I know this is an old thread (2009, and it's now mid 2011), but I thought I would add yet another clarification for the non-mathematicians in the readership.
I first heard the word "nutate" and "nutation" when looking at the new high-efficiency top loading washing machines made by Whirlpool and sold under their name and under the Sears Kenmore brand name. These machines don't have a center agitator inside like the traditional top loaders do. Instead the bottom of the basket does a "nutating" motion, like the analogy made early on in this thread to the motion a spinning coin makes as it slows down just before landing flat. Whirlpool uses "nutating" to describe the motion that their machines use.
That's what gave me the idea of doing a nutating motion when tamping. I thought I had an original idea until I read this thread, and discovered others had come up with the same idea a couple of years or more earlier. It's not the first time I thought I had a great idea only to find out I had covered the same ground as many before me. It certainly won't be the last time either
Here's my method for tamping and pulling the shot.
0. If the machine has been sitting for a while, I start a HX purge to flush the superheated water out of the Heat Exchanger. (My machine is e a single group commercial Elektra machine, a restored late 1970's predecessor to the current GL1 model.)
1. I fill the dry empty basket with loose grounds, sometimes doing a bit of a shake as I fill it from the doser to distribute the grounds more evenly,
2. I do 2 swipes across with my index finger to level it in two directions to fill voids and deal with uneven distribution and to clean stray grounds off the basket rim and the locking tabs on the portafilter,
3. I then place the tamper upright in the filter basket.
4. Then I start applying pressure while doing a nutating motion -- a circular rocking motion (NOT twisting the handle). What this seems to do is to press and distribute the grounds evenly around the perimeter of the basket. (If I pull the tamper out and look at the grounds at this point, there would be a bit of a "hump" in the middle.) I am using a flat tamper, but I think a curved tamper would work as well.
5. I then do a strictly vertical press which eliminates the "hump" and in doing so seems to force the grounds even tighter against the side as the tamper is pressed down. At the end of this vertical press, I do a light twist (not nutating -- the tamper is held vertical) to polish the puck.
6. I insert the portafilter and pull the shot.
This seems to give me a consistently even distribution of extraction as seen by looking at my bottomless portafilter.
Maybe this description of nutation will help others understand the concept if they have seen this kind of top loading washer in action.
I am sure that a person can get a good even tamp without nutation, but for me it helps a lot with my ability to pull shot after shot producing even distribution on the portafilter during extraction. A couple of others I have shown it to in the Portland area also found it helpful.
Beginner and pro baristas share tips and tricks.
- Team HB
Give it time. First the ideas come a couple of decades late; then a couple a years; eventually you'll catch up or get them first.phreich wrote:It's not the first time I thought I had a great idea only to find out I had covered the same ground as many before me. It certainly won't be the last time either