Tamping Technique

elusive espresso... theorize, philosophize!

Postby Chris Davidson on Sun Jun 11, 2006 8:29 pm

As far as I know, convex tamp surfaces are curved to match the degree of reflux on the bottom of the filter basket when under pressure from the brew water. TZ talked a bit about this when I was interviewing him for the article I did on the Naked PF for the SCAA Chronicle. Perforations at the bottom of the filter basket do not spread out to the very edge of the underside of the basket, for structural integrity of the basket as far as I know. Also, as ground coffee is compacted, the bottom half of the coffee cake winds up being less dense than the top half; thus the reason for the bevel in the basket. Coffee is pressed inwards as well as downwards during the tamp for an even cake density. This is one of the brilliant ideas in the engineering of the LM Swift Grinder, coffee is tamped throughout the dose by the impeller resulting in a uniform cake density.
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Postby jepy on Sun Jun 11, 2006 11:05 pm

I've tried the convex tampers, but never got the same amount of uniformity as the flat. After watching baristas in Italy, I wanted to experiment with a simpler method, as many of them seem to use just the grinder mounted tamper. So now it's grind and flat tamp only, no tap, no spin. I see no difference in flavor.

Anyone have a pic of a naked Swift extraction? I'm curious as to how uniform it is.
I made this ultra ristretto to see how even I could get an extraction to form over a longer than normal time. For me the triple down dosed was always harder. If I was to tune this dose any different, how would you change it? Any critique would be helpful.
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Postby Aldo1 on Mon Jun 12, 2006 5:10 am

jepy wrote:I've tried the convex tampers, but never got the same amount of uniformity as the flat. After watching baristas in Italy, I wanted to experiment with a simpler method, as many of them seem to use just the grinder mounted tamper. So now it's grind and flat tamp only, no tap, no spin. I see no difference in flavor.

Anyone have a pic of a naked Swift extraction? I'm curious as to how uniform it is.
I made this ultra ristretto to see how even I could get an extraction to form over a longer than normal time. For me the triple down dosed was always harder. If I was to tune this dose any different, how would you change it? Any critique would be helpful.
John
http://www.youtube.com/watch?v=zwrgctXmB2o


No, but I have both a Swift and a naked PF so I will try and take one today and post it. I will be interested in your thoughts.
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Postby nick on Mon Jun 12, 2006 6:29 am

Your technique pre-tamp (dose, level, distribution) has as much to do with the curved/flat tamper choice as the shape of the basket, etc.

YMMV.
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Postby PureArabica on Wed Jun 14, 2006 12:01 pm

Any progress on that naked portifilter used with the swift?
I'm really interested to see the results.
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Postby Alistair Durie on Wed Jun 14, 2006 12:07 pm

PureArabica wrote:Any progress on that naked portifilter used with the swift?
I'm really interested to see the results.
nick


I couldn't keep my lens out of the channels.
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Postby Jason Haeger on Wed Jun 14, 2006 1:10 pm

alistair wrote:
PureArabica wrote:Any progress on that naked portifilter used with the swift?
I'm really interested to see the results.
nick


I couldn't keep my lens out of the channels.

That's about what I remember as well. It wasn't a very good extraction at all. The Swift is to be avoided, imho.
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Postby Jason Haeger on Wed Jun 14, 2006 1:15 pm

jimmyo wrote:Here we go again...

convex tampers are intended to be used on convex showerscreens, so the distance between the showerscreen and coffeebed is the same - or if it gets squished, at least it's being squished uniformly.

And yes, a curved tamper does lead to a denser centre - if you're leveling flat... however, I find curving your index finger during the final level to create a divot corrects this tendency.

And for the tamp twice technique - I've tried that too, and you can actually use it to fit more ground coffee into a given basket. Try it!

Is the purpose even initial contact? Once the puck swells, it really doesn't make much of a difference what the shape of the showerscreen is, right?

