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  • #31
    I would also say it's the grinder more so than the machine. Opv does make a difference but not for 13 sec pours. You should easily be able to choke the machine with a fine grind. If you can't, the issue is the grinder

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    • #32
      I wouldn't expect the Rocky to be at fault, other than if the Zero point has been incorrectly set. This could also be taken along with the Silvia to have it checked out - Only a five minute job to determine if the Zero position is correct - If it isn't, only another five minutes to put it right...

      Mal.

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      • #33
        It may have been said before, but to reiterate... If you cannot grind fine enough to choke the flow, then you definitely have a grinder problem.
        A simple check should confirm.

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        • #34
          Originally posted by locosam View Post
          I would also say it's the grinder more so than the machine. Opv does make a difference but not for 13 sec pours. You should easily be able to choke the machine with a fine grind. If you can't, the issue is the grinder
          You're right. I took it in to Diamattina and they didn't have any issues with it, had a go using their grinder and it worked great.

          Originally posted by Dimal View Post
          I wouldn't expect the Rocky to be at fault, other than if the Zero point has been incorrectly set. This could also be taken along with the Silvia to have it checked out - Only a five minute job to determine if the Zero position is correct - If it isn't, only another five minutes to put it right...

          Mal.
          Looks like it is the Rocky unfortunately!

          Originally posted by blend52 View Post
          It may have been said before, but to reiterate... If you cannot grind fine enough to choke the flow, then you definitely have a grinder problem.
          A simple check should confirm.
          I've got new burrs coming, will hopefully arrive in the next couple days. Will update the thread after I've installed them.

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          • #35
            I've had a similar problem: bitter, watery coffee that never had the full flavours of the same beans served at the cafe.

            There needs to be more resistance, so the water trickles through slower. The grind is only part of the trilogy of grind/dose/tamp. My hope is that your grinder is fine, and the dosing needs to be by volume, not weight. Tap the handle during the dosing, and a couple of times at the end, to settle and remove air pockets. I use a slightly curved knife to then wipe off the excess before tamping, so it's very consistent.

            But today's breakthrough is that when I measured the flow with a blind filter fitted, it was way too high at 360 ml/min. Pressure valve set too low. I adjusted the valve by 1/6th turns, eventually settling on nearly the full turn inwards, raising the pressure till it gave me the suggested 240 ml/min.

            My best news of the last 3 years is that the first extraction was dark, oily, and full of the caramel flavours I've been lusting after!

            You mentioned that you'd lowered your pressure - my take is that you need finer grind and higher pressure, so you get the required "resistance" from the ground coffee to extract all the good flavours slowly, not the water-soluble caffeine which is what the spluttery low-pressure extraction gives.
            Last edited by BioBrian; 27 January 2014, 01:20 PM. Reason: typo

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            • #36
              Originally posted by BioBrian View Post
              I've had a similar problem: bitter, watery coffee that never had the full flavours of the same beans served at the cafe.

              There needs to be more resistance, so the water trickles through slower. The grind is only part of the trilogy of grind/dose/tamp. My hope is that your grinder is fine, and the dosing needs to be by volume, not weight. Tap the handle during the dosing, and a couple of times at the end, to settle and remove air pockets. I use a slightly curved knife to then wipe off the excess before tamping, so it's very consistent.

              But today's breakthrough is that when I measured the flow with a blind filter fitted, it was way too high at 360 ml/min. Pressure valve set too low. I adjusted the valve by 1/6th turns, eventually settling on nearly the full turn inwards, raising the pressure till it gave me the suggested 240 ml/min.

              My best news of the last 3 years is that the first extraction was dark, oily, and full of the caramel flavours I've been lusting after!

              You mentioned that you'd lowered your pressure - my take is that you need finer grind and higher pressure, so you get the required "resistance" from the ground coffee to extract all the good flavours slowly, not the water-soluble caffeine which is what the spluttery low-pressure extraction gives.
              Unusual advice in this post, the grind may well be only part of the trilogy, however combined with fresh beans its by far the most important part.

              How do you measure the flow with a blind filter in place?

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              • #37
                Originally posted by Yelta View Post
                Unusual advice in this post, the grind may well be only part of the trilogy, however combined with fresh beans its by far the most important part.

                How do you measure the flow with a blind filter in place?
                Measuring the discharge through the OPV, I suspect.

                Because an increase in OPV cracking-pressure will result in a smaller "orifice" (not sure what the correct term is) size when the pump pressure is applied and the valve partially opens, the flow rate will drop and the flow-rate can be used as a rough indication of OPV cracking-pressure setting.

