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Thread: Grinder comparison vid on retention

  1. #1
    Senior Member simonsk8r's Avatar
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    Grinder comparison vid on retention

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    Fairly new vid has come out comparing 8 different grinders and how many grounds they retain, very informative . And I thought the Atom retained more but they got 2 grams.

    https://youtu.be/3_eWwZbEhrI

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    Hi Simon, I absolutely agree with you; the Atom is a good grinder but way more than 2 gms retention. John

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    Are they talking - Grind Chamber retention?
    And / Or - Grind to Grind Variation (retention) ?
    Two different and very real issues.

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    I think they are comparing the total retention in the burr/grind chamber when single dosing. So the measurements do not apply if we are using a hopper, as the grind retention will be much more than what they measured.

    When single dosing, the coffee ground in the burr chamber will be emptied out by the sweepers by running the motor for extended period (the video measured this amount of residual coffee that was not removed by the sweepers). If the grinder has a hopperful of coffee on top, this burr chamber will filled with ground coffee at all times. Trying to turn the sweepers (aka grinding) will continue to fill the burr chamber with more ground...until the hopper is empty...
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    Quote Originally Posted by EspressoAdventurer View Post
    Are they talking - Grind Chamber retention?
    And / Or - Grind to Grind Variation (retention) ?
    Two different and very real issues.
    The two main issues avoided are
    1) The majority of grinders need the weight of the beans in the hopper to give a consistent particle spread. Almost every grinder I know has worse particle spread when "single dosing". His term, I prefer "dosing with exact weight of beans" - single dosing to me is when I use a single basket...
    2) As EspressoAdventurer noted, they are talking about grind to grind variation then measuring the chamber retention - that makes no sense.

    Take my Mahlkonig Varios with the standard ceramic burrs as an example. It has little burr clearance and a very short grind chute so overall retention is quite low (around 0.1 to 0.5g according to Mark Prince in his "gen1 review"). It has a digital timer, dosing is accurate to within 0.1g - i.e. the limit of my scales.

    Any grind retention mainly builds up (very) slowly in the chamber. Assuming you keep a reasonable amount of beans in the hopper the particle spread will be highly consistent (and very narrow) until the chamber is full. That takes a total throughput of about 750g of most of the light / medium SO beans I use. Then the note of the grinder changes and the particle spread and dosing (according to the same timer settings) both go to hell.

    Purging the Vario before each shot does nothing constructive even after two weeks away - I did a blind taste comparison with 4 coffee fiend friends - no difference at all detected between all four shots. The reason seems to be due to the avoidance of all four of the "ground coffee enemies". Heat and moisture are literally zero. I keep the whole unit covered (mainly to cover the beans in the hopper) when the grinder is not in use, so light is also near zero. Airflow - the covered unit would have minimal airflow, and the chute would have minimal airflow into the chamber as there is very little air circulation into the chute. What little airflow there is would only reach as far as the chamber anyway and would not get as far up as the burrs. Not a theoretical zero, however it is practically irrelevant. Presumably the grounds in the chamber would have been totally stale by then.

    Result: no need to purge, just clean the chamber out every 750g or so of coffee. I "lose" about 10 to 15g worth of grounds every 750g (never bothered to measure it, way less than a double basket worth), so I guess that is the actual chamber retention over time.

    Add no clumping, static, mess and very little noise and the Vario is the easiest grinder I have lived with - and that is well over 50 grinders since 1970.

    Another well meaning video with no scientific value...

    TampIt
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  6. #6
    Senior Member simonsk8r's Avatar
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    Ah right fair enough, I thought it was interesting anyways. Still displayed a bit of useful data on retention, albeit with single dosing.

    Quote Originally Posted by samuellaw178 View Post
    I think they are comparing the total retention in the burr/grind chamber when single dosing. So the measurements do not apply if we are using a hopper, as the grind retention will be much more than what they measured.

    When single dosing, the coffee ground in the burr chamber will be emptied out by the sweepers by running the motor for extended period (the video measured this amount of residual coffee that was not removed by the sweepers). If the grinder has a hopperful of coffee on top, this burr chamber will filled with ground coffee at all times. Trying to turn the sweepers (aka grinding) will continue to fill the burr chamber with more ground...until the hopper is empty...
    Ah yep you make a fair point, it would be more with full-hopper dosing.

  7. #7
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    Quote Originally Posted by TampIt View Post
    The two main issues avoided are
    1) The majority of grinders need the weight of the beans in the hopper to give a consistent particle spread. Almost every grinder I know has worse particle spread when "single dosing". His term, I prefer "dosing with exact weight of beans" - single dosing to me is when I use a single basket...
    2) As EspressoAdventurer noted, they are talking about grind to grind variation then measuring the chamber retention - that makes no sense.

    Take my Mahlkonig Varios with the standard ceramic burrs as an example. It has little burr clearance and a very short grind chute so overall retention is quite low (around 0.1 to 0.5g according to Mark Prince in his "gen1 review"). It has a digital timer, dosing is accurate to within 0.1g - i.e. the limit of my scales.

    Any grind retention mainly builds up (very) slowly in the chamber. Assuming you keep a reasonable amount of beans in the hopper the particle spread will be highly consistent (and very narrow) until the chamber is full. That takes a total throughput of about 750g of most of the light / medium SO beans I use. Then the note of the grinder changes and the particle spread and dosing (according to the same timer settings) both go to hell.

