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  • #16
    The whole background is on Stephen Sweeney's TPF - a Transparent PortaFilter - Espresso Machines • Home-Barista.com

    TampIt

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    • #17
      Transparent portafilter

      Tije's Transparent Portafilter clip3 on Vimeo

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      • #18
        Interesting to see, but i do wonder how close it is to what actually happens in a normal basket where the puck is much closer to the shower screen and effectively has no "free surface" to interact with the brew water entering.

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        • #19
          That is fascinating.

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          • #20
            Originally posted by blend52 View Post
            Interesting to see, but i do wonder how close it is to what actually happens in a normal basket where the puck is much closer to the shower screen and effectively has no "free surface" to interact with the brew water entering.
            I agree with this..

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            • #21
              With the puck not expanding until after the extraction is over unless you are over filling your basket the puck does indeed always have a "free surface". The only time this isn't the case is when you smash the puck into the shower screen when locking the portafilter on. In which case you're over filling the basket.


              Java "More Science!" phile
              Toys! I must have new toys!!!

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              • #22
                Originally posted by Javaphile View Post
                With the puck not expanding until after the extraction is over unless you are over filling your basket the puck does indeed always have a "free surface".
                Even so, 0-1mm "headspace" is not the same as water free falling 8-10 mm onto the puck.
                It occurred to me that filter baskets are designed to give minimal clearance between the screen and the puck surface, when correctly dosed....for a reason ?
                Interesting also that you assume the puck doesnt expand until extraction is over ?

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                • #23
                  Originally posted by blend52 View Post
                  Even so, 0-1mm "headspace" is not the same as water free falling 8-10 mm onto the puck.
                  It occurred to me that filter baskets are designed to give minimal clearance between the screen and the puck surface, when correctly dosed....for a reason ?
                  Interesting also that you assume the puck doesnt expand until extraction is over ?
                  Are filter baskets designed to give "minimal clearance" or are they just designed to be just big enough to hold a reasonable dose?

                  Have you ever observed a puck expanding during extraction?

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                  • #24
                    Originally posted by blend52 View Post
                    Even so, 0-1mm "headspace" is not the same as water free falling 8-10 mm onto the puck.
                    It occurred to me that filter baskets are designed to give minimal clearance between the screen and the puck surface, when correctly dosed....for a reason ?
                    Interesting also that you assume the puck doesnt expand until extraction is over ?
                    The water is not truly falling direct from the shower screen but rather it hangs on it until there's enough water mass for the bulge of water to break free and turn into a drop at which point it's already almost halfway to the surface of the puck. There's not a lot of force in a drop of water falling single digit mm distances. Additionally it is only impacting directly on the coffee for a short period of time before the water pools on top of the grounds. While the falling water may well account for the raising of the few fines we see there is no other observable impact that I can spot.

                    The only thing I assumed about the expansion of the puck was the old adage that everyone had assumed to be correct that the puck expanded at the beginning of the extraction as the water soaked into the grounds. As for my statement that we now know it doesn't I assumed nothing. Nine minutes of high definition video including plenty of close up slow motion shots of extractions using a transparent portafilter under a variety of conditions showing that the puck does not expand until pressure is released at the end of the extraction convinced me that it was true, no assumptions necessary.


                    Java "Some assumptions may have been harmed in the writing of this post." phile
                    Toys! I must have new toys!!!

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                    • #25
                      Originally posted by Pete39 View Post
                      Are filter baskets designed to give "minimal clearance" or are they just designed to be just big enough to hold a reasonable dose?
                      Why else are 14,18,21 gm baskets all different heights and all appear to fill to the same " height below the rim" when dosed to those weights.
                      Also have you ever tried a 10gm dose in a 20 gm basket ( hence puck height) ?...you have to adjust a few other factors to get any reasonable pour out if you do, and even then it certainly wont be the same " in the cup"

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                      • #26
                        Originally posted by blend52 View Post
                        Why else are 14,18,21 gm baskets all different heights and all appear to fill to the same " height below the rim" when dosed to those weights.
                        Also have you ever tried a 10gm dose in a 20 gm basket ( hence puck height) ?...you have to adjust a few other factors to get any reasonable pour out if you do, and even then it certainly wont be the same " in the cup"
                        I think its because it aids easy volumetric dosing. If you fill a 14 g basket to the rim and screed it level (pre-tamping) you get pretty close to 14 g.

                        I have never dosed 10 g in a 20 g, but I will try using my current dose of around 17.5 g in a 20 g basket and try and do some comparisons with an 18 g basket at the same dose (these are the only baskets I have). I do know that I have dosed as low as 16 g in the 18 g basket with no problems wrt the appearance of the pour using a bottemless PF and the cup result.

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