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  • #31
    This is for the Talk Coffee post onwards.

    I had Michael Teahan's paper "Fundamental Principals of Espresso Machine Design" in my (paper) library from years ago: good interesting read. Does not seem to be available on line, however there are plenty of references to it. Shows how good science can ask the wrong question and get a valid consistent half true result be failing to deal with all confounding factors.

    http://coffeesnobs.com.au/general-co...-pressure.html has a little info about it. Result: no difference when using a single tamp at 30lbs or a hydraulically stable 300lbs.

    CoffeeGeek - Tamping Science, Theory and Practice, Part One
    "Thirty pounds of tamping pressure was kind of religious in espresso circles back in 2000. David Schomer, a pioneer in espresso crafting was touting that number in his books and his speaking engagements. In the newsgroup alt.coffee, the general consensus was that 30 pounds was the magic pressure for tamping (not all agreed with this though). So I was pretty surprised to hear that the Swift only tamped with 8 pounds of pressure.

    I asked why, and Blackwell went on to explain that during the development of the grinder, they initially set the continuous tamping device at 30 pounds of pressure, and found that they created solid bricks in the filter basket, no matter how coarse the grind was. They were a bit mystified by it all, but eventually figured out two elements were at work.

    First, ground coffee is a wide range of particle sizes within it's scope of "espresso grind", and those grounds form a kind of interlocking puzzle when compressed. The more pressure exerted on the interlocking pieces, and the tighter the overall fit is.

    Second, and most crucial, they believed that in manual hand tamping, no matter how much pressure a person exerts on the top of the bed of ground coffee, by the time one gets down to the bottom third of the bed, almost all that pressure is eaten up, and the bottom portion of the formed puck is barely compacted any more by the tamping pressure. Because the Swift grinder continuously tamps as the coffee is ground and added to the basket, all the pressure comes to bear on the forming puck, a millimeter in height at a time.

    Simply put, when you tamp by hand, you're tightening up the pieces of the puzzle at the top of the formed puck quite a bit; less so by the time you get midway down the puck, and very little, if any tightening at all by the time you get to the bottom few millimeters. The swift interlocks the grind puzzle pieces firmly and tightly from the get go, right through the entire formation of the puck. Result? Water hits a brick wall, even if the coffee is ground coarser.

    La Marzocco were not the only ones to talk about this. I remember discussing this with some folks from Illy back in 2003 at the Boston SCAA show, and they talked about similar theories."

    The earlier posts plus those two quotes to show how little tamping has progressed since 2006. Oddball ideas? My curiosity led me to follow all research in that area I can lay my hands on since 1970. It also led me to do the same experiment as LM via what they call continuous tamping many years ago - with exactly the same result. A single tamp does not give anything like the same result as progressive tamps...

    FWIW, the Northern Italian who trained me to tamp progressively (1979) loved SO's and SO's seem to benefit a lot more from progressive tamping than dark roasts (which I have posted on CS before). Probably why they must have used it "way back when" in Northern Italy.

    I still regard CS as a good way to share info, however this lot has me wondering whether to reassess that belief.

    TampIt

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    • #32
      Hi TampIt,

      I think several people find this stuff interesting. What I don't get is why the relationships / effects you describe are contingent on whether or not you use a naked portafilter (as post#21 seems to imply). And I guess that other bit that people might respectfully wonder about is whether the issue is actually 'so important' or 'critical' in cases with a naked (but nothing wrong with the pursuit of marginal improvements of course). FWIW I sometimes use a vaguely related technique with some beans when I'm trying to get a dose / grind combo that suits.....but I just dose about 30%, tap and rest the tamper on the grinds before completing the dose.
      Cheers
      BOSW

      Comment


      • #33
        In under 1000 words, my theory/opinion (FWIW) is that there is a risk of cross channelling if you aim to build a brick wall. I'd sooner have a a consistent change in density and one brick. To put it another way, the more you d!(k around with a puck, the greater the risk of unwanted results- including channels. In addition, I'm not prepared to spend some minutes on a puck. I don't need to muck around to get consistent, excellent results.

        As for the need to tamp differently with a naked, sorry but unless it can be proven (glass portafilters and baskets anyone?), nup.

        Ultimately though, I really don't care what other users might choose to do. If it works for you and you have 10 minutes to muck around, go for it- however I do fear that this complex talk scares away noobs by making things way more complex than they need to be.

        Meanwhile, I'll have my second....
        Last edited by TC; 2 December 2013, 09:47 AM. Reason: typo

        Comment


        • #34
          My part in this was just stretching things for a laugh, and was in no way any comment on the science of it all.

          My thoughts immediately were that there probably is far less pressure at bottom of puck then top because we are tamping into a cylinder where some of the energy we are applying downward is being converted to outward pressure (against walls of cylinder) and thus dissipating downward force. I didn't know if this was true as I had no real research, but your comment seemed plausible that there is far less pressure at bottom (but zero at bottom with 300 pounds did sound very unlikely indeed).
          I just couldn't help myself once I had an image of pouring coffee on my head in a collapsing building.
          Not meaning to pick on your comments TampIt.

