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Giotto PP: Hot or Not?

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  • Giotto PP: Hot or Not?

    Hi,

    I'm running a Rocket Giotto PP paired with a Mazzer Mini Doser (don't start me). Boiler pressure seems okay vacillating from 1.2-1.3 Bar. Plenty of steam. Last time I weighed I was packing about 20 grams into a double basket (naked PF) aiming for between 22 - 30 grams of espresso in around thirty seconds depending on where I'm at in dialling in the latest beans. Distribution seems fine usually. No spritey stuff going on. Crema varies with beans, but it's not as a rule overly dark, but it's never exactly profuse either.

    So all that sounds pretty normal, but I've been plagued for some time with shots that taste, for want of a better description, "aggressive," - so probably a touch bitter, but with coffee I find it hard to differentiate what's "bitter," "sour" or "lacking caramels."

    Whatever the case, it's brought me to the door that's marked "temperature."

    Changing my flushing routine from "flush and wait" to "flush and go" seems to have helped somewhat. That made me think I might be running a touch hot.

    So like many others before me, I shelled out on Eric's thermometer. This one: Digital Thermometer & Adapter for Exposed E61 Groupheads



    Here's what I found: after allowing the machine to heat up - I leave it on all day - according to this thermometer, and where it's placed, I'm pulling shots at around 203.5-204.0 F (95C).

    Does that sound too hot to you, and would you dial it back a touch or experiment with some more complex flushing routine?

  • #2
    One more thing: the Pstat appears to click off at 1.3 Bar, and eventually idles down to 1.1.

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    • #3
      Originally posted by Kochman View Post
      One more thing: the Pstat appears to click off at 1.3 Bar, and eventually idles down to 1.1.
      Mine idles down to 1.0, so I'm running a touch cooler. I haven't measured the group head temp, but if I pull say 200ml from the boiler to make a tea or long black, it's a lot closer to 90 than 95.

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      • #4
        It will depend on how it's setup.

        We modified plenty of Premium Plus to run at 93 deg and 1.5 Bar. Without a Scace or accurate datalogging method, I'd be using my palate.

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        • #5
          Originally posted by Talk_Coffee View Post
          It will depend on how it's setup.

          We modified plenty of Premium Plus to run at 93 deg and 1.5 Bar. Without a Scace or accurate datalogging method, I'd be using my palate.
          So I'm guessing to lower the temperature at the group head AND raise the boiler pressure you'd have to increase the brew flow rate by fiddling with the OPV. Or am I overlooking something else to adjust?

          Last time I measured my brew pressure it was about 9 Bar. Not sure I want to raise that. Would you?

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          • #6
            Originally posted by Kochman View Post
            So I'm guessing to lower the temperature at the group head AND raise the boiler pressure you'd have to increase the brew flow rate by fiddling with the OPV. Or am I overlooking something else to adjust?
            Nope and yes. My advice is that unless you can have someone log it with a Scace, it's best left alone. I think you may get better results by looking at technique. Try no flush and just a rinse and I'd ignore the meat thermometer and concentrate on your senses

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            • #7
              Originally posted by Talk_Coffee View Post
              Try no flush and just a rinse
              I think I covered that in the OP. Any other suggestions?

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              • #8
                Originally posted by Kochman View Post
                I think I covered that in the OP. Any other suggestions?
                Ok. If your technique is faultless and confirmed by your palate, sure thing. You could take the machine to an expert and pay to have it Scace tested, datalogged and calibrated to your requirements.

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                • #9
                  Originally posted by Talk_Coffee View Post
                  Ok. If your technique is faultless and confirmed by your palate, sure thing. You could take the machine to an expert and pay to have it Scace tested, datalogged and calibrated to your requirements.
                  I do it like this:

                  How to get the best out of your Giotto

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                  • #10
                    There is a substantial temperature gradient from front to back of the E61 group, it acts as a heat sink and the large, flat area at the front radiates more heat energy. Nothing against EricS' temperature sensor, but the temperature you are reading in the main casting, even during a shot, is not what the coffee sees, there will be a small but significant offset, not to mention any small error in the calibration of the instrument itself. As chris says, if you really want to know, consult someone with a Scace and the knowledge to interpret the results. Sounds to me like it's performing pretty well temperature wise.

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                    • #11
                      Thanks for your advice.

                      The more I watch the temperatures the more I think there might be something amiss with my machine, and yes, as advised, it does appear a date with a Scace is inevitable. Perhaps it's to do with the Thermosyphon Restrictor. I don't know.

                      I found by dropping the Pstat to 1.2 and flushing to bring the group down to around 208 F, the first shot is good and the second is good to go straight away with little to no flush. The result in the cup has improved.

                      Backing the Pstat down to 1.1 dropped the temperature too low. Good for one shot only.

                      And moving it back up to 1.3 merely lengthened the first flush.

                      Summary: I don't think trying to tweak boiler pressure is the cure-all.

                      The more enduring problem is recovery time in consecutive shots. Oh my God it's slow.

                      Even with the Pstat wound back up to cut off at 1.3 (factory setting) by the third shot I find the group continues to fall in temperature for 80 seconds, and takes at least a further three minutes to return back into the zone where I could extract again. But realistically, more like four.

                      I'm losing it here.

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