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Bought a Diadema Perfetta

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  • #16
    Grinder upgrade - Compak K6

    I've finally upgraded my grinder from a Sunbeam EM0480 to a 2nd hand Compak K6 (thanks to benspawn, great to deal with and game me plenty of help and advice). It's too big to fit on the kitchen bench under the cupboards with the large hopper so I've got to try a few ad-hoc ~250g hoppers made from juice bottles and vitamin containers (functional but not pretty).

    It's amazing the difference a proper grinder makes! I chewed through all my fresh beans dialling in the grind, even the over/under extracted shots were passable. Playing around with some stale beans at a slightly finer grind was also able to pull edible shots, something that was not remotely possible with the sunbeam.

    Next step is to head on over to a Dibella training course to iron out the kinks in my technique. I'm also going to follow Ben's advice and stick with some large brand name beans while I'm learning to ensure the blend/roast is consistent. To date I've been trying beans from all over the place, mostly small roasters that supply my favourite cafes.

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    • #17
      I've done a bit of shopping and decked out the kitchen bench with all the required coffee apparel. I can no longer blame my tools for a bad cup, it's all down to the operator.

      Equipment in the photo…
      • Diadema Perfetta E61 single boiler machine (steam takes a while to heat up but pressure is very good)
      • Compak K6 grinder (need to find a small hopper)
      • Sunbeam EM0480 grinder (might sell this or keep it for French press beans)
      • Naked portafiller (triple basket) + 2x standard portafillers (double basket & blind)
      • Knock box, 70ml measuring cup, 400 & 600ml milk jugs and other accessories


      I still regret not going for a HX machine over the single boiler, I now drink espresso at home instead of macchiato's due to impatience. The doser on the K6 is taking a bit of getting used to (plus it's a pain to clean). I've got the fineness of the grind dialed in for a 30ml in 25sec shot, but it clumps up when leaving the grinder making even distribution difficult. I purchased some 'precision baskets' from Talk Coffee which are ridgeless with straighter side walls then the previous double basket, hopefully this will allow me to play around with different tamping pressures as previously the tamp would stop at the ridge.

      Finally I'm keen to get familiar with the machine's settings. I note the pressure gauge always ramps up to 14bar when pouring a shot, however the optimum extraction pressure is 9bar. Presumably the gauge is just reading the pump, however it would be nice to measure extraction pressure at the group head. Similarly I would like to acquire a temp probe and check the set point of the boiler vs. extraction temperature. More reading / research is required!

      Once (i believe) the machine is set up properly I'll finally get around to do a home barista course.
      Attached Files

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      • #18
        After a bit of tinkering, mostly thanks to the info in this thread, I've dropped the brew pressure from 14bar to 10.5bar as per the gauge. I've put my name on the list to hire Greg Pullman's portafilter pressure gauge so I can have another go at adjusting it properly. I'm also going to acquire an allen nut thermocouple and maybe another thermocouple for the boiler, the idea being to calibrate brew temp via the boiler thermostat and get an idea of overall temperature stability.

        Opening up the Perfetta shows that it is in fair condition with a bit of corrosion here and there. This leads me to think that the E61 mechanism and boiler could probably do with a clean and descale. More reading required to learn how to service it properly and a few more things to buy.


        After adjusting the pressure I've found extracting a shot to be much more forgiving. I'm still all over the shop with my grind and tamping, however now the sour/bitter flavours are much more mellow and I'm hitting the sweet spot more frequently (but still not on demand). Getting there...!
        Attached Files

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        • #19
          You can also get a pressure gauge like this one; it screws onto your portafilter; manometer I've got one of these for my Oscar.

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          • #20
            Cheers iampivot, that's almost as cheap as hiring Greg's travelling.

            I might grab it + a thermocouple and have a stab at turning my spare portafilter into a DIY scace tool.

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            • #21
              For a while now I have been wondering why I am consistently either under or over extracting and why I had to overdose to get a passable shot. I went to grab my triple basket this morning to try making a long ristretto, only to find the double basket on the shelf and realised I had been using the triple for the past few weeks (trying to get 50-60mls in 25-30sec from the triple). After popping the triple basket back in and a bit of fiddling with volume and timing, I managed to pour a passable 50ml ristretto in 20s from 23g of beans.

              Can anyone offer advice on a ballpark time/volume to target when trying to make a triple ristretto? (18-21g TalkCoffee precision basket) From my reading thus far I am thinking it should be 45-60ml in 15-20sec, however there is a lot of conflicting info.

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              • #22
                After purchasing an EricS e61 temp gauge, I have confirmed that my Perfetta has been running hot - idling at 105degC. Turning the thermostat down as far as possible adjusted the idle to 100degC and brew around 103-105degC.

                A while later I started noticing thermosyphon stall - idle at ~ 90degC, which would ramp up to 100degC over 5mins after pulling a shot. At present I have been temp-surfing the perfetta by running water through the group until it's 95-96degC, then purging the top of the tank using steam pressure, a bit of a top up with cold water via the pump and then pull a shot. Using this method the group allen key pre-shot is 94-95degC and mid shot around 96-97degC. This method has significantly improved the flavour and consistency in the cup and I speculate that the tank refill/pressurisation acts like a low pressure pre-infusion over 6sec (mainly due to a lot less channelling).

                Anyway I'm sick of temp surfing and love to tinker so I've purchased some cheap eBay PID gear to replace the thermostat & insul-Bright for the boiler. Once I've redone the e61 seals in an attempt to fix the thermosyphon stall, I'll dive in and try my luck with PID control.

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