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Tamping Science, Theory and Practice, Part One by Mark Prince
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andys
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andys
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Posted Sun Nov 12, 2006, 11:28am
Subject: Re: Tamping Science, Theory and Practice, Part One by Mark Prince
 

Hey Mark, g'day, mate.

I tried to skim the myriad comments in this thread, but I may have missed something. So I hope what I'm about to say isn't mere repetition....

You said:

curved, convex shapes came about because of a theory - the tamper's piston applies pressure to give an extra squeeze at the edges - the lower middle portion of the piston pushes down, and out (to the sides); or so the theory went.


That's the conventional wisdom, but I doubt it.

First of all, the outward force on coffee particles at the edge of the basket is very small. Outward force is related to downward force via a sine function, and the sine of the shallow angles we have on convex tampers is very small. In other words, the outward force on a coffee particle near the edge is miniscule.

But more importantly, if you're concerned about thorough compaction along the edge of your coffee cake, the convex tamper is the last thing you'd want. The convex tamper applies LESS force at the edge, because it contacts the center first. The center gives only so far before it has compacted as far as it can with the amount of force you're applying. Then it resists, preventing further downward movement. The result is a pattern where the degree of compaction is greatest in the center and least at the edge, which presumably is just what you DON'T want.

So if (and it's a BIG if) you're serious about wanting an "extra squeeze" at the edges, you should use, IMHO, a CONCAVE tamper -- with or without a synthetic diamond in the center.  Besides, the Gourmet Espresso Tamper people have better music on their site than Reg.  :-P

The best shape for edge compaction might be slightly concave with a flat edge a few mm wide. Go figure!  :-)

 
-AndyS
picture page:  http://flickr.com/photos/andy_s/sets/
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andys
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andys
Joined: 10 May 2003
Posts: 845
Location: NY
Expertise: Just starting

Espresso: Speedster, Londinium 1
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Posted Sun Nov 12, 2006, 4:57pm
Subject: Re: Tamping Science, Theory and Practice, Part One by Mark Prince
 

Mark:
I just came back from a long walk with the dog, during which I took my mind completely off this tamping thing. Do you find that when you DON'T have your conscious mind on something, you often have your most original ideas about it? That's the way it seemed to be for me here.

You said:

I came up with somewhat similar conclusions that Carl Staub was famous for discussing and writing about. Basically, the "staub tamp" is the act of tamping squarely, then tamping at for corners of the "compass" inside the filter basket to push down on the loose coffee, and further create a tighter seal at the filter basket's wall.


The N-S-E-W Staub tamp is a crude way of doing exactly what a CONCAVE tamper can do with a lot less effort: apply extra compression around the edge to make sure it's sealed. Below is a really crude drawing of a tamper base (I suck in Illustrator) that would be worth experimenting with. Perhaps it could be made even more functional (chamfered edges, etc), but you get the idea. Actually, I had a phone conversation with a certain coffee friend of ours who is a superb machinist, and hopefully he'll have time to make some concave bases for us to test.

If it works, it could be great for the tamper manufacturers: after years of selling us flat and convex bases, now they can sell us concave ones as well.  :-)

andys: tamper2.gif
(Click for larger image)

 
-AndyS
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MarkPrince
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Posted Sun Nov 12, 2006, 7:35pm
Subject: Re: Tamping Science, Theory and Practice, Part One by Mark Prince
 

Hola Andy

I'm posting to say I'm not ignoring your comments, but just up to my eyeballs getting the silent auctions and holiday gift list off the ground right now, and have a lot of responses for what you wrote - some of the stuff is in part two and three articles.

Fuggit - I'll email those to you and see what you say via email. Basically, the culimination is something I've been working on with Reg for a while, and we're still not "there" yet, as it were. But a lot of my theorizing has to do with the play between dispersion screen and coffee bed - especially with regards to the disperson screen's typical 1-2mm smaller diameter and the solid metal ring on the outer edge of the dispersion screen - both the side facing the puck, and the horizontal sides.

Stand by for an email from my gmail account...

Mark

 
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iZappa
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Posted Sun Nov 12, 2006, 11:35pm
Subject: Re: Tamping Science, Theory and Practice, Part One by Mark Prince
 

AndyS:

Could one use a curved tamper on the first tamp, then a flat tamper after the knock?

 
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MarkPrince
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Posted Mon Nov 13, 2006, 1:08am
Subject: Re: Tamping Science, Theory and Practice, Part One by Mark Prince
 

That would achieve what Andy was describing - the first tamp would leave more coffee at the outer diameter, and the secondary tamp with a flat piston would further compress the outer edge, sealing up the sidewalls more.