The only advantage I could see in such a situation is fitting more coffee into the basket without stuffing up the surface of the puck when the PF is locked into place, but the extraction is still not going to be as even. Gravity still points downward.. even if the pressure inside the filterbasket is relatively uniform. Extractions from the center of the puck are most likely to end up in the cup before the extractions from the edges.

Isn't the goal an even-density puck?
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Postby Matthew Kolehmainen on Wed Jun 14, 2006 3:01 pm

Gravity still points downward.. even if the pressure inside the filterbasket is relatively uniform. Extractions from the center of the puck are most likely to end up in the cup before the extractions from the edges.


Huh? Are we talking about the force of gravity on the puck? 9 bars of pressure kind of makes the force of gravity negligible in comparison.

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Postby Jason Haeger on Wed Jun 14, 2006 5:50 pm

macchiattomatthew wrote:
Gravity still points downward.. even if the pressure inside the filterbasket is relatively uniform. Extractions from the center of the puck are most likely to end up in the cup before the extractions from the edges.


Huh? Are we talking about the force of gravity on the puck? 9 bars of pressure kind of makes the force of gravity negligible in comparison.

Matthew

No, I'm talking about the behavior of the extraction once it reaches the perforations in teh bottom of the basket. Which will have an easier time escaping, the extractions from the center of the puck, or the extractions from the outter edges?

How do we know that the extracted espresso is leaving the pressurized environment at an even rate?
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Postby Andy Schecter on Wed Jun 14, 2006 6:54 pm

Jasonian wrote:Once the puck swells, it really doesn't make much of a difference what the shape of the showerscreen is, right?


IF the coffee is in contact with the showerscreen during the extraction, then the shape of the showerscreen might make a subtle difference (it would affect the distance water has to travel through the puck before it exits the bottom).

But we hear rumors about experimental glass portafilters showing that the coffee is NOT in contact with the showerscreen until after pressure is released. This would make showerscreen shape unimportant.

Jasonian wrote:Isn't the goal an even-density puck?


Most people say that the goal is an even-density extraction. To achieve that, an even-density puck may or not be required. Schomer thinks that a convex tamper provides a better extraction.
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Postby Matthew Kolehmainen on Wed Jun 14, 2006 9:02 pm

No, I'm talking about the behavior of the extraction once it reaches the perforations in teh bottom of the basket. Which will have an easier time escaping, the extractions from the center of the puck, or the extractions from the outter edges?

How do we know that the extracted espresso is leaving the pressurized environment at an even rate?


Unless you are referring to the fact that the bottom of the basket is curved (slightly), I still don't understand what effect gravity would have.

Most people say that the goal is an even-density extraction. To achieve that, an even-density puck may or not be required. Schomer thinks that a convex tamper provides a better extraction.


So, basically, we want to extract the the same amount from each particle of coffee. Or do we? Illy states that for a good extraction, we need variable particle sizes. But this means that we will extract different amounts from the differently sized particles (due to the volume to surface area ratios being different). Unless I'm completely misinterpreting the meaning of an even-density extraction. :)

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Postby Jason Haeger on Wed Jun 14, 2006 9:37 pm

AndyS wrote:Schomer thinks that a convex tamper provides a better extraction.

Actually, if you read the article, Schomer thinks that a convex tamper provides a bit of assistance in distribution with less chance of "missing the pour"(verbatim). In other words, it's a crutch.
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Postby Alistair Durie on Thu Jun 15, 2006 1:03 am

AndyS wrote:But we hear rumors about experimental glass portafilters showing that the coffee is NOT in contact with the showerscreen until after pressure is released. This would make showerscreen shape unimportant.


Illy, 12-14 grams. yup, tons of headroom.
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Postby Alistair Durie on Thu Jun 15, 2006 1:13 am

This is all very interesting and fun to talk about, but lets remember the question that Robert asked that wasn't addressed:

Dasein wrote:I don't have anywhere near the experience of any of you guys with this kind of thing, and I'd defer to your knowledge any day -- but I am curious as to how some of this stuff is known.


