HB wrote:Steve and I discussed this point after reading How to Preinfuse; Extraction Pressure Redux; we wanted to see how a lever's puck saturation compared to your results. Problem is, we haven't figured out how to promptly remove the portafilter after preinfusion without splattering everything within a 10 foot radius with wet coffee grinds. Then there's the question of how intact the puck would be after such a sneeze.

Forgive me if I am misunderstanding this or it was already settled elsewhere. But it seems like a La Peppina could yield one answer your question. As you know preinfusion on Peppina is achieved near the bottom of the lever's arc, with a pumping motion. The meeting of water and puck can be sensed by both sound and feel. As per this site, proper Peppina technique involves waiting for that meeting, then taking the lever all the way down to the bottom, waiting for a 5 second preinfusion, and then allowing the lever to rise.

When the lever is at the bottom of the arc, it seems that there is little to no pressure on the puck, and PF can be removed without a sneeze. That's always how I remove my Peppina portafilter after a shot, tug the lever down (while holding the base), twist off PF, and take it to the sink.

I only forgot to take down the lever once...

~tMb

At first, I'm a bit struggling to "decode" Jim and Ken experiment.
So, I copied their raw data to a Stat software to figure out their analysis and conclusion.

This is just my attempt to interpreting Jim's & Ken's data analysis using some graphs, so maybe nothing new in the conclusion.
But hopefully these pictures could make this topic more accessible to other readers

The analysis of variance model also showed that our reactions to the fruity blend were much more biased towards the vibe machine than the other coffees.

.. I(Jim) liked the preinfusion rotary produced shots better, and that Ken liked the vibe shots better, no matter how the rotary was set up.

...It used to be almost dogma on alt.coffee and other coffee related websites that rotary pump driven machines produce better shots than vibe pump machines. This is now the second blind tasting study that Jim and I have done in the last 3 years that fails to confirm this supposition.

Note: the red graph are box-plot, the green graph are mean-diamond-plot.

It's just killing me, so I'll ask: What's ∑ for a population of two?

BDL

Hi Rich, when you asked about the "∑", did you mean the standard deviation?
Cause the capital sigma ("∑") symbol usually means "the sum of data",
Since I've used "Student t-test" as suggested by Jim, the formula use small caps sigma ("σ") for population and "s" for sample data standard deviation.

The detail are here : http://en.wikipedia.org/wiki/Student%27s_t-test

Standard deviation. The standard deviation -- or sigma, if you will; or "s" if you insist -- "for a population of 2," is a joke. Get it?

Reminds me why I changed majors from math to philosophy.

BDL

Hi all,

Great thread and interesting read!

I wanted to add a word of caution about automatically thinking that pre-infusion will always benefit a machine....

On some machines, like the Elektra I own, there is a built-in pressure ramp-up delay that basically performs the same function as pre-infusion. If you read the thread on the 1988 Elektra rebuild (look at the last page or so), and look at the restorer's response to my question you'll see that adding pre-infusion actually worsened the shot.

It all depends on your individual machine's design.... I, personally would NOT add preinfusion to commercial Elektras for this reason. I am sure there are other machines out there with similar built-in pressure ramp-up designed into the brew path. If you do decide to add pre-infusion to a machine, I recommend that you do it in a way that allows you to bypass it and compare the difference in taste between pre-infused and not. Also do your research to see what others have experienced with your particular machine. You might be surprised by what you learn....

ASIDE: I think this caution might also apply to adding PID's to machines with heat exchanger (HX) boilers as well. HX machines are much more temperature stable by design than non-HX machines -- they just need the cooling flush when they've been sitting for a while to purge superheated water out of the HX (yes, even if PID'd). However, this mod probably can't hurt the taste of a shot like doing unneeded pre-infusion can.

I hope this helps,

Philip

interesting resurrected thread. imo, machines are like pianos. you can buy a yamaha, or you could buy a bosendorfer. whatever good comes out of either instrument, however, is the result of a lot of practice. pre-infusion is a component of technique that benefits from repeated rehearsal.

pre-infusion is a component of technique that benefits from repeated rehearsal.

Statistician always says "we need more samples to declare it's a statistically significant finding"
Home-barista always says "we need more rehearsal"
Either way, it simply means more delicious shot to taste , yippee!
So I raise my cup to you all for the exploration and every God-shot you'll tasting

i am trying out pre-infusing for 6 sec., full pressure for 15 sec., post-infusing for 6 sec. (roughly) for shot times of 25-30 sec on a mocha java blend. this thread gives you ideas...

i think my shots taste softer, but i lose track of some of the flavors compared with full pressure to the end. overall i like the taste better. also note i am no coffee expert, but it is much fun and i am alert.

precision/reproduction capacity of the gs/3 paddle is very nice.