Mark

 
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andys
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andys
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Posted Mon Nov 13, 2006, 4:42am
Subject: Re: Tamping Science, Theory and Practice, Part One by Mark Prince
 

iZappa Said:

Could one use a curved tamper on the first tamp, then a flat tamper after the knock?

Posted November 12, 2006 link

Good idea; that may or may not accomplish roughly the same thing. It would be fun to try it and see.

But I believe Mark's intent (and mine, too) is to come up with a single tamper design that works optimally, with no extra steps. It has to be compatible with the rapid work flow of a commercial barista (which is what you are, according to your sig).

 
-AndyS
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iZappa
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iZappa
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Posted Mon Nov 13, 2006, 5:02am
Subject: Re: Tamping Science, Theory and Practice, Part One by Mark Prince
 

andys Said:

Good idea; that may or may not accomplish roughly the same thing. It would be fun to try it and see.

But I believe Mark's intent (and mine, too) is to come up with a single tamper design that works optimally, with no extra steps. It has to be compatible with the rapid work flow of a commercial barista (which is what you are, according to your sig).

Posted November 13, 2006 link

Yes of course. My suggestion was mearly for experimenting. I'm off to have a coffe testing now so maybe I'll try it. I'm just concerned that the middle off the puck will break when you push down the edges with a flat  tamper. But only one way to find that out!

(Isn't this what coffee is all about :-D )

 
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anarlpo
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anarlpo
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Posted Sat Nov 18, 2006, 11:26am
Subject: Re: Tamping Science, Theory and Practice, Part One by Mark Prince
 

this is my first comment on the site.
we are distributors for illycaffe and faema in azerbaijan.
illy's own cheap plastic tampers are also flat/shallow.
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unidonburi
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Posted Sat Nov 25, 2006, 9:01pm
Subject: Re: Tamping Science, Theory and Practice, Part One by Mark Prince
 

Thanks for the article Mark.  I am still a newbie and my anecdotes about tamping technique won't add much to this forum.  However there is one issue that I learned about the hard way that is only refered to here indirectly.  It is probably something of a no-brainer for most of the people posting here, but might not be general knowledge for those about to purchase their first tamper.

When I first got my E-61 clone HX machine, I received a double basket and a single basket and was told by the seller that they were each 58mm and would therefore require a 58 mm tamper.  I bought a 58 mm tamper from a local espresso machine retailer and began the journey...

I also subsequently got a bottomless pf and a triple basket.  The bottomless pf allowed me to learn that my shots were faster around the perimeter of the basket and also that I often had channeling.  When I finally measured my baskets with calipers, i found that the 2x and 3x baskets were each 59mm.  

I have since aquired a 58.5mm tamper from RB and despite the fact that this tamper is only 0.5mm larger than the original, with this, most of my channeling problems seem to have disappeared.  

The point of my story is that even though tamper manufacturers are aware that basket sizes vary quite a bit (and RB is very careful about informing customers about this), many retailers I have spoken to only sell a narrow range of tamper sizes.  Furthermore...some sales associates aren't even aware of this issue.

cheers,
Geoff
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MarkPrince
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Posted Sat Nov 25, 2006, 10:52pm
Subject: Re: Tamping Science, Theory and Practice, Part One by Mark Prince
 

anarlpo Said:

this is my first comment on the site.
we are distributors for illycaffe and faema in azerbaijan.
illy's own cheap plastic tampers are also flat/shallow.

Posted November 18, 2006 link

Hi Anar - thanks for joining up on CoffeeGeek, welcome, and wow, very cool to hear frm someone in Azerbaijan!

It's ironic that you posted - I had in my 2nd article, some discussion of the Illy modified tamper that ships with the X-series machines over here - the tamper that you use, then unscrew to leave a top dispersion screen on top of the ground coffee. I took it out because it was a bit of a tangent, but it's an interesting development by Illy nonetheless, and played a role in my further development of some tamping theories.

Geoff - yeah, basket sizes are a challenge. I still remember some discussion that the machine sponsor for the USBC last year put out a late recommendation that Baristas competing should consider a 57mm tamper (or 57.5 - can't recall exactly) for the comp so as not to have any difficulties with tampers getting stuck in baskets - and it kind of took the community aback a bit; the thought was, maybe instead, someone should be going through a box of baskets, all with apparently different sizes (differing by 0.1, 0.2, 0.3mm or more) and just dig out 25 or 50 baskets that were spot on 58.0mm - it wouldn't take long with a good set a good set of calliper measuring tools and a LOT less expensive than expecting the baristas to drop another $50 or more each on a custom sized piston.

In my third article, I talk about ways and a means to pretty much completely avoid channeling issues.

For folks waiting for Article II, it is done, ready to go, but waiting on one video I still need to shoot. I'm hoping to get on it in the next few days, once I deal with a few more Holiday Gift List things and auctions to get onboard.

Mark

 
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