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  • #16
    Re: Channelling!?

    dsc - am curious, when you use a grind a tad to fine, does it drip to start with, but then blonde 15sec? So the whole shot happens fast, even though it poured to slow to start with?

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    • #17
      Re: Channelling!?

      Gday Tom,

      I know this is not your thread, but my query may apply to Kiwi too. Out of interest, what happens if you change to a different basket.... from a double back to a single (or visa versa) for example? Maybe even interesting to try a completely different make of basket if thats possible?

      Mal.

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      • #18
        Re: Channelling!?

        Gday everyone,

        Kiwi: yup definitely on the same boat mate I also took my shower screen off, cleaned everything, even took the shower back plate off and also cleaned it. Nothing changed. I agree with you that light tamping and over dosings seems to work. A lot depends on the coffee you use. Today I defroze a pack of Brazil Fancy Santos and Im choking my machine when working on the same grinder setting as I did when I was using Bali God Mountain. My MDF grinder is incapable of grinding the Bali so that it chokes my machine, but it does a good job with Brazil. So today I was able to test how my machine works when choked and it looks like this:

        1. Split dose method, dose: 18.5g, light tamp in between dosing, followed by a light tamp on the whole dose and NSWE to finish.

        Result: freakin choked after around 20s a small cone was formed and a continous pour started, but still blonding appeared after 15-17s (so 35-37s of the whole extraction). As you said Kiwi the whole thing starts to flow pretty fast even if it started slow (not freakishly fast, but faster than I would have thought)

        2. No split dose, dose: 18.5g, just a light tamp to finish and NSWE.

        Result: choked again, but it the flow started earlier this time. Went blond pretty fast though:|

        Mal: I dont know if youve seen the Gaggia single, but its a really bad basket. I tried using it 4-5 times and always got massive channeling and coffee everywhere on the counter. Tried using a triple that came with my NPF and the results where similar to the double.
        If I was to try a completly new basket I would have to order it online and pay 2-3 times the basket price for shipping:|

        I think I can say that this situation sucks

        Thanks for the support Mal

        And Kiwi: be strong mate!! sooner or later we will find a solution even if it involves upgrading to a 3000$ machine

        Cheers,
        dsc.

        Comment


        • #19
          Re: Channelling!?

          No worries mate,

          Sounds like a real bugger alright. Ive never really experienced this kind of problem in that the pour couldnt be controlled by adjusting the grind. When you think about it, the physical process is pretty simple really and you should be able to control the flow rate by varying the resistance to that flow, especially with a fixed pressure. Doesnt really make any sense :-?

          Out of interest, how did you set the OPV on your Classic Tom? Did you use an actual pressure gauge in parallel with a bleed off valve to control flow, i.e. to simulate 30/60ml flow in 25-30 seconds? I realise that there are other ways to do this but this is the only really sure-fired method to calibrate your OPV to a "real" 8.5-9.0 Bar. Might be worth pursuing? :-?

          Mal.

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          • #20
            Re: Channelling!?

            Gday Mal,

            I agree with you that this is strange. One would think that making the grind finer will give the correct extraction. But nope, if I make the grind finer, I choke my machine and get less than 60ml in 25s. If I leave it as it is, I get 60ml in 25s, but I get blonding around the 15s. :-?

            (60ml because Im only using a double)

            As for the OPV setting I used the reverse volume method, where you measure how much water returned through the OPV with a blind filter inside the PF.

            Cheers,
            dsc.

            Comment


            • #21
              Re: Channelling!?

              Hmmm,

              Well, maybe its the grinder after all? Perhaps the burr plates are not parallel creating a particle spectrum that results in too high a proportion of fines? Any chance of trying a different grinder? Maybe take your Classic and coffee with you to a café or similar and ask the owner operator if they wouldnt mind trying to help you out. Dont know what else to try as you seem to have covered pretty well everything. You roast your own coffee dont you Tom? If not, are the beans you use of good quality and freshly roasted? Kind of clutching at straws now :-?,

              Mal.

              Comment


              • #22
                Re: Channelling!?

                Hi Mal,

                I also think its a grinder problem, but sadly I have no place where I can try a different one. All of the cafes in my area have their grinders set by "specialists" and you cant even think of touching the settings (its stupid yeah I know, and the coffee is yuck). I maybe able to go to a friends cafe during summer and he has a good commercial grinde, so Im planning to try it out.

                You roast your own coffee dont you Tom? If not, are the beans you use of good quality and freshly roasted?
                Nope I dont roast yet, dont have the money to build a roaster, but I use freshly roasted coffee. I mean it is freshly roasted during the first week, but I freeze larger unused batches so it stays fresh longer. I tried different kinds of coffee: stale, 4 days old, 7 days old, 14 days old... I could go on and on. The same thing happends everytime (well except for stale coffee which gives a massive blond gusher after 3s and coffee everywhere on the counter), the extraction starts slow and goes blond around the 15s.

                I know someone who has a Classic and a different grinder and he doesnt have these problems. He says the stream stays thin and brown for the whole duration of the extraction. Thats another reason not to like my grinder

                Cheers,
                dsc.

                PS. Again I appreciate the support Mal

                Comment


                • #23
                  Re: Channelling!?

                  Youre most welcome mate ,

                  Weve got to try and get you sorted out so that God shots flow freely from the Classic of dsc 8-)

                  Mal.

                  Comment


                  • #24
                    Re: Channelling!?

                    Just a theory.

                    You say you prefer a ristretto. If you coursen the grind and aim for 50-60ml in 25ish seconds from the double basket, can you get a good pour all the way through.
                    My theory is that you are over extracting because with domestic machines, doesnt the pressure climb as the shot pours? I may be mistaken, but doesnt the pressure start at 9-10 bar and climb to 15 with the resistance of the puck? This could explain why the shot blondes for no reason.

