You guys are doing a great job!

First thing this morning, and before I saw last nights later posts, I did a little experiment aligned with Michael's preinfusion rate thoughts. I had been doing a 20 second trickle preinfusion (number pulled from thin air) and thought I'd rather know when the puck was saturated. So I went ahead and trickled until I saw the first drop at the basket bottom, which was 27s. Then I pulled the shot as normal, and after that I went back to the machine with a graduated shot and timed the volume for 25s of trickle time (reduced because you want the volume just before a drop would show). This volume came to 1.25 oz. I did this just for kicks because I can't at this point control my flow rate. FWIW

This also reminds me that I wanted to mention something as I read through this thread (still not finished), appreciating yours and Assaf's discussion, having to do with Assaf expressing a limitation with the E61 group with regard to the volume available for preinfusion being a fixed volume based upon the E61 version design. I think one additional nice feature of the E61 is that with the lever cam's dimensional relationship with (or distance to) the pump switch, you can set the switch position such that with the lever rotated to where the exhaust is closed and the upper valve is just cracked, you can get a pre-wetting or preinfusion (depending upon definitions) flow from the boiler that is not limited by the group PI volume. My example above is with a tank reservoir and it relies on boiler pressure similar to a Cremina, but I would guess that if plumbed the flow rate may be higher, and probably adjustable with the pressure reducer valve typical with plumbed installations. So did I miss Assaf's points back there, or is this helpful?

I'm finding I cannot get to the last page in this thread, so this is a test. Never seen anything like this here. Gremlins......

I've had this happen from time to time as well. Had to use the reply screen to read posts, but haven't tried posting to see if it fixed it. Did posting get you to view the last page?

Tonefish wrote:...I went back to the machine with a graduated shot and timed the volume for 25s of trickle time (reduced because you want the volume just before a drop would show). This volume came to 1.25 oz.

1.25 oz is just shy of 37ml, so you have a water debit that is very close to 1.5ml/s. That's Slayer territory, and pretty cool to be able to accomplish this purely by expansion of the water in the heat exchanger. It is different than what Slayer does in that the trickle method doesn't likely generate any pressure at the puck. Yes, expansion valves play a critical role in venting pressure generated by the expansion of water that is heated in a sealed system, but the system isn't sealed when it's trickling... I do wonder what implications this approach has on the temperature profile of the shot. Clearly, the water in the heat exchanger loop is heating up while you use the resulting trickle to preinfuse. To that point, any HX machine would be "recovering" while using a slow preinfusion, but even under line pressure, there is an influx of cool water into the HX, which makes things somewhat different. By how much I do not know.

Tonefish wrote:So did I miss Assaf's points back there, or is this helpful?

Your commentary is most helpful. I believe that using the E61 in the way you do, or how David (Bluesman) does with line pressure on a plumbed machine, is outside of the critique of the E61. Well, I don't think it warrants the critique null and void, it simply circumvents the shortcomings of the design, with respect to variability in dose and the ability to preinfuse completely. Moreover, I think Assaf was making the point that the design of the mechanical PI system on the E61 was intolerant in changes of dose. Using line pressure preinfusion renders the PI chamber useless, trickling probably renders the chamber unnecessary...

Any luck reading the last page?

- Jake

Jake_G wrote: I do wonder what implications this approach has on the temperature profile of the shot. Clearly, the water in the heat exchanger loop is heating up while you use the resulting trickle to preinfuse.

I pull ristretto, 18g in 27g out and the volume is pretty close to the preinfusion volume (well the water is less tho 27ml-ish) so my guess is that it would be preinfusion water that's in the cup, yes?. I also have an erics thermometer which I use during the pull and I did not see any difference (from normal) in temperature although apparently not much of what I read during extraction makes it to the cup.

Any luck reading the last page?

- Jake

Went to another computer and all was well. It will be interesting to see what happens on the other one next time. Cheers!

Random Update!

2 days ago, I finally swallowed my pride and and decided to try WDT. I've always accepted that WDT was effective, but I made petty excuses about how "it wasn't for me" and how "I get good looking extractions without it".

Nonsense...

Here's my process in pictures:

Basket after WDT with some side taps to level the mound.


Basket after being groomed with my 8mm grooming tool.


Basket after very light tamp with only fingertip pressure.

And the results... Fast pour, but absolutely delicious. Tamping makes almost zero difference in flow, but getting the surface of the puck away from the shower screen makes for much easier cleanup. Just locking on with an 8mm depth on the grooming tool leaves me with quite a few grinds in the gasket area around the shower screen, so I tamp a bit to provide clearance and it works well. Long term, I will adjust my grooming tool to stick out 10mm. After seeing these results consistently over the last 9 shots I've pulled, I can't justify not doing WDT every single time.

Wow.

One of these days I'll try RDT...

Cheers!

- Jake

Mighty tasty looking shot there Jake! The preinfusion results look even-Steven. What's your extraction pressure after you throw the 2nd switch?

Tonefish wrote:Mighty tasty looking shot there Jake! The preinfusion results look even-Steven. What's your extraction pressure after you throw the 2nd switch?

While clearly not a God Shot, it was one of the tastier shots I've pulled in the last little while. I nailed the temperature, and the flavor was astonishingly good, even with a fairly fast pull. Not a hint of sour or bitter. Loads of bakers chocolate, with granny smith apple acidity and a lingering sweet and smooth aftertaste. I have the rotary pump set to 9 bar right now. With the 0.5mm gicleur in the group before the 3 way valve, I suspect I have a bit of a declining profile at the puck, but I won't know for sure till I get my puck gauge installed.

Cheers!

- Jake

One other thing that shot (and its similarity to others) made me think about with respect to what's going on in the puck through the process, is that while the earliest part of the process, the preinfusion, results in that thick syrupy dark flow, the later part seems to have more air that gives that Guiness draw-like 3 part stratification: 1) the dark liquid bottom, 2) the middle effervescentish part that seems to kind of split itself between the dark liquid and the crema over time, and 3) the top layer of crema. So where is that latter air coming from? MOst seem to think the air in the system is pushed through the puck prior to the liquid doing much, but since the wetting/preinfusion at lower pressure may not be doing that, how do you think the air rejection occurs, or is it in fact a part of the coffee product until it fizzles out in the cup? I wonder if the preinfusion changes the air removal process relative to a straight high pressure extraction? Could be even different depending on whether its sub 1 bar trickle preinfusion or the 3-4 bar camber filling and/or plumbed line backed preinfusion. What do you think?

I don't think the "air" is actually air (as in the air we breath). AFAIK the "air" in the espresso comes from outgassing (so mainly carbon di-oxide).

That is why old stale coffee has so little crema.

Edit - I added originally:
I would assume the air in the puck (i.e. the air around the coffee grinds) gets pushed out much like a doctor purges air from a syringe.

More accurately:
I assume that some of the air in the puck (i.e. the air around the coffee grinds) gets pushed out much like a doctor purges air from a syringe and some - like the air cought in the headspace would compress until released post extraction.