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Finding the right Grind Setting for Espresso

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  • Finding the right Grind Setting for Espresso

    Something that plagues me on the day-to-day basis is finding the right grind setting for espresso brewing. Setting the right coffee grind is perhaps the most important variable in producing that famed and ephemeral “God-shot”.

    I have been brewing home espresso for a year and a half now, and having to change the grind setting each time I brewed a cup of coffee has driven me to distraction. While there is no absolute way to “predict” the correct grind setting, knowledge of the variables that affect the grind is a good way to produce a decent cup more often.

    So what are these variables? From research and experience, I have found that the grind will vary on these variables:

    Humidity (and therefore Temperature)
    The higher the humidity, the coarser the grind needed. The reason that this is the case is because coffee is hygroscopic – it absorbs moisture from the air. The coffee grinds will absorb moisture, and increase in size.

    I have also found that the higher the temperature (with humidity remaining constant), the finer the grind needed. My guess is that – as temperature rises, relative humidity drops, hence needing a finer grind.

    As a rule of thumb, I have a thermometer at home that I use to measure air temperature. Each time I brew, I note the temperature. If the temperature has increased since the last brew, I increase the fineness of the grind, and vice versa. With experience you will find that you are able to guess the correct grind setting given the current temperature.

    Roast level
    The darker the roast, the coarser the grind needed.

    Coffee Bean Size
    The larger the size of the bean, the finer the grind needed.

    Age of Roast
    It does seem that the older the roasted coffee, the finer the grind needed. But the effect of this variable does seem subtle when compared to the previous three, and will be only be impactful when seen in terms of days, rather than hours.

    Hope you found this post useful


  • #2
    Re: Finding the right Grind Setting for Espresso

    Great post Avi.
    It can be a very difficult to nail a grind setting. Especially when you have a blend which has some light and some dark beans or some larger or smaller there are so many factors present, the grind setting is hard to predict.
    You can also get to the same shot by a number of different routes. A finer grind lighter tamp or coarser harder tamp can produce a 60 ml shot in 25 - 30 secs. Whilst both produce the correct time volume relationship the taste can be quite different.
    There are just so many variables in producing a good coffee it can get a bit overwhelming in the home environment where you only produce a limited number of coffees per day and hence can only ever get to play with a few of the variables.



    • #3
      Re: Finding the right Grind Setting for Espresso

      Very good info Avi,

      Because of the effect of Humidity on correct grind, Ive bought a small weather station that includes a Hygrometer, Thermometer, Barometer, etc; and keep this in the kitchen near where the coffee equipment is.

      By taking note of the Humidity and Temperature prior to grinding and brewing, Ive become quite adept at selecting the right grind setting for any particular set of parameters. Ive noticed that more than anything else, Humidity is by far the biggest influence on what is the correct grind setting.

      Where we are, the Humidity can vary quite a bit during the passage of a single day and particularly in the Summer storm season. Fluctuations in R.H. of 20% or less dont seem to effect the ideal grind setting too much but when the fluctuation is 30% or more, the effect will definitely require a grinder setting change on my Rocky.

      It is a very interesting phenomenom without doubt and certainly keeps you on your toes. All part of the fun I guess. By and large, I would imagine that cafes and specialist coffee shops located in large malls and shopping centres these days, dont have to worry about it too much because of the controlled atmosphere created by large air conditioning systems. Probably a completely different story for the retailers sited in roadside shop fronts.



      • #4
        Re: Finding the right Grind Setting for Espresso

        The importance of correct grind settings highlights the need for a good accurate and consistent grinder. I dont regret the large amount of money I spent on a Mini Mazzer E.
        It makes the difficult job of grind setting adjustment a lot easier.