    Purging the Vario before each shot does nothing constructive even after two weeks away - I did a blind taste comparison with 4 coffee fiend friends - no difference at all detected between all four shots. The reason seems to be due to the avoidance of all four of the "ground coffee enemies". Heat and moisture are literally zero. I keep the whole unit covered (mainly to cover the beans in the hopper) when the grinder is not in use, so light is also near zero. Airflow - the covered unit would have minimal airflow, and the chute would have minimal airflow into the chamber as there is very little air circulation into the chute. What little airflow there is would only reach as far as the chamber anyway and would not get as far up as the burrs. Not a theoretical zero, however it is practically irrelevant. Presumably the grounds in the chamber would have been totally stale by then.

    Result: no need to purge, just clean the chamber out every 750g or so of coffee. I "lose" about 10 to 15g worth of grounds every 750g (never bothered to measure it, way less than a double basket worth), so I guess that is the actual chamber retention over time.

    Add no clumping, static, mess and very little noise and the Vario is the easiest grinder I have lived with - and that is well over 50 grinders since 1970.

    Another well meaning video with no scientific value...

    TampIt
    Cool.

    So you don't think retention is an issue at all, or just your grinder doesn't retain much therefore is not an issue for you? I've found shot to shot retention to play a big factor (as in if there's 30 minutes between shots)

    And yeah I don't single dose, so the vid would be of a little limited use for me. Just interesting the output and how much was retained still.

    Ah actually I think I see what you mean.. so do you mean the grounds that gets retained slowly that basically stay in the grinder (and don't move/come out of the chute), hence why it's not a great test? Makes sense as that just stays stuck in there and is not useful to even weigh that...

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    Quote Originally Posted by simonsk8r View Post
    Cool.

    So you don't think retention is an issue at all, or just your grinder doesn't retain much therefore is not an issue for you? I've found shot to shot retention to play a big factor (as in if there's 30 minutes between shots)

    And yeah I don't single dose, so the vid would be of a little limited use for me. Just interesting the output and how much was retained still.

    Ah actually I think I see what you mean.. so do you mean the grounds that gets retained slowly that basically stay in the grinder (and don't move/come out of the chute), hence why it's not a great test? Makes sense as that just stays stuck in there and is not useful to even weigh that...
    G'day simonsk8r

    Actually I know grind retention is critical for a home user. Coffee grounds actually start to oxidise in under 5 minutes (probably starting at the 30 second mark) if there is enough oxygen available.

    I have had numerous stale coffees (to the point that most friends know I always "am polite and have the last cuppa"!) when people do not bother to purge a grinder that needs it. That is particularly true of anything with a doser for "non cafe use". Stale is then 100% guaranteed unless it has just been used and cleaned out properly. That is one reason I removed the doser from my Major for home use (it is still one of my favourite cafe grinders) - it dropped the retention down to about a single 7g shot - which unfortunately gets pushed out the next time you fire the Major up. For home use that is still way too much retention unless you are doing a fairly large number of coffees "on the trot".

    The Vario's retention is literally a few grounds in the chute (maybe a dozen on a bad day, usually well under five unless it is humid) plus a very small amount in the chamber. None of those grounds tend to migrate much.

    You are correct - the chamber just slowly fills (in layers I guess) so very little of the stale stuff (if any) ever leaves the chamber until you remove the upper burr and clean said chamber out. Weighing that would only be useful if it were a significant amount of grounds - it isn't. Even if it were an entire double shot worth (i.e. 15g, it is nowhere near that much, probably more like 4g) and considering it takes around 750g to get to that point it would be less than 2% wastage. Any cafe I know would be delighted with a figure that low...

    A number of domestic grinders are now offering the same approach as the Vario for the same reason. Stale coffee sucks almost as much as scalded milk (don't get me started on that one).

    Enjoy your cuppa, that is what counts


    TampIt

  9. #9
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    Quote Originally Posted by TampIt View Post
    G'day simonsk8r

    Actually I know grind retention is critical for a home user. Coffee grounds actually start to oxidise in under 5 minutes (probably starting at the 30 second mark) if there is enough oxygen available.

    I have had numerous stale coffees (to the point that most friends know I always "am polite and have the last cuppa"!) when people do not bother to purge a grinder that needs it. That is particularly true of anything with a doser for "non cafe use". Stale is then 100% guaranteed unless it has just been used and cleaned out properly. That is one reason I removed the doser from my Major for home use (it is still one of my favourite cafe grinders) - it dropped the retention down to about a single 7g shot - which unfortunately gets pushed out the next time you fire the Major up. For home use that is still way too much retention unless you are doing a fairly large number of coffees "on the trot".

    The Vario's retention is literally a few grounds in the chute (maybe a dozen on a bad day, usually well under five unless it is humid) plus a very small amount in the chamber. None of those grounds tend to migrate much.

    You are correct - the chamber just slowly fills (in layers I guess) so very little of the stale stuff (if any) ever leaves the chamber until you remove the upper burr and clean said chamber out. Weighing that would only be useful if it were a significant amount of grounds - it isn't. Even if it were an entire double shot worth (i.e. 15g, it is nowhere near that much, probably more like 4g) and considering it takes around 750g to get to that point it would be less than 2% wastage. Any cafe I know would be delighted with a figure that low...

    A number of domestic grinders are now offering the same approach as the Vario for the same reason. Stale coffee sucks almost as much as scalded milk (don't get me started on that one).

    Enjoy your cuppa, that is what counts


    TampIt
    Ah yep gotcha, cheers mate.

    For some reason when watching the video it didn't really click to me those grounds that get retained but actually stick within the grinder and don't get pushed out. So only for single dosing purposes it would be useful, and then only to a completely cleaned out grinder (which would retain more upon the first shot wouldn't it!).



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