop a sense of humour and calm down a tad.......,
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  40. #90
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    Quote Originally Posted by gavisconi007 View Post
    i think someone needs to develop a sense of humour and calm down a tad.......,
    ommmmmmmmmmmOMM.jpg
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  41. #91
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    We measure extraction regularly. Large conicals tend to be a problem outside of high volume cafes. We get great extraction numbers from large planars with sharp burrs combined with VST baskets and a properly sized tamper. Having said that I have a soft spot for the Mazzer Kony.

  42. #92
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    Quote Originally Posted by Blue_House View Post
    We measure extraction regularly. Large conicals tend to be a problem outside of high volume cafes. We get great extraction numbers from large planars with sharp burrs combined with VST baskets and a properly sized tamper. Having said that I have a soft spot for the Mazzer Kony.

    Blue_House can you please elaborate on said extraction problem outside of high volume cafe. I measure extraction from my conical grinder every day- I look in my cup and say damn what a superb extraction. I also regularly weigh the grind and the yield. No problems whatsoever so please elaborate.

  43. #93
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    "Blue_House can you please elaborate on said extraction problem outside of high volume cafe. I measure extraction from my conical grinder every day- I look in my cup and say damn what a superb extraction. I also regularly weigh the grind and the yield. No problems whatsoever so please elaborate."

    When we enter barista competitions we "season" Mazzers Roburs with about 30kg and they seem to "peak" soon after that. I'm sure that that would be problematic in a domestic situation. We seem to get great consistency from our Mazzer Majors. Playing with a Malkonig E30 Peak at present, could well be one of my favourite bean cutters to date.

  44. #94
    Senior Member Gavisconi007's Avatar
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    Quote Originally Posted by Blue_House View Post
    "Blue_House can you please elaborate on said extraction problem outside of high volume cafe. I measure extraction from my conical grinder every day- I look in my cup and say damn what a superb extraction. I also regularly weigh the grind and the yield. No problems whatsoever so please elaborate."

    When we enter barista competitions we "season" Mazzers Roburs with about 30kg and they seem to "peak" soon after that. I'm sure that that would be problematic in a domestic situation. We seem to get great consistency from our Mazzer Majors. Playing with a Malkonig E30 Peak at present, could well be one of my favourite bean cutters to date.

    Ok- your observations may be based only on the Robur, and I agree, they aren't the best for domestic use, especially when changing bean types regularly like so many of us do. However not all conicals have the same issue as the Robur in this regard. Even the problem with the Robur can be overcome by single dosing if one so desires. I personally don't single dose and there are plenty of conicals that are used successfully in domestic situations without significant wastage.

  45. #95
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    Quote Originally Posted by Gavisconi007 View Post
    Ok- your observations may be based only on the Robur, and I agree, they aren't the best for domestic use, especially when changing bean types regularly like so many of us do. However not all conicals have the same issue as the Robur in this regard. Even the problem with the Robur can be overcome by single dosing if one so desires. I personally don't single dose and there are plenty of conicals that are used successfully in domestic situations without significant wastage.
    Agreed, I use a Kony at home with my Strega it's a fabulous combination.
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  46. #96
    Senior Member gonzob's Avatar
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    This is all very interesting. However, no-one has answered my question about WHY coffee from a conical tastes different. There must be a mechanical reason. Maybe something like "they grind slower so it's cooler and the flavour volatiles don't flash off before extraction"

    Where are our experts?

    Gonzo

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    The grind particles distribution are very different. ie. Grinding doesn't yield mono-sized grind particles, but a range of particles of different sizes. These distribution of grind sizes are different among different grinders.
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  48. #98
    Life-long Learner DesigningByCoffee's Avatar
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    Quote Originally Posted by Gavisconi007 View Post
    Ok- your observations may be based only on the Robur, and I agree, they aren't the best for domestic use, especially when changing bean types regularly like so many of us do. However not all conicals have the same issue as the Robur in this regard. Even the problem with the Robur can be overcome by single dosing if one so desires. I personally don't single dose and there are plenty of conicals that are used successfully in domestic situations without significant wastage.
    I've actually just been playing with single dosing the Robur. Used to do that for the M4, but never really tried with this one - thought it was impossible! It's certainly not as simple as the smaller grinder, but I'm getting there. Here is my technique:

    • Weigh beans into the micro hopper
    • Grind manually until all the beans are ground.
    • Use the tamp which seals the micro-hopper to act like a plunger to 'pump' through all grinds out of the grind path while the grinder is running (I think the burrs create their own airflow too) - works a treat!
    • DDT blah blah blah…

    One interesting note though - this technique requires serious grind adjustment. When fully hoppered and grinding for events etc, I normally have the grind set around 7-7.5. To get a decent pour single dosing style using the above method, I've had to go to around 4-4.5 - which is a massive swing for those who know the grinder. I guess this is related to the compression effect of a full hopper which is negated when only using 20g beans, which basically just drop into the burrset!