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                • #38
                  Originally posted by Dragunov21 View Post
                  Because an increase in OPV cracking-pressure will result in a smaller "orifice" (not sure what the correct term is) size when the pump pressure is applied and the valve partially opens, the flow rate will drop and the flow-rate can be used as a rough indication of OPV cracking-pressure setting.
                  Yes... and no.

                  Most pumps have a sort-of-inverse flow-pressure curve (essentially, they are near constant power modulo efficiency factors). So the higher the back pressure, the lower the flow.

                  This curve is well described for the Ulka pumps used in these coffee machines.

                  When you have the blind filter in, the only place for water to go is the return tube. So you measure the flow out the return tube, and you can use the P-F curve to estimate what pressure the pump is pushing against.

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                  • #39
                    Whups, my mistake. Cheers Hildy.

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                    • #40
                      Yes, I was a bit daunted by the "post quick reply" button, and also had lost my entire post shortly before, so cut a lot out the 2nd time.

                      Should have said that I have the same Silvia v3, and use the supplied 40-100-102 double basket. Compak K3T grinder.

                      Not being a regular user, I thought everybody would have read the thread I was reading only yesterday, where they talked about the Ulka pumps, and printed the pressure/flow curve (more a straight line).

                      I measured the back flow from the tube that flows from the OPV (over-pressure valve??) back to the reservoir. This gave inconsistent results from taking the tubes in and out, until I standardized the process: remove group and run the brew switch for at least 10 sec to get rid of any air in the tubes; then fit blind filter and hit brew switch for about 6 seconds, until back-flow appears from return pipe. Only then could I start the brew switch on the clock, with the little pipe sitting in a measuring jug.

                      From the initial flow of 360 ml/min, the graph indicated to me that my machine had been set at about 6.25 bar, scandalously far from the proper 9 bar!

                      Sorry, I haven't time to find the thread, but I'm sure it would be easy.

                      Also, as you may have gathered, I'm still proudly wearing L-plates, even after 3 years of Silvia-smithing, and hope to keep learning lots more.

                      Thanks for the helpful discussion, all.

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                      • #41
                        Welcome to Coffee Snobs Brian, we're all learning.

                        Are you using the baskets supplied with your Silvia? if so I suggest you throw the single in the bin, they're useless, and replace the double with a Precision double 14 to 18 gram Precision filter basket 58mm- Espresso parts will make a world of difference to the quality of your shots.

                        I owned a Silvia/Rocky combo for almost 10 years, they make excellent coffee, however have limitations when making multiple milk drinks i.e. cappuccino etc

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                        • #42
                          Which Precision Basket do you use Yelta?

                          Mal.

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                          • #43
                            Double 14 to 18 gram Mal, dose 18 grams, does the job for me.

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                            • #44
                              Rightio mate, sounds good...

                              Mal.

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                              • #45
                                Well Yelta, I put my money where your mouth is, and bought a "Precision 58 mm" basket. I have to report that it is neither "Precision", nor 58 mm.

                                The ID is actually 59mm, making a very sloppy fit with my Rancilio tamper, and varies from 58.8 to 59.2 mm, meaning it's actually oval.

                                I put a piece of sandpaper on a flat table and rubbed the inverted basket on it, and inspection of the top showed flat abrasion in THREE points around the rim.

                                However, the coffee it made tasted good, so maybe it should be re-named the "3-pointed oval 59 mm taste-nice" basket.

                                In contrast, my double and double-and-a-half Rancilio baskets are both round, and flat-topped, and have smaller IDs.

                                All 3 have very cleanly drilled/cleaned holes; the holes in the new one are smaller and fewer, possibly adding some resistance, but I can't be sure on that.

                                My concern with all these is that none fit the shower screen/group head of the Silvia well, it being 57.8 mm, and the closest basket is the double, at 58.6 mm. The puck shows that grounds get blasted up the sides towards the seal, which would to me indicate a likely weakness in the puck, leading to channelling/weak, watery, bitter coffee.

                                I agree that the Silvia is not suitable for milk drinks. Fortunately my primary school destroyed any desire to ever smell hot milk again, so I only enjoy short blacks. In the '60s, the Vic government gave every child a gill (quarter pint) of milk each day, and these bottles would sit in a tray of water on the wood heater of the class-room until recess, when all 45-50 (that was our class size) were handed out. On sunny days it was even worse.

                                Cheers from "Junior Member".

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