                    Comment


                    • #25
                      Re: Channelling!?

                      Originally posted by Pioneer Roaster link=1174961569/15#23 date=1179998400
                      I may be mistaken, but doesnt the pressure start at 9-10 bar and climb to 15 with the resistance of the puck? This could explain why the shot blondes for no reason.
                      Yeah I think this holds true for all domestic machines sans an OPV. I think the machine that Tom has though is fitted with an OPV that he has adjusted to maintain maximum brew pressure to 8.5-9.0 Bar.

                      Mal.

                      Comment


                      • #26
                        Re: Channelling!?

                        Gday,

                        The Classic has an OPV and it is set at around 9bars, so nope its not a too high pressure issue.

                        If I coursen the grind and aim for 60ml in 25s I get a blond stream at around 15s. Theres no way I can get a nice brown thin stream for the whole duration of the extraction. If I use a coarser grind it blonds, if I use a finer grind the machine chokes, drips, finally a continous stream appears which goes blond pretty fast anyway >

                        One question: if my used coffee puck is darker around the edges at the bottom, does it mean that most water goes "around" it? I mean near the sides of the basket? the middle of the bottom of the puck is lighter than the edges. I can take a picture if you need one.

                        Cheers,
                        dsc.

                        Comment


                        • #27
                          Re: Channelling!?

                          Here is a photo of a pluck with the channelling. Note, this is prob the worst one, and was before the Pullman tamper, so isnt normally this bad but illistrates the point we both are showing...The sunbeam tamper isnt an exact fit at all, but its a lot more exact then the channelling is suggesting. This channelling was with proper dose, tamping etc as well.

                          Please copy below link to browser:

                          http://i91.photobucket.com/albums/k318/Kiwi_Jonno/560A0217.jpg

                          I also dont think Im over-extracting the coffee. IF i do overextract, it drips for a couple seconds, pours normally for a few secs then goes blonde to early in the extraction. Also, if the coffee was underextracted for a normal double, it blondes even faster then if ristretto. I use a commerical machine most days, and the shots there start at the same speed as the Sunbeam for the first few secs, only with the commercial blonding isnt til 25sec +! Same doze size approx to.

                          Have just tried proper commercial beans and the Pullman, the shots seem to be on the improve. With the home-roast the channelling is far worse then with commercial beans. I have only started roasting but can the beans make this much difference?

                          With the Sunbeam tamper and commercial beans however there was as bad of channelling as the home roasted beans. So perhaps in my case at least, its half sunbeam tamper half home roasted beans?

                          hmm....

                          Comment


                          • #28
                            Re: Channelling!?

                            Gday,

                            I was refering to a puck that looks like this:



                            as you can see the edges of the bottom of the puck are darker than the rest. The picture that Kiwi posted above looks even more scary, as you can really see that the middle of the upper part of the coffee cake is really bright.

                            For the last couple of days I tried various things and nothing seems to work. Tried dosing 14g and got a soupy puck, tried 16g and a similar result. Went back to 18g and a light tamp, massive cone and fast blonding. I dont know what it is. As someone stated on these forums it shouldnt be so hard, you shouldnt need to have perfect fitting tampers, perfect dosing and distribution to get a decent cup of coffee. When I look at youtube movies showing extractions made on professional machines and I observe the techniques used there it makes me wonder, why the hell cant I do that? I mean it looks so easy, dose, light tap to settle, stockfleth and tamp, lock in and brew away. And that gives perfect pulls. I have to use wierd needle tools, split dosing, various tamp pressures and I end up with s**t in my cup.

                            Cheers,
                            dsc.

                            Comment


                            • #29
                              Re: Channelling!?

                              Originally posted by dsc link=1174961569/15#27 date=1180091657
                              I have to use wierd needle tools, split dosing, various tamp pressures and I end up with s**t in my cup.  

                              Cheers,
                              dsc.
                              i know exactly what you mean, dsc... and i am reading your thread avidly, and trying doggedly all the solutions offered.... in our case, though, i think it is the humidity in the motorhome which causes a lot, if not most of the problems.
                              i still get blond, bitter gushes with black "pre-gushes" immediately after locking and switching the pump on.... i dumped 9 shots this morning ( some choked, some dripped "oil") before i had one resembling a steady thin crema pour over 15 sec before it gushed and blonded.
                              in the end i went back to the single basket, ground at 9 on the rocky, didnt overfill, didnt use the needle, tapped once, palmed the grounds level, tamped once at app 12-14 kg locked, pulled and stopped the shot at 15 sec.
                              reasonable crema, steady thin stripey flow, fruity and not bitter.
                              oh, and it is raining here... so the humidity is through the roof, almost literally speaking!! ;D

                              i am just wondering whether your "frozen" beans have too high a level of humidity , therefore producing the same stuff as i am getting here when the water is hanging off the ceiling???

                              cheers,L

                              Comment


                              • #30
                                Re: Channelling!?

                                Gday,

                                I thought that frozing can be bad for coffee, but it turns out its not. I get the same results from coffee that was frozen and defrozen to use and coffee that wasnt frozen at all.

                                I never use the single basket because when I used it a couple of times I got awful shots with massive blodning and fast pours. Now I use a very light tamp and no additional techniques like split dosing and get pretty good pours. It drips oil for a couple of seconds but after a while a steady thin stream appears which, to my surprise, doesnt blond for a longer time. When I tamped with 15kg or more I used to get blonding AND a huge cone, now I dont get the big cone and I slowed down the blonding so I guess something is getting better.

                                Cheers,
                                dsc.

                                Comment

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