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  • #16
    Re: EM6910 stuck puck

    Im confident my grind, dosing etc is consistant so disagree that more or less coffee is the answer.

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    • #17
      Re: EM6910 stuck puck

      Originally posted by Honest Gaza link=1226019023/0#9 date=1226048564
      Ive been using the 6900/6910 for more than 2 years and have never had this occur.

      I feel inadequate now :-(
      Dont feel inadequate..  It is no ideal outcome  ;D

      1: Stuck Vs Wet are different and not to be confused.

      I have had  one or two stuck at times and it is due to a combination of Grind,Tamp and UP/Overdosing  

      Now I know some will jump at that......  BUT the pure physics and evidence proves it  8-)

      A: To be stuck to the shower screen; it must have been up there to start with AND OR has expanded with the infusion; such that the grinds are in physical contact with the shower screen.

      If not,  then many scientists would like to know how you can suspend a puck in mid air  : and defeat gravity.  Unless your in  space...  :

      B: When you unlock the PF;  if you also have the right consistency and dryness/wetness  then there is enough bonding throughout the puck and the interface with the shower screen (Unless your defeating gravity) to hold it to the shower screen and ALSO break it from the smooth walls of the PF.

      Thus while I can not comment on your beans, grind, tamp and any other variables:  it still stands to reason, that to become stuck to the shower screen.

      Then it must be in contact AND with some level of force; be it overdosing and or expansion (beans / grind etc).  8-)   I do not thing it is any one thing but more a combination of the product and significant contact with the shower screen.

      Note: I have had my wife do it, where she has left the system in place and had to rush out.  Only to come back a few hrs later, go to make a coffee and can not put a new filled PF in. Only to find the old puck was still in place... Then again that is her and not me  ;D

      Feel free to explain it any other way...  

      Comment


      • #18
        Re: EM6910 stuck puck

        AngerManagements theories make perfect sense - there has to be enough coffee in the portafilter to make good seal with the showerscreen. Unless, somehow, high pressure physics and the fluid dynamics can cause the coffee to "float" to the top - which is not very likely.

        If I also apply my scientific hat and start postulating theories, then I have another plausible explanation:

        Cold filter basket?
        When you start with a cold filter basket, the coffee makes a tight contact with the walls. As the basket warms up, the diameter increases and the adhesion of the puck to the side walls becomes weaker than the adhesion to the shower screen. At the end of the pull, the puck ends up stuck to the shower screen and loose in the filter.

        The temperature of the filter basket is not one of the variables that I paid too much attention to in the past. However, thinking back to when I had the most frequent troubles with a stuck puck, I was sometimes dosing the filter basket on its own, while the portafilter handle was pre-heating in the coffee machine. Ill run a couple of tests where I will only vary the temperature of the filter basket to see if that is the culprit.

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        • #19
          Re: EM6910 stuck puck

          Cold filter basket might be an answer.

          I warm the cup and the empty PF with hot water but the basket is only at room temp or at best the temp of my shirt pocket before its loaded into the PF just before I add the grinds.

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          • #20
            Re: EM6910 stuck puck

            I did one test run. Cold basket and portafilter vs. warm/hot basket and portafilter. Neither of them resulted in a stuck puck.

            Cold basket gave me what I considered a nicer extraction with richer crema, but the puck was a bit "patchy" and inconsistent at the end. It sort of broke up in segments/layers. Blonding onset was gradual.

            Warm basket was a bit drippy at the start and then extracted OK. The puck came out nicely as one unit and cleanly too. The blonding stage had a well defined and sudden onset.

            Both were dosed to the same level, at the same grind and tamped on scales to 15kg.

            Inconclusive, so I will repeat the experiment a few more times over the next few days.

            Comment


            • #21
              Re: EM6910 stuck puck

              I upped the dose for two doubles today. It was a 1g increase for both. Tamped the first a bit soft and ended up with some fissures and a slightly wet puck. Was dryer than the previous ones. Tamped harder on the next one and voila! Dry puck with a reasonable imprint of the shower screen on it.

              Ill start using the scales to get the scientific method going.

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              • #22
                Re: EM6910 stuck puck

                Well, I can report that coffee does not seem to obey simple laws of physics.

                Ive been running a number of experiments over the last few days, trying to find a single reason for a stuck puck, but it seems its a combination of a number of factors that causes the issue.

                Heres a way of making a stuck puck (and a disgusting coffee):

                1. Start with cold portafilter/basket.
                2. Use a finer than normal grind.
                3. Underfill the basket (normal tamp pressure should make all of the silver part of the tamper disappear in the basket)
                4. Overextract the coffee to the point where it blonds to white crema and starts turning into stained water.
                5. Wait about a minute before removing the portafilter handle from the head.

                Of course I dont make coffee like that, the point was to make the puck stick - which I accomplished. The lesson learned? Stuck puck is not due to overdosing.

                Comment


                • #23
                  Re: EM6910 stuck puck

                  IMO any of you that are experiencing this must be over-dosing. Thats the only explanation for the puck to be that close to the screen. Back off a few grams and see how that changes things. Later!

                  Comment


                  • #24
                    Re: EM6910 stuck puck

                    shadow, as I said before, my dosing is consistant.
                    Even if I was overdosing, the puck has only stuck 5 or 6 times in the last 2 years.
                    I make 10 coffees a week on the 6910.
                    You do the math.

                    Therfore, overdosing cant be "the only explanation".

                    Comment


                    • #25
                      Re: EM6910 stuck puck

                      Shadow,

                      As I have empirically proven, it is not over-dosing.

                      If I fill and tamp to normal level, I dont get a stuck puck. If I fill about 4mm lower than normal, tamp to same pressure AND do the above steps, the puck sticks.

                      So, under-dosing is part of the stuck puck phenomena. Perhaps over-extraction is the other half.

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                      • #26
                        Re: EM6910 stuck puck

                        I said previously that a cold basket may be a possibility for me and maybe another factor may have been not removing the PF soon enough.

                        Comment


                        • #27
                          Re: EM6910 stuck puck

                          Thundergod,

                          Those two seem the most plausible and are probably a (major) contributing factor for me. One thing I would add: When I was having these problems, I was using beans that benefited from a longer than normal extraction.

                          I agree that from a simple Newtonian physics point of view, ever-dosing is the most likely explanation, however empirical evidence shows that more complex forces are at work.

                          Comment


                          • #28
                            Re: EM6910 stuck puck

                            "Help me ObiWanKenobi, youre my only hope..."

                            ;D

                            Okay, nothing valuable to contribute, I just couldnt help myself... [smiley=lolk.gif]

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                            • #29
                              Re: EM6910 stuck puck

                              These are not the beans you are looking for. Roast along. Nothing to grind here. ;D

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                              • #30
                                Re: EM6910 stuck puck

                                good coffee will be with you, always...........

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