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  • "popcorning" inside grinders

    Gday,

    I was reading the "Choice of grinders..." thread on this part of the forum and it struck me that some of the members suggested not to weigh the beans for every shot but to keep around 4cm of beans in the hopper. This is to ensure that no "popcorning" goes on inside the grinder while we grind. Frankly this is the first time I have ever heard this term and I have to say Im a bit surprised.

    I have an MDF grinder, its not top notch and not perfect but it does the job quite ok. I always weigh the beans before grinding and dose only what is needed for one shot. After reading about popcorning I thought about switching to more beans in the hopper but there could be a problem with the freshness. You see I order fresh coffee from a local roaster and dont roast myself. This means that I try to keep the beans as tightly packed as possible to get the most out of them for the maximum amount of time. Keeping my daily dose in the grinder (thats around 70g as I do four doubles a day, each being 18.5g) means the beans will go stale faster.

    Maybe if I seal the joint between the hopper and its cover and put some black paper around the hopper to protect the inside from light the beans will stay fresh longer? On the other hand its just a one day batch of coffee in there, so maybe Im overreacting?

    I hope this will turn into an interesting conversation

    Cheers,
    dsc.

  • #2
    Re: "popcorning" inside grinders

    Just about the hopper bit.
    Air will still get in from the coffee exit chute through the burrs, unless you want to seal that up to and take it off for each time you grind.

    Comment


    • #3
      Re: "popcorning" inside grinders

      This "popcornin" is most definitely real. It exists. Its a pain. The beans, having no weight on top of them, fall on to the spinning burrs and get tossed up into the air. They then fall onto the spinning burrs and get tossed up into the air. Etc.

      But DSC, you are not leaving beans in there for days at a time to go stale. In your case, about 70 grams worth will disappear in one day.

      I dont believe that beans are so fragile that, having survived in a one-way valve container for up to weeks, theyll suddenly go stale in a day in a hopper.

      In any case, beans on the bottom will get little exposure to air as they are covered by their mates on top.

      I wouldnt worry about it.

      -Robusto

      Comment


      • #4
        Re: "popcorning" inside grinders

        Ive got an EMO480 and I definately notice a significantly courser and uneven grind when there isnt enough beans in the hopper.

        I have a glass thingy that I put inside the hopper to put weight on the beans/burrs when the hopper goes lower than about 1/2 full. Then, when the beans are so low that the glass jar cant do the job anymore (the "burr protector" gets in the way with the EMO480) I either romove and store the beans to use in a blend or throw another load of beans in.

        Paul Bassett said that its important to "always keep the hopper FULL" to maintain weight on the burrs, which is a pretty tough ask if you trying differenct beans and origins. The glass weight hopefully simulates a full hopper. Does anyone else do this or something similar?

        Comment


        • #5
          Re: "popcorning" inside grinders

          Disagree with Mr Bassetts advice -- would be more applicable in a commercial environment where they go through the hopper in
          hours or even minutes.

          --Robusto

          Comment


          • #6
            Re: "popcorning" inside grinders

            Hi everyone,

            Im wondering how the popcorning effects grind evenness. I understand that some of the beans jump when they hit the spinning burrs, but what is wrong with that? They can break into pieces, but still those pieces will be much bigger that the output of the grinder. They will still need to be grind into finer particles, plus that breakage still goes on when the bean gets between the burrs. I just cant understand whats so bad about the whole popcorning effect. Has anyone ever done any experiments that show the bad influence that popcorning has on the grind evenness?

            Yup I agree with Robusto, a 100% full hopper is a good thing in commercial environment, but not in home applications.

            Cheers,
            dsc.

            Comment


            • #7
              Re: "popcorning" inside grinders

              Well, I must say I only notice the difference in the grind when the beans get REALLY low... as in, the last shot or two before my weight cant put any weight on the beans anymore.

              Robusto, what makes you so confident in dismissing Lord Bassetts divinely inspired wisdom ;D? You didnt say why you disagree, you just that you disagreed. Just as a matter of interest that is.

              Comment


              • #8
                Re: "popcorning" inside grinders

                Experiments are for labs...its known from experience

                Comment


                • #9
                  Re: "popcorning" inside grinders

                  Hi again,

                  Well, I must say I only notice the difference in the grind when the beans get REALLY low... as in, the last shot or two before my weight cant put any weight on the beans anymore.
                  Cant that be somehow connected with the fact that the last beans of the present hopper batch are more stale than the rest? Of course thats only possible if you have a large amount of coffee in the hopper, like 90-100% full.

                  Wushoes: I understand that you have experienced the effect of popcorning? if so what does it do? are the extractions faster? faster blonding?

                  Im still wondering how "jumping" beans can affect the grind evenness.

                  Cheers,
                  dsc.

                  Comment


                  • #10
                    Re: "popcorning" inside grinders

                    Has anyone ever done any experiments that show the bad influence that popcorning has on the grind evenness?
                    *hand shoots up*

                    Firstly, Im going to presume that by "grind evenness" you mean "repeatability of particle size distribution spectrum." Thats because Im not aware of a skerrick of evidence that having a bunch of particles of exactly the same size is actually a good thing.

