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Espresso Extraction

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  • Espresso Extraction

    Hi All!

    I have been reading the forums for a while but this is my first post. My starter pack arrived today Looking foward to having a go at roasting.

    I have been trying to understand the significance of each step involved in extracting espresso and how each factor effects the final result. These questions might sound dumb but they seem to me the foundations.

    Does the general rule of 25 seconds increase to 50 seconds if you are making 2 cups at once?

    What is the role of tamping? Is this to add further density to the packed coffee? Wouldnt a smaller grind do the same thing? Or is it more for cohesion?
    Will the packed coffee expand to a smaller degree after a harder tamp?

  • #2
    Re: Espresso Extraction

    Hi Bentony,

    Welcome to the site and good luck with your starter pack.

    The 25 or 30 second rule stays the same for 1 or 2 cups. The basket you use in the portafilter would be the change.
    If you are making one cup, you might use a single basket (around 7g).
    If you are making 2 cups at once, you will use a double (around 14g).
    Some people still prefer to use a double basket even when making a single ( EG: Silvia owners like me - because the supplied single basket is cr*p), and make larger or stronger coffees.

    Anyway, single shot - 30mls in 30 seconds. Double shot, 60mls in 30 seconds.

    Heres my take on tamping. It compacts the coffee and hopefully sets up a firm mass for the water to pass through when making your espresso. The benefit of this is that the water does not channel or find a path of least resistance. If the water does channel, the net effect is that a portion of your ground coffee is not getting fully extracted, whilst some of your coffee is getting over extracted.

    As for the expansion, I couldnt really say. All I know is that after a good shot in my machine, the puck is firm, has no pool of water on top when I release the portafilter and the impression of the shower screen screw is visible. Also bangs out in one hit and stays in one piece.

    Hope that helps.



    • #3
      Re: Espresso Extraction

      Thanks for the help.

      So, would you need to increase the grind size between 7 and 14 grams to keep the flow time the same?

      Does the larger amount of coffee make up for the water traveling through twice as fast?


      • #4
        Re: Espresso Extraction

        Well you might need a different grind, but the idea is that you shouldnt.
        Different baskets can sometimes neccessitate a change in grind, but it should not be a big one (if at all).
        I think its best to stick to one basket and try to master things without changing too many things around.
        Once you get consistent results with the one basket, try the other one and see how you go.

        Does the larger amount of coffee make up for the water traveling through twice as fast?


        • #5
          Re: Espresso Extraction


          First welcome to CoffeeSnobs, hold on for the journey.

          First lets clarify something, you need to use the right basket for the right job.
          - Single shot - single basket (7gms)
          - Double shot - double basket (14 - 18gms)
          You should not be using 7gms in the double basket for a single shot.

          Second, if you look at the bottom of each basket you will see that the double has about twice as many holes as the single. This allows a greater flow of extracted coffee from the double which is the reason the golden rule is 30mls in 25-30 seconds for a single and 60mls for the double.

          The grind level is dependant of so many factors that most likely you will have to change the size between the two baskets, which way is anyone’s guess.