2014-02-15

Nutation? And Precession

In espresso tamping, there is a technique known as "nutation," highly search-optimised discussions of which range back to 2009 - they did not seem to resolve the definition thoroughly. So let me give it a shot.
SUMMARY:
So it turns out that multiple parties are right, and what we are doing involves both nutation and precession.
THE technique is this:
1. Centre the tamper on the basket.
2. Tip the tamper to one side, slightly, as if you are pressing down on a marble that is on the inside edge of the basket. This is roughly a 5 to 15 degree movement in the SECOND Euler Angle, and so we call it a Nutation.
3. Turn the tamper, in a full circle, as if you are tracing the movement of the marble around the circumference of the basket. This is a 360 degree movement in the FIRST Euler Angle, and so we call it a Precession.
4. Apply step (3.) with whatever tamping pressure is deemed appropriate, as many times as is deemed appropriate, in order to achieve the desired puck resistance/ distribution/ density.
5. Reverse step (2.) and then apply an even tamp to level off the puck - as with simple, standard tamping.
MAIN utility of technique:
Reduces channelling. Your flow may be slower, but it will cone sooner.
REFERENCES:
http://en.m.wikipedia.org/wiki/Euler_angles
http://en.m.wikipedia.org/wiki/Precession
http://en.m.wikipedia.org/wiki/Nutation



Update 2016-08-13:

I have been discussing nutating tamps with our staff. Then I found this post. (I still recommend nutating tamps because... coping my comment:)

"I find that "nutating" (perhaps it should be "precessing") produces a more even tamp, at any level of fineness. My thought about this tends to be that it increases the probability that larger spaces in the heap of grinds are forced to cave-in. I've compared nutated and non-nutated shots, the latter taking 10-15s longer to reach the same brew ratio... and often enough the former will cone more symmetrically, and taste cleaner. Does anyone else have similar experiences?"

Perhaps I just work in a cafe where most shots are shorter in duration and messier in coning. Who knows. No time to collect all that data on everyone else.

/

Well, it's not like Perger invented it (it's not a hard thing to invent). I was making coffee like that in 2008. I just find nutation to provide a more even tamp. ;)

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