Socrates seems to have a solid background in experimental design. The conclusion was that tamp pressure over a range of 5 kg, 10 kg, 15 kg, and 20 kg - or 12 lb, 22 lb, 32 lb, 42 lb resulted in: "no significant difference in TDS (and, by extension, extraction yield) was observed due to tamping pressure." In another series of experiments examining the impact of several lovely tampers on TDS, Socrates (et al) conclude that, except for a negative impact on TDS of one particular tamper: ...."all others were statistically not different".

The 'magic' value of 30 lb seems to have become dogma, with no basis in objective study. Can we consider it simply a myth? In reviewing videos of experienced baristas, I now see some tamp hard, and some tamp hardly at all.

Is tamp pressure really important, and if so, is there some additional data, or only opinions? If there are no data to the contrary, can we consider tamps and tamp pressure guidance - myths?

Thanks.

http://socraticcoffee.com/category/misc/

There are many people on this and other coffee forums who believe that "data" is the plural of "anecdote." The folks at Socrates and Jim Schulman are notable (rare) exceptions.

What you are missing is that this is a forum. People contribute what they believe at the time to be true, what works for them, and what doesn't. Time and experience and equipment changes; and the determination of taste is dependent on individuals. Your job is to try what seems pertinent and to determine what of the information is applicable to your situation.

In reference to your questions, as in all things the more that is done by more people the more dogma changes. As an example look at the medical world, things we were told to do years ago for our health are today verboten.

My own experience suggests that tamping pressure has little or no effect on the extraction.

I used to think that higher tamping pressure slowed the flow rate, but only slightly. I could swear that I saw evidence of this, but recently I switched from about a 30 lb tamp to only enough pressure to ensure a level puck (which is very important.) When I did the switch, I couldn't detect a difference in the flow rate. Go figure. Maybe it had something to do with the coffee.

The general opinion seems to be that the water pressure of the machine is far greater than any pressure you might apply with the tamper. I'm not so sure because there must be a difference between the effect of a solid meta surface pressing down on the top of the grounds and water droplets falling on the grounds during preinfusion, followed by water soaking into the puck, followed by massive pressure from a liquid. But maybe not.

Regardless of what actually happens, I think there's no need to obsess over tamping pressure. If there's any effect, its minimal.

There seems to be some anecdotal evidence that tamper shape and size might make a difference. Some swear by curved bottoms and others swear by flat bottoms. VST recommends a slightly different size for their baskets than the standard 58mm. I suppose it's possible that there'a a best shape and size for a particular basket with a particular dose, but we don't have any reliable experimental data on that.

Finally, the Socratic study is based on extraction yield measurements. I'm a proponent of using such measurements for various purposes, like dialing in, ensuring consistency, troubleshooting equipment, etc., but it's not a given that a higher extraction yield is always better. It's certainly not better when it leads to over-extraction (bitterness.) I think most of the recent hype about increasing extraction yield applies to today's lightly roasted SOs. With some of thses coffees it can be difficult or impossible to obtain enough extraction to get into the "sweet zone", so techniques that supposedly extract more are talked about a lot. But such techniques may not be relevant for other coffees and roast levels.

FirstBetta wrote:In reference to your questions, as in all things the more that is done by more people the more dogma changes. As an example look at the medical world, things we were told to do years ago for our health are today verboten.

When dogma changes in medicine, teaching changes, opinions change and practices change. New 'baselines' are established, representing true contributions. Examples include estrogen replacement therapy, cholesterol intake, RDA for VitD, certain lipid-lowering drugs....etc. Maybe one day, we'll see that Woody Allen in Sleepers was ironically more right than we could imagine--things we thought were bad for health, end up being good. As for coffee, as far as I have read, and from everything I have read, it's a wonderful medicine. Can taste like it, sometimes, which is what this forum might help folks prevent. Quackery will not help. Pointing others to data might.

