Cafelat Robot user here but I’m rather late to the thread, I’ve skimmed the other replies so apologies if I’ve missed or am repeating anything.

As others have mentioned, the thermal stability of the Robot is very good and the beans you’re using are dark. I know you mentioned you’re letting the water sit for 20 sec in the kettle but the temperature is unlikely to significantly decrease in that time in an insulated kettle. This will definitely be contributing to the bitter flavour - try a thermometer and aim for lower temps, you’ll be surprised at how much it improves the shot.

If you’re still struggling with bitter notes I’d shorten your brew ratio, decrease the pressure you apply (6 bar is fine) and finally decrease the preinfusion time. Don’t worry too much about brew times, but again with it being dark roast I’d guess shorter will be better. Finally do as you’re doing, change one variable at a time and record how different grind settings, ratios, temps all taste.

Also see if the cafe who brewed the espresso you liked with those beans can give any tips on how they do it.

As others have mentioned the Robot is a very good and capable machine (and the JX-pro a great hand grinder) but manual levers can be challenging even for experienced home brewers. It sounds like you’re on the right track so stick in there and please shout if you have any more questions or issues.

    MWJB noted. I was kind of worried that the pull was too easy leading to inadequate extraction. So I tried to use the bathroom scale approach and make sure I make 40lb pressure. But then I found the shot very fast (15s to produce 50g liquid) even when the ready was 30lb. Will try coarser and see how it goes and report back.

      FadedFrontiers

      Thanks for the advice. Can’t wait to see the result after lower the temp. I actually taste some burnt taste in the bitter (with my untrained tongue) so maybe temp is really the cause. Do you also recommend me to fill the PF 1cm to full?

      Re the pressure, I previously did underestimate how much force I should apply for 9 bar. After I put a bathroom scale underneath to check, I found I really have to muscle it down at the end. Will try 6 bar and reduce the length of shot and see how it goes. I think that will improve the brew time although it should not be the focus.

      I will finish this bean in two days. Next ones will be medium dark and medium roast. How would you approach the first dial in in term of ratio?

      thanks

          Knluk After I put a bathroom scale underneath to check, I found I really have to muscle it down at the end.

          Bear in mind that a lever (spring or manual) usually has a declining pressure profile, and this is generally seen as a positive characteristic. You may want to try NOT to maintain a steady 9 bar pressure through the very last seconds of the shot, and see if things improve. However, as others have said, change one thing at a time.

              Knluk no problem, I imagine you would have found the best grind setting before but the high temperature made it taste too bitter. It’s easily done.

              Because of its design that minimises the contact (and heat transfer) from basket to portafilter, the Robot doesn’t drop temperature so quickly like the Flair. Off the boil water into the basket usually results in a starting brew temp of round 90c-ish so for your beans I would aim to lower the basket temp down gradually towards a minimum floor of 85c to see how that tastes.

              Yes I usually find that filling the basket with water to around 1cm from top works fine. You can leave slightly less space at the top you just run the risk of spilling hot water when you lock it in. I can’t imagine this will affect taste dramatically unless you do what Hoffman did in his review and underfill it too far as that could make it harder to generate pressure.

              You’ll soon get a feel for the pressure and it comes more naturally now you have an idea of the correct range. As CoyoteOldMan mentioned usually you build up to pressure quite quickly then you slowly decline towards the end of the shot, so don’t worry about sustaining the max pressure for any period of time. I usually go off the feel and flow from the basket and adjust accordingly but it took time and plenty of bad shots!

              Once you dial in a few different roasts you’ll also end up defaulting to different starting parameters depending on your preferences, but I’d say aim for a 1:2 ratio for dark roasts and nearer 1:2.25 for medium ones (lowering the dose and raising the ratio and water temp for even lighter beans since they’re harder to extract). As mentioned the important thing is to keep your starting temperature, ratio and preinfusion consistent as you dial in the grind. Then tweak them one at a time to perfect the taste in cup.

              Lastly don’t beat yourself up for a bad cup, just write down notes that you might find useful for next time so you can improve with the next attempt. Your shots look a lot better than what my early shots were like. Good luck!

                  The best thing I got here besides the technical advice was the encouragement. Here you go for another experiment incorporating the valuable comments:

                  Same: beans/ tampering technique/ dosage (17.7g)

                  Change: coarser grind/ temp 92.1 degree Celsius (measured at kettle)/ zero preinfusion/ 1:2 ratio/ brew time

                  Learning: I cleaned and calibrated the JX Pro and I thought I set the same burrs gap. (Maybe I messed it up). However, it seems to me that the resultant ground is way too coarse (unless it is channelling, what do you think after viewing the clip below?)

