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Thread: Advice want: slow extraction with Breville Double Boiler BES920 + Smart Grinder Pro

  1. #1
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    Question Advice want: slow extraction with Breville Double Boiler BES920 + Smart Grinder Pro

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    I've got a Breville BES920 Double Boiler and a BCG820 Smart Grinder Pro at home. I've had the Smart Grinder Pro for around 6 months, which I was originally using to make Aeropress. Around 2-3 months back we got a BES920 at my work, and after a few weeks of learning I was able to make consistently good coffee, so we decided to get one for home when Harvey Norman were doing a clearance deal.

    At work, with the exact same models of grinder+machine, I'm able to make a consistently very good flat white. When pressing the single shot button on the BDB at work, as soon as pre-infusion finishes, the pressure gauge usually goes up to just above 9, then hovers there, and coffee starts to flow a few seconds later. The 30s timed extraction usually leads to the right volume, and adjusting the grind has the expected effect on flow and volume.

    At home, however, if I use the same settings on the grinder and machine, after pre-infusion, the pressure gauge goes straight up to the top of the "optimal" range (around 10), then drops back slightly to around 9.5, and it often takes 5-10 seconds before anything comes out. When it does, it's often a slow drip, not a consistent flow, and once or twice nothing has come out at all. To counter this, I've increased the grind coarseness a few notches (so it's around 13 vs 9 on the same model grinder work), but I don't get a "good" looking extraction in terms of volume and rate unless I go up to 15-16 on the grind, at which point the coffee seems to have less flavour and body.

    I've been buying the same beans at home as we use at work, and have gone through a few bags both at home and at work whilst trying to work out what's wrong with my home setup, so I don't think variations in the roast/bag of the beans is a factor.

    Does anyone have any advice on whether this is likely due to the grinder or the machine? Is it possible that the Smart Grinder Pros aren't objectively calibrated consistently, so 15 on my grinder could be the equivalent of 9 on another Smart Grinder Pro?

    I've tried cleaning the grinder (with the brush that came with it) and backflushing the BDB a bunch of times. One thing that's may be completelyunrelated that I've noticed is that on the BDB at work, when I lock the group handle, it always quite easily goes a little way past "perpendicular", whereas at home there's a lot more friction, and it usually locks slightly before being perpendicular to the machine.

    Many thanks in advance!

  2. #2
    Super Moderator Javaphile's Avatar
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    Ignore what the numbers are on the grinder. The settings are not transferable between different machines. Adjust the grinder until you get the extraction you like.


    Java "Ignore the numbers, use your tongue" phile
    sten186 likes this.
    Toys! I must have new toys!!!

  3. #3
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    Thanks Javaphile!

    When I adjusted the grind up to 15 and got good rate/volume it seemed like there was less body, but it may have just been a one off bad shot.

    I'll adjust it up a few notches then adjust purely for flow/volume, ignoring any preconceptions I had about what the settings "should" be.
    zeezaw likes this.

  4. #4
    Senior Member Jackster's Avatar
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    Grind a shot at work and rush it home and see what happens

  5. #5
    Senior Member Erimus's Avatar
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    Quote Originally Posted by Jackster View Post
    Grind a shot at work and rush it home and see what happens
    Or take the grinder home with you

  6. #6
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    Hah, I was actually considering taking my grinder in to work so I could do an apples to apples comparison ;-)

    This morning I cranked up the grind on the Smart Grinder Pro to 17, and got the best shot I've pulled from this machine in about a month. Thanks for the advice! ☕️

  7. #7
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    So, Java's advice was two days ago... did you try grinding finer?

    There are only two ways to slow the flow:
    1) increase the obstruction by grinding finer or stuffing more coffee in the basket (don't overstuff)
    2) reduce pump pressure.*

    * One of the neater tricks you can do with the BDB is experiment with low pressure extraction: You can do this on the BDB by reprogramming the pre-infusion duration out to something way longer than you need, say, 90 seconds, than you can bump up the pump pressure to whatever you like, say, 80%. Then if you grind right, you can extract at like 3-4 bars or pressure. This is an area that very advanced baristas are experimenting with, and using $10,000USD Slayers to do it. You can do a reasonable imitation by extracting using the programmable pre-infusion of the BDB. Pretty cool, huh?

    -Peter



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