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Thread: Under pressure ...... dum dum dum de de dum dum

  1. #1
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    Under pressure ...... dum dum dum de de dum dum

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    Apologies re the title to the late great Freddie Mercury but I;m struggling with some pressure related theory and was hoping that someone could enlighten me (or at least confirm my suspicions).

    After a couple of years of devoted SB 6910 (or whatever the series no is), I have become accustomed to the quoted 15 bar pressure. Recently I had an opportunity to have an extended play with a commercial machine rated at 9 bar and found some really significant taste difference between beans.

    All beans were single origin and consisted of dominicans, panamanians, malawais, yirgs, and australians and I also tested with beans from 7hrs post roast to 4 weeks. I also tried a variety of roast depths from light to dark.

    The commercial machine appeared to be far more forgiving of the beans in terms of more muted pours. The deeper noted coffees were significantly less prominent and while the higer acidity coffees features were still there, they were significantly less than when tasted via the home machine.

    So is this the pressure difference? And if so, is this a similar influence that produces such differences in tastes between stove tops, home machines & commercial machines? Did the old hand pulled pumps provide more control for the barista in influencing this pressure feature?

    Finally - Ive found that the home machine (if it truly does have 15 bar) is giving more detailed or amplified flavours in each pour and is definitely preferrable when getting into experiencing the nuances of origins. Any thoughts re this, have I just stated the obvious or am i off on a strange and wildly incorrect tangent?

    cheers
    j :o

  2. #2
    Sleep is overrated Thundergod's Avatar
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    Re: Under pressure ...... dum dum dum de de dum dum

    The stated 15 bar is the maximum rating of the pump.
    It should still be only pushing 9 bar through the coffee.

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    Senior Member Koffee_Kosmo's Avatar
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    Re: Under pressure ...... dum dum dum de de dum dum

    Quote Originally Posted by 5B677A616B6A7D68606B0F0 link=1246719244/1#1 date=1246722664
    The stated 15 bar is the maximum rating of the pump.
    It should still be only pushing 9 bar through the coffee. *
    Jaxxx
    The (OPV) over pressure valve controls this
    e.g. the pump at full pressure will pump @ 15 bars
    The OPV is set at 9 bars and controls the *pressure accordingly at the OPV set level

    In addition if you had a pump that was for example 30 bars the OPV can be used in the same way to set it to 9 bars

    KK

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    Senior Member GregWormald's Avatar
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    Re: Under pressure ...... dum dum dum de de dum dum

    1--What they said above.
    2--If you like your inexpensive machine better then its ALL good.

    Greg

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    Re: Under pressure ...... dum dum dum de de dum dum

    Thanks for the fast feedback guys! Thanks for the clarification as well - so if the pressure is the same then it should be more down to the individual machine?

    Just out of interest - did the older manual lever pump machines allow greater pressure range or where they limited in some way to allow only a certain amt of pressure?


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    Re: Under pressure ...... dum dum dum de de dum dum

    Never used an old lever machine myself,
    but as I understand it from comments posted by some who have had experience with them, they were more difficult to be consistent with, so that would indicate the operator had some influence on the pressure, etc.

    In regards to your comments regarding the differences between your machine and the commercial machine,....did you use the same grinder for both, as the grinder, and its internal condition, can have a great influence on flavours, etc.

    However its always good to know that what you can do at home is better than what is done at many cafes/coffee shops.

    Bullitt

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    Re: Under pressure ...... dum dum dum de de dum dum

    Quote Originally Posted by 5C574E4E4E360 link=1246719244/0#0 date=1246719244

    The commercial machine appeared to be far more forgiving of the beans in terms of more muted pours. The deeper noted coffees were significantly less prominent and while the higer acidity coffees features were still there, they were significantly less than when tasted via the home machine.
    As other noted your pressure is set by your grind/dose/tamp and is [or should be] "capped" by the OPV at 9 bar anyway.

    I would say different grinders and temperature [both initial set point and consistancy through shot] make up the difference.

    From what you describe it sounds like your home machine is running cooler.
    Lower temperatures will sharpen and/or sour up the flavour and put less emphasis on the sweetness and body of the shot .
    Low temps usually yield a thinner mouthfeel as well.

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    Re: Under pressure ...... dum dum dum de de dum dum

    Thanks again guys - the grinder was the same one so that rules that out - temp is an interesting thought - I checked the temp on my home one not long ago but Ill run a check on both as see what comes out.


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    Re: Under pressure ...... dum dum dum de de dum dum

    Behmor Brazen - $249 - Free Freight
    I use lever machines all the time- i love them. there is no doubt that you have quite a bit of control over the pressure on some levers. Amongst the small domestic lever machines that offer such control you have your Pavoni, Caravel, Mini gaggia, La Peppina and a few more.

    Most spring levers however offer no real control over the pressure as the spring does all the work. A few spring levers allow the user to help the spring return and thereby change the pressure and speed of the pour. In general I would say most lever machines would not quite make it to 9 BAR- perhaps an average would be around 6 (pure guesstimate).






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