                  So, I finished the pull at 9s with 4bar pressure at peak. The liquid is watery and bitter. Think I should make the grind setting much finer.

                  Another thing was I greatly underestimated how much force I should use for the indicative pressure eg 4bar/ 6bar. That’s why the shot became much faster now after I paid attention to it

                  Probably worthless to watch but here is the clip:

                    Knluk the resultant ground is way too coarse (unless it is channelling

                    One thing does not rule the other out; I think you have both: see the spritzing at 0:03 0 0:04 as well as the general speed of the shot and the not great taste result. Definitely grind finer!

                      Knluk yes I would definitely go finer but I’d probably go with 95c at kettle as a rough starting temp for those beans (as it will drop immediately when it goes in the basket). I know it seems like a small amount but in my experience it can have a noticeable effect on taste.

                      Instead of working your way backwards grinding finer and finer again, it could be worthwhile finding the grind setting where you had the best shot and try that just with 95c kettle temp water. Then adjust accordingly, if it’s still too bitter, takes long, or requires a lot of pressure to pull the shot then go coarser with the grind, and vice versa.

                          Knluk Grind 2.2.1 (coarser than last shot)/ 1:3/ 16.7g to 50.1g, pull time: 15s/ 6 bar by feel [5.0/10] (taste wise a bit more balanced and more creamy)

                          By far, this was your best shot, unless I missed something, thanks to @MWJB. As FadedFrontiers advised you, please start at those parameters, take your temp at about 95c, and post the details of your shot and the score.

                          Furthermore, please don’t forget this :

                          MWJB Don’t worry about the pressure.

                          Try coarser until you get unpleasant sourness/thin shots.

                          It’s easy to get lost. You are doing great and being helped by those who have similar set ups, knows what it takes to get a good cup and also by our own go to person for coffee/brews/beans @MWJB. He is our Coffee / Brew God !

                          😊

                                Thanks all for the helpful inputs. I have to sit down to think about my next trial. I still have the same beans for ⅔ shot to try. I have a fantasy that the Blackcat and Northstar beans will make a night and day difference

                                No matter what, through all the advices here, I start to get a little more sense on how I assess the espresso based on taste and get some improvement on the next shot. Although sometime it may be confusing but I think experience counts. Will report back my next shot if you don’t mind.

                                Knluk Please keep everything the same as per your last best shot, where you had scored 5/10. Change only the temperature to the required level.

                                  I’ll say it again at the risk of sounding like a broken record: temperature is a significant determinant of flavor. And it’s tough to get it right with a manual lever.

                                  It will help a lot to get yourself a temperature strip or BBQ thermometer because the group head draws a lot of heat out of the water even when you pour water in that has just boiled from a kettle. I’m aware that the makers of manual espresso machines (flair, portapresso and others) tend to downplay how important temperature is but I’ve found that it’s actually very important.

                                  You’ll be able to make great coffee with the Robot but making a great shot consistently will require a lot of practice. But it is achievable. Good luck with your journey, I’m sure that with persistence you will enjoy some superb espresso.

                                    Agree with tompoland. It will help you a lot if you get at least a temp strip for your group. You will get an idea of what the prevailing temp is after the cold group has absorbed a few C. A pre-heated group vs a cold group does make a difference to the cup.

                                    Once you get a shot, which you think you like, try and repeat the shot with the pre-heated group and the portafilter.

                                        LMSC tompoland

                                        Agree with you both that understanding temperature is very important, but the usual E61 gadgets like temp strips won’t work on the Robot due to its design. There’s nowhere you can place it where it’s visible and will give meaningful temp reading.

                                        A BBQ or digital thermometer could be more helpful for determining the water temp drop from kettle to inside the basket before you lock it in, but there’s also plenty of YouTube videos that explore that same subject (Cafelat has its own channel with several temp experiments, as do some of the reviews such as The Wired Gourmet).

                                        For maximising your results long term it’s definitely important and worth delving into in detail but I also think this risks overcomplicating a the issue at hand.

                                            Would love to share the latest progress for some advice please.

                                            I have just open a new bag of coffee - the Brazilian Blend from Blackcat. I think it is medium dark roast (although BC didn’t mention it in the package).

                                            At the last shot of my old bean (on which I have been trying to dial in above), I was finally able to pull a shot with 7/10 score with 1:2, 15g in and 30g out with 1.7.0 grind size. The brew time was 20s and pressure was 30lb. So not ideal but taste reasonably good. So i am using the similar recipe today on the Brazil blend but start with grinding a bit finer due to the short brew time and not enough pressure above. Different beans but use as reference for starting point.

