Replies to This Discussion

Permalink Reply by N. Freeman on May 31, 2009 at 1:13pm

Chandler,

I agree with you. I use a light tamp, just enough to level the puck and keep it solid enough to polish it without moving the coffee. This method gives me a consistency I can't get when applying 30-40 pounds of pressure.

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Permalink Reply by Kevin Kerkhof on May 31, 2009 at 7:46pm

I'm new at this myself, but have a few thoughts:

The machine you use could make difference. If there is a pre-infusion then once the grounds get wet they would expand, taking away any sort of pressure resistance from the tamp.

Also, a higher and consistent pressure would have no problem pushing the water through the puck. The only resistance would be the size of the coffee grounds or amount of coffee.

The blonding that would occur early in the shot with an excessive force tamp makes me think that somewhere in the puck is the path of least resistance (maybe a coffee particle size slightly larger than another not really visible to the naked eye), where it takes longer for the rest of the coffee in the portafilter to become saturated. Thus you get a "crack" where the water starts to flow.

I could definitely be wrong in any of these statements, so please consider them only for further discussion.

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Permalink Reply by Terika on May 31, 2009 at 11:47pm

I do not have scientific data to back up my experiences, but at the coffee shoppe that I currently work at, we have an Anfim grinder and a Mahlkonig grinder. Whenever I take over bar, I have to adjust the grind on these to compensate for my tamp that is a bit harder than most of my coworkers. If your theory is true that tamp does not make a difference, I would not have to adjust the time or grind on either of these grinders because they are consistent in how much they produce each time you hit the button. Once again, these are just my experiences, and not scientific by any means. :)

I have heard that tamping harder than 50lbs of pressure makes no difference...so an 80lb tamp would produce the same result as a 50lb tamp. Has anybody else heard or know anything about this?

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Permalink Reply by The Barista Formerly Known As JavaJ on June 1, 2009 at 12:05am

Chandler, would you mind sharing a little more information about what you are doing? What kind of machine are you on? What kind of grinders are you using? How are you measuring your dose? More importantly, how are you measuring your tamp?

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Permalink Reply by Chandler Rentz on June 1, 2009 at 7:28am

at both shops I work at we use La Marzocco Linea 3AVs... grinder: Super Jolly, burrs are replaced regularly. At the roastery I also have an Aurelia at my disposal. I use very accurate scales (at least .1g increments, also have a pocket scale with .05g increments). Tamp is measured with a standard bathroom scale. I don't use the volumetric buttons... when I experiment I use the manual brew switch and just watch the shot glass and timer.

I train at Aurora Coffee... I would notice that adjustments would have to be made when relieving other baristas... as I trained them and we looked at their dosing habits I noticed that some people dosed relatively very light while others were really packing it in (16g - 21g)... (not to mention individual baristas being all over the board from shot to shot, hence the need for a dosing test to be incorporated into the certification program).

The Barista Formerly Known As JavaJ said:

Chandler, would you mind sharing a little more information about what you are doing? What kind of machine are you on? What kind of grinders are you using? How are you measuring your dose? More importantly, how are you measuring your tamp?

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Permalink Reply by Nathan Lyle Black on June 1, 2009 at 9:18am

Terika,

Whenever I take over the bar, I have to make a very slight adjustment to my grind as well. This is not because of the differences in the pressures applied by each barista when tamping their espresso, but because each barista doses a slightly different amount into the portafilter whenever they pull a shot. I brought my scale to work one day and asked everyone to weigh their dose before they pulled their shot. Their was a two gram difference between the person at the shop who doses the least and the person who doses the most. This would account for the need to adjust the grind.

I'll bring my scale with me to work tonight, and do some tests. I suspect the difference between a light (but firm) tamp, and a 50- 80 lb tamp is negligible.

Terika said:

I do not have scientific data to back up my experiences, but at the coffee shoppe that I currently work at, we have an Anfim grinder and a Mahlkonig grinder. Whenever I take over bar, I have to adjust the grind on these to compensate for my tamp that is a bit harder than most of my coworkers. If your theory is true that tamp does not make a difference, I would not have to adjust the time or grind on either of these grinders because they are consistent in how much they produce each time you hit the button. Once again, these are just my experiences, and not scientific by any means. :)

I have heard that tamping harder than 50lbs of pressure makes no difference...so an 80lb tamp would produce the same result as a 50lb tamp. Has anybody else heard or know anything about this?

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Permalink Reply by Nathan Lyle Black on June 1, 2009 at 9:21am

EDIT: Reread your comment, and I completely missed the crucial phrase "they are consistent in how much they produce". How light are some of your coworkers tamping?

Nathan Lyle Black said:

Terika,

Whenever I take over the bar, I have to make a very slight adjustment to my grind as well. This is not because of the differences in the pressures applied by each barista when tamping their espresso, but because each barista doses a slightly different amount into the portafilter whenever they pull a shot. I brought my scale to work one day and asked everyone to weigh their dose before they pulled their shot. Their was a two gram difference between the person at the shop who doses the least and the person who doses the most. This would account for the need to adjust the grind.

I'll bring my scale with me to work tonight, and do some tests. I suspect the difference between a light (but firm) tamp, and a 50- 80 lb tamp is negligible.

