Big Dog -

Excerpted from Section 4.3 of this post:

http://www.home-barista.com/forum...perature-t516.html

Water absorption by the coffee cake: A series of measurements were performed, in which a dry portafilter was dosed with coffee and weighed. The portafilter was reweighed after espresso was brewed from the coffee. The measurements show that a dry coffee cake absorbs approximately its own weight in water during the brewing process, about 18ml for a double espresso shot.

Just for the heck of it, I measured the weight of the originally dry 15 gram "used" puck this AM and it tracked very closely with the above - 15.5 ml. That's about 0.5 ounces of water.

In this post:

http://www.home-barista.com/forum...1-t5472.html#64086

There were conflicting (harmless) reports of exactly what happens when the brew lever is moved to the mid position - a very pronounced detent. A short perusal of lots of posts on the subject would show, I believe, that the brew valve is nudged slightly open when the lever is in this position HOWEVER I would tend to agree with Ian when he responded that all valves are closed when the lever is in the mid position - it seems natural. In any event, whether the valve is nudged open or remains shut could rather easily be changed by the end-user by swapping a few parts or adding/removing a shim in the right place. I, for one, don't make any use of this mid-position (although my Anita is one of the nudgers) as the inherent pre-infusion of the group seems to work OK.

But back to your 1.75 ounces - that's a lot of water and, exactly how much of it is used to saturate or partially saturate your puck can be seen/measured simply by removing your portafilter after "X" seconds of having the lever in the mid-position and "catching" the water that escapes. Keep in mind, of course, that when you start the pump, that 1.75 ounces has to be made up before any flow through the puck takes place. In addition, that 1.75 ounces was a VERY RUDE interruption to the thermosyphon flow that was happily moving along.

Skol and,

Even LM thought it was a good idea at one time:

http://www.google.com/patents?id=...ec=abstract&zoom=4

I too am curious about the importance of preinfusion. I realize that most of the discussion on this thread has related specifically to the Anita so perhaps my question isn't perfectly related, but... I have a plumbed-in Izzo Alex. When I put my lever in the mid position, I get steady watermain pressure at about 2.5 bar for as long as I leave it in this position, and the rotary pump does not turn on. So I'm assuming that doing this for a few seconds is what is normally referred to as preinfusion. I can soak the puck at a very low pressure before fully engaging the lever and starting the pump. My question is - should I bother? I've done some limited testing with and without preinfusion, and came up with ambiguous results. My feeling is that technique in the grind/tamp/dose was more important to achieving shot consistency, but frankly, I haven't yet taken enough time to really examine the difference between preinfused and non-preinfused shots. I'd be glad to hear from anyone who has a pre-infuse capable plumbed-in machine. Does preinfusion matter? Will it effect quality in the cup?


Thanks.
Alex.

Alex G wrote:I too am curious about the importance of preinfusion. I realize that most of the discussion on this thread has related specifically to the Anita so perhaps my question isn't perfectly related, but... I have a plumbed-in Izzo Alex. When I put my lever in the mid position, I get steady watermain pressure at about 2.5 bar for as long as I leave it in this position, and the rotary pump does not turn on. So I'm assuming that doing this for a few seconds is what is normally referred to as preinfusion. I can soak the puck at a very low pressure before fully engaging the lever and starting the pump. My question is - should I bother? I've done some limited testing with and without preinfusion, and came up with ambiguous results.

A recent post on a Barismo discusses this (see http://www.barismo.com/labels/delay%20timer.html) on an older LM (I think). They seemed to be happy with the results. Ken Fox has also added a delay timer to add preinfusion to his Cimbali Junior(s?), see here and here.