Extraction is a chemistry science term. Socrates takes a step in this direction. After months lurking here, I stumbled across the data in one post, versus hundreds, if not thousands, of posts pertaining to opinions that set me off course. A few side-by-side comparisons on my gear set me straight-er than before on tamping.

Thanks.

nurxhunter wrote:Endnote: Right before posting this I did another check. Now, using the right keywords, I find others suggesting that tamp pressure is not important (and there is even a bit of 'data'). But, this was not evident to me before, even though I have read quite a bit earlier.

Yes, and I think on this forum the predominant opinion may be that tamping force has little effect on shot extractions and shot times, which might explain why the Socratic Coffee experiment caused no big stir. I think this opinion has been around for over 10 years. Some of it, including an informal experiment on tamp force vs shot time was written up here: htt p://partsguru.com/user/SCAA%20Presentation%20Espresso%20machine%20design.pdf *. In addition to the experiment discussion at the end of that article there's an illustrative anecdote in that write-up:

When Luigi Lupi, a barista working with Elektra at SCAA 2005 was approached by small contingent of consumer members, he was quizzed as to the role tamping played in his profession. He shrugged and produced the same quality shot he had produced moments earlier without tamping at all.

* Edit addition: That partsguru link with Michael Teahan's SCAA 2006 tamping experiment is dead. Try here: https://manualzz.com/doc/23624385/table-of-contents

Peppersass wrote:My own experience suggests that tamping pressure has little or no effect on the extraction.
.................................

"Regardless of what actually happens, I think there's no need to obsess over tamping pressure. If there's any effect, its minimal."

"There seems to be some anecdotal evidence that tamper shape and size might make a difference."
.........................
"Finally, the Socratic study is based on extraction yield measurements. I'm a proponent of using such measurements for various purposes, like dialing in, ensuring consistency, troubleshooting equipment, etc., but it's not a given that a higher extraction yield is always better.

Thanks for the detailed answer, which I edited to show only some highlights. I might think if pressure matters not, hard to see how tamper shape might matter. Socrates compared 4-5 nice tampers, but all were flat. Elsewhere, here on the site, there seems to be data that shape matters not, which would be no surprise.

To me, the take home message from the data is, not that there is more effect on TDS, not less effect on TDS of tampers or tamping, but: NO MEASURABLE SIGNIFICANT DIFFERENCES.

Maybe, until proven otherwise with data:

"Make everything as simple as possible, but not simpler."
Albert Einstein

homeburrero wrote:Yes, and I think on this forum the predominant opinion may be that tamping force has little effect on shot extractions and shot times, which might explain why the Socratic Coffee experiment caused no big stir. I think this opinion has been around for over 10 years. Some of it, including an informal experiment on tamp force vs shot time was written up here:

http://partsguru.com/user/SCAA%20Presen ... design.pdf

In addition to the experiment discussion at the end of that article there's an illustrative anecdote in that write-up:

Hey--thanks for the link to the great PDF. Direction to literature like this is what I was hoping my post might lead to. The chapter on tamping strongly supports it has no impact. I see now why the data from Socrates did not cause such a stir. Thanks again!
http://partsguru.com/user/SCAA%20Presen ... design.pdf

Funny topic in an era when tamper prices keep increasing, all promising euphoria in a cup.

nurxhunter wrote: This hobby seems to this amatuer like a house of mirrors, with respect to all.

Doesn't every hobby?

"Flip a steak ONLY ONCE!!! Flip it all the time. Don't prod it..."
"Speakers must have toe in. Otherwise they sound like AM radios."
"Red wine goes with red fish and white wine always goes with chickens."

Tamping I think, was important for everyone involved as it served as an anchor to the process of distributing, grooming and levelling (before anyone knew any better). These remain very important to prevent channeling and you'll see everyone doing a NSEW or a Stockfleth's and measuring the done and doing WDT....

One thing I'll say about tamping is that after a while it becomes a quality control of sorts. A tamp can tell me if my dose is level and if the grinds are sufficiently fluffy. I don't push hard - I just get a feeling for how it sinks into the basket.