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  1. #121
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    Sorry Bob, I was referring to their manual tamper. It uses an alignment system similar to your diagram.

  2. #122
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by pippin88 View Post
    Sorry Bob, I was referring to their manual tamper. It uses an alignment system similar to your diagram.
    Thanks.
    I had thought of doing it that was but there is an important difference needed for my application.

    When the ezytamp is initially put onto the PF and before the 15kg tamping force is applied, the ezytamp tamper pressure plate starts out below the level of the coffee and so immediately tamp the coffee - this is not desirable for my approach. My design sits over the PF with the tamper plate initially sit above the level of the untamped coffee. This will hopefully allow the untamped coffee to be vibrated into place with only the few hundred gram weight of force from the tamper weight itself doing any tamping.

    Our experiments show that tamping does very little by way of improving coffee extraction since all it does is push the pre-existing positioned coffee grains together. The vibration approach hopes to improve the packing of the coffee to reduce voids and channeling. Of course it could all be a complete pile of BS.

  3. #123
    BobL is offline Member: Blue and white apron brigade
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    Default More coffee machine antics

    Every few months the plumbed in waste drain to the coffee machine blocks up. The waste drain at the machine starts out as a 12 mm clear PVC hose and is coiled once under the machine before running across the bench to a hole in the bench where it is connected to a 20 mm black PE (irrigation pipe) and goes vertically down through the bench and wooden kitchen floor to underneath the house where it extends on a slight slope about 3m before connecting with the sink waste pipe.

    Even though used coffee is not disposed of via this route (that goes in something called a "knock box") some grounds do escape and enter this relatively tortuous and at times flat pathway and block the line. If not flushed often the used wet coffee seems to grow a mould/slime which doesn't help either . I try to remember to flush lots of water on a daily basis down the waste line but over time some coffee grounds still settle out in the flat sections of the line occasionally block the waste line. The result is dirty brown water all over the bench, floor and inside the cupboards underneath the machine.

    Usually I make clearing the waste drain line part of a monthly machine service cycle but lately the machine has been getting a hammering so it blocked up sooner than usual. To unblock the line I usually attach a short length of PVC hose to the drain and blow the line clear but this time no amount of huffing and puffing would clear the line so this time I brought in a bit more pressure to deal with it.

    I use the cream coloured gas cylinder as a portable compressed air source around the house etc. So I filled it with air to about 60 PSI and connected it up and it had no trouble clearing the line. Once clear I then run some hot water containing some dishwashing power through the line to help dissolve some of the crud.

    Pflush.JPG

  4. #124
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    Bob,
    Thanks for your interesting and detailed write up of this.

    Quote Originally Posted by BobL View Post
    Our experiments show that tamping does very little by way of improving coffee extraction since all it does is push the pre-existing positioned coffee grains together. The vibration approach hopes to improve the packing of the coffee to reduce voids and channeling. Of course it could all be a complete pile of BS.
    Sounds to me like a pile of careful observation + practical sense.

    As you say, coffee being tamped seems to compress in the direction of tamper application without dealing with variations in packing density. When tamping I do try to sense if one side is compressing too easily and if so correct it a bit, but it's really not an effective method.

    I find that ground coffee decanted into the filter is not inclined to settle evenly, despite tapping the pf before tamping. While pre-tamp tapping of the portafilter onto the benchtop seems to settle the coffee down and reduce voids, it does not make the surface level (it's often high in the centre), and I am theorising that a non-level surface before tamping results in an uneven puck density after tamping. Overall, it seems to me that a combination of pre-tamp surface levelling + tapping the pf on the benchtop might give a better result.

    I note your earlier trial of mechanical vibration would throw the coffee about. Tapping the pf on the bench does not have that problem, and it should not be too hard to mechanise that action (slow rise, sudden drop to a hard stop and repeat). My preference is for doing it all by hand (level, tap, tamp), so my next step is to think about making a levelling device: if someone has a nice simple design for that I would love to hear the story and see the pix!

    Cheers,
    Bill

  5. #125
    BobL is offline Member: Blue and white apron brigade
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    Thanks for your thoughts Bill. It sounds like we are in the same wavelength band.

    Levelling these days seems to be being done by folks with money using OCD or OCD type devices - should not be too hard to emulate although I don't se them as the answer.

    I have not done any extraction tests on tapping but others have and there's no difference in extraction between gentle tapping and not tapping.
    There also does not appear to be any real difference in extraction between using an OCD levelling device and not using an OCD, If anything using an OCD reduces extraction and slightly tightens up the range of extraction.
    see Examining the Impact of the OCD (and OCD 2) on Total Dissolved Solids Extraction – Socratic Coffee

    A tap would be similar to a square wave pulse which would be possible to generate electromagnetically but of course at greater expense but I may yet end up going that way yet.
    When vibe or taps are generated automatically it becomes possible to introduce a ramped frequency vibe which may further improve things.

