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Thread: Grind repeatability vs speed

  1. #1
    Senior Member gonzob's Avatar
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    Grind repeatability vs speed

    Hi all.

    Some background:
    I have a Mazzer mini without the digital timer, but with a home-made scale platform. See photo below:



    I weigh my dose into the little black cup then tip it into the pf. Because the Mazzer grinds slowly, I leave the grinder set on the max time for a double shot, run an automatic double-shot grind, then top it up with the manual button until I get to about 16.5 g. I am perfectly happy with this arrangement.

    I've timed the timer, and it goes for between 19.9 and 19.7 secs, so a total variation of ~1%. The automatic dose delivers about 14g, but the total variation in weight is about 1.5g, which is about 10 times the variation in time. I can only conclude that the feed of beans to the grinder varies. Now, for me, this is not a problem, because i just top it up to the required weight, and make the coffee. However, it does raise questions...

    My questions:

    1. There are a number of high-speed grinders available with digital timers. Has anyone done testing to see how much the grind weight varies?

    2. Given my experience, are timers a waste of time?

    3. For my slow-speed grinder, a short "tap" on the manual button gives about 0.2g more. If you have a high speed grinder (that produces a double shot in about 5 secs or so) the manual button must give heaps - is that a problem?

    Gonzo

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    Gonzo,

    Interesting experiment!

    What I would note is that the beans will jump around quite a bit without a hopper on and that will make it very unpredictable to determine when all 16.5g will be ground. However with the added weight of beans on top in the hopper the grind time will be faster as there is more force down and the grinder is 'waiting' to catch the last bean.

    It would make for an even more interesting experiment doing single dose timing vs a hopper full of beans. Maybe 16.5 g will be significantly shorter with a hopper full of beans?

    My 10 cents anyway.

  3. #3
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    I have the Macap M4D and have the timer set to 9.2 seconds to return roughly 16 grams. I then top up to 18 grams on continuous mode. I used to always weigh after the initial dose and it was reasonably repeatable but certainly not 100% everytime. I use a cup like you and now as I have become more used to the level of dosing in the portafilter I don't weigh anymore, I do my 9.2 seconds, stick it in the portafilter and if it looks like it needs a bit more then throw in a bit more. With my previous grinder, without a timer, it would take me about 3-4 goes to get the required dose. So to answer your question timers aren't a waste of time but they aren't set and forget particularly where grind retention is an issue.

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    Senior Member level3ninja's Avatar
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    I have a Eureka Atom which is quicker than your mini, but not super quick like a Robur. The beans I use are on the other side and it takes about 13s to get 20g. I've tried other brands and they were about 9s for 20g. I find with a consistent level of beans in the hopper the timer produces very consistent results; of I keep the beans within a 1cm level of height in the middle of the hopper I get within 0.2g every time, usually within 0.1g or spot on. When I top up in manual mode I can get 0.2g if I'm careful, more often it's about 0.6-1g.

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    I use a very similar set up with my Mazzer Super Jolly E. I grind approx 10 seconds which will usually give me ~17.x g, I then gauge by eye and pulse quickly to get to 18.0-18.5g which is my target.

    I don't think the timer is a waste of time at all because I don't have to stand there for 17 seconds holding a button or waiting to turn the grinder off.
    Last edited by Brian88; 3 Weeks Ago at 05:12 PM.

  6. #6
    Senior Member level3ninja's Avatar
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    Quote Originally Posted by Brian88 View Post
    I don't think the timer is a waste of time at all because I don't have to stand there for 17 seconds holding a button or waiting to turn the grinder off.
    I agree, they may not be perfect but there's a lot less wastage with a timer than without.

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    Senior Member simonsk8r's Avatar
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    I love the timer function on my Compak K3 Touch Adv and I use it all the time, it's not 100% accurate and i don't expect it to be. Timed dose half, collapse, timed dose second half, but always have to add a bit more (I usually plan it this way so I can scoop coffee out the chute so I don't have to waste it), it really depends if the chute is full of grinds or if the diagonal chute has some stuck too. But if the chute is full it's usually scarily accurate and drops in very consistent amounts!

    But honestly I mainly use the timer so that I'm free to move the portafilter around to get an even distribution in the basket, if I use the manual push I have to keep the portafilter pretty much in the one spot, so the timer is great for that purpose!

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    I have not timed my Robur but guessing close to 4 seconds for 20 grams.

