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Thread: Coffee Extraction Time Clarification

  1. #1
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    Coffee Extraction Time Clarification

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    Hi Guys,

    Firstly, loving this forum. Have been getting into the home coffee making over the last 3 - 4 months and this is a great resource. I have the Sunbeam Cafe Series eM6910.
    I have been reading that a good extraction time is around the 25 second mark so I just wanted to check something. I have been using the double basket as the single one never comes out right. When I use the double I press the double shout button which my understanding will pour a double shot of coffee (ie 60ml). Is the 25 second extraction time for a 60ml shot or a single 30ml shot. My double shots have been coming out in about 25 seconds from the time I press the button and the pour looks and taste good most of the time but I read somewhere people saying 25 seconds for a 30ml shot. Just wanted to clarify this
    Thanks
    Gav

  2. #2
    Super Moderator Javaphile's Avatar
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    Re: Coffee Extraction Time Clarification

    Welcome to CS Gav. The time should remain the same whether youre using a single, double, or even a quad basket. Only the volume should change.


    Java "Quad shots, WooHoo!" phile

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    Senior Member GregWormald's Avatar
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    Re: Coffee Extraction Time Clarification

    And the correct volume is the volume that gets you the taste you want.

    The double basket and 25 ml extraction is known as a ristretto and many think it is the best tasting volume for an espresso.

    Greg

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    Senior Member dr.a.j.pickering's Avatar
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    Re: Coffee Extraction Time Clarification

    Quote Originally Posted by 102532300038253A363B33570 link=1320876269/2#2 date=1321259731
    double basket and 25 ml extraction is known as a ristretto
    or is it ?

    The definition of ristretto is hotly debated in these pages and many others.

    Many say a true ristretto can only be "pulled" with a leaver.* As it comes from the the Italian for restricted.* The restriction in this instance is time ie the same volume (the leaver piston size) is pulled quicker.

    The right time and volume is the one you like drinking, end of story!

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    Mal Dimal's Avatar
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    Re: Coffee Extraction Time Clarification

    As it happens, I prefer about 40-45ml from a Double - A nice balance between a true espressos impact and the sweetness of a Ristretto.... 8-)

    Mal.

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    Senior Member askthecoffeeguy's Avatar
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    Re: Coffee Extraction Time Clarification

    The old adage of 30mls from 30sec often applies - and its the same regardless of wherever you use a single or double basket

    And I would argue that a ristretto is somewhere between a 10 and 15ml coffee extraction - where you fine your grind and updose specifically to restrict the flow of your pour by:

    a) slowing the extraction down by the above process

    b) cutting the pour short at the 10ml mark

    In many commercial environments a double ristretto or 20 to 25ml pour using double or even triple sized baskets forms the basis of every extraction

    But timing is only one aspect of a good extraction - the proof is in the cup, and keeping an eye on the pour and stopping it when it blonds or wobbles is just as important as timing

    Hope this helps,

    Pat

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    Re: Coffee Extraction Time Clarification

    Okay - forgetting about the fact Ive been playing with time vs colour of pour, beans, depth of roast, date/days since roast, grind, basket size and dose size - and assuming I *can* achieve 30ml in 25-30 secs before blonding when I want....
    My question is:
    How do I pour 2x30ml (ie* 30ml in two cups) simultaneously on my Silvia v3?
    As with most of us, my standard portafilter has the requisite two spouts. Surely if the dose doubles for two cups and if the time is to stay at 25-30 secs some else has to change.

  8. #8
    Sleep is overrated Thundergod's Avatar
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    Re: Coffee Extraction Time Clarification

    Quote Originally Posted by 7C797A7A747D6A180 link=1320876269/6#6 date=1322988957
    Surely if the dose doubles for two cups and if the time is to stay at 25-30 secs some else has to change.
    The size of the basket changes.

    Single basket for one cup - double basket for two cups.


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    Re: Coffee Extraction Time Clarification

    Thanks Thundergod
    How does a double basket increase the volume/flow rate? I guess different shaped basket profiles have something to do with resistance?

    To be honest I dont use the single much and so Ive done few direct comparisons. I usually prefer doppio shots at home and work to a colour unless going long black. Ill have to revisit the single.
    dabbler

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    Super Moderator Javaphile's Avatar
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    Re: Coffee Extraction Time Clarification

    Quote Originally Posted by 363330303E3720520 link=1320876269/8#8 date=1322992815
    How does a double basket increase the volume/flow rate? I guess different shaped basket profiles have something to do with resistance?
    A different profile with more and/or larger holes. You can see the difference in the profile and the number of holes of various baskets in the attached pic.


    Java "A real basket case!" phile


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    Re: Coffee Extraction Time Clarification

    Once again CS shows us the critical details and differences.

