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  • #16
    Hi Jackstar,
    Unfortunately it's not feasible for me to swap grinders with my friend temporarily.

    An update for those interested.
    I was determined to understand what's going on and started keeping a log of my extractions from 11/2.
    I used the same technique each time, same dose, same boiler temperature, and persevered with the same grind settings until I was able to pull several consistent shots.

    Some observations:
    - after some initial variances I seemed to reach a level were my extractions were very consistent - after I changed beans and dialled in the grind, the inconsistencies returned.
    - ambient temperature and humidity does not seem to significantly affect extraction.
    - despite paying particular attention to how I handle the grinds and using a distribution tool, i consistently get channelling and spritzing.
    ​​​​​
    I feel I have hit a level of consistency now with the occasional outlier which I can't explain.

    I've not put around 1kg through the new burrs...
    Perhaps my new burrs are starting to wear in.. but in any case I'm much happier than I was a week ago.

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    • #17
      An additional note. My friend with the same grinder changed burrs at the same time I did and he did not see the variable extractions as I did.

      The only thing I can think of that may attribute to this is that he overdoses his basket, whereas I dose to basket rating (18gm VST).

      ​​​​​I do think overdosing introduces a buffer and a greater margin of error

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      • #18
        How much retention do you normally have? Do you purge?

        I used to have a similar experience until I got the niche

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        • #19
          Originally posted by Rami View Post
          How much retention do you normally have? Do you purge?

          I used to have a similar experience until I got the niche
          I generally purge on the first shot of the day, subsequent shots I don't purge, even if the second shot is several hours later.
          the strange thing is that if shot variance is due to technique or stale retention, you would expect that shot to be shorter; I'm finding most of my shots are reasonably consistent with an occasional outlier that is a much longer shot.

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          • #20
            Originally posted by Kit666 View Post

            I generally purge on the first shot of the day, subsequent shots I don't purge, even if the second shot is several hours later.
            the strange thing is that if shot variance is due to technique or stale retention, you would expect that shot to be shorter; I'm finding most of my shots are reasonably consistent with an occasional outlier that is a much longer shot.
            What do you mean shorter?

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            • #21
              Originally posted by Rami View Post

              What do you mean shorter?
              Shorter as in Underextracted

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              • #22
                Originally posted by Kit666 View Post

                Shorter as in Underextracted
                So you get the occasional channeling? That’s what it sounds to me

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                • #23
                  Actually it's quite the opposite; despite paying a lot of attention to my technique, I consistently get channelling and some degree of spritzing. I obviously can do better otherwise it wouldn't channel all the time. Although this has me thinking about other factors...

                  ​​​​​​If I was getting occasional channelling, I would expect that shot to be short.. in my case it's strange that my outlier shots are longer yet still show signs of channelling.

                  Some thoughts:

                  - is this a case of my new grinder burrs breaking in and slowly becoming more consistent?

                  - is it clumping of my grinds? (Which the compak K3 is known to do)

                  - would overdosing my basket alleviate the problem?

                  ​​​​​

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                  • #24
                    Kit666

                    i think channeling is when you get a weak spot in the puck where more water is forced through the channel and you end up end up with a longer shot.

                    not the other way around.

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                    • #25
                      Originally posted by Rami View Post
                      Kit666

                      i think channeling is when you get a weak spot in the puck where more water is forced through the channel and you end up end up with a longer shot.

                      not the other way around.
                      Under/ Over Extraction is generally a reference of extraction yield and time.

                      So let's say you're pulling a 1:2 ratio from 18gms then your yield is 36gms.
                      Now let's factor in time; you generally target an extraction time of 25-30s as a starting point; once you reach that target, you then tweak the grind and dose to your liking (and tweak brew head temperature even)

                      If the time taken to extract your yield is much quicker than your target, that's known as under extraction (or quick, or short extraction).

                      If the time taken to extract your yield is much longer than your target, that's known as over extraction (or long).

                      Channelling is when the water has found a quicker path through the puck (as you mentioned, puck weakness); so in that sense, channeling will always result in under (or short) extraction.

                      So bringing this back to my scenario... If my inconsistencies in my extractions were due to occasional bad technique or stale grind retention, then I would expect the outlier shot to be underextracted (or short)... Instead I'm seeing outliers that are well overextracted (or long).... Unless of course I consistently have bad technique and occasionally have good technique which results in my over extracted outlier!

                      ​​
                      ​​​
                      Last edited by Kit666; 24 February 2021, 02:32 PM.

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                      • Rami
                        Rami commented
                        Editing a comment
                        Not sure I understand with your definitions.

                        under extracted coffee would take more time to give me my yield.

                        Over extracted coffee would take much shorter time to give me my yield.