Terika said:

I do not have scientific data to back up my experiences, but at the coffee shoppe that I currently work at, we have an Anfim grinder and a Mahlkonig grinder. Whenever I take over bar, I have to adjust the grind on these to compensate for my tamp that is a bit harder than most of my coworkers. If your theory is true that tamp does not make a difference, I would not have to adjust the time or grind on either of these grinders because they are consistent in how much they produce each time you hit the button. Once again, these are just my experiences, and not scientific by any means. :)

I have heard that tamping harder than 50lbs of pressure makes no difference...so an 80lb tamp would produce the same result as a 50lb tamp. Has anybody else heard or know anything about this?

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Permalink Reply by Jonathan Jarrow on June 1, 2009 at 10:10am

According to The Professional Barista Handbook by Scott Rao, when a puck is hit with 9 bars of atmospheric pressure, it is equivalent to around 150 lbs. of pressure across the surface of a 58mm+ puck(I don't have the book on me at the moment to give the exact #, but I know it's around 150). He also has the math in the book explaining how he got that #. Because of this, it doesn't really matter if you tamp the hell out of that shot, it's nothing compared to what the machine is putting the puck through.

The purpose of the tamp is to remove "pockets" of air from inside the coffee bed to prevent channeling.

This said, I have a theory about tamping pressure which I have yet to prove involving reduction in crema due to over tamping. If crema is the result of oils in the coffee wrapping themselves around the air in the coffee bed, then it would seem that a tamp with excessive pressure would remove a lot of the air from the bed as the particles compress together, creating less available material for the creation of crema. I have seen hands on evidence of this, especially when working with a much finer grind.
Any feedback on this in particular would be much appreciated.

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Permalink Reply by Jason Dominy on June 1, 2009 at 10:59am

This is very interesting. This morning in a training, I was going to show the gal what a bad shot tasted like, both extremes, so on the second one, the one meant to go blonde quick, I barely tamped. And I mean barely, and when I pulled the shot, the flow rate was perfect, just like when I tamped it normally! I immediately thought of this post! So, we both tried the shots, and I realized the difference was in the taste of the espresso. Our espresso here is really sweet and rich, the espresso out of the lightly tamped shots were bland, a little sour, and not that good to drink. Which makes sense, it's not extracting the coffee fully, going through the grounds faster. So, this was a surprising study, one in which I will continue to look into.

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Permalink Reply by Jesse -D-> on June 1, 2009 at 11:18am

"This said, I have a theory about tamping pressure which I have yet to prove involving reduction in crema due to over tamping. If crema is the result of oils in the coffee wrapping themselves around the air in the coffee bed, then it would seem that a tamp with excessive pressure would remove a lot of the air from the bed as the particles compress together, creating less available material for the creation of crema. I have seen hands on evidence of this, especially when working with a much finer grind.
Any feedback on this in particular would be much appreciated."

I don't think that I agree, but I'm not sure I understand fully. The gases that create crema are coming from inside the grounds, so the fact that you tamp harder really would have no effect on this. You are essentially saying that if you squeeze a roasted coffee bean you can get CO2 to come out, and that you cannot do.

Again if I misunderstood your post please correct me and accept my apologies.

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Permalink Reply by Joe Marrocco on June 1, 2009 at 11:28am

Tamping does not make a huge difference in shots. The dose has far more to do with inconsitencies between baristas. It is not simply the grams in the portafilter, but the distrobution of those grams. Obviously, grind is a huge component, but not between baristas. If one barista taps the portafilter 3 times during dosing before tamping, and the next taps it 6, this is a huge difference in distrobution. Try it. Dose tapping once, then twice and so on and see how much time changes over the next ten shots; increase one tap every shot. This is why the tech judges at a competition keep track of portafilter taps and not tamping PSI. Tapping is distribution, distribution is consistency.

I will add that there is a slight to moderate taste difference and time difference between no tamp and 30#. Tamping is necisary for a good shot. It helps the water diffuse properly across the surface of the puck before it gets hit with the pressure. Once the pressure is engaged, 9 bars over powers 30 PSI.

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Permalink Reply by Nathan Lyle Black on June 1, 2009 at 11:31am

At 9 bars, a machine is pushing against the espresso with a force of 130.68 psi. Pretty close to the 150 you estimated.

Jonathan Jarrow said:

According to The Professional Barista Handbook by Scott Rao, when a puck is hit with 9 bars of atmospheric pressure, it is equivalent to around 150 lbs. of pressure across the surface of a 58mm+ puck(I don't have the book on me at the moment to give the exact #, but I know it's around 150). He also has the math in the book explaining how he got that #. Because of this, it doesn't really matter if you tamp the hell out of that shot, it's nothing compared to what the machine is putting the puck through.

The purpose of the tamp is to remove "pockets" of air from inside the coffee bed to prevent channeling.

This said, I have a theory about tamping pressure which I have yet to prove involving reduction in crema due to over tamping. If crema is the result of oils in the coffee wrapping themselves around the air in the coffee bed, then it would seem that a tamp with excessive pressure would remove a lot of the air from the bed as the particles compress together, creating less available material for the creation of crema. I have seen hands on evidence of this, especially when working with a much finer grind.
Any feedback on this in particular would be much appreciated.

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