    Flavourwise? Pretty consistent so far with the Lido and the full hoppered Robur - although I haven't had enough of a go yet to confirm this. Might have been a hint of bitterness in the latest brew, which I'm not used to with the Robur. I suspect there might be some additional grind inconsistency with this method - but will need to get it dialled in for espresso that I'm happy with, then compare with the Lido to check.

    Will report back!

  49. #99
    Senior Member skidquinn's Avatar
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    Quote Originally Posted by gonzob View Post
    This is all very interesting. However, no-one has answered my question about WHY coffee from a conical tastes different. There must be a mechanical reason. Maybe something like "they grind slower so it's cooler and the flavour volatiles don't flash off before extraction"

    Where are our experts?

    Gonzo
    Hey Gonzo
    Far from an expert but have had both large conical and flat burr on my bench for about 6 months now.
    I can see with the naked eye the difference between the grinds on the flat burr and conical. The conical has larger bits or chunks amongst the fine grinds - certainly a lot more inconsistent looking anyway. Compared to the flat burr that look 100% consistent.
    This, to me, has to be the reason for the differing flavours.
    Cheers

  50. #100
    Senior Member Yelta's Avatar
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    For them that are inclined this may or may not throw some light on the subject of grinders and the grinding process, bit of a marathon read, here's a link to the whole blog if your interested in the graphs and illustrations.
    The Grinder Paper: Explained - Matt Perger

    The Grinder Paper: Explained

    by Matthew Perger | Apr 24, 2016 | All Hustles, Fresh Hustles | 66 Comments
    The act of grinding coffee is full of mystery and myth. A group of likeminded people recently embarked on a project to shed some light on coffee grinding, and found some interesting results. So interesting, that we decided to turn it all into a paper; subjecting our methods to peer review and the rigorous process of publication. Last week, this paper was published in a Nature sub-journal -Scientific Reports- as open access. This means anyone can read and benefit from the results. Yay for science!
    Scientific papers like this must be written in a certain way that can be hard to digest. I’d like to spend some time tearing apart the paper; describing what we did, and what I think it means. Feel free to follow along with the actual paper here. The effect of bean origin and temperature on grinding roasted coffee : Scientific Reports
    I’m going to include my personal and sometimes debatable opinions/remarks in bold like this so you don’t fall asleep.
    The effect of bean origin and temperature on grinding roasted coffee.
    Introduction
    This is a super basic rundown of what’s up with coffee and this experiment. Not everyone peer reviewing this knows as much about coffee as most of you do, so we thought it relevant to include some pertinent details:

    • There are two main considerations with green coffee; variety and processing.
    • Roasting plays a large role in how coffee tastes.
    • Most compounds in roasted coffee are products of Maillard reactions, but there’s a lot going on.
    • We used four different coffees for the experiment:


    And finally, that this experiment is primarily interested in how bean origin, processing method, roast level and temperature can affect the results of grinding.
    Method
    Coffee is extremely complex. It’s nearly impossible to create a computer model of how it fractures during grinding, so we have to do it experimentally.
    We did two main things for the experiment:

    1. We ground coffee of different origins/roasts/processes at the same setting and measured the resulting grind samples.
    2. We changed the temperature of one coffee to four distinct levels, ground a sample while it was still at each temperature, and measured the resulting grind samples.

    To measure the grinds we used…
    Laser diffraction particle size analysis
    We assumed that the most important metric for measuring ground coffee is the particle distribution. That is, a measurement of the size (diameter) of every single coffee grind in a sample. Yes, flavour is important, but it’s much much more difficult to measure flavour with any accuracy and precision.
    Measuring particle distribution of coffee is performed with a laser diffraction particle analyser (LSA). Essentially, it sucks coffee grinds down a tube, shines a light across their path and measures the “shadows” that each individual grind casts onto a detector. It’s actually much much more complex than that, but this description will suffice. My brain hurt trying to delve further. They’re incredibly precise, sensitive machines and need to be calibrated often. Here’s a simple diagram showing the usual setup inside an LSA.