                        My process I keep dose constant. Then adjust grind to hit the right yield. If time is in the ball park I am done.

                      • Ronin
                        Ronin commented
                        Editing a comment
                        Rami you have your under and over around the wrong way.
                        Under extraction is faster shots
                        Over extraction is slower shots

                    • #26
                      Originally posted by Kit666 View Post
                      If my inconsistencies in my extractions were due to occasional bad technique or stale grind retention, then I would expect the outlier shot to be underextracted (or short)... Instead I'm seeing outliers that are well overextracted (or long).... Unless of course I consistently have bad technique and occasionally have good technique which results in my over extracted outlier!
                      ​​​
                      I have often wondered exactly this point, and whether it boils down to the following question: Is the longest possible extraction time for any grind size/bean/freshness/temperature combination actually the target for perfection (in preparation) at those settings?

                      Brett

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                      • #27
                        Originally posted by biffel View Post

                        I have often wondered exactly this point, and whether it boils down to the following question: Is the longest possible extraction time for any grind size/bean/freshness/temperature combination actually the target for perfection (in preparation) at those settings?

                        Brett
                        I think the answer is.... It depends!

                        I've often found my longer extractions still had some visible channeling and spritzing.. which means.. it's still sub optimal!

                        Comment


                        • #28
                          Just an update...

                          It's been a number of weeks now, and Ive chopped and changed technique, equipment, beans etc etc etc...

                          I dont think I'm closer to achieving consistency and a good looking extraction that didn't have some channelling when viewed from the naked filter.

                          I've found that the OEM basket did give some better consistency but it still would vary more than I liked... I've since gone back to my 7 year old VST.

                          I got a batch of beans that although were over 2 weeks old would be super gassy and extractions would just fluctuate on a daily basis.

                          Then I encountered this video:
                          https://youtu.be/6TMkDe1XtIM

                          An interesting finding is that fresh beans (less than two weeks old) would have wildly varying extractions as they de gassed. Even to the point of significant differences intra day. Interesting!!!
                          I always thought fresh beans didn't have a developed flavour, I never considered it could result in wildly fluctuating extraction times.
                          with the number of boutique roasters now roasting to order, this could potentially explain a lot in my situation...

                          Anyway I've since started overdosing (19gm in an 18gm) basket... So far after 3 days have had some very consistent shots...

                          The testing continues...

                          Maybe bean freshness (i.e. they were too fresh) has been my problem all along... ?

                          Comment


                          • emslibbles
                            emslibbles commented
                            Editing a comment
                            Freshness as a variable is a hard one, unless you’re quite familiar with the beans and their roast. Some need 5 days, some 10, some 20! Due to Canberra roasters only typically selling 200 or 1kg bags, i often use rather gassy beans at the start. In my experience does have an impact on other things, but not channeling or shot-shot consistency specifically. At least not to the values you’re suffering!

                            My experience is that different machines with different factors like head space can significantly impact the likelihood of channeling too... on my Breville Dual Boiler i use to sometimes dose up to 24g in my 20g VST with great consistency, but on my Profitec Pro 600 I can’t go much over the rating without causing fluctuating channeling (all else being equal). So i now use 22g in a 22g VST most of the time.

                            Another factor, i started using a dosing cup rather than grinding straight into my portafilter (for cleaning and ease of weighing purposes...) and that also decreased instances of channeling.

                            Continued luck!

                        • #29
                          Here's another idea to throw out there... have you thought about trying to turn you brew pressure down? Maybe to 7-8 bars instead of 9-10 bars? I understand 9ish bars is the recommended; but if the grind/puck prep isnt perfect; reducing the brew pressure may reduce the channeling. It would be a tradeoff of course; consistent good shots vs the occasional perfect one.

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                          • #30
                            Originally posted by maltur View Post
                            Here's another idea to throw out there... have you thought about trying to turn you brew pressure down? Maybe to 7-8 bars instead of 9-10 bars? I understand 9ish bars is the recommended; but if the grind/puck prep isnt perfect; reducing the brew pressure may reduce the channeling. It would be a tradeoff of course; consistent good shots vs the occasional perfect one.
                            Thanks maltur, this is certainly an option to consider, however, I would much prefer to fix the cause rather than alleviate the symptom.
                            this is also the reason why I went back to the VST basket after seeing some success with the OEM.
                            The way I see it, there is either a problem with my technique or my equipment, and I really want to fix it there (at this I'm leaning towards equipment as I've been so careful to eliminate potential technique variances).

                            I've attached a portion of my log.. technique and grind setting is the same throughout this period.

                            You can see some consistency but then an occasional outlier that's totally off.
                            Are most people seeing similar results? Or are most people getting much better consistency in their extractions?
                            Click image for larger version

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