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89 or 94 degrees?; 8.5 bar or 12 Bar?

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  • 89 or 94 degrees?; 8.5 bar or 12 Bar?

    Hi all,
    was hoping to get a pointer - does anyone recommend any good links to reading about what minute adjustments to temperature and pressure can do for espresso flavour?

    I'm also interested in beans and light/dark roasting colours eventually, but at this stage primarily interested in what to expect from things like reducing the temperature; or increasing the pressure; etc.

    Thank you.

    (Hope this is in the right forum section....)

  • #2
    Asking how minute adjustments to the nominal pressure or temperature affect qualitative, subjective properties of espresso (which are highly dependent on other variables), when both the pressure and temperature vary continuously during preparation, will likely not result in a stratforward nor consistent (nor useful) answer.

    Which will hopefully suggest to you that you may be asking the wrong question.

    There are general trends relating P & T to taste, sure. But can anyone reliably tell you what a 0.1 bar variation in set pressure or 0.5 °C variation in temperature will do to your espresso? I seriously doubt it.

    But of course, that's only my opinion.


    • #3
      It's bit of a 'string' question as no-one can tell what will theoretically happen to a coffee they have no personal knowledge of, ( as per Mr Jack's post above).

      Generally, the lower the brew temp is (<<90°C) the more sour the shot will become but how any one coffee will behave can't be predicted.

      As far as pressure goes there is a fairly wide tolerance. Pour times will be affected by higher or lower pressure ( along with the necessary adjustments to grind,

      dose and tamp) and it seems that historically ( see Illy et al) 9 bar was 'chosen' for the convenience of the 30 second factor.

      Pressure profiling is nothing new as it precedes e61 and/or saturated groups via lever piston groups. Newer machines, such as the Synesso Hydra, LM Strada,

      Vesuvius and others can be programmed to manipulate the brew pressure during a pour but for the most part are programmed to somewhat replicate a lever

      machine's pressure profile.

      If you google 'espresso brew pressure high or low' you will find plenty to read, if you add the word 'profiling' after 'pressure' you will get more to read.
      Last edited by chokkidog; 2 December 2014, 08:48 AM. Reason: correction


      • #4
        Slayers don't pressure profile they flow restrict ( I'm so bad! )



        • #5
          Cheers. Correction noted. Nothin' bad about that.


          • #6
            Thanks all.
            The following guide was an amazing read, gave me so much to look forward to on my soon to be delivered new machine and specifically dealt with so many questions I have, including the ones above.

            Gives me great confidence to play, experiment and even get more out of my current machine. Well worth the long read.
            (not sure if I should direct link to another site...) Pretty sure most of the experienced CSers have read it or gained the same knowledge from Espresso Yodas elsewhere.

            Please look for:


            This introduction by Jim Schulman shares his passion for good coffee and expertise in home espresso. It covers a lot of ground and demystifies the key elements of espresso preparation. It is not just about techniques and equipment, but also about the reasons behind them. More...