    Particle Analytical ApS

    Grinding
    We used an EK43 for the study, because it holds a negligible amount of grinds in the chute after the burrs. This study relied on coffee beans being ground at specific temperatures, and not suffering from any cross-contamination. We couldn’t allow the beans to lose any energy to a hopper, grinder throat, or burrs for any appreciable amount of time before they were ground.
    There were 3 EK43’s present during the experiment. One was found to be producing the most delicious coffee, and was used for the samples. It had Turkish burrs installed. EK43’s have quite a large potential for burr misalignment, so this grinder was likely the least misaligned.
    We kept the grind setting precisely the same for every sample. 2.7 on the dial if you must know. We also let the grinder cool down to room temperature between every sample to rule out frictional/electrical heat as a variable.
    Temperature-specific samples were kept in paper cups within different environments. Room temperature (20C), freezer (-19C), dry ice (-79C), and liquid nitrogen (-196C). They were ground within one second of retrieval and showed no water condensation.
    We took 3 samples for each data set, and performed each of those twice. So, 6 data sets per temperature/coffee. The results of these data sets were also passed through an analysis of variance (ANOVA) to make sure they were similar enough to be considered accurate.
    Do Differences in the Green Bean Affect the Final Grind?
    Here’s where things get tricky to understand. You might be familiar with this kind of graph to communicate particle size distributions:

    Along the x-axis (horizontal) is the size of the grinds in microns. 1 micron equals 1/1000th of a millimeter. This axis is on a logarithmic scale, which places 1 & 10 as far apart as 100 & 1000. This is because a sample of coffee grinds covers a huge 3 orders of magnitude (0 to ~1000 microns) and we need to fit it all in without losing too much resolution at the smaller sizes.
    The y-axis (vertical) is the volume% of the grinds. This one’s easy: the higher the peak, the more of that size particle there are.
    Eg. trace vertically above 400um to the brown line. That particle size makes up 8.5% of the sample by volume (not weight!).
    We took this style of data presentation a few steps further for this particular experiment.

    Firstly, let’s look at a count of the particles. Instead of showing volume, we simply graph how many of each size particle there are (blue). The first thing that’s rather obvious; there’s an INCREDIBLE number of tiny grinds in each sample. 99% of the particles are below 70 microns (0.07mm) in diameter. This means that for every single grind with a diameter above 100 microns, there’s one hundred million with a diameter below 100 microns. That’s an excellent piece of trivia with which to sound smart at dinner parties.
    When analysing coffee grinds, a very important factor is their surface area. The more surface area they have, the faster and more easily water can extract its flavours. To turn the data above into something resembling surface area, we firstly assume that every particle is a sphere (this is fairly common practice, and for gnarly, uneven coffee it’s a “conservative estimate”). Then, we take the size of every particle and calculate what the surface area would be if it were a sphere.
    This gives us some really cool data!
    The solid lines below are the ‘counts’. The same as the blue line above
    The dotted lines below are the ‘relative surface area contribution’. That is to say, the proportion of the total surface area that is provided by each particle size. Once again, something is quite obvious. The smaller grinds contribute the overwhelming majority of the total surface area. ~70% to put a number on it.

    This graph also shows the particle distributions of the various coffees used in the experiment. Straight away, you will notice that they’re all incredibly similar. The Tanzanian, Ethiopian, El Salvadorian and Guatemalan profiles are shown in black, purple, red and blue, respectively.
    Turns out that origin/processing/roast has much less of an effect on PSD than I had ever previously thought. This is arguably a good thing: we have less variables to worry about!
    The next thing to wrap your thoughts around is that fines contribute 70% of the total surface area. Yes, water moves inside the grinds to extract solubles, but it takes exponentially longer for the water to get inside, do the work, and move back out into the brew. Fines are our friends!
    Do Differences in the Roasted Bean Grind Temperature Affect the Final Grind?
    This is where things get really interesting.
    Coffee is amorphous – it’s made up of thousands of different molecules jammed together within an irregular plant structure.
    The diamond in an engagement ring is crystalline – it’s a perfectly repetitious pattern of carbon atoms.

