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Sudden issue with clumping

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  • Sudden issue with clumping

    Hi guys,

    Bit of background, I've got a Macao m2m (two and a half years old) and a gaggia classic which I've had for about 3 years and is about 15 years old.

    I use the same fresh beans every week, with the same technique but suddenly I've noticed on my normal adjustment setting for the m2m I am getting a very clumpy grind that seems to be affecting my extraction times greatly and I'm scratching my head trying to get to the bottom of it.

    Usually on my regular setting I grind 18g and this yeilds about 60ml over 25-30 seconds, suddenly now with those same setting nothing happens for about 20 seconds and a really really slow poor that tastes horrible.

    I thought maybe the burrs on the m2m need replacing but I've worked out it's only had about 30kg of beans through it in the last 2 and a half years.

    Any ideas would be greatly appreciated.

  • #2
    I have the same grinder and have had occasional problems with clumping. Now I usually just run some grinder cleaner through it when the problem occurs. If you want to get fancy you can take the top off and clean the burrs manually with a soft brush. This isn't that difficult, although you will need a fine Phillips head screwdriver (jeweller's screwdriver or equivalent). Just take the hopper off, undo the screws on the plastic top and unwind the adjuster until it comes off. Reverse the process to reassemble. You will need to dial in your grind again after doing this.


    • #3
      Tip Before you remove the top burr / adjustment collar...
      1/ Remove the hopper and as many beans in the grind chamber.
      2/ Mark The setting as it is on the body and the collar.
      3/ Now run the grinder again and slowly adjust collar a little towards the finer setting.
      4/ Turn off grinder and disconnect from power point.
      5/ Turn grinder ( lightly) finer as far as it will go and mark a 0 with a line thru it.
      That marks true Zero

      Now note the notches between your previous grind setting and the true zero,
      disassemble clean reassemble and turn the adj collar all the way thru to true zero.
      If the exact same spot return your collar to the previous grind setting .
      If not take note of variance and adj accordingly.
      Good Luck


      • #4
        PS to my previous post, after only 30kg of beans it is unlikely the burrs need replacing, unless you have put some stones through it inadvertently. That should be obvious from a visual inspection of the burrs. Here's a link to a youtube video which shows the dismantling and reassembly process. Note that the top burr holder undoes clockwise.

        BTW, the appropriate brush is a soft metal brush, one of the ones with bristles made of (I think) brass or copper.

        One final hint. It seems to be common for the outlet spout to become blocked when clumping starts to occur. Make sure you clean it out thoroughly and give the whole grinder mechanism a thorough vacuum.


        • #5
          Hey, thanks so much.

          So I actually took your advice and found a video demonstationg the removal of everything so I did that and cleaned/vacuumed everything because it was all quite dirty.

          I set everything back to zero, and upon reassembly it was still clumping. I decided to make the grind coaser and this resulted in no clumping but now a very quick pour, so some further adjustments are needed but I ran out of beans.

          I THINK I might be on the right track though, thank you very much for your help. I'll keep you filled in with how I go once I get beans and can make it a bit finer without clumping hopefully.

          Stay tuned!


          • #6
            Also, any tips for cleaning the outfeed spout?


            • #7
              Poke something like a toothbrush down it from the inside, then vacuum from the outside with your hand covering over the grinder as much as possible.

              Further tip: clumping per se is not a problem. Only worry about it if it affects the quality of your extraction. Some people think it is better to grind into a container other than your portafilter, then stir up the grounds with a fine object like a large needle before filling the portafilter. However, I can't see the point. Clumps are caused by the coffee particles joining together. You want them compressed, that is why you tamp the coffee before you lock the portafilter in. After tamping, I doubt if the areas that were clumps are any different from the rest.


              • #8
                If you can pick up a clump and throw it at someone it will be a problem. If it falls apart as soon as you try to pick it up it won't be an issue.


                • #9
                  Okay, so this is really frustrating and it's getting to the point where I want to throw this grinder in the bin haha.

                  Went through half a kilo of beans dialing it all in and finally got it perfect. Minimal clumping, and a really nice shot.

                  The following morning I went to make another coffee,same grinder settings and it's started clumping again! Short was horrible, pour was way too slow. I can't for the life of me figure out what the hell is going on and it's driving me absolutely insane.


                  • #10
                    Okay, my final contribution on this subject. Coffee is a variable beast and can be greatly affected by eg humidity. I anticipate you would find clumping more of a problem in humid weather. Baristas commonly find they have to vary the settings on their grinder according to the time of day. All I can suggest is, if your first shot is too slow back off the grinder a couple of notches and try again. I assume your tamping pressure doesn't vary too much.

                    Although the Macap is not a perfect grinder, I don't think it is the main cause of your problem.


                    • #11
                      Like Alex mentioned above - It won't be your grinder.
                      Much more likely to be the beans you're using coupled with variations in ambient conditions.

                      As an aside, have you had your Classic checked out by a reputable service centre to ensure that all parameters are set within acceptable limits for the attainment of consistently excellent coffee? At 15 years old, it wouldn't hurt to have this done...



                      • #12
                        Originally posted by Dimal View Post
                        Like Alex mentioned above - It won't be your grinder.
                        Much more likely to be the beans you're using coupled with variations in ambient conditions.

                        As an aside, have you had your Classic checked out by a reputable service centre to ensure that all parameters are set within acceptable limits for the attainment of consistently excellent coffee? At 15 years old, it wouldn't hurt to have this done...

                        See the strange thing is I've used these same beans for years now and have never ran into this issue until now. Likewise with ambient temperature, I agree humidity will effect thing's bit I'm sure we've had humidity in the last three years but it seems only now this issue has arised.

                        The machine is 15 years old but after purchasing it I stripped it down and did a "rebuild". New upgraded shower screen, new gasket seals, new brass dispersion disc ect, the only thing I haven't done is check to see if it's running 10 bar of pressure.

                        I really think the issue lies with the grinder, as when I get a nice grind with minimal clumping I pull a perfect, and excellent tasting shot. I've never had this issue in the three years of running this machine/grinder combo until now, where it's grinding quite fine and pulling a nice shit, and then the next day giving me giant lumps big enough to throw across the room.

                        I really so hope I can solve it, I'll keep playing around with the grind some more and keep you posted.


                        • #13
                          Any chance of changing to a different batch of beans, just for argument sake...
                          Beans being a natural product, are subject to a lot of variability and no matter how careful the Roaster is, a lot of this variability can end up in the final product.

                          Grinders are such simple pieces of machinery, there is next to Sweet Felicity Adams that can go wrong with them. You've also had the grinder apart and nothing appeared to be drastically mechanically wrong with the innards. If you still think it is the grinder after trying a different batch of beans, take it to your trusted specialist service person and ask them to go over it with a fine tooth comb. Nothing much else to do really...



                          • #14
                            I would concentrate on what is causing the change in pour time.
                            Asumming at this stage it's not coffee machine related then it is either the grind is too fine or the dose has increased.
                            Maybe start weighing the dose to see how consistent this is between shots.


                            • #15
                              Clumping itself wouldn't effect pour time greatly but it may be a symptom or cause of retention in the grinder.
                              On some shots only a portion of the dose is being expelled by the grinder and on others a significantly larger amount.
                              Weighing the dose should identify this.