    I have five baskets of differing profile and capacity and while I had considered basket size and profile as variables my brain never registered the effect of the differing number of holes let alone considered hole size.

    Its a timely reminder to vary one thing at time when experimenting or youll end wasting time as well as coffee!0

    dabbler

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    [THREAD BUMP ALERT]

    I've been thinking about the same question as dabbler had, and I do not think it has been answered properly yet.

    Let's assume that it is correct that the 25 seconds applies to BOTH a single AND a double, as has been stated in this thread, and elsewhere on the web. If it is true that this is achieved by designing the single basket to have more resistance to the flow than the double basket (which does appear to be the case), then there is something else that MUST change as well, and that is the shot PRESSURE. The reason the pressure must change is that the area through which the water flows IN to the filter basket, at the top, is the same between a double and a single baskets. If the pressure was held constant (e.g by the use of an over pressure valve), I can't see any way that the shot time could also stay the same!

    So, is it in fact the case that the shot PRESSURE is SUPPOSED to change between a single and a double? If that's the case, does the recommended 9 bars of pressure apply to a single, or a double?

    Greg.

  13. #13
    Senior Member Barry O'Speedwagon's Avatar
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    Skip,

    Have you looked at a standard single basket for an E61 group? The shape is typically different, with tapered sides and the base in which the 'holes' are located is of considerably less diameter than a double basket. It's not like its a double basket cut in half.

    Cheers
    BOSW.

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    Quote Originally Posted by Skip View Post
    Let's assume that it is correct that the 25 seconds applies to BOTH a single AND a double, as has been stated in this thread, and elsewhere on the web. If it is true that this is achieved by designing the single basket to have more resistance to the flow than the double basket (which does appear to be the case), then there is something else that MUST change as well, and that is the shot PRESSURE. The reason the pressure must change is that the area through which the water flows IN to the filter basket, at the top, is the same between a double and a single baskets. If the pressure was held constant (e.g by the use of an over pressure valve), I can't see any way that the shot time could also stay the same!So, is it in fact the case that the shot PRESSURE is SUPPOSED to change between a single and a double?
    For twice the volume in the same amount of time, you need twice the flow rate.

    Flow = pressure / resistance.

    Hence, twice the flow == same pressure, half the resistance.

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    Consider that the pressure is relatively constant:

    - the pressure at the pump is the result of a balance between the pressure that the pump can achieve at a given flowrate, and the pressure drop which results as that flowrate passes through the downstream system.

    - the OPV effectively determines the pressure drop in the downstream system by compensating for changes in flow resistance (which is not the same as pressure drop) in the puck.

    - The OPV does this by increasing or decreasing in area, allowing more or less flow through with minimal corresponding change in pressure drop across the OPV. This means it fixes the pump discharge pressure (which fixes the pump flowrate)


    - Thus, within the limits of the OPV's capacity to compensate, and the limitations of the pump, you can alter the flowrate of the pour by changing the resistance to flow in the puck and basket (I.e. changing grind, dose, basket perforations and, to some extent, tamp).

    The key factor that everyone always seems to forget, is the result of an edpresdo pour being what would be classified in engineering as a dynamic, open system, batch process:
    Because the puck resistance changes as solubles are extracted during the shot, the pour flowrate is not constant; the resulting shot volume is a function of the area under the flowrate curve, not the peak (or initial) flowrate.

    It's thus very unlikely to be a simple matter of "double the (initial) resistance to get half the shot volume"; even if this were to result in a halving of the initial flowrate.

    This is also the reason "brew ratio" data is so variable.

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    Thanks, I understand now, and in fact, I had forgotten that I had already understood the situation some time ago, where I posted along similar lines here: http://coffeesnobs.com.au/brewing-eq...tml#post519426



    No-one replied to that post. (btw, I think there is a larger difference in capacity than I thought back then, between the double and single baskets of the EM6910)

    Would you agree that a machine that does not actually have an OPV (or any kind of pressure regulation) must be "tuned" optimally for a certain pressure and flow rate? In the case of my EM6910 (which does not have an OPV), would they perhaps tune it somewhere in the middle of a single and double shot? (or perhaps tune it for a double, since that seems to be much more popular?)

    Greg.

  17. #17
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    How can you 'tune' a machine with no adjustable variables?

  18. #18
    Mal Dimal's Avatar
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    Quote Originally Posted by MrJack View Post
    How can you 'tune' a machine with no adjustable variables?
    By design...

    Mal.
    Skip and Dragunov21 like this.

  19. #19
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    Behmor Brazen - $249 - Free Freight
    Yes, I see that now

    Pressurised baskets perhaps.



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