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
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



Comment