                                            I pull 3 shots today. Btw the roast date was July 7th (7 day rest time). All three shots were 1:2, roughly 15g in and 30g out, 95c brew temp, 15s preinfusion. My plan was to identify the right grind size by achieving the ballpark pressure and brew time. And then I will fine tune maybe the dose or ratio, or other things. Here are the results:

                                            1/ G1.5.2/ brew time: 40s @55lbs/ too fine, 1:2.0 <4.5/10>

                                            2/ G1.6.2/ brew time: 31s @55lbs/ too fine/ 1:2.1 <4.6/10>

                                            3/ G1.7.2/ brew time: 17s @28lbs/ too coarse/ 1:2.1 <5.5/10>

                                            For the first 2 shots, I know I should stick with 40lb but seems I can hardly extract considerable flow without adding more pressure. I ended up using 55lbs. For the third shot, due to some workflow issue, I did preinfused it for 22s. Just a note.

                                            I think I had enough caffeine for today. :)

                                            Will try 1.7.0 tomorrow. Seems will be okay by interpolation. Assuming i can achieve closer to 27s and 45lbs tomorrow, what else I can refine for the taste further?

                                            Thanks again!

                                            edit: btw the beans smells so nice! Smells so much better than my last oily beans. Also, I noticed there is much less small bean fracture in the bag compared to my last bag without roast date.

                                              Knluk My plan was to identify the right grind size by achieving the ballpark pressure and brew time. And then I will fine tune maybe the dose or ratio, or other things. Here are the results:

                                              1/ G1.5.2/ brew time: 40s @55lbs/ too fine, 1:2.0 <4.5/10>

                                              2/ G1.6.2/ brew time: 31s @55lbs/ too fine/ 1:2.1 <4.6/10>

                                              3/ G1.7.2/ brew time: 17s @28lbs/ too coarse/ 1:2.1 <5.5/10>

                                              You have this a little backwards, pressure & time are fine tuning. Grind size & ratio are big drivers.

                                              What makes you say shot 3 was too coarse, how do you know there’s not better to come (or not) if you don’t try coarser? You can always back track finer, if things go south.

                                              When you get a noticeably improved shot, make few at those parameters to make sure things are consistent, before making more changes.

                                                  MWJB big thanks for your advice. I think i confused myself by watched quite a number of YouTube video on dialling in. I judged it was too coarse by the brew time and pressure. Probably I should go coarser instead. Sorry if I asked this before. So, if I open the glider to coarse, should I use same pressure (expect to have an even shorter brew time) or should I reduce pressure to avoid having a too short brew time? I think if I don’t think about it and pull, I will reduce pressure naturally when I feel there is less resistance. Will sure give it a try tomorrow! Many thanks.

                                                  • MWJB replied to this.

                                                      Knluk As you grind coarser, pressure reduces, that’s normal. You have the ability to tweak your pressure, most don’t.

                                                      Focus on the taste vs grind setting, too coarse a grind will produce weaker, sharp/tart coffee…in whatever time that takes.

                                                          MWJB it seems like my dial in journey is much longer than others :( I tried 3 shots today:

                                                          4/ G1.8.0/ brew time: 15s @15lbs/ 1:2.2 <2.5/10> Significant channelling, watery shot

                                                          5/ G1.8.3/ brew time: 8s @20lbs/ 1:2.1 <3.0/10> Channelling and watery

                                                          (I also tried a backward shot by going finner than the last shot yesterday)

                                                          6/ G1.7.0/ brew time: 17s @28lbs/ too coarse/ 1:2.1 <4.0/10> Some channeling

                                                          I can’t get any implication from the shots on which direction I wanna go for the next shots. Should I continue going coarser or finer? The only reason I can think about the confusing result is puck prep. But I think I am reasonably careful on puck prep what I did was WDF the ground in robot basket, from bottom to mid, to top grind try to stir a bit more to redistribute even the ground and avoid void in middle I then use the tamper to tamper the coffee by fingers I lower my body at the same level as the top of the basket so I can make adjustment during tamper if the handle of the tamper is not at 90 degree to the opening of the basket I didn’t use lots of force but only a firm downward pressure to tamper.

                                                          Again, appreciate any feedback or advice you may have thanks

                                                              Knluk I’m at a loss as to why yesterday’s shot at 1.7.2 was 5.5 & the best you had up to that point, but now 1.7.0 is too coarse & 4.0 ?

                                                              Don’t fret over perceived channelling.

                                                              Make some more at 1.7.2 see how they average.

                                                              I don’t WDT.