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  • Inconsistent shots

    Hi all,

    First post although i have been reading coffeesnobs for a while getting all the info i can. I recently made the jump up from a 12 year old breville machine with a built in grinder to a Diadema Unico Splendor and a Macap M2M Grinder (got them both as a package). The Breville served me well to make Latte's but then I had to get off milk for a while and its shortcomings where obvious when needing to make espressos.

    It has been both fun and frustrating at times trying to get a decent shot that is not sour or bitter. I have learnt a lot and have wasted a lot of coffee trying. I upgraded a few parts such as a IMS shower screen and got a VST 18g and 15g basket. I didn't do too bad on the 18g basket but wanted to switch to the 15 to lower the caffeine dose I was getting. The 15 was too finicky for me in my early stages. I know the VST's require you to have everything else down pat to get that nice shot so I figured I would switch to a more forgiving basket until I got there. My 14g Espresso Parts Basket arrived and it only took me a couple of shots to get what I think was the best shot I have had so far. It was 2.05 on my grinder, 14.1g in and 29.5g out in 25sec.

    I do find it hard to cut the machine off right on the target I am aiming for as it can easily go over in that time. I WDT and believe I am pretty consistent with my tamping from shot to shot. Excited first thing this morning to taste the shot again I went through everything the same only to find the flow rate way slower and I only got out 19g for the same recipe. Confused I tried again but dropped the dose back .1g to 14g and tried to tamp slightly lighter. Still slow and it took me 40sec to get 29g which was very bitter.

    What could be causing this inconsistency? I keep probably 2 days worth of beans in the hopper. The house would have dropped a couple of degrease overnight if that matters. I am wondering if whatever causes this has been the problem so far but because I have been tweaking each shot each time to make it better I haven't noticed until trying to use the exact same recipe.

    Any help would be great, I am expecting new grinder burrs in the next day or two although I didn't really notice a difference in the grind. I roast my own beans (popcorn maker) and they are about 5 days old.

  • #2
    There's a few things that could be contributing such as how warmed up the machine is etc, but my guess is it's the age of the beans. They're probably still off-gassing. How light/dark are they roasted?

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    • #3
      I did think of the temperature but figured the flow of water should be the same through the grinds regardless of temperature? or does hotter water flow through at a quicker rate?

      The beans are a Medium although definitely hit the darker end of medium of these ones unfortunately.

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      • #4
        The higher the temperature, the faster extraction will happen. The faster extraction happens, the faster the flow resistance of the puck goes down and flow increases. Temperature will have a significant effect on overall shot time.

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        • #5
          Hmm, that could be it then as i adjusted the time the machine turns on (on a smart switch) since im working from home and waking up a bit later, it definitely wasn't as steamy when doing my usual cooling flush. Temp is one thing i struggle with and maybe the cause of so much trouble for me, i am thinking of getting one of the Temp gauges that can screw into the E61 to help.

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          • #6
            How old is the machine? The older ones, mostly grey imports, massively overheat the group. There was no thermosyphon restictor installed in most of them so unless it's a newer model or has already been through a competent workshop for adjustment, chances are it's overheating.

            An overheated group will give unpredictable results. After it's initially warmed up for 20-30 minutes, run the group with no handle in place for about 10 seconds. Leave the machine sit idle for 2-3 minutes then activate the group again. Is the water sputtering and steaming when it's coming out? If so, overheating is a problem.

            My most recent Splendor, I ran a 250ml cooling flush yet the lowest I could get the brew temp was 96C. After installing a restrictor, this came down to a reliable 92.5-93C with no cooling flush.

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            • #7
              The machine is about 6 years old (unsure of exact date as purchased it second hand). I did adjust the pressure stat to turn it down from 1.4/5 bar to 1.1 which does help it not get as hot but after a 30min warmup the first cooling flush is definitely sputtering and steaming, second flush still a little.

              I just tried it again after a longer warmup as I think that was the issue this morning. Although not as slow it still was 39 sec for only 24.8 out. I decided to test the temp of the water straight after so pulled a shot of water with not portafilter and it was 87degrease. Assuming it would be a little colder due to just pulling the espresso shot. It seems potentially temp is the cause but am at a loss as to how to know its right and how to get it consistent. Potentially the gauge on the group head? I don't want to have to pull a shot of water each time and check the temp of it and of course that will have an effect of the temp of the next shot anyway.

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              • #8
                So again at a loss. Let it warmup again and tested the water that is sputtering and steaming out and it is 89 degrees. So I let it warmup again after that and pulled another shot with the same recipe again. This time 14g out at 35sec. Why the hell is it this inconsistent. This would have been as hot as the machine was (possibly even hotter) yesterday when I got a perfect delicious shot. I'm really at a loss here

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                • #9
                  Do you purge your grinder before filling the portafilter?

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                  • #10
                    Yes although i dont do what i have read some do with getting a brush up there or anything. Surelly some left over grinds wouldnt cut the flow in half or less then in some attempts? I also make two cups one after the other at times and there can be a big variance in those and thats without a purge but the grind is less then 5mins apart.

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                    • #11
                      What pressure are you getting with a blind filter?

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                      • #12
                        When I was a newbie starting out on a more sophisticated machine and grinder (versus the breville) there were a few things that took me a bit to figure out which was affecting the shots. The most significant was

                        1. making sure to purge the grinder

                        2. adjust the grind to suit the temperature in the morning. Where I live the temperature outside and inside varied by a few degrees every morning meaning that everyday was an exercise in adjusting the grind to get the perfect shot - I got used to it after sometime to watch for the rate that the beans were coming out of the grinder and instinctively knowing based on how the temperature felt how many notches to adjust the grind.

                        3. Different beans and roasts need different recipes and grind settings to get the shot out to perfection. This takes time to learn your equipment and how to adjust.

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                        • #13
                          Thanks for that, I do think it has something to do with a difference in the morning and afternoon like you mention. I purge the grinder by giving it a shake, since i half fill the hopper i cant exactly purge without grinding more beans? I have been thinking about getting a Niche Zero but i do like putting beans in the hopper every few days rather then each time i want a coffee. Potentially the beans were too young although they were 4-5 days.

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                          • #14
                            Originally posted by worthy1 View Post
                            I purge the grinder by giving it a shake, since i half fill the hopper i cant exactly purge without grinding more beans?
                            Purging the grinder requires running the grinder. Even though some comes out when you shake it there are still stale beans between the burrs and inside the grinder, you're only shaking out what's in the spout. Purging means running it for a few seconds and throwing out what comes out during that time.

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                            • #15
                              Gotcha, what effect would not doing that properly have? i would have thought it would just not be as 'fresh' not lowering the flow

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