    When you change the temperature of amorphous things, they sometimes undergo a ‘glass transition’. That is, they change from a soft and rubbery material to a hard and glassy one very quickly. Some materials also undergo a shattering transition, where they tend to break into more and smaller particles. This is all pretty key when discussing how coffee breaks apart in a grinder.

    We found a very pronounced difference in the particle size distribution of one coffee ground at different temperatures. Firstly, make yourself familiar with each colour and the temperature it represents. You’ll notice that the mode (peak) of the PSD gets smaller as the temperature dips (31% drop over the 4 samples). As the coffee gets cooler it also becomes more brittle, throwing off many more tiny particles in the grinder. It also fails to escape the burrs at the larger sizes of the warmer samples (ie. shatters more easily).
    The largest difference is between 20C and -19C. The coffee likely undergoes some kind of shattering/glass transition between these two.
    We also confirmed that this transition is reversible, so you don’t need to worry about a coffee getting too hot and not being able to go back to tasty town.

    The mode is the most-occurring particle, easily identified as the highest “peak” of each line. This gets larger as the temperature increases.
    Skewness is merely a numerical representation of asymmetry in a data set. The colder samples were less skewed because they contained more small particles and fewer large ones, reducing area under the line to the right of the peak.
    Mean is the average. You’ll see the freezer has a higher mean than the room temperature sample. This is because the room temperature sample had many more particles in the 3-5um range, but far fewer in the 8-30um range.
    This transition temperature will likely be a very important discovery for all future grinding technology.
    Concluding Remarks and Thoughts
    Origin and Processing
    Anyone who blends coffee will be happy to note that the surface area of different coffees is pretty much the same at a fixed grind size. This means that the major consideration for blending is to ensure that each blend component is equally soluble. In other words, that they all reach the same level of extraction within the same brewing time. Roasters, dust off your refractometers.
    Temperature
    Remember all those mornings when you dialled in a coffee perfectly, only to have it thrown out the window after you made ~20 coffees? The culprit isn’t the grinder expanding from the heat; it’s the beans soaking up the heat from inside the grinder before they’re ground. That heat energy makes them less brittle, creating a coarser grind even though you didn’t change the grind setting.
    Here’s some more questions with pretty much the same culprit. Ever wonder why…

    • coffee doesn’t taste as good on a hot day?
    • your grinder can seem so inconsistent in quiet periods?
    • the shots run faster during a rush?
    • this all doesn’t happen with an EK43?
    • After grinding finer to achieve the same shot time, that the shots don’t taste the same as they did in the early morning?

    The culprit for all of these is: the beans heating up inside the grinder and grinding differently.
    The less time the beans spend in the grinder, the less they’ll be affected by its heat. It’s extremely difficult and costly to create a grinder throat that evenly heats or cools the beans before grinding. With that, I strongly believe that the only way forward is to use grinders that don’t contain any coffee between doses.
    I’ve never really been a fan of the results with the Mythos grinder’s heating feature, and this experiment is an excellent explanation as to why. Heating the beans to achieve consistency pushes the beans above the shatter transition temperature and significantly reduces the total surface area (read: less and less-even extraction).
    More cold = finer particles = more surface area = higher extraction. Lower temperatures could also mean less evaporation/sublimation of aromatic compounds (aroma loss).
    Keep your pre-weighed doses in the freezer for higher, tastier extractions (though make sure they’re sealed without too much moisture or any oxygen).
    Fines
    Wow. Back in 2012 I won the World Brewers Cup with a routine centred around removing fines. As it turns out, sifting doesn’t really get rid of all the small particles. There’s still millions of them stuck to the larger grinds. When coffee is torn apart in the grinder it leaves pockets of positive and negative charges all over the grinds that attract the fines. Conclusion: sifting is pretty useless for particle segregation and testing.
    Now that we know just how much of the brew is made up of fines extractions, it becomes increasingly obvious that fines aren’t the villain; otherwise every coffee ever made would be horribly over-extracted. Here’s how to think about it: The upper limit of tasty extraction is decided by the most-extracted particle. This is always the smallest particle. So it’s up to you to make sure no portion of the grinds ever get over-extracted.
    It’s also up to you to reduce the amount of coffee that’s under-extracted (ie. the inside layers of the largest grounds). The simplest way to do this is -as I’ve always said- to use a grinder that produces an even particle distribution. Nothing new here.
    Once I figure out how to brew fines properly I’ll be back at the WBrC with an apology routine!
    Last edited by Yelta; 19th May 2016 at 01:57 PM.

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