    Of course none of this says anything about the taste. As the authors of the article in the above link state;
    It is possible the OCD shots of lower extraction would be preferred by the barista/consumer. Further, while somewhat unlikely, it may be possible that the content of extracted solubles differed when using the OCD.

  6. #126
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    Bob,

    Thanks for that link. I checked it out, and it is interesting that while the the OCD distributing (=levelling?) device consistently reduced the total dissolved solids content of the extract, a "BT" levelling device ('chisel' style, something like https://www.coffeeparts.com.au/pullm...ion-tool-black) hardly reduced the TDS at all. So there would seem to be quite a variation in TDS depending on leveller design. Possibly, as suggested in the product link above, the outcome is not so good if the leveller also compacts the coffee too much during redistribution. If I follow that line of thinking, a mental video comes up with some possibilities, but it's still very foggy on implementation detail.

    Disclaimer: my approach to this does not pretend to be properly systematic or precise, and the only measuring technique is my taste test of a shot immediately after delivery into the cup. So basicallly I am following what seems to make the shots taste better to me. To a fair extent I suspect that improvement comes down to reducing variables in the process, then playing with parts of the (hopefully more consistent) process to improve the taste. So while I respect the findings that pre-tamp pf tapping vs no tapping has no effect on the TDS, over time I have a clear impression that my coffee tastes better if the pf is tapped and the coffee is somewhat evenly distributed prior to tamping.
    Quite possibly, if one part of the procedure is altered, you can only get a good result if you change a subsequent step in a specific way, but it's far to complicated for me to work that out.

    Cheers,
    Bill
    Last edited by WCD; 8th Nov 2019 at 06:23 PM. Reason: expression

  7. #127
    BobL is offline Member: Blue and white apron brigade
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    [QUOTE=WCD;1958853]Bob,

    Thanks for that link. I checked it out, and it is interesting that while the the OCD distributing (=levelling?) device consistently reduced the total dissolved solids content of the extract, a "BT" levelling device ('chisel' style, something like https://www.coffeeparts.com.au/pullm...ion-tool-black) hardly reduced the TDS at all. So there would seem to be quite a variation in TDS depending on leveller design. Possibly, as suggested in the product link above, the outcome is not so good if the leveller also compacts the coffee too much during redistribution. {/QUOTE]
    I agree


    Disclaimer: my approach to this does not pretend to be properly systematic or precise, and the only measuring technique is my taste test of a shot immediately after delivery into the cup. So basicallly I am following what seems to make the shots taste better to me. To a fair extent I suspect that improvement comes down to reducing variables in the process, then playing with parts of the (hopefully more consistent) process to improve the taste. So while I respect the findings that pre-tamp pf tapping vs no tapping has no effect on the TDS, over time I have a clear impression that my coffee tastes better if the pf is tapped and the coffee is somewhat evenly distributed prior to tamping.
    Quite possibly, if one part of the procedure is altered, you can only get a good result if you change a subsequent step in a specific way, but it's far to complicated for me to work that out.
    Thanks for these comments
    FWIW I don't notice any difference in taste between tamping or not tamping.
    Disclaimer: I know my taste buds are not that sensitive and when I did my Barista Judging course about 15? years ago that came out in the sensory perception test which I only just passed. I think this is probably because over the years I have partaken of too much and of too strong spicey food, eg I love raw chilli! This is probably why I prefer very strong (double and triple shot) espresso and dark roasts. Light coats just taste mealy (grass / hay / seeds) and I find it difficult to discern between them.

  8. #128
    BobL is offline Member: Blue and white apron brigade
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    Default Coffee research - one for the coffee nerds

    Some recently published research on coffee demonstrates that very similar shot flavour profiles can be obtained using (eg 25%) less coffee, ground more coarsely, at lower (6 bar) pressures, extracted in less than half the time.

    See https://www.cell.com/matter/fulltext...385(19)30410-2

    It's not often I do something this fortuitous but the mods I made on my coffee machine last year make it really easy to adjust the extraction pressure so for the last 24 hours I have been trying this out. Although my grinder is not as ideal as I would like (it does not produce as uniform a grind as is apparently required) so far I have not been able to tell much of a difference between the different extraction conditions.

  9. #129
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    Interesting thread! I've only skimmed over it but anecdotally I agree regarding your vibration vs tamping conclusion. My non-conventional method is to tap the side of the portafilter with the tamper throughout the grinding process and then finish with a very light tamp (couple of kilograms max) and quarter twist. I get great shot consistency, taste and crema so have stuck with it over more conventional methods.

    My shrine below. Have since tossed the double walled glasses in favour of Cup 'n Co ceramic. Profitec 700 Pro w/ Profitec Pro T64 grinder.

    za9yJ0k.jpg

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