Re: where this came from is a head-scratcher

It came from this earlier post. Have a look at the referenced pdf.

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://www.partsguru.com/user/SCAA%20Pr ... design.pdf . In addition to the experiment discussion at the end of that article there's an illustrative anecdote in that write-up:

Note in particular that the volume of the pictured shots did not vary with tamping pressure, and in the article it refers to some particular barista who demonstrated that he could produce the same result with or without tamping. I was doubtful, so I tried to reproduce that experiment.

What I'm saying is that (a) I was unable to reproduce the findings reported in the pdf above using a stock Rancilio double basket and a Rancilio Rocky grinder. To the contrary, tamping pressure and tamping technique had a very large effect on the volume and taste of the result, and (b) with a high precision HQ 14g basket and a corresponding much finer grind needed to get a balanced extraction, tamping pressure and technique seem to make less difference.

Seems as if there likely is a middle of the road tamp, one that works well for most doses with most coffees for a given machine and filter basket.
In my case and using quite fine grind settings my baskert and my machine my tamping pressure is of little importance (though I need to tamp)

I've tried the OE slapshot test in my La Pavoni long ago, and while no tamping at all does work, looks okay in the cup there are 2 problems with it:
1. IT'S MESSY! Cleanup is often a pain after that shot.
2. The flavors in the shot are muddy when compared to even a minimal tamp with the same grind settings.

You can run shots without a tamp in some machines and probably be happy with it once you have all parameters dialed in, but you'll probably find it easier in many ways to at least have a minimal tamp. The mess on the La Pavoni alone was enough reason for me to abandon the practice and further dialing in, so others might have more fun trying that than me.

It's an interesting experiment though to be sure.

I tried not tamping with my ROK ages ago and it was an unmitigated disaster, messy in the up and out!
So I was pleasantly surprised with the Caravel when it wasn't a disaster and drinkable to boot! There was quite a difference in resistance on the lever, however, that I do not notice when experimenting with tamping at different pressure.
The only difference I have noticed with this machine so far (keeping in mind it's a very tapered basket) between an ill-fitting and well fitting tamper is in cleanliness and ease of use (no need for NSEW), no difference in shots.

Re^^^

Earlier today, an insightful poster pointed out that with levers (I have two), a fixed amount of water is delivered, with each (properly primed) pull, no matter how fast or slow, so zero tamp or full body weight tamp will deliver the same liquid.

Further, with the comparatively slower pressure ramp from a lever pull versus a pump, loose or untamped grinds have more time to arrange themselves into a stable "cake filter" (actual engineering term), without a channel being hammered through it, making tamping less important than with a pump machine with a rapid ramp.

-Peter

pcrussell50 wrote:Re^^^

These certainly seem to be important differences as the ROK delivers much more water due to a larger chamber and also seems to have a less effective shower screen (fewer holes and leaves imprints on the puck)...

For me, the finer the grind the more effect tamping pressure seems to have on the output. Used to grind very fine on a Rancilio Silvia and results greatly varied with tamping pressure changes only. With coarser grinds, tamp pressure doesn't seem to effect the outcome very much. Anyone else noticed this?