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Thread: Poor quality shots

  1. #1
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    Poor quality shots

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    Hi all,
    I am struggling to get consistent, good quality shots. I am operating with a mini mazz, vbm domobar super lever with coffeelabs tamper.

    When i pull a shot it seems to take a few seconds to start (which is good) but after about 10 seconds it really starts to gush out. Having inspected my pucks I think I have a channelling problem.

    I have tried being very consistent with dosing and tamping.

    I suspect that maybe i am tamping too hard or have ground too fine and the water is struggling to get through the puck - causing the channelling.

    Does anybody have any suggestions to fix this. :(

    thanks - andy

  2. #2
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    Re: Poor quality shots

    Hi Andy

    Have you checked how hard you are tamping on some bathroom scales?

    The fact that you are aware of the need to be consistent leads me to believe this is just a minor problem.

    Also how is the freshness of your beans?

    cheers

    Nigel

  3. #3
    Senior Member askthecoffeeguy's Avatar
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    Re: Poor quality shots

    Hey Andy,

    Definitely check the freshness of your beans, and how they are being stored.

    Also, try experimenting with the grind a bit to see what different results you get.

    And as a rule of thumb, the finer the grind, the less pressure you need to tamp.

    When Im adjusting my grind settings I always look for what I refer to as pilling in the grind.

    That is, when I have achieved the right consistency, the grind tends to pill or gather together in little ball-like formations, about the size of a small pea!

    Are you adjusting your grind for different temperature / humidity conditions?

    Warm weather means finer grind, but cooler weather means winding the blades out a bit.

    And how much are you dosing? Have you tried either measuring volume or weighing same?

    Under-dosing is more likely to cause channeling whilst up-dosing can choke the extraction, if youve over done it!

    Dont be afraid to experiment until you get a result you like. Yesterday I threw away 5 shots, while I was dialing in my new Supper Jolly, and a new blend.

    Also, do you back-flush between each extraction, by placing the empty group handle back in the machine, and running a blank shot of water through it, whilst gently nudging the group handle back and forth, to remove any excess grind from the previous shot?


    Cheers,


    Pat

  4. #4
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    Re: Poor quality shots

    Sounds like you are tamping too hard and possibly dosing too high (or some combination of the 2). What you want to do is try and get the espresso to pour at the same speed the entire time. If you are tamping too hard, with a course grind, then the water struggles to break the initial seal of the puck, but once it does it gushes. Try grinding finer and not tamping so hard with the same dose. Once you have achieved this balance then you can experiment with dosing.

  5. #5
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    Re: Poor quality shots

    Bean quality should be good. They were roasted on Sunday when I bought them so that are less than a week old. I keep them in an airtight container and only grind what I need for each cup.

    I havent checked tamping pressure so will get hold of some scales over the weekend and let you know how i go.

    I will also try plaing around with dosing and tamping and see what effect this has..

  6. #6
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    Re: Poor quality shots

    Hey andy77

    Just a suggestion, make sure that when you tamp the dose it is even all the way around the basket, I have noticed that even if it slightly uneven channeling occurs on the low side.

    I also weigh the beans/\/dose 17gm for a double with a very firm tamp, with slight grind adjustment throughout the day ( half a tick at most )

    Cheers Gazz


  7. #7
    Senior Member askthecoffeeguy's Avatar
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    Re: Poor quality shots

    Quote Originally Posted by andy77 link=1189114721/0#4 date=1189144751
    Bean quality should be good. They were roasted on Sunday when I bought them so that are less than a week old. I keep them in an airtight container and only grind what I need for each cup.
    Hey Andy,

    if they were only roasted on Sunday then they are most likely still degassing! depending on the beans, you need at least 7 to 10 days to allow them to degas (release CO2) after roasting, and quite possibly a lot longer than that!

    Some roasters even recommend a minimum 3 week period to allow their product to age before using it.

    Cheers,

    Pat

  8. #8
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    Re: Poor quality shots

    Alright - i think i am back in form.

    i think my problem was that i was under dosing and trying to compensate by over tamping. This lead tot he water pressure struggling to get through - eventually it found a weak point in the puck and started gushing. Have made my grind a little finer, increased my dose a little and lightened up on the tamping. Seems to have done the job and have pulled 2 quality shots this morning.

    thanks for your help.

  9. #9
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    Re: Poor quality shots

    Good to read. Ive a similar set-up, so I was keen to see how you rectified the problem.
    Well done and thanks for sharing the experience. I think Ive occasionally had the same problem and scratched my head at times, but I like reading the logic about why particular problems happen, and the solution.
    Coffee brewing is such a fine art ! I never realised.

    Phil.

  10. #10
    Senior Member askthecoffeeguy's Avatar
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    Re: Poor quality shots

    Quote Originally Posted by andy77 link=1189114721/0#7 date=1189204449
    Alright - i think i am back in form.

    i think my problem was that i was under dosing and trying to compensate by over tamping. This lead tot he water pressure struggling to get through - eventually it found a weak point in the puck and started gushing. Have made my grind a little finer, increased my dose a little and lightened up on the tamping. Seems to have done the job and have pulled 2 quality shots this morning.

    thanks for your help.
    sounds like youre on the money!

  11. #11
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    Re: Poor quality shots

    I recently had a similar problem. Extraction times were right and the pour looked pretty good but they tasted rubbish! Quite bitter and harsh in the cup.

    In my case I think I was grinding too fine and underdosing. I backed of the grind a bit and increased the dose. Results are now quite a bit better, though there is still plenty of room for improvement.

    I was ready to create a post in the For Sale section there for a while! [smiley=cry.gif]



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