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LR Dark roast extraction PI issue

Hi everyone,

I’ve had my LR for a couple of weeks now and have been getting great shots on medium and lighter roast beans, usually hitting 32g in 30secs from 18g in basket.

I’ve just started on a bag of Monmouth Organic Espresso (Blend) that is a bit darker in roast and am having real trouble dialling it in. My current process is:

PI set to 1.0
18g in basket
Target 32-34g in cup
Londinium distribution tool and a funnel to distribute
Gentle tap and then St Anthony BT wedge to level out basket
lightish tamp with either St Anthony New Levy or Londinium tamper

I’m getting even extraction, no channeling etc.

My issue is that If I set the grind setting (HG1) to hit 32g in roughly 30seconds like I usually do, the time to first drip during PI is way over 20 seconds and the espresso extremely bitter.

I’ve made the grind setting a fair bit courser in the hope of speeding up the PI time, it’s brought it down to around 10-12, but the shot rushes through in around 15secs. These faster shots are slightly less bitter but still not amazing.

Anyone have any tips on what else I could tweak to reduce bitterness and get the best out of these beans? If I up the PI pressure to 1.2 that does speed up the PI time to first drip a bit, but again still bitter. I read a light tamp is supposed to help darker beans but it doesn’t seem to have made a huge difference for me.

Any help gratefully received,




  • Hi Patrick,

    This sounds as if you got a much darker roast than usual. How fresh is the roast -- do you know the roaster?

    How is the smell from the grinds?

    With darker beans I keep PI low, like 1.2 and I slowly lift the lever after 5-7 seconds. The lever 'catches' rather high which is fine, and the initial pressure helps to complete pre-infusion and start the flow.

    You do not state exactly what brand and type basket you use to fill 18g. Maybe try 15-16g.


  • Hi frans,

    Thanks for this. The beans are these ones:

    It’s says they are a mix of “ coffees from Suke Quto (Ethiopia), La Bolinda (Bolivia) and El Pastoral (Nicaragua).”

    They smell fine and only purchased last week and I believe Monmouth have a fast turnover of coffee so would not think they would have been sat around too long their end. The was no roasting date on the bag however.

    I was thinking I should always wait until the first drips are seen before lifting the lever, I will try your way of lifting after 5-7 seconds irrespective of if it’s started dripping or not and see how that works, il let you know how I get on tomorrow - too much coffee for one day today :)

    Edit:. forgot to say, it’s the londinium 18-20g IMS basket I’m using.
  • if you want to run dark/ish roasts i strongly suggest you add the restrictor to the thermosiphon;

    this will allow you to run a higher pre-infusion setting with no mucking around

  • Where do you see the difference in using the restrictor vs lowering the boiler temperature? Or is the goal to have a higher water temp for a short while with greater cooling from the group during the extraction?
  • raising or lowering the boiler pressure is a very ineffective tool for moving the brew temperature (a significant change in boiler pressure hardly moves the needle on brew temperature - as anyone with a dipper will know)

    for this reason we keep the boiler pressure constant in the range 0.8-1.0 bar and adjust the pressure in the pre-infusion circuit by small increments to achieve significant movements in brew profile

    but if users are only interested in dark roasts you can run out of room to drop the brew temperature low enough, even at low pre-infusion pressures, and it becomes a bit of a stupid fiddle (much beloved on places like home barista with their silly 'hold your face a certain way' routines and i can get my machine to do anything)

    instead you place a restrictor in the thermosiphon and this reduces the rate of flow in the thermosiphon and you can run much higher preinfusion pressures on dark roasts, say 2 bar, and it all works very nicely

    kind regards

  • Hmm, I wasn’t aware of that part. I assume if I fitted it, I’d have permanently lower group temps which would be less than ideal on medium to light roasts.

    To be honest, using frans tip of just cutting PI after 5 seconds helped a small amount, but I was still getting bitter brews. The dark roast is now finished, so I think I’m just going to stick with medium / light roasts more now as I think I prefer them.

    Thanks for everyone’s help though :)
  • Hmmm, didn't know about the restrictor as an option for the LR, either, not that I'm only interested in dark roasts. Recently ordered and received the Wifi dongle (working fine) and maintenance kit but might have also ordered the restrictor ( if, as you thought, it would not effect the ability to brew lighter roasts as well.