                    Basically, whilst experimenting with a bunch of different coffees during a Sunday arvo session at TMR, I was using a number of beans that we only had a few hundred grams of. Dosing the same way with the last shots resulted in a faster extraction. I havent done an experiment to see if that extraction speed is repeatable.

                    One of the internet coffee denizens who is famous for backing up his assertions with experiments is Jim Schulman. In doing an experiment to determine which of a set of conical grinders produced a better shot, he rigged up some small cylindrical paper hoppers for each grinder. He found that then weighing the beans down with a shot glass simulated the effect of a sufficiently full hopper. (BTW; the mazzer robur spanked the two macap conicals and the mazzer mini for normal doses of coffee.)

                    Im wondering how the popcorning effects grind evenness. I understand that some of the beans jump when they hit the spinning burrs, but what is wrong with that?
                    Im not sure that its the beans jumping around that matter. It could just be having less weight feeding the beans into the burrs.

                    Maybe if I seal the joint between the hopper and its cover and put some black paper around the hopper to protect the inside from light the beans will stay fresh longer? On the other hand its just a one day batch of coffee in there, so maybe Im overreacting?
                    Yes, Id say that youre over reacting. If you manage your bean supply freshness it shouldnt be a problem. If your bags seal well, leaving the beans in the hopper might actually make it easier to keep your shots dialed in. At work, I have taken to cutting open bags for my shifts well in advance of using them (usually the night before). Otherwise, I have to chase the grind all over the place as the beans start to enjoy the ambient conditions more. Or whatever they do!

                    Cheers,

                    Luca

                    Comment


                    • #11
                      Re: "popcorning" inside grinders


                      Inspired by another recent post that touched on the popcorning issue, I did a little "amateur" experimenting over the weekend.

                      In my case, I dont use the hopper at all, and measure a double shot [volumetrically] and just drop it into the throat of the grinder.

                      I have looked for evidence of popcorning, and maybe one bean in 5 shots will jump, but otherwise it doesnt seem to be a real issue.

                      I have a flat burr grinder and the beans are flung centrifically into the burrs. As I see it, the spinning whirlpool seems to "hold" all the beans in place.
                      Also, in my grinder, the throat has a diameter of 50mm, and grind chamber is larger again so this too, may assist in keeping the beans down.

                      Over this weekend I tried several methods of weighting down the beans: upside down pullman tamper, cut down chair leg, plastic medicine bottle full of beans etc.

                      Strangely enough, the first two methods seemed to jam the beans, sometimes only 3/4 of the beans would grind through.
                      The med bottle method which approximated the "real weight" of more beans didnt jam but seemed to make no difference.

                      Specifically, I was looking for discernable changes in the grind texture and/or the extraction time and I saw no change.

                      Since I can get repeatable results with 18g of beans sitting by themselves in the hopper, Im happy to stick with this method!

                      I concede that different grinders and burr sets and even beans may behave differently, especially conical burr sets [like the sunbeam] that may rely more on gravity feed, than centrifugal force.
                      Also, I can understand that this issue would be more relevant in a commercial setting.

                      Bottom line, if you can get repeatable shots stick with your preferred method. ...as Luca says "IWITCTC"

                      Comment


                      • #12
                        Re: "popcorning" inside grinders

                        Its not about grind evenness...you need a whole bunch of different sized particles to pack in...

                        Think of say....interstitial and/or substitutional atoms within a lattice for those who know chemistry (I dont know chem but know enough of it to make this analogy). Interstitial atoms fill up the gaps between the larger sized particles.

                        For some reason it screws up my pours like today when my hopper kept on getting empty when I was busy.

                        Im an advocate for keeping a hopper full of coffee....otherwise if you have a compulsion to weigh out beans and grind per shot like that, my advice is to take the hopper off pop your coffee in to the throat of the grinder and leave your tamper on top.

                        Cheers.

                        Comment


                        • #13
                          Re: "popcorning" inside grinders

                          Spot on, Wushoes. Now that I think of it in terms of "interstitial and/or substitutional atoms" it all falls into place.....

                          !!!!!!!!

                          Robusto

                          Comment


                          • #14
                            Re: "popcorning" inside grinders

                            Gday All,

                            This phenomenon doesnt seem to be an issue with the recently acquired LSM grinder. I only drop enough coffee into the hopper as required, either for two brews at a time or just one for me. The resulting grind is very noticeably uniform.... no large pieces and almost no fines at all. Theres probably more to this thing than meets the eye :-?, from one grinder to another.

                            No popcorn for me thanks ,

                            Mal.

                            Comment


                            • #15
                              Re: "popcorning" inside grinders

                              Gday,

                              so today I filled my hopper with around 80g of coffee and made two shots each with 18.5g. The results where quite different to what I usually get when weighing coffee per shot. I almost choked my machine two times and had to wait 20s each time before a steady stream of coffee appeared. Will check how it works with the next two shots that I plan to make later today, but Im expecting to see faster pours.

                              Anyway it all seems to be true and as Mal says it also depends on the grinder you use. I guess its best to try both weighing per shot and having a half full hopper to make sure.

                              Cheers,
                              dsc.

                              Comment

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