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Why is the top of my puck always splattered over the shower screen? (with pics)

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  • Why is the top of my puck always splattered over the shower screen? (with pics)

    Hey CSers,

    Does anyone have any ideas why the top layer of my coffee puck seems to be 'disturbed' and 'splattered' all over the shower screen?

    Click image for larger version

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    VBM Domobar Super (literally just serviced)
    Pesado PF/Tamper
    VST 18g
    Dosing 17.5-18.0g in (TalkCoffee Brazilian beans)
    Tried tamping at medium & at a high pressure
    Generally extracting 36-38g in about 25-30sec from pull of lever (no pre-infusion because not plumbed in)

    I recently noticed my brew pressure has drifted lower (it's about 7-7.5 PSI with a blind basket) - could this be affecting this?

    I'm not sure if it's related but I'm not getting the taste of shots I want (but big chance it's because I'm new at this); and also a lack of crema (but I know this is not the main goal/indicator of anything).

    Keen to hear your thoughts!

  • #2
    Spicy food does it for me.

    If it is 7 PSI then that is the problem rather than spicy food. A valve is probably not functioning properly. The puck is obviously not compressing as it is normal under pressure.

    Comment


    • #3
      Originally posted by wattgn View Post
      Spicy food does it for me.

      If it is 7 PSI then that is the problem rather than spicy food. A valve is probably not functioning properly. The puck is obviously not compressing as it is normal under pressure.
      Are you talking about the OPV? Or another valve?

      Comment


      • #4
        Mine does it too. If everything is correct, it might be normal.
        Get your pressure sorted first, then you could try lowering dose by 1g and recheck.
        I am considering a aeropress filter above the puck...

        Comment


        • #5
          Originally posted by snoffee View Post
          I recently noticed my brew pressure has drifted lower (it's about 7-7.5 PSI with a blind basket) - could this be affecting this?
          I take it you mean 7.0-7.5 BAR, not PSI....
          Surmising the former, the pressure is a tad too low and should be increased so that 8.5-9.0 BAR is delivered to the top of the puck. If using the machine's own gauge with a blind basket installed, then you'd want to read about 10 BAR on the gauge.

          Regarding the top of the puck in the photo, it looks pretty typical for a Rotary Pump powered machine with no pre-infusion. As Jackster mentions above, after you've got the delivery pressure where it should be, you might like to experiment with a lower dose and work your up to see if that improves things for you in the cup...

          Mal.

          Comment


          • #6
            Thanks all. I'm guessing I do mean BAR

            I'll try adjust the OPV tomorrow, will borrow an insulated screwdriver off a mate. (I'm meant to use an insulated one right?)

            I'm guessing I just put the blind basket in, crank the lever, and then slowly adjust the valve until it hits around 10 BAR?

            Is there a limit on how long I can leave it running at one time while I try to adjust? (Like can it overheat or something?)

            Comment


            • #7
              Snoffee there was a post a few days ago from someone who shorted their machine. If it was me (and I haven't done this) I would completely turn the machine off and make minor adjustments till achieving the required pressure, testing after each adjustment. Slower but no chance of needing to buy spare boards, etc after accidental shorts. Unless of course you have a machine with easy (possibly external ) access to the adjustment

              Comment


              • #8
                Originally posted by snoffee View Post
                Thanks all. I'm guessing I do mean BAR
                If the indicated pressure was higher before the service, I'd refer it back to the service people, as machine gauges can be inaccurate. Your service bloke may have adjusted it with the use of Scace device and you simply have a gauge which is not operating correctly. Adjusting the OPV would then result in incorrect pressure.

                That said, I have an old leva machine which was until a recent group service delivering 6Bar shots. They're a thing and they were excellent as well.

                Comment


                • #9
                  Originally posted by snoffee View Post
                  Hey CSers,

                  Does anyone have any ideas why the top layer of my coffee puck seems to be 'disturbed' and 'splattered' all over the shower screen?
                  That shower screen "splatter" is quite normal. When the pressure release solenoid opens after extraction, it creates a vacuum which sucks up the top of the puck.

                  Comment


                  • #10
                    The Portafilter jiggle is a habit I got into very early in my espresso career, a simple practice that goes a long way toward keeping the shower screen and seal clear of used coffee grounds and general gunk.

                    After, or during a session if you desire, sit the portafilter lightly in place, turn on the brew switch, lever or whatever, then when water begins to flow jiggle the portafilter from light lock to unlock rapidly for a few seconds, works even better with a blind filter.

                    I do this at the finish of each session, could even be done between shots if desired, keeps everything nice and clean.

                    I also do a chemical back flush weekly.

                    Comment


                    • #11
                      I have to say my puck is always in good shape maybe a 3 or 4 on the Bristol scale.

                      I do as Yelta does in that I always run some water through the portafilter after knocking the puck out and make sure it is clean for the next shot.

                      Comment


                      • #12
                        Originally posted by snoffee View Post
                        will borrow an insulated screwdriver off a mate. (I'm meant to use an insulated one right?)
                        Not necessary as you should never undertake adjustments with the power On - It's dangerous.

                        Originally posted by snoffee View Post
                        I'm guessing I just put the blind basket in, crank the lever, and then slowly adjust the valve until it hits around 10 BAR?
                        No, as 338 mentions above, increase the pump bypass valve (OPV) incrementally with the power Off, say a quarter turn at a time, until you observe approx. 10 BAR indicated on the Brew Pressure Gauge when you operate the Brew Lever with the Blind Filter in place. Continuous operation of the pump against a Blind Filter is not recommended.

                        Originally posted by snoffee View Post
                        Is there a limit on how long I can leave it running at one time while I try to adjust? (Like can it overheat or something?)
                        Refer to above...
                        If you're unsure of doing any of the above safely, then it is highly recommended you return the machine to your service provider and request that the pressure be adjusted accordingly. If they have adjusted the Brew Pressure using a Scace or similar device previoously and proven that the pressure is correct, you may want to order a replacement Brew Pressure Gauge...

                        Mal.

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