    I searched but might still have missed it, was there a follow-up (in the description above from 30Jan2020) about testing the 'impact at both ends of the temperature spectrum'?


  • hi carl

    yes, adding a restrictor pulls the brew temperature down, quite a lot, across the range

    a machine with a restrictor in will be fine with medium roasts but it won't get hot enough for nordic/ultra light roasts

    kind regards

  • Is it possible to solve this issue without a restrictor simply by lowering the brew ratio into ristretto territory? Then any bitterness in the tail end of the extraction will never make it to the cup.
  • i think there are many ways to over extract. running it short will help, but it won't protect against a brew water temperature that is too high. shortening the pre-infusion time will also help by grinding more coarsely (reducing the time for the first drip to fall to 2s)

    but i think you are much better to put the restrictor in because then you can keep the pre-infusion pressure much higher and in doing so you get a lot more body than you will achieve at boiler pressure pre-infusion settings (1.0-1.5 bar), which a lot of people enjoy in a dark roast.
  • I actually ordered the restrictor and fitted it to my machine. It is quite unnerving to unscrew the nut. I did fit the restrictor (against the advice on the store page) to the side with the heating element since there is way more space. I don't see how you would fit a 24 mm wrench without removing all other tubing as well. Just stuff some rags under the pipe to protect the heating elements contacts and possibly let it dry before plugging in again. Also I heated the nut with a torch to burn the glue which seems to be used and to widen the nut. Then bending the tube to the side just enough to put the restrictor in, which fits very snug by the way, while water spills out. Fun!

    Now the machine runs noticeably cooler. I can drink store-bought Italian espresso and it tastes like it should. As someone who started on a Europiccola I think I prefer the lower temperatures on my machine. Normally I would drink espresso from the mid-range while sometimes dabbling in very light or dark roasts.

    I hope this helps someone to decide if the mod makes sense for you. The installation is definitely doable but you should not rush it.
  • hi nico. i completely agree that it is a lot easier to fit to the right hand (heating element) side of the boiler. i completely agree that the restrictor is the way to go for owners who are only interested in traditional espresso roasts.
  • Wouldn’t another option be to adjust the pressurestat a little lower to bring the boiler temperature down a bit?
    I can’t help but think that the issue with dark roasts are only with the darkest roasts. I struggled for awhile to get good results with dark roasts on my Cremina but eventually I nailed it. And the Cremina can run much hotter than the LR and doesn’t have the same consistency.
  • the key difference with our machines is you can move the brew temperature without pushing the machine out of equilibrium. with our machines you dont need thermometers stuck all over the machine like a high school science experiment; you walk up and pull a shot and you get the same result as the last one you pulled

    shifting boiler pressure doesnt move the brew temperature that much, that is the basic problem; by the time you have dropped the boiler pressure enough you've got anaemic steam power, and its the same at the top end. that is why on all of our current range of londinium machines you leave the boiler pressure alone to run 0.8-1.0 bar and adjust brew temperature using the thermosiphon where small changes induce large changes in the taste in the cup; that is what the last 8 years of my life has been spent doing; investigating this age old issue and finding a solution to it. its now done, it works.

    sticking a restrictor in the thermosiphon pipe is about as easy a task as you will get; you certainly should not consider buying our machines if you feel concerned about opening the thermosiphon pipe where it screws onto the heat exchanger and pushing in a restrictor and screwing the pipe on tight again; it is the largest and therefore most robust pipe on the whole machine

    kind regards

  • Thanks for clarifying Reiss. I agree with everything you’ve said. In fact, it’s the main reason I prefer the Londinium to the other spring levers out there. Some have PIDs, yes. But when you lower the temperature enough to have an effect, people report that steam pressure becomes anemic - this seems like a design flaw. I’d prefer the simplicity of the londinium.
  • Hi Reiss, if ordering a new machine could you ask for this to be fitted prior to delivery. Thanks
  • hi sean

    sure, but be sure to write it in the notes field during the checkout process on the website, that way it appears on the sales order and is transferred to the purchase order that i send to the factory

    kind regards

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