With your plumbed Alex, no need to have the timer. You do need to control the inlet water pressure with a pressure regulator (and maybe an accumulator would be a nice addition). If the lever mid position on the Alex wets the puck, you can play until your hearts content. My gut feeling is that this will not have drastically different results on an E61 machine in comparison to a LM with no gicleurs, La Cimbali or other machines with no preinfusion.

this is a fun thread.

i messed with this a bit. my wife is usually my "blind" guinea pig. if i know im doing something different its going to skew my results. so i experiment on my self then do the same fer her without telling her that anything is different. so she gets a full blind opinion i just ask her how it is, she doesn't know if its a different bean or pre-infused or what...

so we are in probably our 7th pound in a row of bigfoot espresso we love it. so its the same each day as far as technique goes then i try this preinfusion 10 seconds @ line pressure of 3.745ish bar, then lift he lever to full brew. it seemed to produce a different cup for sure but its like its smoother or more blended or texturally different. anyway i make one for her with the preinfusion and don't say anything. she takes a sip... "WOW! this is REALLY GOOD are these different beans?" nope.. she said it tasted fruitier and more sweet. so this is just what happened for me.

i like it. i am thinking of changing the shape of the cam on the lever so it will be easier to put in the correct position without activating the pump accidentally.

thanks for the time.

jon

Have become addicted to reading these exchanges since my 13 year old Black & Decker pump died 3 months ago. I have since learned how hard it is to know what you don't know, especially about the prosumer E61 Hx technology.

I will plunge ahead with some likely naive questions to further unveil my ignorance, and perhaps one day (soon) I will have the wisdom to own an espresso machine again. I have relied heavily on some of the schematics and cartoons on this site and perhaps that is my problem.

Concerning the idea of preinfusion and how it happens -

My understanding is that preinfusion means subjecting the puck to (some) water prior to the fully pressurized bolus which makes the shot. When the handle on the manual E61 is down, the pressure in the cam pocket and preinfusion chamber is room pressure. In the middle (horizontal) position, the preinfusion chamber is closed by the 1.5 bar spring, the upper chamber (upper sleeve assembly) is now open to the cam pocket area and therefore the puck. Pressure builds in the cam pocket (& above the puck) until it reaches the thermosyphon pressure, which I take to be greater than 1.5 bar (the spring tension needed to open preinfusion chamber spring). There is some debate about how much communication between cam chamber and upper chamber there is at horizontal position, but my sense is that the critical difference is pump pressure, which is only activated when handle is up (is this right? As you must know by now, I have never been in personal contact with an E61). So the preinfusion is exposing the puck to the thermosyphon pressure before any pump pressure. (What is the thermosyphon pressure, I should ask.) It is unclear to me precisely what function the preinfusion chamber has, as the puck is already exposed to the thermosyphon pressure. The preinfusion chamber fills once the preinfusion spring pressure is overcome (about 1.5 bar) by the increasing pressure in the cam chamber. Once it fills and is isobaric to the cam chamber, the spring will close again. I am not sure what its function is.

I am also confused by the E61 drain valve - the drain valve spring as mentioned in the patent, is around 7 atmospheres. So why doesn't the pump water (greater than 7 atmospheres?) go out the drain valve instead of through the puck? What pressure is needed to push a shots-worth of hot water through the puck in 25 seconds? (Less than 7 atmospheres?)

There was discussion about the differences of preinfusion between reservoir and plumbed units. I don't see the difference, if the preinfusion is a result of the exposure of the puck to the thermosyphon pressure (at least for the E61 Hx) and not the main pressure (which is "behind" the pump, and which is off during preinfusion...)

Well, no doubt my points will be met with frustrated head shaking among the engineering and PhD types who vigilantly parole this site, but I'll be stronger for it. Thanks for your help and forbearance.

Bluer Ridge wrote:Well, no doubt my points will be met with frustrated head shaking among the engineering and PhD types who vigilantly parole this site, but I'll be stronger for it. Thanks for your help and forbearance.

Eric's diagram shows us the "big picture":

erics wrote:

From Can anyone explain preinfusion on the E61?

The image of the E-61 group is copyright 2005 by Verna Design, Inc. It is shown in the brew position.

My attempt to explain the rest of the story is excerpted below from Is there a purpose for the E61 middle brew lever position? My terminology is slightly different than yours. I refer to the chamber containing the orange cam as the brew chamber and the chamber beneath it as the expansion chamber.

HB wrote:Please do not copy these images.

The first image shows the E61 lever at the rest position. The two lower valves are open to allow the brew chamber and expansion chamber to drain. The uppermost valve is closed. Water from the HX circulates through the upper port on the left, passes alongside the "mushroom" to heat the grouphead; as the water cools it descends through the lower port on the left. The temperature difference creates a thermosyphon that circulates water between the boiler and grouphead.