          Comment


          • #35
            As a rank amateur coffee maker, I agree with Chris at Talk Coffee. I cannot see a need to tamp differently while naked. I use my naked portafilter most of the time. I can easily see when I get any channelling, it is easier to keep clean and there is less of a lump of steel to cool down the brew.

            I have seen here at CS videos of complicated methods of dosing and tamping and wonder if the results in the cup are any better for it.

            Barry

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            • #36
              At my work, we use a mix of naked and clothed PF'S. I tend to use the naked for LB's or double ristretto's or double shots and the clothed for when we have to split the shots. Does my technique change? No. Does the time of the shot change? No. I see no need to change it up and just create more fuss and more steps to go wrong when, frankly, it's not needed

              (Step off soapbox)
              Michael

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              • #37
                Originally posted by TampIt View Post
                This is for the Talk Coffee post onwards.
                The easiest way to test the hypothesis would be to get a capped clear nylon/pvc pipe, put grounds in it and observe while tamping it with a cylinder.

                Just to clarify, the only assertion I personally have a problem with is that naked PFs are any different (though I don't feel the need to progressively tamp myself).

                Comment


                • #38
                  Originally posted by Barry_Duncan View Post
                  I have seen here at CS videos of complicated methods of dosing and tamping and wonder if the results in the cup are any better for it.
                  Barry
                  Morning Barry, no argument from me here.

                  In fact I would suggest that the more complex the procedure the more chance you have of things going wrong, and of course when they do go wrong the more difficult they are to diagnose.

                  When it comes to espresso the KISS principle is alive and well.

                  Comment


                  • #39
                    Originally posted by Barry O'Speedwagon View Post
                    Hi TampIt,

                    I think several people find this stuff interesting. What I don't get is why the relationships / effects you describe are contingent on whether or not you use a naked portafilter (as post#21 seems to imply). And I guess that other bit that people might respectfully wonder about is whether the issue is actually 'so important' or 'critical' in cases with a naked (but nothing wrong with the pursuit of marginal improvements of course). FWIW I sometimes use a vaguely related technique with some beans when I'm trying to get a dose / grind combo that suits.....but I just dose about 30%, tap and rest the tamper on the grinds before completing the dose.
                    Cheers
                    BOSW
                    James Hoffman: "I am not going to claim to be absolutely right and I hope each article I write fosters healthy debate on the subject discussed."


                    Complexity: HL Mencken circa 1894 "For every complex problem there is always an answer which is neat, simple ... and wrong". If simplicity means excessive reductionism, I am against it.

                    The links I quoted really open up a (much needed in my view) debate on what I will loosely call a progression from not packed / packed at the top / compressed at the top / compressed all the way through. Anyone can test this easily. Tamp at one mm at a time @ 30lb's and get a brick. Use the same dose & grind with one single 30lb tamp in the same basket: it flows a lot faster. Plenty of room for experimentation.

                    Moving on to my previously abbreviated naked / medium SO comments. FWIW, dark roasts seem to be more immune to this effect. A naked has potentially a lot more flow than a standard spout*. Standard baskets in nakeds have the same issues, however VST's reveal it more clearly. Why? VST's have smaller, more consistent holes and a lot more hole area and therefore potential flow rate compared to conventional baskets. The effect of adding them together seems to multiply the flow dynamics (really noticeable). To compensate it is necessary to revisit the whole grinding** (finer is good), dosing (less is good: counteracts the finer grind to a degree) and finally tamping*** to obtain a better balance in the cuppa.

                    *I am still waiting for someone to tell my why a standard p/f spout's method of putting the coffee through an extra drop and spout should improve it. In my view it cannot & does not.

                    ** Grinding finer has a real side issue with a number of commercial & high end domestic grinders. VST's tend to work well at or just below "normal" espresso grinds. Too many commercial grinders start to generate an inordinate amount of fines at those settings. Even poorer conicals tend to do better than "mid range" flat burrs in that context, although that will probably change over the next few years.

                    *** Given what I will coin the "hairtrigger flow dynamics" of that combo, the use of progressive damping to grind finer whilst maintaining the dose within the baskets individual sweet spot seems, at the very least, prudent. How important will always depend on your specific roast & gear. Standard baskets hide a lot of evils AFAIAC.

                    If a three way balance between grinding / dosing tamping is complex, so be it.

                    Hope this helps. Enjoying the result is the only thing that really matters.

                    Cheers


                    TampIt
                    PS: One stray comment: strong tapping has been shown to reduce the stiction between the side of the basket and the coffee. Gentle is OK, however I have never seen any attempt to quantify the difference.

