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  • gregpullman
    replied
    Re: Pressurised or non-pressurised

    The resistance to water flow, and thus the generation of pressure inside the portafilter, is supposed to be provided by the ground coffee, and the pressure differential as you move down the basket is what extracts the oils and aromas from the coffee. A pressurised basket provides no pressure differential through the basket in this regard, so it becomes somewhat like a drip filter system except under pressure. What comes out of the basket then gets forced through a pinhole normally (which you can often see on the underside) and this froths up the liquid to make it appear like crema.

    A day to day example of how this frothing system works is well appreciated by the SNAGs amongst us - a kitchen sink with detergent in the bottom (non-SNAGs insert <bucket with car wash liquid> . Turn the water on at a moderate rate with no nozzle attached and the water runs into the bucket and not much happens to the car wash liquid. But fit a high pressure nozzle to the hose, and the same flow of water produces copious froth and bubble. This same behaviour is what froths up the relatively crema-less coffee otherwise produced in a pressurised basket and makes it look like the real deal.

    Also, by creating the pressure by the basket rather than the coffee, it reduces the importance of tamping, which is one factor you cant rely on the average ignorant home user to get right, especially with the tool they normally supply for the job! The users of some of the tampers Ive made for pressurised baskets have reported better results with a proper tamp, but the difference isnt as marked as on an unpressurised basket.

    Greg

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  • Thundergod
    replied
    Re: Pressurised or non-pressurised

    You are not wrong Secksy.

    tojo1 pressurised basket are designed to produce fake crema with supermarket (pronounded "stale") coffee.

    One would not buy them as optional extras.

    If you have non-pressurised baskets stick with them.
    If you dont, find some.

    Mind you, youll also need a good grinder to go with the fresh coffee in order to get the best out of the right setup.

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  • Secksy
    replied
    Re: Pressurised or non-pressurised

    Hi Tojo1

    Im sure Ill be corrected if Im wrong, bit a pressurised basket normally has 2 layers at the bottom.  The top layer has a lot of holes where the bottom has only one.  This I believe helps in the production of crema, however most members of CS (who know a lot more than I ) seem to say that this is fake crema & not what you would get from a single layer or non-pressurised basket.

    Warm Regards
    Andrew

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  • tojo1
    started a topic Pressurised or non-pressurised

    Pressurised or non-pressurised

    Would some kind soul enlighten a newbie.
    What does a pressurised and non-pressurised portafilter do. I understand the meaning of the word pressurised but I dont have any idea how it applies to a PF.

    Are there pros and cons for each type?

    Does one purchase them as optional extras?

    How do you know if your grinder has a pressurised or non-pressurised PF?

    Maybe you could just point me to some web page for explanations/discussions if this topic is too old hat for the experts.

    Thanks

    [I did try a search but found nothing simple enough]
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