    I keep the hopper neck full and 1cm into the hopper most of the time.

    I waste very little. It doesn’t take long to get used to estimating the run time to 90% then a quick blip to top up. I may end up with a gram or so in the hopper for the next shot and that small amount has no effect I can detect on the next shot.

    I drink maybe four shots a day.

    The grind is very stable. It is possible to do a 2.5kg bag of beans without changing the setting. The Doser means you don’t get clumps as these get broken up. I get very little shot to shot variation in pour times.

    The speed is generally a positive and with 71mm burrs and a 900 Watt motor, little heat is generated. It is also very quiet.
    Last edited by wattgn; 3 Weeks Ago at 07:28 PM.
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    The dose in a certain time is going to vary based on grind size, and your grind size is going to change based on the internal temperatures of the grinder. A mythos one for example, with back to back grinding, will have the dose for the programmed time much the same, but throughout the day it will change. During busy peaks, the grinder gets hot and the grind size changes as well as the dose. When it's quieter, the grinder begins to cool down and again the grind size changes, along with the dose. It's a constant game of cat and mouse. Every grinder I've used has acted the same way. Roburs, for example are a bit worse since the retention can vary shot by shot. In service, I don't want to spend the time slapping the thing and getting all the grinds out, I'll just set it to dose a bit higher than I'm aiming, chuck it on a scale and chuck out any extra.

    In a home environment this is going to be very different as you are probably going to spend the time to get as many grinds out as possible to reduce wastage (so retention isn't as much of a factor), and the main factor for the internal temperatures of the grinder are going to be room/ambient temp. So depending on how much your ambient temperatures change, I wouldn't be surprised if it is the same as your grinders dose.
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  10. #10
    Senior Member simonsk8r's Avatar
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    Quote Originally Posted by vehemence View Post
    The dose in a certain time is going to vary based on grind size, and your grind size is going to change based on the internal temperatures of the grinder. A mythos one for example, with back to back grinding, will have the dose for the programmed time much the same, but throughout the day it will change. During busy peaks, the grinder gets hot and the grind size changes as well as the dose. When it's quieter, the grinder begins to cool down and again the grind size changes, along with the dose. It's a constant game of cat and mouse. Every grinder I've used has acted the same way. Roburs, for example are a bit worse since the retention can vary shot by shot. In service, I don't want to spend the time slapping the thing and getting all the grinds out, I'll just set it to dose a bit higher than I'm aiming, chuck it on a scale and chuck out any extra.

    In a home environment this is going to be very different as you are probably going to spend the time to get as many grinds out as possible to reduce wastage (so retention isn't as much of a factor), and the main factor for the internal temperatures of the grinder are going to be room/ambient temp. So depending on how much your ambient temperatures change, I wouldn't be surprised if it is the same as your grinders dose.
    Really interesting thoughts, thanks for this informative post! So would you say that ambient/room temp affects grind particle size/extractions? Purely anecdotally speaking, but it always seems on much warmer days my shots run so much faster (even it being the exact same dose and grind setting as the day before, or even the mornings shots).. anyone else found this?

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    Grind repeatability vs speed

    Comments seem to be relevant to a busy cafe which is fine but a cafe does in one day what home users do in six months. Some grinders have fans to control temperature such the Robur and others house the motor separately to isolate the heat of the motor from the burrs. I probably adjust my Robur every week maybe two weeks usually in response to bean changes or sudden changes in weather.
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  12. #12
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    Quote Originally Posted by simonsk8r View Post
    Really interesting thoughts, thanks for this informative post! So would you say that ambient/room temp affects grind particle size/extractions? Purely anecdotally speaking, but it always seems on much warmer days my shots run so much faster (even it being the exact same dose and grind setting as the day before, or even the mornings shots).. anyone else found this?
    I think that the temperature of the grinder internals affect how a grinder will grind. This is an issue in a commercial environment, not so much a home one. However I would imagine that when it's a cold morning and everything is under 20 degrees the grinder would produce a different grind then say when it's a hot afternoon and everything is at 30 degrees.

    That being said, I haven't tested this in a home environment, but I see the affects of heat on a grinder every day at work.
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  13. #13
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    I rarely weigh the grounds.

    Using a T64 grinder and it's set for a timed dose of 6.8 seconds. I do a 1-2 second purge before the first coffee of the day, and then just used the timed double for every shot.

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