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  • Pete39
    replied
    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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  • blend52
    replied
    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"

    Leave a comment:


  • Javaphile
    replied
    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

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  • Pete39
    replied
    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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  • blend52
    replied
    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 ?

    Leave a comment:


  • Javaphile
    replied
    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

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  • Robbks
    replied
    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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  • mcetp001
    replied
    That is fascinating.

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  • blend52
    replied
    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.

    Leave a comment:


  • Thundergod
    replied
    Transparent portafilter

    Tije's Transparent Portafilter clip3 on Vimeo

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

    TampIt

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  • Jonathon
    replied
    Originally posted by chokkidog View Post
    Hi Johnathon,

    Is the above a quote or paraphrase from a secondary source, or is the "I" in the text actually you?
    Straight quote from the HB site.

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  • chokkidog
    replied
    Originally posted by Jonathon View Post
    Some very interesting background on this project, from HB, which confirms it's in slo-mo:

    It surprised me that so far there are just these two clips, but after corresponding with Stephen and getting the updates on his first TPF model and the next one, I got a better understanding of the problems that arise when building such a one-off tool.

    One needs to find a way to replace both the wall of the portafilter and the basket itself with something transparent, but it needs to hold the metal bottom of a normal filter basket. Also, the top should lock in securely to the brew group. Then, the combination of very different materials (metal, acrylic, sealant) must be able to all hold together in temperatures rising and falling very quickly from room temperature to temperatures close to the temperature of boiling water, and huge pressure differences from the pressure in the room (on the bottom) to 8 or 9 bar (at the top). Plus, a coffee puck tamped inside, air and water flowing around...

    I can now imagine how the Spaziale team would maybe have felt the urge to push further and use their TPF more, but it's possible that it didn't hold that long and the manager, looking at the cost in time and materials, likely veto'd any further exploits.

    Stephens final TPF held out during a few tests in his workshop and it stayed in one piece during fifteen tests Roemer Overdiep and I did in Amsterdam on the Londinium I lever machine, but then it too began to give. One side is starting to pop open and from what I heard from Stephen, you do not want to be standing very close, peering at the looking glass, when it pops open en explodes hot water and coffee grinds in your face.

    Before we started documenting these TPF experiments, we rented a Sony 4K High Speed camcorder. It fits the Canon prime lenses we have available so we would not miss any detail.

    We also learned something we would maybe not have found out without the TPF: when using a tamper that fits very tight, it's best to tamp lightly. After finishing a firm tamp and pulling back the tamper, the puck can be pulled loose along the sides and this results in the puck jumping up and being slammed down again when the spring lever is being pulled. In a pump machine the puck will not jump up of course, but the seal along the outside of the puck will allow some initial flow.

    The "puck jump" happens very fast but is very clearly seen when we use the super slow motion feature of the camera. It hardly causes a problem but to get a nice and even flow when using a very tight fitting tamper, tamping lightly seems advised.

    When we used the tamper that fits my millennium La Pavoni Europiccola, that proved a very nice fit for Stephens TPF and the puck remained still, allowing the raised piston to suck in air through the puck instead of along the sides. Sadly, by the time we figured that out, the life cycle of the TPF was nearing the end and we couldn't risk damaging the $10.000 camera...

    For a short moment (elongated in the footage) there's a lot more coffee flying around in the TPF than I imagined there would be, but very swiftly, once the pressure is applied, all clears up and you can see the tiniest stream of water along the grains of coffee grinds and air and CO2 struggling to get out of the way.

    We cannot thank Stephen Sweeney enough for making this little project possible!
    Hi Johnathon,

    Is the above a quote or paraphrase from a secondary source, or is the "I" in the text actually you?

    Leave a comment:


  • TC
    replied
    Geez I wish I'd thought to post that....

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  • MrJack
    replied
    Pretty sure I've seen that here before. Even the second shot looked like a gusher to me...

    Leave a comment:

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