The next image shows the E61 lever at the mid position. The two lower valves are closed and the upper valve is barely open. If this pump has line pressure, water will flow through the upper port, grouphead cap and screen, gicleur (yellow), descend towards the brew chamber (orange cam), and finally through the L-shaped channel to the brewhead. It's easy to see the purpose of the Allen screw (gray); it caps the hole drilled during manufacturing for the first leg of the channel.

EDIT: Ian correctly notes the Vibiemme Domobar Super does not allow flow at the mid detent; a number of E61 clones do (e.g., Quickmill, Isomac, and Expobar).



The final image shows the E61 lever in the brew position. The upper valve is held open by the orange cam. The valve at the bottom of the expansion chamber is held tightly closed by a spring. The spring above it holding the second valve closed is weaker; it will open at about 4 bars of pressure. It only takes a second or two for the brew chamber containing the orange cam to pressurize. As the pressure builds, water eeks pass the valve below the orange cam, allowing the pressure to drop. This action is the novelty claim of the E61 patent since the pressure is automatically lower as the expansion chamber fills. Once the lower chamber fills, the pressure equalizes in all chambers and the valve below the cam closes.



The familiar "whoosh" that follows the lever being lowered is water evacuating the brew chamber and expansion chamber. Again at rest, the expansion chamber and brew chamber are empty. Water continues to circulate along the jacket of the uppermost chamber as the thermosyphon re-establishes itself.

Thank you Dan!

I think I've got an understanding of how it works. And I find it very exciting. I don't know what took me so long to get into espresso. But as a mechanical engineer, a coffee lover, and someone who has a genetic predisposition for thermodynamics, this stuff is a lot of fun.

The power of the forum is great. Carry on...

Yes, Dan, your diagrams are helpful. Especially the expanded diagram of the entire machine and not just the E61 (still don't know where the steam frother comes in). I am still confused, but perhaps I just need to study and follow along longer. I assume the cam never closes off or restricts the L channel aperture in any position - is this true?

Still confused about the role of the middle position in those machines for which the upper valve is at least partially opened. As I noted, the puck is subjected to the pressure of the heat exchanger tubing (I assume it is pressurized because it is closed and hot) and therefore must be experiencing some so-called preinfusion, without the lever up (and pump on). Unless it is understood that the (low?) pressure merely from the heat exchanger tubing and the hygroscopic property of the coffee rounds is insufficient to wet the entire puck. What am I missing here? A brain?

The purpose of the operating cam inside the group is strictly mechanical. I can see where you might think it could close off the brew port but, no, that does not occur in any position.



The middle position is a prominent detent on E-61 lever machines and, as such, one would think that the brew valve is not being moved. Certainly, on Ian's machine (and probably on a host of others), it does not; on my machine (and probably on a host of others), it does. Pressure builds up in the heat exchanger when the lever is in the full down position due to the expansion of the water within that circuit. This pressure is typically limited to the setting of the OPV (over-pressure valve) and instantaneously falls to zero or thereabouts when the brew valve is nudged open even the slightest amount.

For most users, this is not relevant because the middle position of the brew lever is simply a "bump in the road" that one must pass through in brewing the espresso. For users that have a plumbed-in machine whose brew path is always subjected to line pressure (and whose brew valve is nudged open when the lever is in the mid-position), this can be used to pre-preinfuse the espresso. I say pre-preinfuse because the E-61 lever machine has an inherent preinfusion stage as part of the brewing process - see Dan's explanation.

The extent to which this preinfusion (really of any type) is advantageous can be debated ad infinitum. Personally, I believe it to be beneficial as regards a more consistent brew but there certainly exists espresso machines which either don't employ it or it is not utilized AND that still produce outstanding results. The espresso grounds can certainly be wetted by the hot water which manages to pass through a nudged open brew valve (non-plumbed-in machine) but the pressure is basically zilch - maybe 2 to 3 inches of water height. Will the entire puck be saturated? - I do not think so unless one wants to take a short nap and this would sorta be counter-productive.

Doing a site search with the key word being "preinfusion" could keep you quite busy for a few days.