                    Comment


                    • #40
                      Originally posted by TampIt View Post
                      .. strong tapping has been shown to reduce the stiction between the side of the basket and the coffee. Gentle is OK, however I have never seen any attempt to quantify the difference.
                      By "tapping" are you referring to the use of the tamper against the side of the PF,..or "settling taps" of the PF vertically down onto the bench ?
                      Many commercial Barista's commonly use a "Settling" tap when dosing the basket in order to give a consistent , even, "fill" of grinds into the basket , and improve the distribution .
                      This settling tap has a similar effect as "progressive" tamping.
                      I personally go further. In order to prevent grind spillage, ( doserless grinder) i use a PF funnel and dose by "guestimated" weight, which is above the basket rim. Before i remove the funnel , i use 4-6 "settling taps" to distribute the puck. This results in an even flat ( and compacted ) puck 4+ mm below the basket rim and no amount of tamping pressure compresses it much further.
                      I get very consistent results ...and very few grinds on the bench !

                      Comment


                      • #41
                        Lately I've been using a pre-tamp side tap, well actually a lot of taps. I dose, then tap the side of the PF gently with my tamper, moving around the PF a few times, so in effect probably 30+ taps, each one about about 170 degrees around from the previous tap. Then I tamp.

                        I've noticed a significant improvement in the evenness of extraction, using a naked.

                        Indeed I can really feel the evenness of the distribution when I tamp.

                        It's clearly not a very efficient process (my wife thinks I'm mad) but for the one coffee I make at home each day I want it to be the very best shot possible each time.

                        Comment


                        • #42
                          Originally posted by TampIt View Post
                          Moving on to my previously abbreviated naked / medium SO comments. FWIW, dark roasts seem to be more immune to this effect. A naked has potentially a lot more flow than a standard spout*. Standard baskets in nakeds have the same issues, however VST's reveal it more clearly. Why? VST's have smaller, more consistent holes and a lot more hole area and therefore potential flow rate compared to conventional baskets. The effect of adding them together seems to multiply the flow dynamics (really noticeable). To compensate it is necessary to revisit the whole grinding** (finer is good), dosing (less is good: counteracts the finer grind to a degree) and finally tamping*** to obtain a better balance in the cuppa.

                          *I am still waiting for someone to tell my why a standard p/f spout's method of putting the coffee through an extra drop and spout should improve it. In my view it cannot & does not.
                          First of all... time for a quote... couldn't help myself

                          "The whole problem with the world is that fools and fanatics are always so certain of themselves, but wiser people so full of doubts." ~ Bertran Russell

                          Secondly... your comments on flow rates of nakeds vs standard spouts might have been relevant if we were discussing fire hoses but at a flow rate of approximately 60ml/30 sec, or 120ml per minute, it hardly matters in the slightest.

                          Lastly, has anyone ever even come close to suggesting that "...putting the coffee through an extra drop and spout should improve it"???

                          Comment


                          • #43
                            Tapping after a firm tamp seems like a bad idea, as the coffee grounds have formed into a more or less solid "cake" at this point and you could easily break a seal with them and sides of the basket. Something however tells me that seal would be re-formed pretty quick after 9 bars of water pressure hits the top of the puck. The other consensus is that it may cause micro-fractures in the puck, leading to channelling. Again, I'm not convinced once you introduce pressure and moisture via a shot that these fractures wouldn't re-seal.

                            I've noticed many decent baristas don't seem to bother with any of this stuff in the cafes and still produce good looking shots. They generally grind into a mound and just tamp it.

                            Of course at home we have a bit more time to go for that consistency.

                            Comment


                            • #44
                              Originally posted by TampIt View Post
                              A naked has potentially a lot more flow than a standard spout
                              Potentially being the operative word. As I have said previously, I do not believe that there is an appreciable flow restriction under typical flow rates for espresso, given the spout sizes I have seen in my limited experience.

                              Do you disagree?

                              I am still waiting for someone to tell my why a standard p/f spout's method of putting the coffee through an extra drop and spout should improve it. In my view it cannot & does not.
                              I completely agree (unless you like the taste of the shite that seems to accumulate in the PFs of even the better cafes I've spied). I love naked PFs for that reason and because of the visual/cleaning factor That's a different issue to what you're talking about though; you haven't shown how there can be an appreciable pressure/flow variation due to naked/spouted PF.

                              Comment


                              • #45
                                Originally posted by Darkfalz View Post
                                I've noticed many decent baristas don't seem to bother with any of this stuff in the cafes and still produce good looking shots. They generally grind into a mound and just tamp it.

                                Of course at home we have a bit more time to go for that consistency.
                                At work we use Robur E's and the timers on them are quite crap. Therefore, my technique is to set the 'timer' to under-dose. At the start of the day I'll figure out what 22g is, set timer to under dose, then I tap the pf on the cradle, manually dose for 0.5 of a second or so, distribute with my index finger with an indent indent that matches the 22g that I weighed in previously and tamp. Works for me at work and at home with my mini doser

                                Michael

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