Theory is entertaining, facts are very useful.
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Postby PureArabica on Thu Jun 15, 2006 5:28 am

alistair wrote:Theory is entertaining, facts are very useful.

...and very few and far between.

As an aside; I don't think the convex is a crutch per se, it is a tool that seems to help prevent side channeling from taking place. If a helpful tool like that is considered a crutch... then bring em' on!!
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P.S. I use a flat tamp =)
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Postby Jason Haeger on Thu Jun 15, 2006 11:29 am

PureArabica wrote:P.S. I use a flat tamp =)

p.s. I use a convex tamp =(
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Postby Andy Schecter on Thu Jun 15, 2006 4:44 pm

Jasonian wrote:Actually, if you read the article, Schomer thinks that a convex tamper provides a bit of assistance in distribution with less chance of "missing the pour"(verbatim). In other words, it's a crutch.


With his coffee and his equipment, Schomer says he found the round bottom tamper distinctly superior. YMMV.

Whether it's a "crutch" or not is a lot less fruitful an inquiry than whether it improves your coffee (or not ).
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Postby nick on Thu Jun 15, 2006 5:02 pm

I've been a curved-tamper guy since day 1 (thanks to the person Mark Prince refers to as "my guy"). I did a big espresso-thing at Counter Culture on Tuesday, and used their flat Reg instead of our convex Reg or Espressocraft (cuz they were back home in the shop). Got a little side-channel on a good number of my shots. No such problem when I'm on our turf with our tampers. 18-19g doses... OEM LM double baskets... fyi.

That being said, it's a simple thing for me: use the crotchless pf, with the flat, with the convex, and watch how the espresso emerges from the bottom of the basket. Watch the pours out of the spouts. Taste the coffee. Convex for me. It clearly creates a better seal on the sides. But that's just me. I swear by the convex, but that's just me. Me and all 25 of my baristas.
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Postby barry on Fri Jun 16, 2006 7:55 pm

alistair wrote:This is all very interesting and fun to talk about, but lets remember the question that Robert asked that wasn't addressed:

Dasein wrote:I don't have anywhere near the experience of any of you guys with this kind of thing, and I'd defer to your knowledge any day -- but I am curious as to how some of this stuff is known.


Theory is entertaining, facts are very useful.



gosh, i step away for a couple of days and y'all start an espresso epistemology thread.


has anyone considered that the purpose of the tamp and polish may be to inhibit the absorption of water by the coffee in the pre-extraction phase? as such, tamp and polish may be contra to pre-infusion.


--barry "stirring the pot"
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Postby Jason Haeger on Sat Jun 17, 2006 5:02 pm

barry wrote:
alistair wrote:This is all very interesting and fun to talk about, but lets remember the question that Robert asked that wasn't addressed:

Dasein wrote:I don't have anywhere near the experience of any of you guys with this kind of thing, and I'd defer to your knowledge any day -- but I am curious as to how some of this stuff is known.


Theory is entertaining, facts are very useful.



gosh, i step away for a couple of days and y'all start an espresso epistemology thread.


has anyone considered that the purpose of the tamp and polish may be to inhibit the absorption of water by the coffee in the pre-extraction phase? as such, tamp and polish may be contra to pre-infusion.


--barry "stirring the pot"

That's an interesting thought.

The implied question being, would it be better to have a uniformly coarse surface on the puck rather than the mirror-polish surface currently accepted as the norm?

Who wants to test this one out. I'm not willing to destroy my tamper for a theory.
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Postby barry on Sun Jun 18, 2006 7:41 pm

Jasonian wrote:The implied question being, would it be better to have a uniformly coarse surface on the puck rather than the mirror-polish surface currently accepted as the norm?


the thought is that if the purpose of tamping, and the polish, is to present a cohesive and unified coffee "front" for the incoming brew water, so that water attacks the coffee uniformly when pressure builds, then any thing which would disturb that "front" is undesireable. as pre-infusion allows the coffee cake to change in both density and structure, it may be that pre-infusion is contrary to the designs of the tamp/polish.
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